cm TG 16, Sustainable Construction, Tamp., Florid•. USA , November 6-9, 1994. A STUDY ON THE WASTE OF MATERIALS IN THE BUILD- ING INDUSTRY IN BRAZIL Lucio Soibelman(l), Carlos T. Formoso(2) and Claudia C. Franchi(l) (I)Civil Engineer, M.Sc., graduate student CCRE-Center for Construction Research and Education; Massachusetts Institute of Technology, Cambridge - MA 02139, Email [email protected](2)Civil Engineer, Ph.D., NORJEIUFRGS professor; Av. Osvaldo Aranha, 99, 3° andar, Porto Alegre - RS, CEP 90035-190, Email [email protected](3)Civil Engineer, M.Sc., researcher NORIElUFRGS; Av. Osvaldo Aranha, 99, 3° andar, Porto Alegre - RS, CEP 90035-190 Introduction It is recognized that a significant amount of materials delivered on construction sites are not used for its original purpose. The lack of research on material waste in the Brazilian building industry has as a consequence a high variance in the assumption of the waste index varying from 5% to 10% used for budget purposes, 15% to 30% (Pinto, 1989; Picchi, 1993) and 50% (Melighendler, 1978). The high incidence of waste of materials has been appointed as one of the causes of the high prices of buildings, since their costs are generally passed on to the clients. Deming (1986) co-relates waste with quality when he considers the waste of resources an indicator of the quality of the process. From this point of view, waste is a result of low efficiency in the process, wh ich consequence is also final products of inadequate quality. Wyatt (1978) justifies the reduction of material waste to a possible minimum from an ecological and social point of view, since high levels of waste both reduce the future availability of materials and energy, and create unnecessary demands on the transport system. A reduction in the volume of waste genera ted in construction is also fundamental in order to avoid disruptions in big cities. In the city of Sao Paulo, for instance, around 2,000 tons of was te are produced daily, causing serious problems for the city (Pinto, 1989). Material waste can therefore be related to a large number of problems: decrease in profits, increase in costs for the client and the community, possibly causing problems such as loss of quality, performance and productivity. As important as the theme is, not much has been carried out, in terms of research , in the sense of obtaining consistent data on material waste in the construction industry. Abroad, the most important studies on this theme were developed by Skoyles (1976). Most of these studies were carried out at the Building Research Establishment in England. The first study was initiated in 1963, reaching 249 studied sites in the late eighties. The construction sites studied by this author were mostly housing developments carried out with the employment of traditional technology. In Brazil, few surveys have been carried out. Pinto (1989) carried out a study in the state of Sao Paulo, based on only one site. The research was limited to estimating the material waste occurred during the structuring, walling and plastering stages, through the analysis of fiscal documents of the construction, the verification of designs and inspection of the site after its conclusion, in order to verify alterations made in the execution and to 555
Transcript
cm TG 16 Sustainable Construction Tamp Floridbull USA November 6-9 1994
A STUDY ON THE W ASTE OF MATERIALS IN THE BUILDshyING INDUSTRY IN BRAZIL
Lucio Soibelman(l) Carlos T Formoso(2) and Claudia C Franchi(l)
(I)Civil Engineer MSc graduate student CCRE-Center for Construction Research and Education Massachusetts Institute of Technology Cambridge - MA 02139 Email lucioathenamiledu (2)Civil Engineer PhD NORJEIUFRGS professor Av Osvaldo Aranha 99 3deg andar Porto Alegre - RS CEP 90035-190 Email formosovortexufrgsbr (3)Civil Engineer MSc researcher NORIElUFRGS Av Osvaldo Aranha 99 3deg andar Porto Alegre - RS CEP 90035-190
Introduction
It is recognized that a significant amount of materials delivered on construction sites are not used for its original purpose The lack of research on material waste in the Brazilian building industry has as a consequence a high variance in the assumption of the waste index varying from 5 to 10 used for budget purposes 15 to 30 (Pinto 1989 Picchi 1993) and 50 (Melighendler 1978)
The high incidence of waste of materials has been appointed as one of the causes of the high prices of buildings since their costs are generally passed on to the clients Deming (1986) co-relates waste with quality when he considers the waste of resources an indicator of the quality of the process From this point of view waste is a result of low efficiency in the process wh ich consequence is also final products of inadequate quality
Wyatt (1978) justifies the reduction of material waste to a possible minimum from an ecological and social point of view since high levels of waste both reduce the future availability of materials and energy and create unnecessary demands on the transport system A reduction in the volume of waste genera ted in construction is also fundamental in order to avoid disruptions in big cities In the city of Sao Paulo for instance around 2000 tons of waste are produced daily causing serious problems for the city (Pinto 1989)
Material waste can therefore be related to a large number of problems decrease in profits increase in costs for the client and the community possibly causing problems such as loss of quality performance and productivity As important as the theme is not much has been carried out in terms of research in the sense of obtaining consistent data on material waste in the construction industry Abroad the most important studies on this theme were developed by Skoyles (1976) Most of these studies were carried out at the Building Research Establishment in England The first study was initiated in 1963 reaching 249 studied sites in the late eighties The construction sites studied by this author were mostly housing developments carried out with the employment of traditional technology
In Brazil few surveys have been carried out Pinto (1989) carried out a study in the state of Sao Paulo based on only one site The research was limited to estimating the material waste occurred during the structuring walling and plastering stages through the analysis of fiscal documents of the construction the verification of designs and inspection of the site after its conclusion in order to verify alterations made in the execution and to
555
measure some of the final dimensions Picchi (1993) carried out a survey of material waste in three housing developments built in 1986 and 1987 The buildings were executed with a conventional concrete structure and walls of ceramic blocks The study was carried out from the monitoring of the volume of waste removed during construction without considering the great volumes removed in the first months identified as soil originated from the excavations The study therefore monitored only the direct material waste which was removed from the sites without considering indirect waste
Through the program of Quality and Productivity in Construction of Rio Grande do Sul a link agreement was established involving the MSc Course in Civil Engineering (NORlE) of the Federal University of Rio Grande do Sul the Construction Industry Union of Rio Grande do Sul (SfNDUSCON) the Support Service for Small and Medium Businesses of Rio Grande do Sul (SEBRAE-RS) and the Science and Technology Founshydation (CIENTEC) in order to carry out an in-depth study on the incidence of material waste in the building construction industry
The objectives of this study were to monitor the incidence of material waste in building construction to study its main causes and to propose guidelines for implementing material waste control systems for building firrns On this paper only the main results of the study are described A more detailed description can be found in Soibelman (1993)
CLASSIFICAnON OF WASTE
Waste can be classified as to its onglO as being direct or indirect (Skoyles 1976) Direct waste occurs when the material is damaged and cannot be recovered and used or wasted during the process of construction It is generally easily characterized being its cost the sum of the cost of the wasted material plus its removal costs Direct waste may be a consequence of vandalism theft or management problems in site transportation unloading stocking of the material or in production
Indirect waste consists in the economic waste caused by an excessive use of the material or a different use from that which had been planned In this case the material is not physically wasted with the waste being the difference berween the cost of the material which should have been used and the cost of the material actually used Indirect was te can be subdivided as folIows (a) waste through substitution it is the waste caused by the utilization of a more expensive material than that which had been specified An example of this type of waste is the use of structural bricks in non structural walls (b) waste through negligence it is the waste caused by the excessive use of a material without the reimbursement of the builder with the additional costs For instance the th icker piaster due to problems occurred in the structures geometry is commonly found (c) waste through production is the waste due to the lt)ccurrence of unpredicted situations and therefore not budgeted An example of this kind of was te is the additional use of concrete in foundations due to unexpected eharaeteristies of the subsoil
Waste mayaiso be classified aceording to its moment of ineidenee In this study the following subdivision has been adopted (a) waste oeeurred during site transportation hanshydling and stoeking of the material (b) waste oceurred during produetion itself and (e) waste occurred in any stage in the process due to external factors (theft vandalism accidents loss substitution ete)
Finally waste may be assoeiated to the intervenient(s) in the process which originated it such as designers materials manufacturers company management site management workers etc During this study we have tried to identify both the nature of material waste as weil as its moment of ineidence and origin
556
METHODOLOGY USED IN THIS STUDY
In the planning stage of this study a group was fonned with researchers from the Federal University of Rio Grande do Sul State (UFRGS) and technical managers of building companies with the aim of discussing the methodology to be used in the study As the aim was to develop an in-depth study on the causes of waste adecision was made to limit the study to a sm all number of sites and to a limited group of materials and constructive technology Five building sites were chosen for the monitoring of data The criteria of choice used was the employment of traditional technologies (reinforced concrete structure walls with ceramic bricks and piaster) and the requirement that they were at similar stages of construction It is obvious that the modest size of the sam pie prevents the results of this study from being generalized for the whole sector
The study therefore did not intend to exhaust the theme but to be a first more inshydepth study of the problem also trying to encourage the development of further research which may contribute in the gathering of data on material waste
Besides the specific characteristics of the specified bui Iding sites the choice was also based on trying to find construction finns which would facilitate the search of the necshyessary data and which would keep the site the offices and the accounts accessible for the researchers The sites were selected among on going projects in the city of Porto Alegre desshytined for the upper middle cass due to the fact that this type of project has in the past few years dominated the building industry market in the city
With the aim of identilYing the most significant materials in terms of construction costs the materials ABC curve used in the normal pattern designs of four eight and twelve floors of the NBR-12721 (ABNT 1992) the Brazilian nonn for evaluation of individual costs and construction budget planning for the incorporation of buildings in condominium Were excluded items referring to labor as weil as the materials which have a low probability of waste in spite of their significance in tenns of costs as elevators windows doors locks etc Based on this criteria the foJlowing products were chosen to be observed woods steel premixed concrete cement sand pre-mixed mortar or lime and ceramic bricks which added up represent approximately 20 of the total cost of constructions built by traditional building methods
Before the beginning of the monitoring of data on the sites an inspection was carried out on each building site On these initial inspections represented from now on by 11 detailed measurements of all the services executed were made and the inventory of studied materials stocked on the site was observed
After the conclusion of the 11 observers were placed on the researched construction sites nonnally one per shift on each site The tasks of these observers was to fill out fonns where the data on the construction site and the studied materials were gathered from their arrival at the site through the unloading receipt internal transport stocking and handling on the work front quantilYing waste and registering its causes and respective incidence and frequencies
At the end of the on site data monitoring stage a final inspection was carried out on each site represented from now on as FI repeating the procedures from the 11
With the data gathered on site we have tried to obtain three types of infonnation the incidence of material waste the causes which contribute in the occurrence of this waste and the proportion to which each cause contributed for the final composition of the wasted material index
557
RESUL TS OF THE STUDY
General Analysis
Table 1 presents a synthesis of the results obtained in the five researched construction sites the results of similar studies as weil as the waste commonly adopted by cost compositions (theoretical waste)
TADLE 1 - Indices of total waste on tbe different sites()
Material Site A Site B SilO C Site D SilO E Average Pinto
The data presented confinn one of the main hypotheses of the study which is that material waste in building is significantly higher than what is normally accepted by the building industry in its cost estimates The waste indices found in the study are also much higher than the figures appointed by Skoyles (1976) in Great Britairi
It was verified that the real average loss of material have a big variation interval and are located between 085 and 8 times the usual admitted waste In the same manner for the same material there are very significant variations in the waste indices from one site to another This fact indicates that many of the problems which originate the waste are easily avoidable
Steel
As most of the buildings observed had their structure practically concluded at the beshyginning of the monitoring specific studies on the execution of the steel reinforcement to verify directly the causes of the results obtained were not carried out
The existing literature indicates that steel waste is mainly associated to cutting the reinforcing bar and due to variations in the product dimensions (diameter) However none of the firms had procedures to monitor the cuts in production and to guarantee the dimensions of the bars during the products site arrival
The results presented on site D were considerably better than the results on the other sites mainly due to the specific characteristics of the structural design This building had only one envelope beam and a large slab with 17cm thickness for the whole floor resuIting in few cuts in the steel bars
