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Journal of Cleaner Production 29-30 (2012) 46e52

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Journal of Cleaner Production

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A comparative study on the feasible use of recycled beverage and CRT funnelglass as fine aggregate in cement mortar

Tung-Chai Ling a,b, Chi-Sun Poon a,*

aDepartment of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kongb School of civil engineering, University of Birmingham, Edgbaston, Birmingham, United Kingdom

a r t i c l e i n f o

Article history:Received 5 October 2011Received in revised form11 January 2012Accepted 15 February 2012Available online 22 February 2012

Keywords:Cathode ray tubesRecycled funnel glassBeverage glassLead leachingRadiation shieldingMechanical properties

* Corresponding author. Tel.: þ852 2766 6024; faxE-mail addresses: tcling611@yahoo.com, cetcling@

cecspoon@polyu.edu.hk (C.-S. Poon).

0959-6526/$ e see front matter � 2012 Elsevier Ltd.doi:10.1016/j.jclepro.2012.02.018

a b s t r a c t

The rapid development of the electronic industry has led to a growing hazardous waste management anddisposal problem related to the management of cathode ray tube (CRT) waste. This study aimed tocompare the feasibility of using CRT recycled glass: non-treated funnel glass (n-TFG, crushed withouttreatment) and treated funnel glass (TFG, crushed and treated with acid nitric to remove lead on the glasssurface) as fine aggregates in cement mortar. Fresh and hardened properties of the cement mortars,including their x-ray radiation shielding and potential lead leaching were investigated. The mortarprepared with crushed beverage glass (CBG, lead-free) was also evaluated for comparison purposes. Theexperimental results show that the use of glass cullets, irrespective of glass type, improved the fluidityand drying shrinkage but reduced the strength. About 60% enhancement in x-ray radiation shieldingproperty was achieved with the use of 100% CRT glass in the cement mortar owing to the increase ofmortar density due to the presence of lead in the CRT glass. Furthermore, lead leaching (based on TCLPtest) from the mortar samples prepared with the TFG complied with the regulatory limits. The resultshave demonstrated that the CRT glass (an original hazardous material) can be treated, processed, and re-utilized for making cement mortars. The mechanical performance of the cement mortar is comparable tothat made with beverage glass.

� 2012 Elsevier Ltd. All rights reserved.

1. Introduction

One of the biggest technology revolutions in image displays forTV and PC monitors was the change from the cathode ray tube(CRT) type to LCD (liquid crystal display) and LED (light emittingdiode). One challenge posed by the revolution is the need todispose of and manage the growing magnitude of CRT waste(Socolof et al., 2005; Poon, 2008). It was estimated that the amountof CRT TVs required to be disposed of in United States alone wasapproximately 20 million units each year and the amount wasexpected to increase beyond the next 10 years (Jefferies, 2006).Similar situation are also found in most of the developed anddeveloping countries (Nnorom et al., 2011). If the CRT waste is nothandled properly then the lead (or other heavy metals) includedwithin the CRT glass may pose serious soil and ground waterpollution (Ravi, 2011; Cherry and Gottesfeld, 2009; Nnorom andOsibanjo, 2008).

: þ852 2334 6389.inet.polyu.edu.hk (T.-C. Ling),

All rights reserved.

One of the promising ways to identify opportunities for opti-mizing and reducing environmental impact of this CRT waste is toimplement an environmental management system (EMS) stan-dardized by ISO 14001 (Boudouropoulos and Arvanitoyannis, 1999,2000). According to Rahman and Subramanian (2012), a recyclingcompany in Australia (with an ISO 14001 accredited) applied aninnovative technology of disassembly which was able to reclaimvaluable metals for reuse and divert up to 98% (by weight) from thetotal discarded 60,000 CRT monitors collected each year. Also, a lifecycle assessment (LCA) methodology complying with ISO 14040had been proven to be a reliable approach to assess the entire lifecycle of CRT glass from the environmental perspective (in terms ofextraction and treatment of raw materials, production, trans-portation, reuse, recycling and disposal) as well as its economic andsocial point of view (Arvanitoyannis, 2008; Noon et al., 2011;Andreola et al., 2005).

In Hong Kong, a recycling facility has been in existence since2005 by the Environmental Protection Department (EPD) to recyclediscarded old computer monitors and TV sets. In the facility, theexternal components such as electronic, plastic casing and metallicparts are first removed from the computer monitors and TV sets.The funnel and panel glass from the CRT glass is then separated by

Table 1Chemical compositions and physical properties of cement and fly ash.

