Use of Aggregates From Recycled Construction and Demolition Waste in Concrete

Resources, Conservation and Recycling 50 (2007) 71–81

Use of aggregates from recycled constructionand demolition waste in concrete

Akash Rao a, Kumar N. Jha b, Sudhir Misra a,∗a Department of CE, IIT Kanpur, Kanpur 208016, India

b Department of CE, IIT Delhi, New Delhi 110016, India

Received 2 August 2005; received in revised form 23 April 2006; accepted 24 May 2006Available online 7 July 2006

Abstract

Construction and Demolition (C&D) waste constitutes a major portion of total solid waste pro-duction in the world, and most of it is used in land fills. Research by concrete engineers has clearlysuggested the possibility of appropriately treating and reusing such waste as aggregate in new con-crete, especially in lower level applications. This paper discusses different aspects of the problembeginning with a brief review of the international scenario in terms of C&D waste generated, recycledaggregates (RA) produced from C&D waste and their utilization in concrete and governmental ini-tiatives towards recycling of C&D waste. Along with a brief overview of the engineering propertiesof recycled aggregates, the paper also gives a summary of the effect of use of recycled aggregateon the properties of fresh and hardened concrete. The paper concludes by identifying some of themajor barriers in more widespread use of RA in recycled aggregate concrete (RAC), including lackof awareness, lack of government support, non-existence of specifications/codes for reusing theseaggregates in new concrete.© 2006 Elsevier B.V. All rights reserved.

Keywords: Construction and demolition waste; Waste management; Recycling; Recycled aggregates; Recycledaggregate concrete; Durability

∗ Corresponding author. Tel.: +91 512 2597346; fax: +91 512 2597395.E-mail addresses: akash [email protected] (A. Rao), [email protected] (K.N. Jha), [email protected]

(S. Misra).

0921-3449/$ – see front matter © 2006 Elsevier B.V. All rights reserved.doi:10.1016/j.resconrec.2006.05.010

mailto:[email protected]



dx.doi.org/10.1016/j.resconrec.2006.05.010

72 A. Rao et al. / Resources, Conservation and Recycling 50 (2007) 71–81

1. Introduction

Preservation of the environment and conservation of the rapidly diminishing naturalresources should be the essence of sustainable development. Continuous industrial devel-opment poses serious problems of construction and demolition waste disposal (Topcu andGuncan, 1995). Whereas on the one hand, there is critical shortage of natural aggregates(NA) for production of new concrete, on the other the enormous amounts of demolishedconcrete produced from deteriorated and obsolete structures creates severe ecological andenvironmental problem (Chandra, 2004, 2005). One of the ways to solve this problem isto use this ‘waste’ concrete as aggregates (Khalaf et al., 2004). Such ‘recycled’ aggregatecould also be a reliable alternative to using natural aggregates in concrete construction. Alsothere are instances of imposition of levy for disposal of such waste in landfill, (Gilpin et al.,2004).

Initially, recycling of demolition waste was first carried out after the Second World War inGermany (Khalaf et al., 2004). Since then, research work carried out in several countries hasdemonstrated sufficient promise for developing use of construction waste as a constituent innew concrete. Construction and demolition (C&D) waste could be broken concrete, bricksfrom buildings, or broken pavement. Thus, Recycled Aggregate (RA) could come from thedemolition of buildings, bridge supports, airport runways, and concrete roadbeds. Concretemade using such aggregates is referred to as recycled aggregate concrete (RAC).

An effort has been made in this paper to present a summary of the use of recycled aggre-gates in the construction industry in different countries, and describe the salient propertiesof RA and RAC, especially in relation to strength and durability. The paper also brieflydiscusses the barriers in promoting more widespread use of RAC.

2. Construction and demolition waste management

2.1. United States of America (Gilpin et al., 2004)

Of the approximately 2.7 billion metric tonnes of aggregate currently used in the USA,the pavements account for 10–15%, whereas other road construction and maintenance workconsumes another 20–30%, and the bulk of about 60–70% aggregates are used in structuralconcrete. RA in the US is produced by natural aggregate producers, contractors and debrisrecycling centers, which have a share of 50%, 36% and 14%, respectively. Incentives fortransportation of waste concrete and processed aggregates from production sites are givento promote use of RA, though a large part of the production is suitable only as fill orconstruction base.

