BUILDING COMPONENTS AND BUILDINGS

LCA-based study on structural retrofit options for masonrybuildings

Loredana Napolano & Costantino Menna & DomenicoAsprone & Andrea Prota & Gaetano Manfredi

Received: 10 February 2014 /Accepted: 27 September 2014# Springer-Verlag Berlin Heidelberg 2014

AbstractPurpose Over the last decade, the rehabilitation/renovation ofexisting buildings has increasingly attracted the attention ofscientific community. Many studies focus intensely on themechanical and energy performance of retrofitted/renovatedexisting structures, while few works address the environmen-tal impact of such operations. In the present study, the envi-ronmental impact of typical retrofit operations, referred tomasonry structures, is assessed. In particular, four differentstructural options are investigated: local replacement of dam-aged masonry, mortar injection, steel chain installation, andgrid-reinforced mortar application. Each different option isanalyzed with reference to proper normalized quantities.Thus, the results of this analysis can be used to compute theenvironmental impact of real large-scale retrofit operations,once the amount/extension of them is defined in the designstage. The final purpose is to give to designers the opportunityto monitor the environmental impact of different retrofit strat-egies and, once structural requirements are satisfied, identifyfor each real case the most suitable retrofit option.Methods The environmental impact of the structural retrofitoptions is assessed by means of a life-cycle assessment (LCA)approach. A cradle to grave system boundary is considered foreach retrofit process. The results of the environmental analysisare presented according to the data format of the Environmental

Product Declaration (EPD) standard. Indeed, the environmen-tal outcomes are expressed through six impact categories:global warming, ozone depletion, eutrophication, acidifica-tion, photochemical oxidation, and nonrenewable energy.Results and discussion For each retrofit option, the interpre-tation analysis is conducted in order to define which element,material, or process mainly influenced the LCA results. Inaddition, the results revealed that the recycling of waste ma-terials provides environmental benefits in all the categories ofthe LCA outcomes. It is also pointed out that a comparisonbetween the four investigated options would be meaningfulonly once the exact amount of each operation is defined for aspecific retrofit case.Conclusions This paper provides a systematic approach andenvironmental data to drive the selection and identification ofstructural retrofit options for existing buildings, in terms ofsustainability performance. The final aim of this work is alsoto provide researchers and practitioners, with a better under-standing of the sustainability aspects of retrofit operations. Infact, the environmental impacts of the retrofit options hereinvestigated can be used for future research/practical activi-ties, to monitor and control the environmental impact ofstructural retrofit operations of existing masonry buildings.

Keywords Local replacement . Masonry structures . Mortarinjection . Reinforced grid . Steel chain . Structural retrofit

1 Introduction

It is estimated that in many European areas, such as Italy,masonry buildings constitute a significant portion of existingbuilding stock; in addition, many of them are characterized byimportant historical and cultural values. In general, thesestructures do not comply with current/national engineeringstandards and are sometimes subjected to physical and

Responsible editor: Marzia Traverso

L. Napolano :C. Menna :D. Asprone :A. Prota :G. ManfrediDepartment of Structures for Engineering and Architecture,University ofNaples, Federico II, Via Claudio 21, 80125 Naples,Italy

L. Napolano (*)Stress S.c.ar.l. Sviluppo Tecnologie e Ricerca per l’Ediliziasismicamente Sicura ed ecoSostenibile, vico II S.Nicola alla Dogana9, 80133 Naples, Italye-mail: loredana.napolano@unina.it

Int J Life Cycle AssessDOI 10.1007/s11367-014-0807-1

functional degradation over time as well as structural damagefrom hazardous events. On the other hand, existing buildingscontinue to be upgraded at a very low rate; it is estimated thatthe existing European building stock is currently beingretrofitted at a rate of approximately 1–3 % of total neededper year (Ascione et al. 2011).