Chemical compositions (%) Cement Fly ash

Calcium oxide (CaO) 63.15 <3Silicon dioxide (SiO2) 19.61 56.79Aluminium oxide (Al2O3) 7.33 28.21Ferric oxide (Fe2O3) 3.32 5.31Magnesium oxide (MgO) 2.54 5.21Sodium oxide (Na2O) 0.13 0.45Potassium (K2O) 0.39 1.34Sulphur trioxide (SO3) 2.13 0.68Loss on ignition 2.97 3.90

Physical propertiesSpecific gravity 3.16 2.31Blaine fineness (cm2/g) 3519 3960

Table 2Particle size distributions, physical properties and Pb concentration of fineaggregates.

T.-C. Ling, C.-S. Poon / Journal of Cleaner Production 29-30 (2012) 46e52 47

a hot wire separation method. Since the lead content of these twotypes of glass are different, they are processed using two differentrecycling methods. The recycling process of CRT panel glass mainlyinvolves the removal of fluorescent powder present on the innersurface of the glass by suction, and then using a mechanical crusherto break it down into smaller particle sizes in a safe manner. Theglass can be used directly as a clean recycled aggregate inconstruction products due to its low lead content.

As for the funnel glass, since it contains a significant amount oflead (PbO) with an average content of 22e25% by wt., a specificallydesigned treatment process (elution) is required before it can bedisposal to landfills or reused as a recycled material. The recyclingprocess for the funnel glass involves crushing, acid washing andwater rinsing. The lead present on the surface of crushed funnelglass is removed by immersing the crushed glass cullets (<10 mm)in a bath of 5% nitric acid (HNO3) solution for 3 h. After that, thetreated funnel glass (TFG) is removed from the nitric acid bath andthoroughly rinsed using tap water to remove the remaining acid.The TFG produced is typically considered safe because the leach-able lead concentration is below the toxicity characteristic leachingprocedure (TCLP) limit of 5 mg L�1 as per the requirement of the USEnvironmental Protection Department (1992).

A number of previous studies have been conducted to investi-gate the possibility of using recycled aggregates derived fromdiverse sources as fine aggregates replacement in cement mortarsor concrete for diverse purposes (Ling et al., 2011; Ho et al., 2012;Mohammed et al., 2012; Pelisser et al., 2012; Richardson et al.,2012; Bravo and de Brito, 2012). It was found that the use of glassaggregate in mortar slightly reduced the strength properties, butthis negative effect could be reduced when finer glass particles(700 mm or less) were employed (Shi et al., 2005). This is becausethe pozzolanic property of fine glass powder and its filler role cansignificantly improve the micro-structural and mechanical prop-erties of the cement mortar (Corinaldesi et al., 2005). It is generallyagreed that utilizing recycled beverage glass aggregate in mortar isa promising and effective method for waste glass recycling (Lingand Poon, 2011b; Ling et al., 2011). Although a preliminary studyhas been conducted by the authors to assess the feasible use ofcrushed and treated CRT funnel glass for the production of cementmortar (Ling and Poon, 2011b), a systematic comparison of theeffect of using untreated CRT and other types of glass on theproperties of the produced cement mortar is still relatively limited.

The objective of this study is to investigate the feasible use ofuntreated funnel glass (n-TFG, crushed without treatment) as fineaggregates in cement mortar. The effect of using n-TFG as 50% and100% replacement of total sand volume on the fresh and hardenedproperties, and the x-ray radiation shielding ability of the cementmortar were assessed. The expansions due to alkaliesilica reaction(ASR) and potential leachability of lead from the cement mortarwere also studied. The cement mortar prepared with treated funnelglass (TFG, crushed and treated with nitric acid to remove lead onthe glass surface) and crushed beverage glass (CBG) was alsostudied for comparison purposes.

Sieve size (mm) Percentage passing (%)

River sand n-TFG TFG CBG

5.00 99.5 99.9 99.2 99.62.36 97.6 87.1 73.3 87.41.18 89.8 59.0 43.1 53.50.60 75.3 28.6 18.9 27.60.30 39.5 7.6 4.5 12.70.15 3.7 0.6 0.3 5.1

Fineness modulus 1.94 3.17 3.61 3.14Relative density (g/cm3) 2.62 3.10 2.99 2.49Water absorption (%) 0.87 w0 w0 w0TCLP leachable Pb concentration (mg/L) e 373.5 2.2 e

2. Experimental details

2.1. Materials

2.1.1. Cementitious materialsOrdinary Portland cement (OPC) of strength class 52.5R

complying with American Society of Testing Materials (ASTM) TypeI was used as the primary cementing material in this study. Fly Ashcomplying with ASTM class F was used as a suppressor agent toprevent expansion due to alkaliesilica reaction (Lee et al., 2011).