2.2. Japan (Kawano, 2003)

Although Japan has a history of more than a quarter of a century of research on thereuse of demolished concrete for concrete, yet relatively little concrete has been recycledwith the primary reason being non-acceptance of concrete not complying with JIS A-5308,which lays down specifications for ready mixed concrete. In 1991, the Japanese government

A. Rao et al. / Resources, Conservation and Recycling 50 (2007) 71–81 73

established the Recycling Law, which required relevant ministries to nominate materialsthat they must control and to encourage the reuse and recycling of those materials undertheir responsibility. The former Ministry of Construction (MOC) nominated demolishedconcrete, soil, asphalt concrete, and wood as construction by-products. The MOC presentedthe “Recycle 21′′ program in 1992, which specifies numerical targets for recycling of severalkinds of construction by-products. Further, in April 1994, “Tentative quality specificationsfor reusing materials from demolished concrete for construction works” was issued byMOC. As a result of these initiatives, against a target of 90% recycling ratio, actual resultsimproved from a mere 48% in 1990 to almost 96% in 2000, mostly as sub-base material inroad construction.

2.3. EU Union (European Commission and Report, 1999; European UnionDirectorate General Environment, 2000; LUC Report, 1999; Winter and Hendersonb,2003; Lauritzen, 2004)

It is estimated that the annual generation of C&D waste in the EU could be as muchas 450 million ton, which is the largest single waste stream, apart from farm waste. Evenif the earth and some other wastes were excluded, the construction and demolition wastegenerated is estimated to be 180 million tons per year, and considering a population in ofapproximately 370 million, the per capita annual waste generation is about 480 kg.

Though clear figures about recycling are not available for individual countries in EU,an EU study calculated that an average of 28% of all C&D waste was recycled in thelate 1990s. Most EU member countries have established goals for recycling that rangefrom 50% to 90% of their C&D waste production, in order to substitute natural resourcessuch as timber, steel and quarry materials. Recycled materials are generally less expensivethan natural materials, and recycling in Germany, Holland and Denmark is less costly thandisposal.

UK consumed around 330 million tonnes of aggregates in 1989 of which only about 10%were recycled materials. For England only, it has been reported that in 2001, 220 milliontonnes of aggregates were used of which a quarter were recycled materials. Constructionand demolition waste in England and Scotland make up about two thirds and half of recycledaggregates, respectively.

Realizing the importance of C&D waste, the Scottish Executive Development Depart-ment (SEDD) commissioned research to gather information on the level of use of RA. Itwas found that the total estimated quantity land filled by all sites was approximately 4173kilotonnes, of which 44% was mixed construction and demolition waste, clean soil (34%),contaminated soil (13%), and contaminated construction and demolition waste and asphalt(9%). Among these, 19% of the mixed construction and demolition waste was reused/recycled.

2.4. Bulgaria (Zaharieva Hadejeiva et al., 2003)

Modernization and construction of infrastructural facilities such as roads, bridges, munic-ipal and industrial structures, since 1990s, gave rise to a large amount of construction waste,but in 2000, of the 22% of the total expenditure on environmental protection and rehabilita-


tion, only 0.5% was spent on management of such waste. Efforts are underway by agenciesincluding the Municipality of Sofia, and the Bulgarian Academy of Sciences, besides theMinistry of Environment and Water Resources towards better C&D utilization. Thougha pilot project, called “Recycled Concrete Aggregates”, submitted in collaboration withUniversities in northern France, Krupp Hazemag Group and RMN recycling company onproducing of recycled aggregates from rejected panels could not be funded under the NATOprogramme titled “Science for Peace”, it was highly appreciated by legislative institutions,local authorities, developers, construction companies, etc.