Many governments and international organizations haveprovided policy guidance, financial assistance, and technicalsupport to improve the structural, functional, and energy per-formance of existing buildings (MIT 2014; HUD/U.S. 2005;DOCC&EE 2011). At the same time, a significant amount ofresearches have focused on the assessment of existing build-ings, analyzing, consequently, different types of building ren-ovation strategies. Building renovation, in fact, has gainedincreasing attention as a valuable alternative to demolition,providing opportunities to upgrade the internal and externalbuilding environment, reach energy efficiency, align withmore modern accommodations with respect to new standards,and increase the value of the existing building.

Large-scale retrofitting studies focused intensely on themechanical, functional, and energy performance ofretrofitted/renovated existing structures, while few worksdealt with the LCA of such operations. For example, thestrategies to reduce building heating and cooling demand,promoting the use of energy efficient equipment, and low-energy technologies were investigated by Asadi et al. (2012),Ascione et al. (2011), Biekšaa et al. (2011), Xing et al. (2011),and Užšilaitytea and Martinaitis (2010).

Other research activities included the assessment of othersustainability criteria, such as economical benefits of refur-bishment (Juan et al. 2009; Kanapeckiene et al. 2011) andsocial aspects (Raslanasa et al. 2011). Boylu (2005) andBosiljkov et al. (2010), instead, assessed structural and func-tional performance of a building before and after renovation,by taking into account earthquake damage.

However, few studies focused on the environmental impactof retrofit techniques applied on existing buildings. For example,the environmental impact of different structural retrofit techniquessuch as steel jacketing and fiber-reinforced polymer retrofit hasbeen analyzed by Moliner et al. (2013), Zhang et al. (2012), andDas (2011). Other studies focused on the environmental impactof different structural options such as flat roof, floor on grade, andthe integration of green roof in existing buildings (Rodrigues andFreire 2014; Perini 2013; Allacker 2012).

Given the wide set of possible scenarios (Flourentzou andRoulet 2002; Ma et al. 2012) it should be emphasized thatrefurbishment and retrofit of existing buildings often requirethe fulfillment of several mechanical and functional require-ments (sometimes prescribed by national laws/standards) thathave to be properly taken into account during the design of theoperation itself. Among these requirements, a selection of a setof actions should be pursuit also in the light of common goalsof sustainable development in the construction sector.

Indeed, the decision-making process of a retrofit operation(referred to its design and employed technology) should beintended as a multi-objective multi-criteria optimization prob-lem that usually fairly embodies sustainability purposes in theengineering field (Waheed et al. 2009; Menna et al. 2013;Sahely et al. 2005; Foxon et al. 2002). The best option, in fact,should be a trade-off among a range of factors, such as energy,economic, technical, environmental, regulations, social, andso forth (Juan et al. 2009).

For example, the overall process of a building retrofit couldbe divided in three main steps according to the approachdefined by Juan et al. (2009) (Fig. 1). The first step shouldencompass a performance assessment of the facility. Then,diagnostics tools should be used to identify structural integrityand the current state of individual components of the buildingin order to define a set of possible refurbishment solutionsaimed at extending the building lifetime.

Each solution should be analyzed by using appropriatecriteria (quantitatively expressed by proper indicators) consid-ering financial, environmental, social, and structural aspects(step 2), in order to implement the optimal retrofit solution(step 3). According to this approach, sustainability and struc-tural requirements might be incorporated within the designstage of retrofit of existing structures.

Following the approach of Juan et al. (2009), the purposeof this paper is to analyze different structural retrofit tech-niques applied to masonry structures. In particular, consider-ing that few works have dealt with the LCA of strengtheningsystems for the structural rehabilitation of masonry structures,the present study aims at investigating the environmentalfootprint of different structural retrofit interventions (Figs. 1and 2b), conducted on a masonry structure, once structuralrequirements are satisfied (Figs. 1 and 2d). Four differentstructural options are examined from the environmental pointof view by means of a LCA approach (ISO:14040 2006;ISO:14044 2006): local replacement of damaged masonry(LRDM), mortar injection (MI), steel chain installation(SCI), and application of grid-reinforced mortar (GRM). Thefinal aim of the LCA approach is to compare the environmen-tal impact of the considered options, possibly identifying thescenarios that are characterized by the lowest impact.