The study of the results referent to the consumption of steel on sites B C and E shows the existence of substitution of CA-60 by CA-50 steel which may cause structural
558
problems The average value of steel waste (1907) in spite of being lower than the value admitted in Brazilian cost compositions is much higher than the value obtained by Skoyles (J 976) in England This shows that significant improvements can still be obtained in the management of steel
Cernent
The main causes of cement waste were the excess thickness in mortar coatings and in masonry joints and the lack of control in lhe making of mortar
On average the lhicknesses in mortar coatings were 177 cm on ceilings 264 cm on internal walls and 387 cm on external walls Using as reference values the minimum thicknesses recommended by NBR-7200 (ABNT 1983) of 150 cm and 200 for internal and external coatings respectively lhe cement waste resulting from the excess lhickness in coalings amounls 10 1778 on ceilings 76 on internal walls and 9333 on facades The same problem is appointed by Pinlo (1989) and Vargas (1990)
The main causes of lhis kind of waste are bad quality in lhe structure of lhe reinforced concrete lack of coordination between the architectural and the slructural designs resulling in the necessity of fillings in order to hide structural pieces and lack of coordinashytion between the dimensions of bricks and doar frarnes
Wilh regards to the masonry joints they had average th icknesses of l71 cm for the vertical joints and 217 com for the horizontal joints Using 150 cm as reference value the cement was te resulting from the excess thickness on joints amounts to 1907 on the vertical joints and 3560 on the horizontal joints
lt was not possible to control the consumption of material in mortar making However it was observed thaI except for site D the production of mortar did not receive the necessary attention using shovels as a measuring device
On sites Band E cement waste was not as high as on sites A C and D However it is necessary to consider that on the latter ones up 10 the date of the FI the execution of the mortared coatings had not been initiated On site E a large part of the global incidence of cement waste was caused by the demolition of walls and the execution of walls with thicknesses higher that what had been determined on the design
Finally the cement waste due to the execution of filling to hide pipes did not prove significant in relation to the global waste index On average it reached 174 Similar values were found in the study carried out by Pinto (1989)
Pre-rnixed Concrete
The index of pre-mixed concrete waste in spite of being the lowest among all the materials surveyed was considered surprising 11 reached on average 1319 a considshyerably high value because it is a relatively expensive material which waste is normally assumed as very low
This was te was to a large extent determined by the excess thickness of the slabs On site C for instance the slabs had on average a thickness of 1488 higher than what had been specified on the design On site E il was observed that the waste index detected (2516) was related to the lack of control on receipt 10 errors on the amount of material ordered and poar cond itions of transport
Sand and rnortar
The waste of sand and mortar is closely related to the excess thickness on masonry
559
joints and mortar coatings al ready discussed The sand was used mainly on the execution of masonry while the pre-mixed mortar was employed on the execution of coatings The only exception was site D where the mortar for coatings was totally made on the site
In spite of the existence of several situations where waste of sand and mortar was detected due to poor conditions of transport and stocking it was not possible to quantify the volume wasted on these situations
Except for site D the waste of sand detected in spite of being superior to what is usually admitted for budget purposes did not reach alarming values as was the case with mortar Therefore it may be concluded that the mortar used on the coatings generate more significant waste than the mortar used on brick laying
Ceramic blocks and bricks
Because of its nature it was possible to carry out a much more detailed study on the causes of waste of bricks compared to the other materials On table 2 the percentages of waste related to each of the moments of incidence are shown
T ABLE 42-Distribution of the waste of ceramic blocks according to the moment of incidence ()
Eventual situations 030 223 134 Non quantified causes - - 1219 Total 820 3980 2764
On average the waste due to receipt stocking and site transportation of ceramics blocks added up (853) was significantly higher than the average wastes generated during the execution of the wall itself that is due to the rejection of pieces accidental breakage and cut (558) Looking just at the production itself it was verified that the waste caused by the need to cut the pieces (4 67) due mainly to the lack of half-blocks was significantly higher than the waste caused by rejection and the accidental breakage of the material added up (091 ) On site E for instance the waste due to cuts reached 1092 of the pieces used Also surprising was the high index of waste due to the lack of control of the quantity of material delivered which reached 575 on site A
Among the non-quantified causes two stand out the excess thickoess of walls mainly on site E and the occurrence of vandalism and theft on sites where the blocks were stocked on the sidewalk outside the construction site
Finally the small waste on site B in relation to the other sites was probably mainly due to the fact that up until the FI the masonry execution was at the beginning and wrap up had not beeo carried out
560
With regards to bricks the study of the receipt was carried out only on sites A B and D and of the internal transportation and production on sites Band E as they were the only ones which enabled these verifications to be carried out during the research The small waste of bricks on site C occurred due to the fact that special mortar was used in the execution of last row instead of the bricks as on the other sites
W ASTE AND LABOR PRODUCTIVITY
In order to investigate the existence of a correlation between productivity and waste of materials the labor productivity during the masonry execution was measured through the observation of the number of bricks laid per hour 1n general it can be said that sites Band D presented higher levels of productivity than the others (between 20 and 60 higher than the average of all the sites) Site E presented the poorest performance levels (around 30 and 50 lower than the average of the sites)
Due to the smaJl number of sites the results obtained in the analyses of the producshytivity in relation to the occurrence of waste cannot be generalized However the study carried out showed a tendency that site E with lower productivity presented the highest index of waste of ceramic blocks in the per iod (10725) On the other hand sites Band D with higher productivity presented the Jowest incidence of was te in the period - 820 and 26 50 respectively However it is necessary to make a deeper study of the relation between productivity and waste of materials through the analyses of a larger number of sites
THE COST OF THE WASTE OF THE MATERIALS MONITORED
For the determination of the cost of waste of the materials studied the ABC Curve of the NBR 12721 (ABNT) formulated for 12 floor buildings with three bedrooms and normal finishing standards (HI2-3Q-Normal) was used The original ABC Curve was changed in order to adapt to the materials used on the studied sites
The wastes of the materials studied represented up unti I the end of data collection an increase of 506 (Site C) to 1162 (Site E) in relation to the budgeted costs for the sites studied lt should be considered that these materials represent approximately 20 of the total cost of this type of building The average increase of 798 on the construction cost calculated in this study is of the same magnitude as the 6 estimated by Pinto (1989)
CONCLUSIONS
The main conclusion of the study was the confirmation that much of tbe waste is predictable and avoidable Tbe fact that relatively simple preventive measures were not taken on the sites studied indicates that there is a lack of concern with the waste of materials None of the sites monitored had a defined policy conceming management of materials both with regards to their management and the employment of a systematic conshytrol for their utilization
The magnitude of waste of materials is not known by tbe building firms themselves due to the complete absence of surveying and booking methods The only procedures of control of materials observed on the studied sites were quick verifications of the materials deJivered
The study has also confirmed that there is great variation on the indices of waste of materials on different sites Considering that similar sites presented different levels of waste for the same materials it can be concluded that much of this waste is avoidable
561
It also became evident that improvements may be obtained without the introduction of expensive equipment or advanced managerial techniques but simply through elementary care on receipt stocking handling use and protection of materials This fact indicates that the reduction of waste could easily be used as the focal point in quality improvement programs in building firms
It was also concluded that the lack of interest in controlling materials is an important cause of the occurrence of waste During the study it was observed that the site managers were aware of the waste but did little to prevent it from happening The study showed that a change in the attitude of those involved in the construction process is much more important than changes in building technology in order to obtain better performances from building firms with regards to management of materials It is crucial that the people involved become aware of the high value of materials and of the need to work more carefully
The study confirmed that management is more responsible for the waste than the laborers The latter are normally considered by the entrepreneurs of the building industry as the main responsible for the low productivity poor quality and the high level of material waste
Generally the waste occurred more as a result of a combination of factors than as a consequence of one isolated incident in an operation This proved that the lack of management of the sites is the fundamental cause of the high incidence of waste of mashyterials
Much of the waste originates outside the construction sites due to inadequate designs or bad procurement Through the study of the designs of the live sites studied it was possible to conclude that the lack of specifications project details and quality of the designs and mainly the lack of coordination among them are causes of significant waste of materials The breakages of bricks caused by the lack of half-bricks is an example of a problem generated on the supply sector
As was the case with Skoyles study (1976) there were indications that the occurshyrence of waste on the site happens more intensely during stocking and handling of materials than during production itself
An important data as it contradicts the literature consulted is that in spite of the great variability among actual wastes of a same material on different sites (between one and nine times) the higher or lower incidence of waste is defined by the specific procedures of management of the material or the activities which involve its use In other words if a specific material presents a high index of consumption in one enterprise higher than the other sites studied it does not mean that all materials presented high levels of waste on this enterprise It was observed for instance that some enterprises presented more efficiency on the execution of the reinforced concrete structure others on the employment of bulk materials (cement sand mortar) and others still on the employment of bricks
Conceming the methodology employed on the survey it became clear that the inshydepth study of the causes of waste and its measurement constitutes a rat her complex and expensive study particularly if it is carried out only by extemal observers It is very imporshytant that building firms become aware of the need to monitor and control materials waste and that this way this segment manages to obtain representative indices of waste for the different materials which can became an important quality and productivity indicator for the building industry
REFERENCES
ABNT - Associayaumlo Brasileira de Normas Tecnicas 1992 Avaliariio de cusos uniarios e preparo de orcamenos de consruqiio para incorporaqiio de edijicio em condomznio
562
NBR 12721 Rio de laneiro Brazil
1983 Reveslimenlo de paredes e lelos com argamassas - maleriais preparo aplicaraumlo - e manulenraumlo NBR 7200 Rio de laneiro Brazil
Deming WE 1986 Oul oIhe crisis MITCAES Cambridge Massachusetts
Melinghendler MA 1978 A racionaliza9aumlo das obras na construeyaumlo civil Revisla de Engenharia FMP 23-28
Picchi FA 1993 Sislemas de qualidade uso em empresas de conslruriio PhD thesis USP -Escola Politecnica Saumlo Paul0 Brazil
Pinto TP 1989 Perda de maleriais em processos conslrulivos Iradicionais UFSCARshyDepartamento de Engenharia Civil Saumlo Carlos Brazil 33pp
Skoyles EF 1976 Materials was tage - a misuse of resources Building Research and Praclice JulyAug 232-243
Soibelman L 1993 As perdas de maleriais na conslruriio de edificaroes sua incidencia e seu controle MSc thesis UFRGS-Curso de P6s-Gradualtaumlo em Engenharia Civil Porto Alegre Brazil
Vargas N 1990 A geometria do reboco Conslruriio Saumlo Paulo May 16-17
Wyatt DP 1978 Malerials managemenl - Pari I The Chartered Institute of Building Berkshire England
563
measure some of the final dimensions Picchi (1993) carried out a survey of material waste in three housing developments built in 1986 and 1987 The buildings were executed with a conventional concrete structure and walls of ceramic blocks The study was carried out from the monitoring of the volume of waste removed during construction without considering the great volumes removed in the first months identified as soil originated from the excavations The study therefore monitored only the direct material waste which was removed from the sites without considering indirect waste
Through the program of Quality and Productivity in Construction of Rio Grande do Sul a link agreement was established involving the MSc Course in Civil Engineering (NORlE) of the Federal University of Rio Grande do Sul the Construction Industry Union of Rio Grande do Sul (SfNDUSCON) the Support Service for Small and Medium Businesses of Rio Grande do Sul (SEBRAE-RS) and the Science and Technology Founshydation (CIENTEC) in order to carry out an in-depth study on the incidence of material waste in the building construction industry
The objectives of this study were to monitor the incidence of material waste in building construction to study its main causes and to propose guidelines for implementing material waste control systems for building firrns On this paper only the main results of the study are described A more detailed description can be found in Soibelman (1993)
CLASSIFICAnON OF WASTE
Waste can be classified as to its onglO as being direct or indirect (Skoyles 1976) Direct waste occurs when the material is damaged and cannot be recovered and used or wasted during the process of construction It is generally easily characterized being its cost the sum of the cost of the wasted material plus its removal costs Direct waste may be a consequence of vandalism theft or management problems in site transportation unloading stocking of the material or in production