The chemical compositions and physical properties of the cemen-titious materials are given in Table 1.

2.1.2. Fine aggregatesAll the fine aggregates investigated in this study were of particle

sizes less than 5 mm. River sand with a fineness modulus (FM) of2.09 was used as the natural fine aggregate (as a control) in thesand-mortar mix. The CRT recycled funnel glass with relativelyhigher fineness modulus than sand (FM ¼ 3.17 for n-TFG andFM ¼ 3.61 for TFG) was obtained from a local CRT Waste RecyclingCentre. TCLP results of both CRT funnel glass are presented inTable 2. Crushed beverage glass (CBG) derived from post-consumerbeverage bottles was obtained locally from a waste glass recycler.CBG had an of fineness modulus of 3.14. The particle size distri-butions and physical properties of all the fine aggregates used arepresented in Table 2. Fig. 1 shows the photograph of sand, recycledbeverage and CRT glasses.

2.2. Mix proportions

All the mortar mixes were prepared with an aggregate-to-cementitious material ratio of 2.5 and a water-to-cementitiousmaterial ratio of 0.45. These mix proportions are common forcement mortar applications (Ling and Poon, 2011b; Choi et al.,2009). 25% of the OPC was replaced by fly ash to mitigate thepotential of ASR expansion (Lee et al., 2011). Including the control(sand) mortar mix for comparison, a total of seven mortar mixeswere prepared and investigated. The three different types of glassn-TFG, TFG, and CBGwere used to replace 50% and 100% of the sand(by volume) in the mortar mixes. All the mix proportion mixturesare shown in Table 3.

Fig. 1. Photograph of sand, recycled beverage and CRT glasses with particle size less than 5 mm.

T.-C. Ling, C.-S. Poon / Journal of Cleaner Production 29-30 (2012) 46e5248

2.3. Sample preparation

The proportioned materials in all the mortar mixes were mixedfor 5min using a standard laboratory rotating drum typemixer. Thefresh mortar mix was then put into steel moulds (size40 � 40 � 160 mm and size 25 � 25 � 285 mm) in two layers ofsimilar depth. Vibration was applied by a mechanical vibratingtable after filling up each layer. After casting, the mortar specimenswere covered with a plastic sheet in the laboratory at 23 � 3 �C for24 h. After 1 day, the mortar specimens were demoulded and thenwater cured at an average temperature of 23 � 3 �C until the day oftesting.

2.4. Test methods

2.4.1. Fresh propertiesThe flow table test was used for the determination of fluidity of

fresh mortar mixes. The procedures of the flow table test followedASTM C 1437 (2007b).

2.4.2. Hardened densityThe hardened density was determined according to ASTM C 642

(2006). The presented results are the average values of the threespecimens.

2.4.3. Water absorptionThe water absorption values of the specimens were determined

according to ASTM C 642 (2006) and the results are the averagevalues of the three specimens.

2.4.4. Flexural strengthThe flexural strength of the specimens was tested at 1, 4, 7, 28

and 90 days after casting based on ASTM C 348 (2008a). The mortarbar specimens (40 � 40 � 160 mm prisms) were placed undera central line load with simple support over a span of 120 mm. Adisplacement rate of 0.1 mm min�1 was used. The reported resultsare the average values of the three specimens.

Table 3Mix proportions of mortar mixtures (kg/m3).

No Mix notation Cementitious materials Fine aggregate Water

Cement Fly ash Sand n-TFG TFG CBG

1 Controlmortar (CM)

456 152 1519 0 e e 273

2 n-TFG50 456 152 759 867 e e 2733 n-TFG100 456 152 0 1734 e e 2734 TFG50 456 152 759 e 867 e 2735 TFG100 456 152 0 e 1734 e 2736 CBG50 456 152 759 e e 722 2737 CBG100 456 152 0 e e 1446 273

2.4.5. Equivalent compressive strengthAccording to ASTM C 349 (2008b), the broken pieces (portions

of the prisms broken in the flexure strength test) were used for theequivalent compressive strength test. The broken portions ofprisms used had a length of not less than 65mmandwere free fromcracks, chipped surfaces, or other obvious defects.