2 Methods

The proposed approach, based on the LCA logical schemereported in Fig. 1, aims at contributing to sustainable design ofretrofit interventions in construction sector. This approach hasbeen selected coherently with the requirements of the interna-tional Environmental Product Declaration (EPD) system. TheEPD according to ISO 14025 (ISO: 14025 2006) provides theenvironmental impacts of products from LCA analysis in aformalized and comparable way. In particular, it takes into

Int J Life Cycle Assess

account the whole product life cycle and computes environ-mental data in a “cradle to grave” approach in order to calcu-late a set of internationally recognized indicators, such as “useof primary energy,” “greenhouse gas emission,” and “waterconsumption” (UNI EN 15804 2012).

2.1 Goal and scope definition

The aim of this study is to quantify (separately) the environ-mental footprint of structural retrofit options applied to

masonry structures that usually involves technical operationon masonry walls.

In particular, different scenarios referred to the use ofdifferent mortar binders; reinforcing systems and waste sce-narios are considered in order to define for each investigatedoption what strategy is more sustainable. In this way, theobjective is not a comprehensive comparative LCA studybetween the four investigated options, but is a comparativeenvironmental analysis inside each solution in order to definewhich scenario is characterized by lowest impact. Particularly,within each retrofit option, the analysis is separately referred

Fig. 1 Logical flow chart of the LCA-based approach proposed by (Juan et al. 2009)

Fig. 2 LRDM retrofit: a beforeretrofit and b after retrofit

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to a suitable quantity which is strictly related to the employedtechnique: 1 m2 of masonry wall in the case of LRDM andGRM, 1 m of crack in the case ofMI, and 1 m of steel chain inthe case of SCI. Then, in order to evaluate and compare thetotal environmental impact related to a large-scale retrofitintervention on an existing masonry building (through theinvestigated techniques), each environmental outcome shouldbe referred to the exact amount (in terms of multiples of eachunit), resulting from the structural design and guaranteeing anequivalent structural response of the retrofitted building.

In fact, it is pointed that an effective comparison betweenthe four investigated options would be meaningful only oncethe exact amount of each operation (i.e., number of m2 ofmasonry wall in the case of LRDM and GRM, number of m ofcrack in the case of MI, and number of m of steel chain in thecase of SCI) is defined for a specific retrofit case that requiresa pre-defined structural improvement.

With regard to the specific application to masonry struc-tures of the present study, it should be introduced that themechanism of collapse that occurs, for example, duringseismic events typically regards the partial or total collapseof the wall (out-of-plane mechanisms) and crack forma-tions. After the major earthquake, which hit L’Aquila(Italy) in 2009 and severely damaged many historic centersmainly made of masonry structures, some retrofit tech-niques were largely employed to repair the previous men-tioned types of damage.

The main structural retrofit technologies investigated with-in this study can be summarized as follows.

2.1.1 LRDM retrofit

This technique aims at restoring the wall continuity alongcracking lines (substitution of damaged masonry units withnew ones) and recovering heavily damaged parts of masonrywalls (Fig. 2). Thematerials used are similar in terms of shape,dimensions, stiffness, and strength to those employed in thepristine wall (ReLuis 2011).

The environmental impact of the LRDM retrofit applied to1 m2 of clay brick wall with a thickness of 16 cm (NTC 2008)is quantified. The system boundary includes different lifecycle phases (Fig. 6): (i) the demolition of the old wall, (ii)the construction of the new wall, and (iii) the end of life phasethat includes the demolition of the wall.

In detail, it is assumed that the demolition of the existingwall (i) is made with manual operations in order to avoidfurther brick damage and permanently compromise the integ-rity and appearance of the wall; instead, it is assumed that thedemolition of the new wall (iii) is executed with electricalequipments.

Approximately 140 solid bricks of 11×23×5 cm and 67 kgof mortar are used to restore 1 m2 of wall.

2.1.2 MI retrofit

An economical, structurally effective, and aesthetically satis-factory repair of cracks can be accomplished by the injectionof fine grout into the wall cracks. By filling the cracks and thesurrounding voids inside the wall, the wall strength can berestored and adjacent mortar is not damaged.