Indirect waste consists in the economic waste caused by an excessive use of the material or a different use from that which had been planned In this case the material is not physically wasted with the waste being the difference berween the cost of the material which should have been used and the cost of the material actually used Indirect was te can be subdivided as folIows (a) waste through substitution it is the waste caused by the utilization of a more expensive material than that which had been specified An example of this type of waste is the use of structural bricks in non structural walls (b) waste through negligence it is the waste caused by the excessive use of a material without the reimbursement of the builder with the additional costs For instance the th icker piaster due to problems occurred in the structures geometry is commonly found (c) waste through production is the waste due to the lt)ccurrence of unpredicted situations and therefore not budgeted An example of this kind of was te is the additional use of concrete in foundations due to unexpected eharaeteristies of the subsoil
Waste mayaiso be classified aceording to its moment of ineidenee In this study the following subdivision has been adopted (a) waste oeeurred during site transportation hanshydling and stoeking of the material (b) waste oceurred during produetion itself and (e) waste occurred in any stage in the process due to external factors (theft vandalism accidents loss substitution ete)
Finally waste may be assoeiated to the intervenient(s) in the process which originated it such as designers materials manufacturers company management site management workers etc During this study we have tried to identify both the nature of material waste as weil as its moment of ineidence and origin
556
METHODOLOGY USED IN THIS STUDY
In the planning stage of this study a group was fonned with researchers from the Federal University of Rio Grande do Sul State (UFRGS) and technical managers of building companies with the aim of discussing the methodology to be used in the study As the aim was to develop an in-depth study on the causes of waste adecision was made to limit the study to a sm all number of sites and to a limited group of materials and constructive technology Five building sites were chosen for the monitoring of data The criteria of choice used was the employment of traditional technologies (reinforced concrete structure walls with ceramic bricks and piaster) and the requirement that they were at similar stages of construction It is obvious that the modest size of the sam pie prevents the results of this study from being generalized for the whole sector
The study therefore did not intend to exhaust the theme but to be a first more inshydepth study of the problem also trying to encourage the development of further research which may contribute in the gathering of data on material waste
Besides the specific characteristics of the specified bui Iding sites the choice was also based on trying to find construction finns which would facilitate the search of the necshyessary data and which would keep the site the offices and the accounts accessible for the researchers The sites were selected among on going projects in the city of Porto Alegre desshytined for the upper middle cass due to the fact that this type of project has in the past few years dominated the building industry market in the city
With the aim of identilYing the most significant materials in terms of construction costs the materials ABC curve used in the normal pattern designs of four eight and twelve floors of the NBR-12721 (ABNT 1992) the Brazilian nonn for evaluation of individual costs and construction budget planning for the incorporation of buildings in condominium Were excluded items referring to labor as weil as the materials which have a low probability of waste in spite of their significance in tenns of costs as elevators windows doors locks etc Based on this criteria the foJlowing products were chosen to be observed woods steel premixed concrete cement sand pre-mixed mortar or lime and ceramic bricks which added up represent approximately 20 of the total cost of constructions built by traditional building methods
Before the beginning of the monitoring of data on the sites an inspection was carried out on each building site On these initial inspections represented from now on by 11 detailed measurements of all the services executed were made and the inventory of studied materials stocked on the site was observed
After the conclusion of the 11 observers were placed on the researched construction sites nonnally one per shift on each site The tasks of these observers was to fill out fonns where the data on the construction site and the studied materials were gathered from their arrival at the site through the unloading receipt internal transport stocking and handling on the work front quantilYing waste and registering its causes and respective incidence and frequencies
At the end of the on site data monitoring stage a final inspection was carried out on each site represented from now on as FI repeating the procedures from the 11
With the data gathered on site we have tried to obtain three types of infonnation the incidence of material waste the causes which contribute in the occurrence of this waste and the proportion to which each cause contributed for the final composition of the wasted material index
557
RESUL TS OF THE STUDY
General Analysis
Table 1 presents a synthesis of the results obtained in the five researched construction sites the results of similar studies as weil as the waste commonly adopted by cost compositions (theoretical waste)
TADLE 1 - Indices of total waste on tbe different sites()
Material Site A Site B SilO C Site D SilO E Average Pinto
The data presented confinn one of the main hypotheses of the study which is that material waste in building is significantly higher than what is normally accepted by the building industry in its cost estimates The waste indices found in the study are also much higher than the figures appointed by Skoyles (1976) in Great Britairi
It was verified that the real average loss of material have a big variation interval and are located between 085 and 8 times the usual admitted waste In the same manner for the same material there are very significant variations in the waste indices from one site to another This fact indicates that many of the problems which originate the waste are easily avoidable
Steel
As most of the buildings observed had their structure practically concluded at the beshyginning of the monitoring specific studies on the execution of the steel reinforcement to verify directly the causes of the results obtained were not carried out
The existing literature indicates that steel waste is mainly associated to cutting the reinforcing bar and due to variations in the product dimensions (diameter) However none of the firms had procedures to monitor the cuts in production and to guarantee the dimensions of the bars during the products site arrival
The results presented on site D were considerably better than the results on the other sites mainly due to the specific characteristics of the structural design This building had only one envelope beam and a large slab with 17cm thickness for the whole floor resuIting in few cuts in the steel bars
The study of the results referent to the consumption of steel on sites B C and E shows the existence of substitution of CA-60 by CA-50 steel which may cause structural
558
problems The average value of steel waste (1907) in spite of being lower than the value admitted in Brazilian cost compositions is much higher than the value obtained by Skoyles (J 976) in England This shows that significant improvements can still be obtained in the management of steel
Cernent
The main causes of cement waste were the excess thickness in mortar coatings and in masonry joints and the lack of control in lhe making of mortar
On average the lhicknesses in mortar coatings were 177 cm on ceilings 264 cm on internal walls and 387 cm on external walls Using as reference values the minimum thicknesses recommended by NBR-7200 (ABNT 1983) of 150 cm and 200 for internal and external coatings respectively lhe cement waste resulting from the excess lhickness in coalings amounls 10 1778 on ceilings 76 on internal walls and 9333 on facades The same problem is appointed by Pinlo (1989) and Vargas (1990)
The main causes of lhis kind of waste are bad quality in lhe structure of lhe reinforced concrete lack of coordination between the architectural and the slructural designs resulling in the necessity of fillings in order to hide structural pieces and lack of coordinashytion between the dimensions of bricks and doar frarnes
Wilh regards to the masonry joints they had average th icknesses of l71 cm for the vertical joints and 217 com for the horizontal joints Using 150 cm as reference value the cement was te resulting from the excess thickness on joints amounts to 1907 on the vertical joints and 3560 on the horizontal joints
lt was not possible to control the consumption of material in mortar making However it was observed thaI except for site D the production of mortar did not receive the necessary attention using shovels as a measuring device
On sites Band E cement waste was not as high as on sites A C and D However it is necessary to consider that on the latter ones up 10 the date of the FI the execution of the mortared coatings had not been initiated On site E a large part of the global incidence of cement waste was caused by the demolition of walls and the execution of walls with thicknesses higher that what had been determined on the design
Finally the cement waste due to the execution of filling to hide pipes did not prove significant in relation to the global waste index On average it reached 174 Similar values were found in the study carried out by Pinto (1989)
Pre-rnixed Concrete
The index of pre-mixed concrete waste in spite of being the lowest among all the materials surveyed was considered surprising 11 reached on average 1319 a considshyerably high value because it is a relatively expensive material which waste is normally assumed as very low
This was te was to a large extent determined by the excess thickness of the slabs On site C for instance the slabs had on average a thickness of 1488 higher than what had been specified on the design On site E il was observed that the waste index detected (2516) was related to the lack of control on receipt 10 errors on the amount of material ordered and poar cond itions of transport
Sand and rnortar
The waste of sand and mortar is closely related to the excess thickness on masonry
559
joints and mortar coatings al ready discussed The sand was used mainly on the execution of masonry while the pre-mixed mortar was employed on the execution of coatings The only exception was site D where the mortar for coatings was totally made on the site
In spite of the existence of several situations where waste of sand and mortar was detected due to poor conditions of transport and stocking it was not possible to quantify the volume wasted on these situations
Except for site D the waste of sand detected in spite of being superior to what is usually admitted for budget purposes did not reach alarming values as was the case with mortar Therefore it may be concluded that the mortar used on the coatings generate more significant waste than the mortar used on brick laying
Ceramic blocks and bricks
Because of its nature it was possible to carry out a much more detailed study on the causes of waste of bricks compared to the other materials On table 2 the percentages of waste related to each of the moments of incidence are shown
T ABLE 42-Distribution of the waste of ceramic blocks according to the moment of incidence ()
Eventual situations 030 223 134 Non quantified causes - - 1219 Total 820 3980 2764
On average the waste due to receipt stocking and site transportation of ceramics blocks added up (853) was significantly higher than the average wastes generated during the execution of the wall itself that is due to the rejection of pieces accidental breakage and cut (558) Looking just at the production itself it was verified that the waste caused by the need to cut the pieces (4 67) due mainly to the lack of half-blocks was significantly higher than the waste caused by rejection and the accidental breakage of the material added up (091 ) On site E for instance the waste due to cuts reached 1092 of the pieces used Also surprising was the high index of waste due to the lack of control of the quantity of material delivered which reached 575 on site A
Among the non-quantified causes two stand out the excess thickoess of walls mainly on site E and the occurrence of vandalism and theft on sites where the blocks were stocked on the sidewalk outside the construction site
Finally the small waste on site B in relation to the other sites was probably mainly due to the fact that up until the FI the masonry execution was at the beginning and wrap up had not beeo carried out
560
With regards to bricks the study of the receipt was carried out only on sites A B and D and of the internal transportation and production on sites Band E as they were the only ones which enabled these verifications to be carried out during the research The small waste of bricks on site C occurred due to the fact that special mortar was used in the execution of last row instead of the bricks as on the other sites
W ASTE AND LABOR PRODUCTIVITY
In order to investigate the existence of a correlation between productivity and waste of materials the labor productivity during the masonry execution was measured through the observation of the number of bricks laid per hour 1n general it can be said that sites Band D presented higher levels of productivity than the others (between 20 and 60 higher than the average of all the sites) Site E presented the poorest performance levels (around 30 and 50 lower than the average of the sites)
Due to the smaJl number of sites the results obtained in the analyses of the producshytivity in relation to the occurrence of waste cannot be generalized However the study carried out showed a tendency that site E with lower productivity presented the highest index of waste of ceramic blocks in the per iod (10725) On the other hand sites Band D with higher productivity presented the Jowest incidence of was te in the period - 820 and 26 50 respectively However it is necessary to make a deeper study of the relation between productivity and waste of materials through the analyses of a larger number of sites
THE COST OF THE WASTE OF THE MATERIALS MONITORED
For the determination of the cost of waste of the materials studied the ABC Curve of the NBR 12721 (ABNT) formulated for 12 floor buildings with three bedrooms and normal finishing standards (HI2-3Q-Normal) was used The original ABC Curve was changed in order to adapt to the materials used on the studied sites
The wastes of the materials studied represented up unti I the end of data collection an increase of 506 (Site C) to 1162 (Site E) in relation to the budgeted costs for the sites studied lt should be considered that these materials represent approximately 20 of the total cost of this type of building The average increase of 798 on the construction cost calculated in this study is of the same magnitude as the 6 estimated by Pinto (1989)
CONCLUSIONS
The main conclusion of the study was the confirmation that much of tbe waste is predictable and avoidable Tbe fact that relatively simple preventive measures were not taken on the sites studied indicates that there is a lack of concern with the waste of materials None of the sites monitored had a defined policy conceming management of materials both with regards to their management and the employment of a systematic conshytrol for their utilization