2.4.6. Drying shrinkageDrying shrinkage valuemeasurements on the specimens (size of

25 � 25 � 285 mm) were conducted according to the proceduresstated in a modified British Standard (BS ISO-Part 8, 2009) method.After demoulding, the length and initial reading (regarded as zeroreading) of the prisms was measured. The specimens were thentransferred to a drying environmental chamber at a temperature of23 �C with a relative humidity of 50%. Subsequent readings weretaken at 1st, 4th, 7th, 28th and 90th days.

2.4.7. Expansion due to alkaliesilica reaction (ASR)Three 25 � 25 � 285 mm mortar specimens were used for the

alkaliesilica reaction (ASR) test based on ASTM C1260 (2007a).After 28 days of water curing, a zero reading was taken after furtherstoring the prisms in distilled water at 80 �C for 24 h. The mortarbars were then transferred and immersed in 1 N sodium hydroxide(NaOH) solution at 80 �C until testing time at 1st, 4th, 7th, 14th and28th days.

2.4.8. X-ray radiation shieldingThe x-ray radiation shielding test was performed in an x-ray

laboratory designed for medical diagnostic examination. Thelaboratory was installed with a medium frequency x-ray unit(Toshiba, KXO-30R). The distance between the target of the diag-nostic x-ray tube (DXB-0324CS-A) and the test samples(100 � 100 � 5 mm) was kept at 700 mm. The radiation dose ata point in free air beneath the samples was measured by a 6 c.c.ionization chamber linked to a radiation monitor controller (Model9015, Radcal Corporation). The sensor was placed 100 mm beneaththe test samples.

2.4.9. Toxicity characteristic leaching procedure (TCLP)The toxicity characteristic leaching procedure (TCLP) test was

used to identify the leaching of lead from the tested samples. TheTCLP test was conducted according to the US EnvironmentalProtection Agency method 1311 (1992). The samples were takenafter the mechanical testing at the 28th day and were crushed topass through a 10 mm sieve before the test. This is intended tosimulate the potential lead leaching to assess whether thematerial would be classifiable as hazardous waste. An extractionsolution with a pH value of 2.88 was prepared using glacialacetic acid. As per the TCLP test protocol, 400 mL extractionsolution was added into plastic containers containing 20 g ofcrushed samples and the mixtures were then tumbled by

0

50

100

150

200

250

n-TFG mortar TFG mortar CBG mortar

Flow

tabl

e va

lue

(mm

)

0% 50% 100%

Fig. 2. Effect of n-TFG, TFG and CBG on the flow table value of the fresh cementmortars.

0

2

4

6

8

10

n-TFG mortar TFG mortar CBG mortar

Wat

er a

bsor

ptio

n (%

)

0% 50% 100%

Fig. 4. Effect of n-TFG, TFG and CBG on water absorption of cement mortars.

T.-C. Ling, C.-S. Poon / Journal of Cleaner Production 29-30 (2012) 46e52 49

a rotary shaker. After 18 h, the leachable heavy metals in thesolution were then analyzed using atomic absorption spectro-photometer (AAS).

3. Results and discussion

3.1. Fresh properties

Fig. 1 shows the flow table test results of the freshmortar mixes.The flow table values increased with increasing glass content,regardless of the glass type. The improvement in fluidity of thefresh mortar could be due to the impermeable and smooth surfaceof the glass cullets used (Kou and Poon, 2009). Comparing theinfluence of glass type, the flow values of CRT (both the n-TFG andTFG)mortars were slightly higher than CBGmortar, probably due tothe higher fineness modulus of recycled CRT glass that led toa reduction in total surface area per unit volume which requiredless water to enwrap the solid particle.

3.2. Hardened density

Fig. 2 shows the effect of n-TFG, TFG and CBG content on thehardened density of cement mortars. The hardened density of n-TFG and TFG mortars increased with increasing glass content. Thehardened density for n-TFG100 and TFG100 mortar mixes were2,546 kg m�3 and 2472 kg m�3, an increase of 14.6% and 11.2% incomparison to the control mortar, respectively. In other words, thedensity of the mortars was increased by 7.3% and 5.8% for every 50%replacement of sand n-TFG and TFG used in the cement mortar,

1800

2000

2200

2400

2600

n-TFG mortar TFG mortar CBG mortar

Har

dene

d de

nsity

(kg/

m3)

0% 50% 100%

Fig. 3. Effect of n-TFG, TFG and CBG on hardened density of cement mortars.

respectively. The higher density could be related to the relativelyhigh specific gravity of lead present in the funnel glass. As noticed,the density of TFG mortars was slightly lower than n-TFG mortars.This is understandable because the TFG cullets were slightly lighterthan n-TFG cullets due to the removal of lead through the acidtreatment process. On the other hand, the hardened density for thecontrol (sand) mortar and CBG mortar were lower.