The LCA of the MI retrofit (Fig. 3) applied to one crack of1 m of length, 0.02 m of width, and 0.16 m of depth isprovided; the system boundary includes different life cyclephases (Fig. 6): (i) the preparation phase, (ii) the applicationphase, and (iii) the end of life phase that includes the walldemolition.

Before the injection (ii), all the crack and void cavities arethoroughly flushed with clean water with high pressure jetcleaner water to remove as much dirt, debris, and contami-nants as possible and to pre-saturate the areas that have to begrouted (i) (ReLuis 2011). Approximately 30 kg of mortar areused to restore one longitudinal crack.

In the LRDM and MI retrofit techniques, the “applicationphase (ii)” includes different scenarios, referred to the use ofdifferent mortar binders. According to UNI EN 998-2 (2004)and UNI EN 1015-19 (2008), hydraulic mortars with lowamount of cement material should be used for such operations.In this study, different mortar binders are considered: cement,light, and lime mortars. The main difference of these bindermaterials is the cement content that is 0.2, 0.34, and 0.56 kg,respectively. Moreover, mortar materials (cement, inert) havebeen also mixed with water; it is assumed that this mixingoperation is executed with an electric mixer.

2.1.3 SCI retrofit

Without a good mechanical connection between parallelwalls, a steel chain-based operation is usually employed

Fig. 3 MI retrofit

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(Fig. 4). An effective connection between walls is useful sinceit allows a better load redistribution in case of seismic actionsand applies a restraining action towards the walls’overturning. A satisfactory connection is provided by steelchain anchored on the external face of the wall.

The application of a steel chain (with a diameter of 24 mm)with 1 m of length and with two steel plates [30×30×2 cm] isevaluated from an environmental point of view; the systemboundary includes different life cycle phases (Fig. 6): (ii) theapplication of steel chain and (iii) the end of life phase thatincludes the removal of the steel chain. In this case, the prep-aration phase (i) is not included because, before to apply thesteel chain, the masonry walls are usually restored with otherretrofit techniques such as LRDM and MI (ReLuis 2011).

The (ii) application phase includes two scenarios which arereferred to the method of steel chain elongation that can beexecuted with cold (scenario E) or hot operations (scenario D).In details, in scenario D, it is assumed that the chain is heatedat high temperature in the middle with a welding gas machin-ery until the desired elongation is reached. Scenario E con-siders, instead, the use of a steel sleeve that is placed in themiddle of the steel chain (ReLuis 2011).

2.1.4 GRM retrofit

In this technique, a layer of mortar is applied to the externalsurface of the wall (Fig. 5). A reinforcing system, such as steelgrid, basalt grid, or glass grid, is fixed to the surface by nails orscrews up to covering the entire surface. A second layer ofmortar is then applied to the entire surface of the wall, cover-ing the reinforcing system and fixing it to the structure.

The LCA profile of 1 m2 of grid-reinforced mortar isevaluated; the system boundary includes different life cyclephases (Fig. 6): (i) the preparation of the substrate, (ii) theapplication of grid-reinforced mortar, and (iii) the end of lifephase that includes the demolition of reinforcedmasonry wall.In the preparation phase (i), the wall is thoroughly flushed

with clean water to remove as much dirt, debris, and contam-inants and to pre-saturate the areas that have to be reinforced(ReLuis 2011).

The application phase (ii) is modeled considering threescenarios, referred to the use of different reinforcing systems:scenario G for glass fiber grid, scenario H for basalt fiber grid,and scenario I for steel cord grid.

These investigated scenarios are designed in order toachieve the same structural performance in terms of shearstrength for the retrofitted masonry wall. This condition isachieved by applying a proper number of grid reinforcementlayers to obtain the same tensile strength, i.e., 60 kN/m(Circolaren.617 2009).

In particular, for scenario G, two reinforcement grid layersneed to be applied on the wall external surface since the tensilestrength of the glass grid is 30 kN/m (as an example, see thedatasheet of Mapegrid G120 supplied by Mapei S.p.A). Forscenarios H and I, only one reinforcement grid layer is applied

Fig. 4 SCI retrofit: a side Aviewand b plan view

Fig. 5 GRM retrofit

Int J Life Cycle Assess

on the wall external surface due to their tensile strength ofapproximately 60 kN/m.