The magnitude of waste of materials is not known by tbe building firms themselves due to the complete absence of surveying and booking methods The only procedures of control of materials observed on the studied sites were quick verifications of the materials deJivered
The study has also confirmed that there is great variation on the indices of waste of materials on different sites Considering that similar sites presented different levels of waste for the same materials it can be concluded that much of this waste is avoidable
561
It also became evident that improvements may be obtained without the introduction of expensive equipment or advanced managerial techniques but simply through elementary care on receipt stocking handling use and protection of materials This fact indicates that the reduction of waste could easily be used as the focal point in quality improvement programs in building firms
It was also concluded that the lack of interest in controlling materials is an important cause of the occurrence of waste During the study it was observed that the site managers were aware of the waste but did little to prevent it from happening The study showed that a change in the attitude of those involved in the construction process is much more important than changes in building technology in order to obtain better performances from building firms with regards to management of materials It is crucial that the people involved become aware of the high value of materials and of the need to work more carefully
The study confirmed that management is more responsible for the waste than the laborers The latter are normally considered by the entrepreneurs of the building industry as the main responsible for the low productivity poor quality and the high level of material waste
Generally the waste occurred more as a result of a combination of factors than as a consequence of one isolated incident in an operation This proved that the lack of management of the sites is the fundamental cause of the high incidence of waste of mashyterials
Much of the waste originates outside the construction sites due to inadequate designs or bad procurement Through the study of the designs of the live sites studied it was possible to conclude that the lack of specifications project details and quality of the designs and mainly the lack of coordination among them are causes of significant waste of materials The breakages of bricks caused by the lack of half-bricks is an example of a problem generated on the supply sector
As was the case with Skoyles study (1976) there were indications that the occurshyrence of waste on the site happens more intensely during stocking and handling of materials than during production itself
An important data as it contradicts the literature consulted is that in spite of the great variability among actual wastes of a same material on different sites (between one and nine times) the higher or lower incidence of waste is defined by the specific procedures of management of the material or the activities which involve its use In other words if a specific material presents a high index of consumption in one enterprise higher than the other sites studied it does not mean that all materials presented high levels of waste on this enterprise It was observed for instance that some enterprises presented more efficiency on the execution of the reinforced concrete structure others on the employment of bulk materials (cement sand mortar) and others still on the employment of bricks
Conceming the methodology employed on the survey it became clear that the inshydepth study of the causes of waste and its measurement constitutes a rat her complex and expensive study particularly if it is carried out only by extemal observers It is very imporshytant that building firms become aware of the need to monitor and control materials waste and that this way this segment manages to obtain representative indices of waste for the different materials which can became an important quality and productivity indicator for the building industry
REFERENCES
ABNT - Associayaumlo Brasileira de Normas Tecnicas 1992 Avaliariio de cusos uniarios e preparo de orcamenos de consruqiio para incorporaqiio de edijicio em condomznio
562
NBR 12721 Rio de laneiro Brazil
1983 Reveslimenlo de paredes e lelos com argamassas - maleriais preparo aplicaraumlo - e manulenraumlo NBR 7200 Rio de laneiro Brazil
Deming WE 1986 Oul oIhe crisis MITCAES Cambridge Massachusetts
Melinghendler MA 1978 A racionaliza9aumlo das obras na construeyaumlo civil Revisla de Engenharia FMP 23-28
Picchi FA 1993 Sislemas de qualidade uso em empresas de conslruriio PhD thesis USP -Escola Politecnica Saumlo Paul0 Brazil
Pinto TP 1989 Perda de maleriais em processos conslrulivos Iradicionais UFSCARshyDepartamento de Engenharia Civil Saumlo Carlos Brazil 33pp
Skoyles EF 1976 Materials was tage - a misuse of resources Building Research and Praclice JulyAug 232-243
Soibelman L 1993 As perdas de maleriais na conslruriio de edificaroes sua incidencia e seu controle MSc thesis UFRGS-Curso de P6s-Gradualtaumlo em Engenharia Civil Porto Alegre Brazil
Vargas N 1990 A geometria do reboco Conslruriio Saumlo Paulo May 16-17
Wyatt DP 1978 Malerials managemenl - Pari I The Chartered Institute of Building Berkshire England
563
METHODOLOGY USED IN THIS STUDY
In the planning stage of this study a group was fonned with researchers from the Federal University of Rio Grande do Sul State (UFRGS) and technical managers of building companies with the aim of discussing the methodology to be used in the study As the aim was to develop an in-depth study on the causes of waste adecision was made to limit the study to a sm all number of sites and to a limited group of materials and constructive technology Five building sites were chosen for the monitoring of data The criteria of choice used was the employment of traditional technologies (reinforced concrete structure walls with ceramic bricks and piaster) and the requirement that they were at similar stages of construction It is obvious that the modest size of the sam pie prevents the results of this study from being generalized for the whole sector
The study therefore did not intend to exhaust the theme but to be a first more inshydepth study of the problem also trying to encourage the development of further research which may contribute in the gathering of data on material waste
Besides the specific characteristics of the specified bui Iding sites the choice was also based on trying to find construction finns which would facilitate the search of the necshyessary data and which would keep the site the offices and the accounts accessible for the researchers The sites were selected among on going projects in the city of Porto Alegre desshytined for the upper middle cass due to the fact that this type of project has in the past few years dominated the building industry market in the city
With the aim of identilYing the most significant materials in terms of construction costs the materials ABC curve used in the normal pattern designs of four eight and twelve floors of the NBR-12721 (ABNT 1992) the Brazilian nonn for evaluation of individual costs and construction budget planning for the incorporation of buildings in condominium Were excluded items referring to labor as weil as the materials which have a low probability of waste in spite of their significance in tenns of costs as elevators windows doors locks etc Based on this criteria the foJlowing products were chosen to be observed woods steel premixed concrete cement sand pre-mixed mortar or lime and ceramic bricks which added up represent approximately 20 of the total cost of constructions built by traditional building methods
Before the beginning of the monitoring of data on the sites an inspection was carried out on each building site On these initial inspections represented from now on by 11 detailed measurements of all the services executed were made and the inventory of studied materials stocked on the site was observed
After the conclusion of the 11 observers were placed on the researched construction sites nonnally one per shift on each site The tasks of these observers was to fill out fonns where the data on the construction site and the studied materials were gathered from their arrival at the site through the unloading receipt internal transport stocking and handling on the work front quantilYing waste and registering its causes and respective incidence and frequencies
At the end of the on site data monitoring stage a final inspection was carried out on each site represented from now on as FI repeating the procedures from the 11
With the data gathered on site we have tried to obtain three types of infonnation the incidence of material waste the causes which contribute in the occurrence of this waste and the proportion to which each cause contributed for the final composition of the wasted material index
557
RESUL TS OF THE STUDY
General Analysis
Table 1 presents a synthesis of the results obtained in the five researched construction sites the results of similar studies as weil as the waste commonly adopted by cost compositions (theoretical waste)
TADLE 1 - Indices of total waste on tbe different sites()
Material Site A Site B SilO C Site D SilO E Average Pinto
The data presented confinn one of the main hypotheses of the study which is that material waste in building is significantly higher than what is normally accepted by the building industry in its cost estimates The waste indices found in the study are also much higher than the figures appointed by Skoyles (1976) in Great Britairi
It was verified that the real average loss of material have a big variation interval and are located between 085 and 8 times the usual admitted waste In the same manner for the same material there are very significant variations in the waste indices from one site to another This fact indicates that many of the problems which originate the waste are easily avoidable
Steel
As most of the buildings observed had their structure practically concluded at the beshyginning of the monitoring specific studies on the execution of the steel reinforcement to verify directly the causes of the results obtained were not carried out
The existing literature indicates that steel waste is mainly associated to cutting the reinforcing bar and due to variations in the product dimensions (diameter) However none of the firms had procedures to monitor the cuts in production and to guarantee the dimensions of the bars during the products site arrival
The results presented on site D were considerably better than the results on the other sites mainly due to the specific characteristics of the structural design This building had only one envelope beam and a large slab with 17cm thickness for the whole floor resuIting in few cuts in the steel bars
The study of the results referent to the consumption of steel on sites B C and E shows the existence of substitution of CA-60 by CA-50 steel which may cause structural
558
problems The average value of steel waste (1907) in spite of being lower than the value admitted in Brazilian cost compositions is much higher than the value obtained by Skoyles (J 976) in England This shows that significant improvements can still be obtained in the management of steel
Cernent
The main causes of cement waste were the excess thickness in mortar coatings and in masonry joints and the lack of control in lhe making of mortar
On average the lhicknesses in mortar coatings were 177 cm on ceilings 264 cm on internal walls and 387 cm on external walls Using as reference values the minimum thicknesses recommended by NBR-7200 (ABNT 1983) of 150 cm and 200 for internal and external coatings respectively lhe cement waste resulting from the excess lhickness in coalings amounls 10 1778 on ceilings 76 on internal walls and 9333 on facades The same problem is appointed by Pinlo (1989) and Vargas (1990)
The main causes of lhis kind of waste are bad quality in lhe structure of lhe reinforced concrete lack of coordination between the architectural and the slructural designs resulling in the necessity of fillings in order to hide structural pieces and lack of coordinashytion between the dimensions of bricks and doar frarnes
Wilh regards to the masonry joints they had average th icknesses of l71 cm for the vertical joints and 217 com for the horizontal joints Using 150 cm as reference value the cement was te resulting from the excess thickness on joints amounts to 1907 on the vertical joints and 3560 on the horizontal joints
lt was not possible to control the consumption of material in mortar making However it was observed thaI except for site D the production of mortar did not receive the necessary attention using shovels as a measuring device
On sites Band E cement waste was not as high as on sites A C and D However it is necessary to consider that on the latter ones up 10 the date of the FI the execution of the mortared coatings had not been initiated On site E a large part of the global incidence of cement waste was caused by the demolition of walls and the execution of walls with thicknesses higher that what had been determined on the design
Finally the cement waste due to the execution of filling to hide pipes did not prove significant in relation to the global waste index On average it reached 174 Similar values were found in the study carried out by Pinto (1989)
Pre-rnixed Concrete
The index of pre-mixed concrete waste in spite of being the lowest among all the materials surveyed was considered surprising 11 reached on average 1319 a considshyerably high value because it is a relatively expensive material which waste is normally assumed as very low
This was te was to a large extent determined by the excess thickness of the slabs On site C for instance the slabs had on average a thickness of 1488 higher than what had been specified on the design On site E il was observed that the waste index detected (2516) was related to the lack of control on receipt 10 errors on the amount of material ordered and poar cond itions of transport
Sand and rnortar
The waste of sand and mortar is closely related to the excess thickness on masonry
559
joints and mortar coatings al ready discussed The sand was used mainly on the execution of masonry while the pre-mixed mortar was employed on the execution of coatings The only exception was site D where the mortar for coatings was totally made on the site
In spite of the existence of several situations where waste of sand and mortar was detected due to poor conditions of transport and stocking it was not possible to quantify the volume wasted on these situations
Except for site D the waste of sand detected in spite of being superior to what is usually admitted for budget purposes did not reach alarming values as was the case with mortar Therefore it may be concluded that the mortar used on the coatings generate more significant waste than the mortar used on brick laying
Ceramic blocks and bricks
Because of its nature it was possible to carry out a much more detailed study on the causes of waste of bricks compared to the other materials On table 2 the percentages of waste related to each of the moments of incidence are shown
T ABLE 42-Distribution of the waste of ceramic blocks according to the moment of incidence ()
Eventual situations 030 223 134 Non quantified causes - - 1219 Total 820 3980 2764