3.3. Water absorption

The water absorption results are shown in Fig. 3. The controlmortar shows the highest water absorption value and the waterabsorption reducedwith increasing glass content. This could be dueto the nature of glass which does not absorb water.

3.4. Flexural and compressive strength

The flexural strength test results are shown in Fig. 4. The 90-dayflexural strength of the control mortar, n-TFG50, TFG50 and CBG50mortars were 9.0MPa, 6.7MPa, 7.9MPa and 7.8MPa, respectively. Itcan be seen that the flexural strength of mortar was reduced byapproximately 13% when 50% of the sand was replaced by TFG andCBG, respectively. The strength reduction is probably due to thepoorer bond strength between the smooth surface of the glasscullets and the cement paste (Ismail and AL-Hashmi, 2009; Lingand Poon, 2011a). As for n-TFG50, a greater reduction (approxi-mately 25%) in 90-day flexural strengthwas observed, probably dueto the retardation effect of lead on the hydration of cement (Shiet al., 2005; Cheeseman and Asavapisit, 1999). The results show

Fig. 5. Flexural strength of cement mortars with 50% and 100% n-TFG, TFG and CBG.

Fig. 6. Compressive strength of cement mortars with 50% and 100% n-TFG, TFG andCBG.

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0 5 10 15 20 25 30Curing age (day)

ASR

exp

ansio

n (%

)

Contro mortar

n-TFG50

TFG50

CBG50

n-TFG100

TFG100

CBG100

Fig. 8. Expansion due to alkaliesilica reaction of cement mortars with 50% and 100%n-TFG, TFG and CBG.

T.-C. Ling, C.-S. Poon / Journal of Cleaner Production 29-30 (2012) 46e5250

that the flexural strength was further reduced by 19.5% as the n-TFGcontent was increased from 50% to 100%.

Fig. 5 shows the compressive strength results. As can be seen,a similar trend to that of flexural strength was observed. Thedetrimental effect of n-TFG was again shown, particularly at the100% replacement level.

3.5. Drying shrinkage

Fig. 6 shows the effect of glass type and replacement level on thedrying shrinkage of the cement mortars. During the first 4 days, thedifference of drying shrinkage of all the cement mortars wasinsignificant. From the 7th up to the 90th day, the positive effect ofusing glass cullets as fine aggregates in reducing the dryingshrinkage became more obvious. The possible reason for this maybe the lower absorption capacity of the glass cullet when comparedwith natural river sand.

Comparing Fig. 6(a) and (b), it can be clearly observed that thedrying shrinkage decreased with increasing replacementpercentage of glass cullets. This is consistent with the results of Lingand Poon (2011b). For a given replacement level, the mortarprepared by using n-TFG showed the greatest reduction in dryingshrinkage. This might be due to the retardation effects of lead oncement hydration and is consistent with the strength results.

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0 20 40 60 80 100

Curing age (day)

Dry

ing

shri

nkag

e (%

)

Contro mortarn-TFG50TFG50CBG50n-TFG100TFG100CBG100

Fig. 7. Drying shrinkage of cement mortars with 50% and 100% n-TFG, TFG and CBG.

3.6. Expansion due to alkaliesilica reaction

Fig. 7 shows the expansion due to alkaliesilica reaction (ASR) ofthe cement mortars. It can be clearly noticed that the expansion ofthe mortar bars containing glass cullets was higher than that of thecontrol mortar. The higher the glass content the higher theexpansion. This is consistent with the results reported by Park andLee (2004).

For a given glass content, the ASR expansion of the n-TFG andTFG mortars was relatively higher than that of the CBG mortar. Areason for this is believed to be the higher solubility (higher %weight loss in 1 N NaOH) of CRT glass than that of CBG glass,resulting in higher amount of dissolved glass available in solutionfor ASR gel formation. This results and hypothesis had also beenconfirmed by other studies (Saccani and Bignozzi, 2010; Trocellieret al., 2005). The highest ASR expansion was found in the n-TFG100 mortar mix. Except for the n-TFG100 mortar, at the age of14 days, all the mortar bar mixes showed ASR expansion below thepermissible limits (0.10%) according to ASTM C1260 Fig. 8.