2.2 End of life phase: hypothesis

In all the retrofit techniques, the end of life phase (iii) ispresented with regard to two scenarios: disposal (scenario 1)and recycling (scenario 2). These scenarios represent thecommon practice of final disposal of generated waste current-ly applied in Italy.

Both scenarios are computed in order to present, for eachtechnique, the environmental impact of both options. Each ofthe two scenarios can possibly take place in a real case, and thedesign decision process needs to be informed with data relatedto both of them.

Given these consideration, in scenario 1, it is assumed thatall materials (100 % brick and mortar) are dumped in

authorized landfill; in scenario 2, instead, it is assumed that10% of the waste wall materials are landfilled and 90% of thewaste is recycled.

In particular, bricks and mortar could be converted intorecycling aggregates and used as filling materials, on the basisof the information reported in Chen et al. (2011) andWu et al.(2011).

With regard to SCI retrofit option, recycling is applied forthe production of steel (ii) (e.g., used for chain and platemanufacturing) and for the end of life (iii) of the employedsteel. In particular, according to the dataset of Ecoinvent 2.2(Hedemann and König 2007) related to the steel productionprocess, it is estimated that 37 % of the steel is produced inelectric arc furnaces (EAFs) and the remaining 63 % in basicoxygen furnaces (BOFs). Generally, pig iron is used in theBOF; on the contrary, only cold scrap metal is used in theEAF. Given these considerations, in the production of steel (i),

Fig. 6 System boundaries ofretrofit options

Fig. 7 LCA results: mortarcomparison in LRDM retrofitoption

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on average, 30 % of raw materials are replaced by recycledsteel. Similarly, the end of life (iii) scenario includes therecovery of 37 % of steel products that could replace primarysteel material.

For the retrofit technique GRM, scenario 1 includes thegrid landfilling; instead, in scenario 2, it is assumed that thegrids could be re-used, as they are, in other structural engi-neering applications.

2.3 Inventory analysis

In this study, primary and secondary data are used forthe inventory analysis. In particular, primary data areused to model recycling scenarios, steel materialmanufacturing (e.g., chain, plate), and reinforced gridproduction. In order to model recycling scenarios, asmentioned in the last paragraph, the information

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Fig. 8 LRDM retrofit: comparison scenario 1 and scenario 2. a Global warming, b ozone layer depletion, c photochemical oxidation, d acidification, eeutrophication, and f nonrenewable, fossil

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reported in Chen et al. (2011), Wu et al. (2011), andHedemann and König (2007) are used, whereas techni-cal data reported in AFV Beltrame Group (2012) areused to model steel material manufacturing. Finally, infor-mation reported in datasheets of Mapegrid G120 by MapeiS.p.A. are used to model reinforced grid production.

Secondary data, instead, are retrieved from databasesavailable in the SimaPro 7.3 LCA software package. Inparticular, inventory data for building materials, use of

building equipment, transport operation, and electricityare retrieved from Ecoinvent 2.2 database (Hedemannand König 2007).

The amount of materials involved in each retrofit optionalong with the set of construction operations, includingequipment/machinery use, are derived on the basis of com-mon practice and retrofit design according to the structuralrequirements reported in Italian national codes (CNR-DT 2002004; NTC 2008).

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Fig. 9 MI retrofit: comparison scenario 1 and scenario 2. a Global warming, b ozone layer depletion, c photochemical oxidation, d acidification, eeutrophication, and f nonrenewable, fossil

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Several assumptions have been made regarding the trans-port phase:

– The transport distance between construction site andlandfill is supposed to be 20 km.

– The material-supplying site is located at 15 km from theconstruction site.

– The average distance of the workers to the constructionsite is 15 km.

– The transport of the building materials and mobile equip-ment from/to construction site is supposed to be done bylorry, while the transport of building workers is supposedto be done by van.