On average the waste due to receipt stocking and site transportation of ceramics blocks added up (853) was significantly higher than the average wastes generated during the execution of the wall itself that is due to the rejection of pieces accidental breakage and cut (558) Looking just at the production itself it was verified that the waste caused by the need to cut the pieces (4 67) due mainly to the lack of half-blocks was significantly higher than the waste caused by rejection and the accidental breakage of the material added up (091 ) On site E for instance the waste due to cuts reached 1092 of the pieces used Also surprising was the high index of waste due to the lack of control of the quantity of material delivered which reached 575 on site A
Among the non-quantified causes two stand out the excess thickoess of walls mainly on site E and the occurrence of vandalism and theft on sites where the blocks were stocked on the sidewalk outside the construction site
Finally the small waste on site B in relation to the other sites was probably mainly due to the fact that up until the FI the masonry execution was at the beginning and wrap up had not beeo carried out
560
With regards to bricks the study of the receipt was carried out only on sites A B and D and of the internal transportation and production on sites Band E as they were the only ones which enabled these verifications to be carried out during the research The small waste of bricks on site C occurred due to the fact that special mortar was used in the execution of last row instead of the bricks as on the other sites
W ASTE AND LABOR PRODUCTIVITY
In order to investigate the existence of a correlation between productivity and waste of materials the labor productivity during the masonry execution was measured through the observation of the number of bricks laid per hour 1n general it can be said that sites Band D presented higher levels of productivity than the others (between 20 and 60 higher than the average of all the sites) Site E presented the poorest performance levels (around 30 and 50 lower than the average of the sites)
Due to the smaJl number of sites the results obtained in the analyses of the producshytivity in relation to the occurrence of waste cannot be generalized However the study carried out showed a tendency that site E with lower productivity presented the highest index of waste of ceramic blocks in the per iod (10725) On the other hand sites Band D with higher productivity presented the Jowest incidence of was te in the period - 820 and 26 50 respectively However it is necessary to make a deeper study of the relation between productivity and waste of materials through the analyses of a larger number of sites
THE COST OF THE WASTE OF THE MATERIALS MONITORED
For the determination of the cost of waste of the materials studied the ABC Curve of the NBR 12721 (ABNT) formulated for 12 floor buildings with three bedrooms and normal finishing standards (HI2-3Q-Normal) was used The original ABC Curve was changed in order to adapt to the materials used on the studied sites
The wastes of the materials studied represented up unti I the end of data collection an increase of 506 (Site C) to 1162 (Site E) in relation to the budgeted costs for the sites studied lt should be considered that these materials represent approximately 20 of the total cost of this type of building The average increase of 798 on the construction cost calculated in this study is of the same magnitude as the 6 estimated by Pinto (1989)
CONCLUSIONS
The main conclusion of the study was the confirmation that much of tbe waste is predictable and avoidable Tbe fact that relatively simple preventive measures were not taken on the sites studied indicates that there is a lack of concern with the waste of materials None of the sites monitored had a defined policy conceming management of materials both with regards to their management and the employment of a systematic conshytrol for their utilization
The magnitude of waste of materials is not known by tbe building firms themselves due to the complete absence of surveying and booking methods The only procedures of control of materials observed on the studied sites were quick verifications of the materials deJivered
The study has also confirmed that there is great variation on the indices of waste of materials on different sites Considering that similar sites presented different levels of waste for the same materials it can be concluded that much of this waste is avoidable
561
It also became evident that improvements may be obtained without the introduction of expensive equipment or advanced managerial techniques but simply through elementary care on receipt stocking handling use and protection of materials This fact indicates that the reduction of waste could easily be used as the focal point in quality improvement programs in building firms
It was also concluded that the lack of interest in controlling materials is an important cause of the occurrence of waste During the study it was observed that the site managers were aware of the waste but did little to prevent it from happening The study showed that a change in the attitude of those involved in the construction process is much more important than changes in building technology in order to obtain better performances from building firms with regards to management of materials It is crucial that the people involved become aware of the high value of materials and of the need to work more carefully
The study confirmed that management is more responsible for the waste than the laborers The latter are normally considered by the entrepreneurs of the building industry as the main responsible for the low productivity poor quality and the high level of material waste
Generally the waste occurred more as a result of a combination of factors than as a consequence of one isolated incident in an operation This proved that the lack of management of the sites is the fundamental cause of the high incidence of waste of mashyterials
Much of the waste originates outside the construction sites due to inadequate designs or bad procurement Through the study of the designs of the live sites studied it was possible to conclude that the lack of specifications project details and quality of the designs and mainly the lack of coordination among them are causes of significant waste of materials The breakages of bricks caused by the lack of half-bricks is an example of a problem generated on the supply sector
As was the case with Skoyles study (1976) there were indications that the occurshyrence of waste on the site happens more intensely during stocking and handling of materials than during production itself
An important data as it contradicts the literature consulted is that in spite of the great variability among actual wastes of a same material on different sites (between one and nine times) the higher or lower incidence of waste is defined by the specific procedures of management of the material or the activities which involve its use In other words if a specific material presents a high index of consumption in one enterprise higher than the other sites studied it does not mean that all materials presented high levels of waste on this enterprise It was observed for instance that some enterprises presented more efficiency on the execution of the reinforced concrete structure others on the employment of bulk materials (cement sand mortar) and others still on the employment of bricks
Conceming the methodology employed on the survey it became clear that the inshydepth study of the causes of waste and its measurement constitutes a rat her complex and expensive study particularly if it is carried out only by extemal observers It is very imporshytant that building firms become aware of the need to monitor and control materials waste and that this way this segment manages to obtain representative indices of waste for the different materials which can became an important quality and productivity indicator for the building industry
REFERENCES
ABNT - Associayaumlo Brasileira de Normas Tecnicas 1992 Avaliariio de cusos uniarios e preparo de orcamenos de consruqiio para incorporaqiio de edijicio em condomznio
562
NBR 12721 Rio de laneiro Brazil
1983 Reveslimenlo de paredes e lelos com argamassas - maleriais preparo aplicaraumlo - e manulenraumlo NBR 7200 Rio de laneiro Brazil
Deming WE 1986 Oul oIhe crisis MITCAES Cambridge Massachusetts
Melinghendler MA 1978 A racionaliza9aumlo das obras na construeyaumlo civil Revisla de Engenharia FMP 23-28
Picchi FA 1993 Sislemas de qualidade uso em empresas de conslruriio PhD thesis USP -Escola Politecnica Saumlo Paul0 Brazil
Pinto TP 1989 Perda de maleriais em processos conslrulivos Iradicionais UFSCARshyDepartamento de Engenharia Civil Saumlo Carlos Brazil 33pp
Skoyles EF 1976 Materials was tage - a misuse of resources Building Research and Praclice JulyAug 232-243
Soibelman L 1993 As perdas de maleriais na conslruriio de edificaroes sua incidencia e seu controle MSc thesis UFRGS-Curso de P6s-Gradualtaumlo em Engenharia Civil Porto Alegre Brazil
Vargas N 1990 A geometria do reboco Conslruriio Saumlo Paulo May 16-17
Wyatt DP 1978 Malerials managemenl - Pari I The Chartered Institute of Building Berkshire England
563
RESUL TS OF THE STUDY
General Analysis
Table 1 presents a synthesis of the results obtained in the five researched construction sites the results of similar studies as weil as the waste commonly adopted by cost compositions (theoretical waste)
TADLE 1 - Indices of total waste on tbe different sites()
Material Site A Site B SilO C Site D SilO E Average Pinto
The data presented confinn one of the main hypotheses of the study which is that material waste in building is significantly higher than what is normally accepted by the building industry in its cost estimates The waste indices found in the study are also much higher than the figures appointed by Skoyles (1976) in Great Britairi
It was verified that the real average loss of material have a big variation interval and are located between 085 and 8 times the usual admitted waste In the same manner for the same material there are very significant variations in the waste indices from one site to another This fact indicates that many of the problems which originate the waste are easily avoidable
Steel
As most of the buildings observed had their structure practically concluded at the beshyginning of the monitoring specific studies on the execution of the steel reinforcement to verify directly the causes of the results obtained were not carried out
The existing literature indicates that steel waste is mainly associated to cutting the reinforcing bar and due to variations in the product dimensions (diameter) However none of the firms had procedures to monitor the cuts in production and to guarantee the dimensions of the bars during the products site arrival
The results presented on site D were considerably better than the results on the other sites mainly due to the specific characteristics of the structural design This building had only one envelope beam and a large slab with 17cm thickness for the whole floor resuIting in few cuts in the steel bars
The study of the results referent to the consumption of steel on sites B C and E shows the existence of substitution of CA-60 by CA-50 steel which may cause structural
558
problems The average value of steel waste (1907) in spite of being lower than the value admitted in Brazilian cost compositions is much higher than the value obtained by Skoyles (J 976) in England This shows that significant improvements can still be obtained in the management of steel
Cernent
The main causes of cement waste were the excess thickness in mortar coatings and in masonry joints and the lack of control in lhe making of mortar
On average the lhicknesses in mortar coatings were 177 cm on ceilings 264 cm on internal walls and 387 cm on external walls Using as reference values the minimum thicknesses recommended by NBR-7200 (ABNT 1983) of 150 cm and 200 for internal and external coatings respectively lhe cement waste resulting from the excess lhickness in coalings amounls 10 1778 on ceilings 76 on internal walls and 9333 on facades The same problem is appointed by Pinlo (1989) and Vargas (1990)
The main causes of lhis kind of waste are bad quality in lhe structure of lhe reinforced concrete lack of coordination between the architectural and the slructural designs resulling in the necessity of fillings in order to hide structural pieces and lack of coordinashytion between the dimensions of bricks and doar frarnes
Wilh regards to the masonry joints they had average th icknesses of l71 cm for the vertical joints and 217 com for the horizontal joints Using 150 cm as reference value the cement was te resulting from the excess thickness on joints amounts to 1907 on the vertical joints and 3560 on the horizontal joints
lt was not possible to control the consumption of material in mortar making However it was observed thaI except for site D the production of mortar did not receive the necessary attention using shovels as a measuring device
On sites Band E cement waste was not as high as on sites A C and D However it is necessary to consider that on the latter ones up 10 the date of the FI the execution of the mortared coatings had not been initiated On site E a large part of the global incidence of cement waste was caused by the demolition of walls and the execution of walls with thicknesses higher that what had been determined on the design
Finally the cement waste due to the execution of filling to hide pipes did not prove significant in relation to the global waste index On average it reached 174 Similar values were found in the study carried out by Pinto (1989)
Pre-rnixed Concrete
The index of pre-mixed concrete waste in spite of being the lowest among all the materials surveyed was considered surprising 11 reached on average 1319 a considshyerably high value because it is a relatively expensive material which waste is normally assumed as very low
This was te was to a large extent determined by the excess thickness of the slabs On site C for instance the slabs had on average a thickness of 1488 higher than what had been specified on the design On site E il was observed that the waste index detected (2516) was related to the lack of control on receipt 10 errors on the amount of material ordered and poar cond itions of transport
Sand and rnortar
The waste of sand and mortar is closely related to the excess thickness on masonry
559
joints and mortar coatings al ready discussed The sand was used mainly on the execution of masonry while the pre-mixed mortar was employed on the execution of coatings The only exception was site D where the mortar for coatings was totally made on the site
In spite of the existence of several situations where waste of sand and mortar was detected due to poor conditions of transport and stocking it was not possible to quantify the volume wasted on these situations
Except for site D the waste of sand detected in spite of being superior to what is usually admitted for budget purposes did not reach alarming values as was the case with mortar Therefore it may be concluded that the mortar used on the coatings generate more significant waste than the mortar used on brick laying
Ceramic blocks and bricks
Because of its nature it was possible to carry out a much more detailed study on the causes of waste of bricks compared to the other materials On table 2 the percentages of waste related to each of the moments of incidence are shown
T ABLE 42-Distribution of the waste of ceramic blocks according to the moment of incidence ()
Eventual situations 030 223 134 Non quantified causes - - 1219 Total 820 3980 2764