3.7. Radiation shielding properties

The X-ray radiation shielding properties of the mortar mixes areshown in Table 4. The linear attenuation coefficient of the sampleswas significantly increased when sand was replaced by either n-TFG or TFG. This could be attributed to the dense atomic structurein both types of CRT funnel glass actively interacting with x-rayradiation, thus reducing its energy and the depth of radiationpenetration (Calabrese et al., 1996). However, the mortar mixesprepared with CBG had no significant effect on the attenuationcoefficient.

Table 4Linear attenuation coefficients, half-value layer and tenth-value layer of cementmortars.

Sample Linear attenuationcoefficient (mm�1)

Thickness (mm)1 mm lead Eq.

HVL (mm) TVL (mm)

Standardlead sheet

4.010 1.0 0.2 0.6

CM 0.069 57.7 10.0 33.1n-TFG50 0.121 33.2 5.7 19.1n-TFG100 0.171 23.4 4.0 13.4TFG50 0.118 34.1 5.9 19.6TFG100 0.167 24.1 4.2 13.8CBG50 0.069 58.2 10.1 33.4CBG100 0.069 58.5 10.1 33.6

Table 5TCLP results of crushed mortar samples.

Number Crushed mortar sample Pb (mg/L)

1 Control mortar 0.412 n-TFG50 14.653 n-TFG100 32.724 TFG50 0.545 TFG100 0.756 CBG50 0.467 CBG100 0.57

T.-C. Ling, C.-S. Poon / Journal of Cleaner Production 29-30 (2012) 46e52 51

The half-value layer (HVL) and tenth-value layer (TVL) were alsocomputed, and they show that the HVL provided by the n-TFG100and TFG100 mortars were about 4.0 mm and 4.2 mm, respectively,which was about 60% more than the attenuation provided by thecontrol sand mortar. This shows that the mortar prepared with therecycled funnel glass had a superior performance in shieldingagainst the x-ray radiation.

3.8. Lead leaching

Table 5 shows the TCLP test results for all types of cementmortar. The results showed that the leaching of lead from thecontrol, TFG and CBG mortars regardless of replacement glasscontent was below the permissible limit of 5 mg L�1.

Comparing the original concentration of the leachable lead fromuntreated funnel glass alone (373.5 mg L�1) shown in Table 2, thelead leaching for crushed n-TFG50 and n-TFG100 mortar sampleswas significantly reduced to 14.7 and 32.7 mg L�1, which indicatesthat the alkaline environment in the cement mortar matrix couldprovide a medium to immobilize the lead to some extent. Thesevalues were still above the permitted limit of 5 mg L�1. But furtherreduction of lead leaching was realized by pre-treating the crushedfunnel glass by acid washing. Alternatively, a higher percentage offly ash and/or ground blast furnace slag can be used in the cementmortar mixes to further enhance the immobilization of Pb toprevent leaching (Qiao et al., 1999; Rha et al., 2000).

4. Conclusions

Crushed CRT funnel glass and other types of beverage glasseswere tested for potential use as a fine aggregate to replace naturalriver sand by volume (50% and 100%) in cement mortars. Based onthe experimental investigation, the following conclusions can bedrawn:

1. Incorporation of impermeable glass cullets as fine aggregates incement mortar increased the fluidity of freshmortar mixes andreduced the water absorption and drying shrinkage of thecement mortars.

2. The higher the glass cullets used for replacing sand in thecement mortar the lower the flexural and compressivestrengths. This is due to the weak bonding between the glasscullets and the cement paste. n-TFG mortar showed the loweststrength due to the retardation effect of lead on cementhydration.

3. Increasing glass cullets content led to an increase in theexpansion due to ASR. All the cement mortars satisfied thepermissible limits of 0.10% at the 14th day, except the mortarcontaining 100% n-TFG cullets.

4. The performance of the control mortar in radiation shieldingwas similar to that of the CBGmortar. However, the inclusion ofCRT funnel glass (n-TFG and TFG) increased the hardened

density of the mortar which in turn enhanced the shieldingproperties.

5. The alkaline environment in the cement mortar matrix wasable to reduce the leaching of lead. The TCLP results of thecement mortar prepared with the treated CRT glass compliedwith the regulatory standard.

6. For the untreated CRT funnel glass, adjustments to the cementbinders used is necessary to provide additional immobilizationof lead to satisfy the TCLP limit.

Acknowledgement

The authors would like to thank the Environment and Conser-vation Fund and the Woo Wheelock Greed Fund, and The HongKong Polytechnic University for funding support.

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