2.5. Hongkong and Taiwan

Hong Kong and Taiwan have also initiated programmes to promote C&D waste utilizationin new concrete. About 14 million tons of (C&D) is generated in Hong Kong each year. In thepast, the inert portion of this material was reused in land reclamation (Fong Winston et al.,2002). However, due to increasing opposition most of these projects have been either delayedor drastically scaled-down. In 2002, a pilot C&D materials recycling facility, with a handlingcapacity of 2400 tonnes per day was established by the Hong Kong SAR government toproduce RA for use in government projects and relevant R&D work. The facility producesmaterial for rockfill and both coarse and fine RA. Only crushed rocks and concrete are usedin this facility as part of quality control measures, which include screening out contaminantssuch as bricks and tiles, and a daily sampling and testing of products. The plant has alreadyproduced 240,000 tons of high quality RA. As of the end of October 2003, more than 10projects involving reinforced pile caps, ground slabs, beams and parameter walls, externalbuilding and retaining walls, and mass concrete have consumed over 22,700 m3 of concreteusing RA.

In Taiwan, a comprehensive plan for management of C&D waste was initiated only in1999, after the severe in earthquake in Central Taiwan caused severe structural damage toabout 100,000 dwellings (Huang et al., 2002). It was expected that C&D waste in excessof 30 million tons would be generated during rehabilitation of damaged structures. Theplan required an immediate subsidiary program and a complete quality assurance/qualitycontrol system to support the private sectors, and establishing pilot sorting plants. Theseplants recycle about 80% of the material used in landfills and 30% of the material used asroad base in Taiwan.

3. Properties of aggregate made from C&D waste

Recycled concrete aggregate could be produced from (a) recycled precast elements andcubes after testing, and (b) demolished concrete buildings. Whereas in the former case, theaggregate could be relatively clean, with only the cement paste adhering to it, in the lattercase the aggregate could be contaminated with salts, bricks and tiles, sand and dust, timber,plastics, cardboard and paper, and metals. It has been shown that contaminated aggregateafter separation from other waste, and sieving, can be used as a substitute for natural coarseaggregates in concrete (Nagataki et al., 2004). As with natural aggregate, the quality ofrecycled aggregates, in terms of size distribution, absorption, abrasion, etc. also needs to


be assessed before using the aggregate. Some of the important properties of such recycledaggregate are discussed in the following paragraphs.

3.1. Size distribution

It has been now generally accepted that, recycled aggregates, either fine or coarse, canbe obtained by primary and secondary crushing and subsequent removal of impurities.Generally, a series of successive crushers are used, with oversize particles being returned tothe respective crusher to achieve desirable grading. The best particle distribution shape isusually achieved by primary crushing and then secondary crushing, but from an economicpoint of view, a single crushing process is usually most effective. Primary crushing usuallyreduces the C&D concrete rubble to about 50 mm pieces and on the way to the secondcrusher, electromagnets are used to remove any metal impurities in the material (Corinaldesiet al., 2002). The second crusher is then used to reduce the material further to a particle sizeof about 14–20 mm. Care should be taken when crushing brick material because more finesare produced during the crushing process than during the crushing of concrete or primaryaggregates.

3.2. Absorption

The water absorption in RA ranges from 3 to 12% for the coarse and the fine fractions(Jose, 2002; Katz, 2003; Rao, 2005) with the actual value depending upon the type ofconcrete used for producing the aggregate. It may be noted that this value is much higherthan that of the natural aggregates whose absorption is about 0.5–1%. The high porosity ofthe recycled aggregates can mainly be attributed to the residue of mortar adhering to theoriginal aggregate.

This, in fact, also affects the workability and other properties of the new concrete mixas discussed separately.

3.3. Abrasion resistance

Very limited literature is available on the abrasion resistance of RA. However, studieson the use of such aggregates as sub-base in flexible pavements show promising results.These recycled aggregates have also been used in generating concrete that is further usedin rigid pavements. As discussed earlier in the paper, they are extensively used in USA, UKand other countries as new material for rigid pavements (Gilpin et al., 2004; Khalaf et al.,2004).

4. Properties of concrete made with recycled aggregate

Concrete mixes using RA can be designed in much the same way as those using NA,provided the extra absorption in the former is appropriately accounted for when determiningthe unit water content. The salient features of the recommendations of the RILEM committee


(RILEM, 1994) for proportioning of RAC are given below:

• When designing a concrete mix using recycled aggregate of variable quality, a higherstandard deviation should be employed in order to determine a target mean strength basedon a required characteristic strength.