On average the waste due to receipt stocking and site transportation of ceramics blocks added up (853) was significantly higher than the average wastes generated during the execution of the wall itself that is due to the rejection of pieces accidental breakage and cut (558) Looking just at the production itself it was verified that the waste caused by the need to cut the pieces (4 67) due mainly to the lack of half-blocks was significantly higher than the waste caused by rejection and the accidental breakage of the material added up (091 ) On site E for instance the waste due to cuts reached 1092 of the pieces used Also surprising was the high index of waste due to the lack of control of the quantity of material delivered which reached 575 on site A
Among the non-quantified causes two stand out the excess thickoess of walls mainly on site E and the occurrence of vandalism and theft on sites where the blocks were stocked on the sidewalk outside the construction site
Finally the small waste on site B in relation to the other sites was probably mainly due to the fact that up until the FI the masonry execution was at the beginning and wrap up had not beeo carried out
560
With regards to bricks the study of the receipt was carried out only on sites A B and D and of the internal transportation and production on sites Band E as they were the only ones which enabled these verifications to be carried out during the research The small waste of bricks on site C occurred due to the fact that special mortar was used in the execution of last row instead of the bricks as on the other sites
W ASTE AND LABOR PRODUCTIVITY
In order to investigate the existence of a correlation between productivity and waste of materials the labor productivity during the masonry execution was measured through the observation of the number of bricks laid per hour 1n general it can be said that sites Band D presented higher levels of productivity than the others (between 20 and 60 higher than the average of all the sites) Site E presented the poorest performance levels (around 30 and 50 lower than the average of the sites)
Due to the smaJl number of sites the results obtained in the analyses of the producshytivity in relation to the occurrence of waste cannot be generalized However the study carried out showed a tendency that site E with lower productivity presented the highest index of waste of ceramic blocks in the per iod (10725) On the other hand sites Band D with higher productivity presented the Jowest incidence of was te in the period - 820 and 26 50 respectively However it is necessary to make a deeper study of the relation between productivity and waste of materials through the analyses of a larger number of sites
THE COST OF THE WASTE OF THE MATERIALS MONITORED
For the determination of the cost of waste of the materials studied the ABC Curve of the NBR 12721 (ABNT) formulated for 12 floor buildings with three bedrooms and normal finishing standards (HI2-3Q-Normal) was used The original ABC Curve was changed in order to adapt to the materials used on the studied sites
The wastes of the materials studied represented up unti I the end of data collection an increase of 506 (Site C) to 1162 (Site E) in relation to the budgeted costs for the sites studied lt should be considered that these materials represent approximately 20 of the total cost of this type of building The average increase of 798 on the construction cost calculated in this study is of the same magnitude as the 6 estimated by Pinto (1989)
CONCLUSIONS
The main conclusion of the study was the confirmation that much of tbe waste is predictable and avoidable Tbe fact that relatively simple preventive measures were not taken on the sites studied indicates that there is a lack of concern with the waste of materials None of the sites monitored had a defined policy conceming management of materials both with regards to their management and the employment of a systematic conshytrol for their utilization
The magnitude of waste of materials is not known by tbe building firms themselves due to the complete absence of surveying and booking methods The only procedures of control of materials observed on the studied sites were quick verifications of the materials deJivered
The study has also confirmed that there is great variation on the indices of waste of materials on different sites Considering that similar sites presented different levels of waste for the same materials it can be concluded that much of this waste is avoidable
561
It also became evident that improvements may be obtained without the introduction of expensive equipment or advanced managerial techniques but simply through elementary care on receipt stocking handling use and protection of materials This fact indicates that the reduction of waste could easily be used as the focal point in quality improvement programs in building firms
It was also concluded that the lack of interest in controlling materials is an important cause of the occurrence of waste During the study it was observed that the site managers were aware of the waste but did little to prevent it from happening The study showed that a change in the attitude of those involved in the construction process is much more important than changes in building technology in order to obtain better performances from building firms with regards to management of materials It is crucial that the people involved become aware of the high value of materials and of the need to work more carefully
The study confirmed that management is more responsible for the waste than the laborers The latter are normally considered by the entrepreneurs of the building industry as the main responsible for the low productivity poor quality and the high level of material waste
Generally the waste occurred more as a result of a combination of factors than as a consequence of one isolated incident in an operation This proved that the lack of management of the sites is the fundamental cause of the high incidence of waste of mashyterials
Much of the waste originates outside the construction sites due to inadequate designs or bad procurement Through the study of the designs of the live sites studied it was possible to conclude that the lack of specifications project details and quality of the designs and mainly the lack of coordination among them are causes of significant waste of materials The breakages of bricks caused by the lack of half-bricks is an example of a problem generated on the supply sector
As was the case with Skoyles study (1976) there were indications that the occurshyrence of waste on the site happens more intensely during stocking and handling of materials than during production itself
An important data as it contradicts the literature consulted is that in spite of the great variability among actual wastes of a same material on different sites (between one and nine times) the higher or lower incidence of waste is defined by the specific procedures of management of the material or the activities which involve its use In other words if a specific material presents a high index of consumption in one enterprise higher than the other sites studied it does not mean that all materials presented high levels of waste on this enterprise It was observed for instance that some enterprises presented more efficiency on the execution of the reinforced concrete structure others on the employment of bulk materials (cement sand mortar) and others still on the employment of bricks
Conceming the methodology employed on the survey it became clear that the inshydepth study of the causes of waste and its measurement constitutes a rat her complex and expensive study particularly if it is carried out only by extemal observers It is very imporshytant that building firms become aware of the need to monitor and control materials waste and that this way this segment manages to obtain representative indices of waste for the different materials which can became an important quality and productivity indicator for the building industry
REFERENCES
ABNT - Associayaumlo Brasileira de Normas Tecnicas 1992 Avaliariio de cusos uniarios e preparo de orcamenos de consruqiio para incorporaqiio de edijicio em condomznio
562
NBR 12721 Rio de laneiro Brazil
1983 Reveslimenlo de paredes e lelos com argamassas - maleriais preparo aplicaraumlo - e manulenraumlo NBR 7200 Rio de laneiro Brazil
Deming WE 1986 Oul oIhe crisis MITCAES Cambridge Massachusetts
Melinghendler MA 1978 A racionaliza9aumlo das obras na construeyaumlo civil Revisla de Engenharia FMP 23-28
Picchi FA 1993 Sislemas de qualidade uso em empresas de conslruriio PhD thesis USP -Escola Politecnica Saumlo Paul0 Brazil
Pinto TP 1989 Perda de maleriais em processos conslrulivos Iradicionais UFSCARshyDepartamento de Engenharia Civil Saumlo Carlos Brazil 33pp
Skoyles EF 1976 Materials was tage - a misuse of resources Building Research and Praclice JulyAug 232-243
Soibelman L 1993 As perdas de maleriais na conslruriio de edificaroes sua incidencia e seu controle MSc thesis UFRGS-Curso de P6s-Gradualtaumlo em Engenharia Civil Porto Alegre Brazil
Vargas N 1990 A geometria do reboco Conslruriio Saumlo Paulo May 16-17
Wyatt DP 1978 Malerials managemenl - Pari I The Chartered Institute of Building Berkshire England
563
problems The average value of steel waste (1907) in spite of being lower than the value admitted in Brazilian cost compositions is much higher than the value obtained by Skoyles (J 976) in England This shows that significant improvements can still be obtained in the management of steel
Cernent
The main causes of cement waste were the excess thickness in mortar coatings and in masonry joints and the lack of control in lhe making of mortar
On average the lhicknesses in mortar coatings were 177 cm on ceilings 264 cm on internal walls and 387 cm on external walls Using as reference values the minimum thicknesses recommended by NBR-7200 (ABNT 1983) of 150 cm and 200 for internal and external coatings respectively lhe cement waste resulting from the excess lhickness in coalings amounls 10 1778 on ceilings 76 on internal walls and 9333 on facades The same problem is appointed by Pinlo (1989) and Vargas (1990)
The main causes of lhis kind of waste are bad quality in lhe structure of lhe reinforced concrete lack of coordination between the architectural and the slructural designs resulling in the necessity of fillings in order to hide structural pieces and lack of coordinashytion between the dimensions of bricks and doar frarnes
Wilh regards to the masonry joints they had average th icknesses of l71 cm for the vertical joints and 217 com for the horizontal joints Using 150 cm as reference value the cement was te resulting from the excess thickness on joints amounts to 1907 on the vertical joints and 3560 on the horizontal joints
lt was not possible to control the consumption of material in mortar making However it was observed thaI except for site D the production of mortar did not receive the necessary attention using shovels as a measuring device
On sites Band E cement waste was not as high as on sites A C and D However it is necessary to consider that on the latter ones up 10 the date of the FI the execution of the mortared coatings had not been initiated On site E a large part of the global incidence of cement waste was caused by the demolition of walls and the execution of walls with thicknesses higher that what had been determined on the design
Finally the cement waste due to the execution of filling to hide pipes did not prove significant in relation to the global waste index On average it reached 174 Similar values were found in the study carried out by Pinto (1989)
Pre-rnixed Concrete
The index of pre-mixed concrete waste in spite of being the lowest among all the materials surveyed was considered surprising 11 reached on average 1319 a considshyerably high value because it is a relatively expensive material which waste is normally assumed as very low
This was te was to a large extent determined by the excess thickness of the slabs On site C for instance the slabs had on average a thickness of 1488 higher than what had been specified on the design On site E il was observed that the waste index detected (2516) was related to the lack of control on receipt 10 errors on the amount of material ordered and poar cond itions of transport
Sand and rnortar
The waste of sand and mortar is closely related to the excess thickness on masonry
559
joints and mortar coatings al ready discussed The sand was used mainly on the execution of masonry while the pre-mixed mortar was employed on the execution of coatings The only exception was site D where the mortar for coatings was totally made on the site
In spite of the existence of several situations where waste of sand and mortar was detected due to poor conditions of transport and stocking it was not possible to quantify the volume wasted on these situations
Except for site D the waste of sand detected in spite of being superior to what is usually admitted for budget purposes did not reach alarming values as was the case with mortar Therefore it may be concluded that the mortar used on the coatings generate more significant waste than the mortar used on brick laying
Ceramic blocks and bricks
Because of its nature it was possible to carry out a much more detailed study on the causes of waste of bricks compared to the other materials On table 2 the percentages of waste related to each of the moments of incidence are shown
T ABLE 42-Distribution of the waste of ceramic blocks according to the moment of incidence ()
Eventual situations 030 223 134 Non quantified causes - - 1219 Total 820 3980 2764
On average the waste due to receipt stocking and site transportation of ceramics blocks added up (853) was significantly higher than the average wastes generated during the execution of the wall itself that is due to the rejection of pieces accidental breakage and cut (558) Looking just at the production itself it was verified that the waste caused by the need to cut the pieces (4 67) due mainly to the lack of half-blocks was significantly higher than the waste caused by rejection and the accidental breakage of the material added up (091 ) On site E for instance the waste due to cuts reached 1092 of the pieces used Also surprising was the high index of waste due to the lack of control of the quantity of material delivered which reached 575 on site A
Among the non-quantified causes two stand out the excess thickoess of walls mainly on site E and the occurrence of vandalism and theft on sites where the blocks were stocked on the sidewalk outside the construction site
Finally the small waste on site B in relation to the other sites was probably mainly due to the fact that up until the FI the masonry execution was at the beginning and wrap up had not beeo carried out
560
With regards to bricks the study of the receipt was carried out only on sites A B and D and of the internal transportation and production on sites Band E as they were the only ones which enabled these verifications to be carried out during the research The small waste of bricks on site C occurred due to the fact that special mortar was used in the execution of last row instead of the bricks as on the other sites
W ASTE AND LABOR PRODUCTIVITY
In order to investigate the existence of a correlation between productivity and waste of materials the labor productivity during the masonry execution was measured through the observation of the number of bricks laid per hour 1n general it can be said that sites Band D presented higher levels of productivity than the others (between 20 and 60 higher than the average of all the sites) Site E presented the poorest performance levels (around 30 and 50 lower than the average of the sites)