– For construction material transport, a load factor of 50 %is also considered to take into account that the return tripis donewith an empty lorry (Hedemann and König 2007).

2.4 Impact assessment

The EPD environmental indicators are adopted to representthe environmental impacts of the structural retrofit options.Particularly, the environmental impacts on global warming,ozone depletion, photochemical oxidation, acidification, eu-trophication, and nonrenewable energy are evaluated.

2.4.1 LRDM retrofit

In the case of the LRDM retrofit option, the three mortarscenarios are compared. Figure 8 reports the results of LCAanalysis in terms of EPD categories, when scenario 1 and 2 areconsidered; it can be observed that the major environmentalload, in each of the examined end of life scenarios, is related toscenario B.

Figure 7 shows the environmental profile of the mortarmaterials used, and the results are in agreement with Fig. 8.

Light mortar (scenario B) has the highest environmentalburden in almost all categories due to the use of expanded claymaterials. In fact, the main environmental emissions influenc-ing ozone layer depletion, photochemical oxidation, acidifi-cation, and non-renewable energy categories (methane, sulfur,nitrogen oxide) are linked to the firing and expansion processof clay.

Lime mortar presents, instead, the highest impact in theglobal warming category; it is related to the amount of CO2

emissions mainly due to the decomposition of limestone andcombustion of fossil fuels during cement production; in thiscase, the cement amount is larger than in other scenarios. Theenvironmental results of scenario B reveal that the construc-tion phase is responsible for the major environmental impact,ranging between 70 and 80 % of total impact. These percent-ages are due, in particular, to brick and mortar production.These materials affect the results of the whole constructionphase in percentages of 66 and 23%, respectively.When brickmaterial is analyzed, the energy consumption related to firingprocess involves the major impact; it is estimated, in fact, that1.24 MJ of natural gas are needed to produce 1 kg of productas reported in Ecoinvent 2.2 database report (Hedemann andKönig 2007).

Moreover, the comparison between scenarios 1 and 2 forend of life management of each LRDM retrofit scenariodemonstrates that the recycling of building materials (scenario2) generates environmental benefits in all damage assessmentcategories for all options A, B, and C.

In fact, with regard to the end of life phase, a negativeenvironmental contribution in terms of avoided impact isintroduced; the avoided impact corresponds to brick and mor-tar recycling and is taken into account assuming as “avoidedproduct” the production of virgin aggregates. In fact, suchrecycled aggregates can be used primarily as filling materials,while other possible uses in other engineering applications arereported in UNI EN 13242 (2002). In this way, the emissions

Fig. 10 LCA comparison:LRDM and MI comparison(scenario A)

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and use of resources associated with the production of naturalgravel and sand are subtracted from the environmental burdenof the construction phase.

In addition, as it can be seen in Fig. 8, scenario A is the bestenvironmental option, due the use of the mortar with thelowest impact in the construction phase.

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Fig. 11 SCI retrofit: comparison scenario 1 and scenario 2. a Global warming, b ozone layer depletion, c photochemical oxidation, d acidification, eeutrophication, and f nonrenewable, fossil

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2.4.2 MI retrofit

Figure 9 reports the results of LCA for MI retrofit option,when scenarios 1 and 2 are considered; it can be observed thatthe major environmental load is related to scenario B due tothe same reasons illustrated for the previous technique pre-sented. The environmental assessment of this scenario

reveals that the end of life phase, considering scenario1, is responsible for the major environmental load dueto the disposal of waste materials in landfill. On thecontrary, the construction phase, considering scenario 2,has the highest environmental burden due to the mortarproduction and to the recycling of waste materials pro-vided in the end of life phase.

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Fig. 12 GRM retrofit: comparison scenario 1 and scenario 2. a Global warming, b ozone layer depletion, c photochemical oxidation, d acidification, eeutrophication, and f nonrenewable, fossil

Int J Life Cycle Assess

In fact, the recycling of building materials (scenario 2)generates environmental benefits in all categories for all op-tions A, B, and C. In addition, in all categories, scenario Apresents the lowest environmental burden, due to the lowestenvironmental impact provided by cement mortar.