Due to the smaJl number of sites the results obtained in the analyses of the producshytivity in relation to the occurrence of waste cannot be generalized However the study carried out showed a tendency that site E with lower productivity presented the highest index of waste of ceramic blocks in the per iod (10725) On the other hand sites Band D with higher productivity presented the Jowest incidence of was te in the period - 820 and 26 50 respectively However it is necessary to make a deeper study of the relation between productivity and waste of materials through the analyses of a larger number of sites
THE COST OF THE WASTE OF THE MATERIALS MONITORED
For the determination of the cost of waste of the materials studied the ABC Curve of the NBR 12721 (ABNT) formulated for 12 floor buildings with three bedrooms and normal finishing standards (HI2-3Q-Normal) was used The original ABC Curve was changed in order to adapt to the materials used on the studied sites
The wastes of the materials studied represented up unti I the end of data collection an increase of 506 (Site C) to 1162 (Site E) in relation to the budgeted costs for the sites studied lt should be considered that these materials represent approximately 20 of the total cost of this type of building The average increase of 798 on the construction cost calculated in this study is of the same magnitude as the 6 estimated by Pinto (1989)
CONCLUSIONS
The main conclusion of the study was the confirmation that much of tbe waste is predictable and avoidable Tbe fact that relatively simple preventive measures were not taken on the sites studied indicates that there is a lack of concern with the waste of materials None of the sites monitored had a defined policy conceming management of materials both with regards to their management and the employment of a systematic conshytrol for their utilization
The magnitude of waste of materials is not known by tbe building firms themselves due to the complete absence of surveying and booking methods The only procedures of control of materials observed on the studied sites were quick verifications of the materials deJivered
The study has also confirmed that there is great variation on the indices of waste of materials on different sites Considering that similar sites presented different levels of waste for the same materials it can be concluded that much of this waste is avoidable
561
It also became evident that improvements may be obtained without the introduction of expensive equipment or advanced managerial techniques but simply through elementary care on receipt stocking handling use and protection of materials This fact indicates that the reduction of waste could easily be used as the focal point in quality improvement programs in building firms
It was also concluded that the lack of interest in controlling materials is an important cause of the occurrence of waste During the study it was observed that the site managers were aware of the waste but did little to prevent it from happening The study showed that a change in the attitude of those involved in the construction process is much more important than changes in building technology in order to obtain better performances from building firms with regards to management of materials It is crucial that the people involved become aware of the high value of materials and of the need to work more carefully
The study confirmed that management is more responsible for the waste than the laborers The latter are normally considered by the entrepreneurs of the building industry as the main responsible for the low productivity poor quality and the high level of material waste
Generally the waste occurred more as a result of a combination of factors than as a consequence of one isolated incident in an operation This proved that the lack of management of the sites is the fundamental cause of the high incidence of waste of mashyterials
Much of the waste originates outside the construction sites due to inadequate designs or bad procurement Through the study of the designs of the live sites studied it was possible to conclude that the lack of specifications project details and quality of the designs and mainly the lack of coordination among them are causes of significant waste of materials The breakages of bricks caused by the lack of half-bricks is an example of a problem generated on the supply sector
As was the case with Skoyles study (1976) there were indications that the occurshyrence of waste on the site happens more intensely during stocking and handling of materials than during production itself
An important data as it contradicts the literature consulted is that in spite of the great variability among actual wastes of a same material on different sites (between one and nine times) the higher or lower incidence of waste is defined by the specific procedures of management of the material or the activities which involve its use In other words if a specific material presents a high index of consumption in one enterprise higher than the other sites studied it does not mean that all materials presented high levels of waste on this enterprise It was observed for instance that some enterprises presented more efficiency on the execution of the reinforced concrete structure others on the employment of bulk materials (cement sand mortar) and others still on the employment of bricks
Conceming the methodology employed on the survey it became clear that the inshydepth study of the causes of waste and its measurement constitutes a rat her complex and expensive study particularly if it is carried out only by extemal observers It is very imporshytant that building firms become aware of the need to monitor and control materials waste and that this way this segment manages to obtain representative indices of waste for the different materials which can became an important quality and productivity indicator for the building industry
REFERENCES
ABNT - Associayaumlo Brasileira de Normas Tecnicas 1992 Avaliariio de cusos uniarios e preparo de orcamenos de consruqiio para incorporaqiio de edijicio em condomznio
562
NBR 12721 Rio de laneiro Brazil
1983 Reveslimenlo de paredes e lelos com argamassas - maleriais preparo aplicaraumlo - e manulenraumlo NBR 7200 Rio de laneiro Brazil
Deming WE 1986 Oul oIhe crisis MITCAES Cambridge Massachusetts
Melinghendler MA 1978 A racionaliza9aumlo das obras na construeyaumlo civil Revisla de Engenharia FMP 23-28
Picchi FA 1993 Sislemas de qualidade uso em empresas de conslruriio PhD thesis USP -Escola Politecnica Saumlo Paul0 Brazil
Pinto TP 1989 Perda de maleriais em processos conslrulivos Iradicionais UFSCARshyDepartamento de Engenharia Civil Saumlo Carlos Brazil 33pp
Skoyles EF 1976 Materials was tage - a misuse of resources Building Research and Praclice JulyAug 232-243
Soibelman L 1993 As perdas de maleriais na conslruriio de edificaroes sua incidencia e seu controle MSc thesis UFRGS-Curso de P6s-Gradualtaumlo em Engenharia Civil Porto Alegre Brazil
Vargas N 1990 A geometria do reboco Conslruriio Saumlo Paulo May 16-17
Wyatt DP 1978 Malerials managemenl - Pari I The Chartered Institute of Building Berkshire England
563
joints and mortar coatings al ready discussed The sand was used mainly on the execution of masonry while the pre-mixed mortar was employed on the execution of coatings The only exception was site D where the mortar for coatings was totally made on the site
In spite of the existence of several situations where waste of sand and mortar was detected due to poor conditions of transport and stocking it was not possible to quantify the volume wasted on these situations
Except for site D the waste of sand detected in spite of being superior to what is usually admitted for budget purposes did not reach alarming values as was the case with mortar Therefore it may be concluded that the mortar used on the coatings generate more significant waste than the mortar used on brick laying
Ceramic blocks and bricks
Because of its nature it was possible to carry out a much more detailed study on the causes of waste of bricks compared to the other materials On table 2 the percentages of waste related to each of the moments of incidence are shown
T ABLE 42-Distribution of the waste of ceramic blocks according to the moment of incidence ()
Eventual situations 030 223 134 Non quantified causes - - 1219 Total 820 3980 2764
On average the waste due to receipt stocking and site transportation of ceramics blocks added up (853) was significantly higher than the average wastes generated during the execution of the wall itself that is due to the rejection of pieces accidental breakage and cut (558) Looking just at the production itself it was verified that the waste caused by the need to cut the pieces (4 67) due mainly to the lack of half-blocks was significantly higher than the waste caused by rejection and the accidental breakage of the material added up (091 ) On site E for instance the waste due to cuts reached 1092 of the pieces used Also surprising was the high index of waste due to the lack of control of the quantity of material delivered which reached 575 on site A
Among the non-quantified causes two stand out the excess thickoess of walls mainly on site E and the occurrence of vandalism and theft on sites where the blocks were stocked on the sidewalk outside the construction site
Finally the small waste on site B in relation to the other sites was probably mainly due to the fact that up until the FI the masonry execution was at the beginning and wrap up had not beeo carried out
560
With regards to bricks the study of the receipt was carried out only on sites A B and D and of the internal transportation and production on sites Band E as they were the only ones which enabled these verifications to be carried out during the research The small waste of bricks on site C occurred due to the fact that special mortar was used in the execution of last row instead of the bricks as on the other sites
W ASTE AND LABOR PRODUCTIVITY
In order to investigate the existence of a correlation between productivity and waste of materials the labor productivity during the masonry execution was measured through the observation of the number of bricks laid per hour 1n general it can be said that sites Band D presented higher levels of productivity than the others (between 20 and 60 higher than the average of all the sites) Site E presented the poorest performance levels (around 30 and 50 lower than the average of the sites)
Due to the smaJl number of sites the results obtained in the analyses of the producshytivity in relation to the occurrence of waste cannot be generalized However the study carried out showed a tendency that site E with lower productivity presented the highest index of waste of ceramic blocks in the per iod (10725) On the other hand sites Band D with higher productivity presented the Jowest incidence of was te in the period - 820 and 26 50 respectively However it is necessary to make a deeper study of the relation between productivity and waste of materials through the analyses of a larger number of sites
THE COST OF THE WASTE OF THE MATERIALS MONITORED
For the determination of the cost of waste of the materials studied the ABC Curve of the NBR 12721 (ABNT) formulated for 12 floor buildings with three bedrooms and normal finishing standards (HI2-3Q-Normal) was used The original ABC Curve was changed in order to adapt to the materials used on the studied sites
The wastes of the materials studied represented up unti I the end of data collection an increase of 506 (Site C) to 1162 (Site E) in relation to the budgeted costs for the sites studied lt should be considered that these materials represent approximately 20 of the total cost of this type of building The average increase of 798 on the construction cost calculated in this study is of the same magnitude as the 6 estimated by Pinto (1989)
CONCLUSIONS
The main conclusion of the study was the confirmation that much of tbe waste is predictable and avoidable Tbe fact that relatively simple preventive measures were not taken on the sites studied indicates that there is a lack of concern with the waste of materials None of the sites monitored had a defined policy conceming management of materials both with regards to their management and the employment of a systematic conshytrol for their utilization
The magnitude of waste of materials is not known by tbe building firms themselves due to the complete absence of surveying and booking methods The only procedures of control of materials observed on the studied sites were quick verifications of the materials deJivered
The study has also confirmed that there is great variation on the indices of waste of materials on different sites Considering that similar sites presented different levels of waste for the same materials it can be concluded that much of this waste is avoidable
561
It also became evident that improvements may be obtained without the introduction of expensive equipment or advanced managerial techniques but simply through elementary care on receipt stocking handling use and protection of materials This fact indicates that the reduction of waste could easily be used as the focal point in quality improvement programs in building firms
It was also concluded that the lack of interest in controlling materials is an important cause of the occurrence of waste During the study it was observed that the site managers were aware of the waste but did little to prevent it from happening The study showed that a change in the attitude of those involved in the construction process is much more important than changes in building technology in order to obtain better performances from building firms with regards to management of materials It is crucial that the people involved become aware of the high value of materials and of the need to work more carefully
The study confirmed that management is more responsible for the waste than the laborers The latter are normally considered by the entrepreneurs of the building industry as the main responsible for the low productivity poor quality and the high level of material waste
Generally the waste occurred more as a result of a combination of factors than as a consequence of one isolated incident in an operation This proved that the lack of management of the sites is the fundamental cause of the high incidence of waste of mashyterials
Much of the waste originates outside the construction sites due to inadequate designs or bad procurement Through the study of the designs of the live sites studied it was possible to conclude that the lack of specifications project details and quality of the designs and mainly the lack of coordination among them are causes of significant waste of materials The breakages of bricks caused by the lack of half-bricks is an example of a problem generated on the supply sector
As was the case with Skoyles study (1976) there were indications that the occurshyrence of waste on the site happens more intensely during stocking and handling of materials than during production itself
An important data as it contradicts the literature consulted is that in spite of the great variability among actual wastes of a same material on different sites (between one and nine times) the higher or lower incidence of waste is defined by the specific procedures of management of the material or the activities which involve its use In other words if a specific material presents a high index of consumption in one enterprise higher than the other sites studied it does not mean that all materials presented high levels of waste on this enterprise It was observed for instance that some enterprises presented more efficiency on the execution of the reinforced concrete structure others on the employment of bulk materials (cement sand mortar) and others still on the employment of bricks