Finally, the environmental impact of the LRDM and MIretrofit options are compared in Fig. 10 for scenario A. In thiscase, the quantitative unit is the repair of one longitudinalcrack of 1 m of length, 0.02 m of width, and 0.16 m of depthand the system boundary includes only the preparation phase(i) and application phase (ii), while the end of life phase (iii) isexcluded from analysis because it would contribute with equalenvironmental impact for both the options. Approximately 77solid bricks of 11×23×5 cm and 30 kg of mortar are used torestore one longitudinal crack with LRDM and MI retrofitoptions, respectively.

The environmental results depicted in Fig. 10 reveal thatthe environmental impact ofMI is lower than LRDM in all theinvestigated categories mainly because smaller amount ofmaterials is used to restore the crack. Particularly, MI showsan environmental impact 50–65 % lower than the impact ofLRDM.

2.4.3 SCI retrofit

Figure 11 reports the results of LCA of SCI retrofitoption. It can be observed that the major environmentalload is related to scenario E. In fact, the use of a steelsleeve in scenario E influences the environmental re-sults; its environmental impact corresponds to approxi-mately 3 % of total environmental burden if comparedwith the use of welding gas in scenario D.

In addition, the recycling of steel materials (at level of37 %) generates environmental benefits in all environmentalcategories and particularly in global warming and non-renewable categories. The recycling of steel materials, in fact,involves environmental benefits due to avoided impact ofprimary steel production.

2.4.4 GRM retrofit

For this retrofit technique, the three previously de-scribed scenarios are compared. According to Fig. 12(reporting the comparison between each GRM option),when scenario 1 is considered, the I option presents thehighest environmental impact, instead G and H havesimilar environmental loads in all the investigated cate-gories. In particular, all GRM options present similarenvironmental impacts in the end of life phase while,the I option presents the highest environmental burdenin the construction phase. The environmental impact ofconstruction phase of I option is 5–30 % higher thanother GRM options.

In addition, when scenario 2 is considered, the optionpresents the lowest impact mainly due to the end of lifephase. In fact, in the end of life phase, the steel gridrecycling determines environmental benefits in all thecategories; its impact is 30–80 % lower than the impactof scenarios G and H.

3 Conclusions

In the present study, the environmental impact of differenttechnological options for typical retrofit operations on mason-ry structures has been assessed. In particular, four differentstructural options have been examined by means of LCA a:local replacement damaged mortar, mortar injection, steelchain installation, and application of grid-reinforced mortar.

In all the retrofit options, it clearly appears that therecycling of building materials generates environmental ben-efits in all the categories. In particular, the recycling of build-ing materials involves environmental benefits due to avoidedimpact of virgin material production.

In the LRDM and MI retrofit options, the use of lightmortar as a possible scenario (construction phase) is respon-sible for the major environmental impact in all LCA catego-ries. When the LRDM and MI option comparison is done, theresults show that the LRDM option is the major responsiblefor the environmental impact in all the categories.

In the SCI retrofit option, the investigated scenarios pre-sented similar environmental profiles, with the E scenario(cold steel chain elongation) that determines an impact thatis only 3 % larger than the impact of the D scenario for all thecategories.

In the GRM retrofit option, the use of the steel-reinforcedgrid with any recycling at the end of life produces the highestenvironmental impact in all LCA categories. On the contrary,when the reinforced grid is re-used in other structural engi-neering applications, steel GRM option presents the lowestenvironmental impact.

Finally, the authors want to emphasize that the retrofitoptions and related scenarios presented in this paper and thecorresponding environmental results can be used both infuture research activities and in retrofit design stages to assessthe environmental performance of retrofit strategies applied toexisting buildings. This means that different retrofit alterna-tives can be considered and compared in a specific case, byconsidering the constraint of providing the same (minimum)requested structural performance. Indeed, a LCA-based com-parative study can be then conducted on a real case consider-ing the outcomes of this study, i.e., multiplying the obtainedenvironmental impacts by the amount/extension of materialsneeded for the considered retrofit technique, possibly identi-fying the option characterized by the lowest impact.

Int J Life Cycle Assess

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