Conceming the methodology employed on the survey it became clear that the inshydepth study of the causes of waste and its measurement constitutes a rat her complex and expensive study particularly if it is carried out only by extemal observers It is very imporshytant that building firms become aware of the need to monitor and control materials waste and that this way this segment manages to obtain representative indices of waste for the different materials which can became an important quality and productivity indicator for the building industry
REFERENCES
ABNT - Associayaumlo Brasileira de Normas Tecnicas 1992 Avaliariio de cusos uniarios e preparo de orcamenos de consruqiio para incorporaqiio de edijicio em condomznio
562
NBR 12721 Rio de laneiro Brazil
1983 Reveslimenlo de paredes e lelos com argamassas - maleriais preparo aplicaraumlo - e manulenraumlo NBR 7200 Rio de laneiro Brazil
Deming WE 1986 Oul oIhe crisis MITCAES Cambridge Massachusetts
Melinghendler MA 1978 A racionaliza9aumlo das obras na construeyaumlo civil Revisla de Engenharia FMP 23-28
Picchi FA 1993 Sislemas de qualidade uso em empresas de conslruriio PhD thesis USP -Escola Politecnica Saumlo Paul0 Brazil
Pinto TP 1989 Perda de maleriais em processos conslrulivos Iradicionais UFSCARshyDepartamento de Engenharia Civil Saumlo Carlos Brazil 33pp
Skoyles EF 1976 Materials was tage - a misuse of resources Building Research and Praclice JulyAug 232-243
Soibelman L 1993 As perdas de maleriais na conslruriio de edificaroes sua incidencia e seu controle MSc thesis UFRGS-Curso de P6s-Gradualtaumlo em Engenharia Civil Porto Alegre Brazil
Vargas N 1990 A geometria do reboco Conslruriio Saumlo Paulo May 16-17
Wyatt DP 1978 Malerials managemenl - Pari I The Chartered Institute of Building Berkshire England
563
With regards to bricks the study of the receipt was carried out only on sites A B and D and of the internal transportation and production on sites Band E as they were the only ones which enabled these verifications to be carried out during the research The small waste of bricks on site C occurred due to the fact that special mortar was used in the execution of last row instead of the bricks as on the other sites
W ASTE AND LABOR PRODUCTIVITY
In order to investigate the existence of a correlation between productivity and waste of materials the labor productivity during the masonry execution was measured through the observation of the number of bricks laid per hour 1n general it can be said that sites Band D presented higher levels of productivity than the others (between 20 and 60 higher than the average of all the sites) Site E presented the poorest performance levels (around 30 and 50 lower than the average of the sites)
Due to the smaJl number of sites the results obtained in the analyses of the producshytivity in relation to the occurrence of waste cannot be generalized However the study carried out showed a tendency that site E with lower productivity presented the highest index of waste of ceramic blocks in the per iod (10725) On the other hand sites Band D with higher productivity presented the Jowest incidence of was te in the period - 820 and 26 50 respectively However it is necessary to make a deeper study of the relation between productivity and waste of materials through the analyses of a larger number of sites
THE COST OF THE WASTE OF THE MATERIALS MONITORED
For the determination of the cost of waste of the materials studied the ABC Curve of the NBR 12721 (ABNT) formulated for 12 floor buildings with three bedrooms and normal finishing standards (HI2-3Q-Normal) was used The original ABC Curve was changed in order to adapt to the materials used on the studied sites
The wastes of the materials studied represented up unti I the end of data collection an increase of 506 (Site C) to 1162 (Site E) in relation to the budgeted costs for the sites studied lt should be considered that these materials represent approximately 20 of the total cost of this type of building The average increase of 798 on the construction cost calculated in this study is of the same magnitude as the 6 estimated by Pinto (1989)
CONCLUSIONS
The main conclusion of the study was the confirmation that much of tbe waste is predictable and avoidable Tbe fact that relatively simple preventive measures were not taken on the sites studied indicates that there is a lack of concern with the waste of materials None of the sites monitored had a defined policy conceming management of materials both with regards to their management and the employment of a systematic conshytrol for their utilization
The magnitude of waste of materials is not known by tbe building firms themselves due to the complete absence of surveying and booking methods The only procedures of control of materials observed on the studied sites were quick verifications of the materials deJivered
The study has also confirmed that there is great variation on the indices of waste of materials on different sites Considering that similar sites presented different levels of waste for the same materials it can be concluded that much of this waste is avoidable
561
It also became evident that improvements may be obtained without the introduction of expensive equipment or advanced managerial techniques but simply through elementary care on receipt stocking handling use and protection of materials This fact indicates that the reduction of waste could easily be used as the focal point in quality improvement programs in building firms
It was also concluded that the lack of interest in controlling materials is an important cause of the occurrence of waste During the study it was observed that the site managers were aware of the waste but did little to prevent it from happening The study showed that a change in the attitude of those involved in the construction process is much more important than changes in building technology in order to obtain better performances from building firms with regards to management of materials It is crucial that the people involved become aware of the high value of materials and of the need to work more carefully
The study confirmed that management is more responsible for the waste than the laborers The latter are normally considered by the entrepreneurs of the building industry as the main responsible for the low productivity poor quality and the high level of material waste
Generally the waste occurred more as a result of a combination of factors than as a consequence of one isolated incident in an operation This proved that the lack of management of the sites is the fundamental cause of the high incidence of waste of mashyterials
Much of the waste originates outside the construction sites due to inadequate designs or bad procurement Through the study of the designs of the live sites studied it was possible to conclude that the lack of specifications project details and quality of the designs and mainly the lack of coordination among them are causes of significant waste of materials The breakages of bricks caused by the lack of half-bricks is an example of a problem generated on the supply sector
As was the case with Skoyles study (1976) there were indications that the occurshyrence of waste on the site happens more intensely during stocking and handling of materials than during production itself
An important data as it contradicts the literature consulted is that in spite of the great variability among actual wastes of a same material on different sites (between one and nine times) the higher or lower incidence of waste is defined by the specific procedures of management of the material or the activities which involve its use In other words if a specific material presents a high index of consumption in one enterprise higher than the other sites studied it does not mean that all materials presented high levels of waste on this enterprise It was observed for instance that some enterprises presented more efficiency on the execution of the reinforced concrete structure others on the employment of bulk materials (cement sand mortar) and others still on the employment of bricks
Conceming the methodology employed on the survey it became clear that the inshydepth study of the causes of waste and its measurement constitutes a rat her complex and expensive study particularly if it is carried out only by extemal observers It is very imporshytant that building firms become aware of the need to monitor and control materials waste and that this way this segment manages to obtain representative indices of waste for the different materials which can became an important quality and productivity indicator for the building industry
REFERENCES
ABNT - Associayaumlo Brasileira de Normas Tecnicas 1992 Avaliariio de cusos uniarios e preparo de orcamenos de consruqiio para incorporaqiio de edijicio em condomznio
562
NBR 12721 Rio de laneiro Brazil
1983 Reveslimenlo de paredes e lelos com argamassas - maleriais preparo aplicaraumlo - e manulenraumlo NBR 7200 Rio de laneiro Brazil
Deming WE 1986 Oul oIhe crisis MITCAES Cambridge Massachusetts
Melinghendler MA 1978 A racionaliza9aumlo das obras na construeyaumlo civil Revisla de Engenharia FMP 23-28
Picchi FA 1993 Sislemas de qualidade uso em empresas de conslruriio PhD thesis USP -Escola Politecnica Saumlo Paul0 Brazil
Pinto TP 1989 Perda de maleriais em processos conslrulivos Iradicionais UFSCARshyDepartamento de Engenharia Civil Saumlo Carlos Brazil 33pp
Skoyles EF 1976 Materials was tage - a misuse of resources Building Research and Praclice JulyAug 232-243
Soibelman L 1993 As perdas de maleriais na conslruriio de edificaroes sua incidencia e seu controle MSc thesis UFRGS-Curso de P6s-Gradualtaumlo em Engenharia Civil Porto Alegre Brazil
Vargas N 1990 A geometria do reboco Conslruriio Saumlo Paulo May 16-17
Wyatt DP 1978 Malerials managemenl - Pari I The Chartered Institute of Building Berkshire England
563
It also became evident that improvements may be obtained without the introduction of expensive equipment or advanced managerial techniques but simply through elementary care on receipt stocking handling use and protection of materials This fact indicates that the reduction of waste could easily be used as the focal point in quality improvement programs in building firms
It was also concluded that the lack of interest in controlling materials is an important cause of the occurrence of waste During the study it was observed that the site managers were aware of the waste but did little to prevent it from happening The study showed that a change in the attitude of those involved in the construction process is much more important than changes in building technology in order to obtain better performances from building firms with regards to management of materials It is crucial that the people involved become aware of the high value of materials and of the need to work more carefully
The study confirmed that management is more responsible for the waste than the laborers The latter are normally considered by the entrepreneurs of the building industry as the main responsible for the low productivity poor quality and the high level of material waste
Generally the waste occurred more as a result of a combination of factors than as a consequence of one isolated incident in an operation This proved that the lack of management of the sites is the fundamental cause of the high incidence of waste of mashyterials
Much of the waste originates outside the construction sites due to inadequate designs or bad procurement Through the study of the designs of the live sites studied it was possible to conclude that the lack of specifications project details and quality of the designs and mainly the lack of coordination among them are causes of significant waste of materials The breakages of bricks caused by the lack of half-bricks is an example of a problem generated on the supply sector
As was the case with Skoyles study (1976) there were indications that the occurshyrence of waste on the site happens more intensely during stocking and handling of materials than during production itself
An important data as it contradicts the literature consulted is that in spite of the great variability among actual wastes of a same material on different sites (between one and nine times) the higher or lower incidence of waste is defined by the specific procedures of management of the material or the activities which involve its use In other words if a specific material presents a high index of consumption in one enterprise higher than the other sites studied it does not mean that all materials presented high levels of waste on this enterprise It was observed for instance that some enterprises presented more efficiency on the execution of the reinforced concrete structure others on the employment of bulk materials (cement sand mortar) and others still on the employment of bricks
Conceming the methodology employed on the survey it became clear that the inshydepth study of the causes of waste and its measurement constitutes a rat her complex and expensive study particularly if it is carried out only by extemal observers It is very imporshytant that building firms become aware of the need to monitor and control materials waste and that this way this segment manages to obtain representative indices of waste for the different materials which can became an important quality and productivity indicator for the building industry
REFERENCES
ABNT - Associayaumlo Brasileira de Normas Tecnicas 1992 Avaliariio de cusos uniarios e preparo de orcamenos de consruqiio para incorporaqiio de edijicio em condomznio
562
NBR 12721 Rio de laneiro Brazil
1983 Reveslimenlo de paredes e lelos com argamassas - maleriais preparo aplicaraumlo - e manulenraumlo NBR 7200 Rio de laneiro Brazil
Deming WE 1986 Oul oIhe crisis MITCAES Cambridge Massachusetts
Melinghendler MA 1978 A racionaliza9aumlo das obras na construeyaumlo civil Revisla de Engenharia FMP 23-28
Picchi FA 1993 Sislemas de qualidade uso em empresas de conslruriio PhD thesis USP -Escola Politecnica Saumlo Paul0 Brazil
Pinto TP 1989 Perda de maleriais em processos conslrulivos Iradicionais UFSCARshyDepartamento de Engenharia Civil Saumlo Carlos Brazil 33pp
Skoyles EF 1976 Materials was tage - a misuse of resources Building Research and Praclice JulyAug 232-243
Soibelman L 1993 As perdas de maleriais na conslruriio de edificaroes sua incidencia e seu controle MSc thesis UFRGS-Curso de P6s-Gradualtaumlo em Engenharia Civil Porto Alegre Brazil
Vargas N 1990 A geometria do reboco Conslruriio Saumlo Paulo May 16-17
Wyatt DP 1978 Malerials managemenl - Pari I The Chartered Institute of Building Berkshire England
563
NBR 12721 Rio de laneiro Brazil
1983 Reveslimenlo de paredes e lelos com argamassas - maleriais preparo aplicaraumlo - e manulenraumlo NBR 7200 Rio de laneiro Brazil
Deming WE 1986 Oul oIhe crisis MITCAES Cambridge Massachusetts
Melinghendler MA 1978 A racionaliza9aumlo das obras na construeyaumlo civil Revisla de Engenharia FMP 23-28
Picchi FA 1993 Sislemas de qualidade uso em empresas de conslruriio PhD thesis USP -Escola Politecnica Saumlo Paul0 Brazil
Pinto TP 1989 Perda de maleriais em processos conslrulivos Iradicionais UFSCARshyDepartamento de Engenharia Civil Saumlo Carlos Brazil 33pp
Skoyles EF 1976 Materials was tage - a misuse of resources Building Research and Praclice JulyAug 232-243
Soibelman L 1993 As perdas de maleriais na conslruriio de edificaroes sua incidencia e seu controle MSc thesis UFRGS-Curso de P6s-Gradualtaumlo em Engenharia Civil Porto Alegre Brazil
Vargas N 1990 A geometria do reboco Conslruriio Saumlo Paulo May 16-17
Wyatt DP 1978 Malerials managemenl - Pari I The Chartered Institute of Building Berkshire England