• When coarse recycled aggregate is used with natural sand, it may be assumed at thedesign stage, that the free w/c ratio required for a certain compressive strength will bethe same for RAC as for conventional concrete.

• For a recycled aggregate mix to achieve the same slump, the free water content will beapproximately 5% more than for conventional concrete.

• The sand-to-aggregate ratio for RAC is the same as when using NA.• Trial mixes are mandatory and appropriate adjustments depending upon the source and

properties of the RA should be made to obtain the required workability, suitable w/cratio, and required strength, of RAC.

4.1. Properties of fresh recycled aggregate concrete (RAC)

The workability of RAC for the same water content in the concrete is lower as reported bymany researchers, especially when the replacement levels exceed 50% (Topcu and Sengel,2004). In order to improve the workability, certain measures in the direction of changing themoisture condition of the RA, have been suggested (Oliveira et al., 1996; Poon et al., 2002,2004). In another study several concrete mixes were prepared with varying methods ofrecycled coarse aggregate preparation, in terms of saturation. It was found that, extra watercorresponding to absorption of the aggregate mixed during concrete preparation producedthe most consistent results as far as workability is concerned (Rao, 2005).

The air content of the RAC is slightly higher (∼4% to ∼5.5%) than concrete made withNA (Katz, 2003) at 100% replacement. This increased air content could be attributed to thehigher porosity of the RA. The bulk density of fresh concrete made with natural aggregatesis in the range of ∼2400 kg/m3, whereas the concrete made with recycled aggregates issignificantly lighter, ∼2150 kg/m3, regardless of the type of cement (Topcu and Guncan,1995; Katz, 2003). The lower density is the result of the specific gravity of the aggregates,which is related to the type of concrete used for producing the aggregate. In addition,increased air content in the recycled concrete, leads to an additional reduction in the densityof the fresh concrete.

4.2. Properties of hardened RAC

4.2.1. Compressive strengthThough researchers have reported a reduction in strength in RAC, it should be noted that

the extent of reduction is related to the parameters such as the type of concrete used formaking the RA (high, medium or low strength), replacement ratio, water/cement ratio andthe moisture condition of the recycled aggregate (Crentsil et al., 2001; Ajdukiewicz andKliszczewicz, 2002). For example, Katz found that at a high w/c ratio (between 0.6 and0.75), the strength of RAC is comparable to that of reference concrete even at a replacementlevel of 75% (Katz, 2003). Rao found the strength of RAC and reference concrete to be


comparable even at 100% replacement, provided that the water–cement ratio was higherthan 0.55 (Rao, 2005). However, as the water–cement ratio is reduced to 0.40, the strengthof RAC was only about 75% of the reference mix (Rao, 2005).

Apart from the water–cement ratio, the moisture condition of the RA also appears toaffect the compressive strength. Limited work has been reported attempting to relate thestrength to the condition of the aggregates (oven dried, air dried, saturated surface dry, etc.),though the findings are inconclusive (Rao, 2005; Poon et al., 2004).

4.2.2. Flexural and tensile strengthThe ratio of the flexural and the splitting strengths to the compressive strength is in the

range of 16–23% and 9–13%, respectively (Katz, 2003). These values are about 10–15%lower compared to the recommendations of ACI 363R. A study by Rao, shows a reductionin strength of 15–20% compared to reference concrete at 100% replacement (Rao, 2005). Inanother study, where the direct tensile strength of concrete was determined, it was found thatdifference in the tensile strength of RAC and reference concrete at 28 days was less than 10%(Ajdukiewicz and Kliszczewicz, 2002). Studies have also shown that use of supplementarycementitious admixtures, such as silica fume, etc. helps improve the properties of RAC(Ajdukiewicz and Kliszczewicz, 2002).

4.2.3. Bond strengthVery limited work on bond strength of RAC has been done. Nevertheless, it has been

reported that, the effect of use of RA on the bond stress at failure is quite small compared tofactors such as the type of bars used (plain rounds or ribbed bars). A reduction of upto 10% inthe bond strength of the RAC has been reported at 100% replacement by RA (Ajdukiewiczand Kliszczewicz, 2002).

4.2.4. Modulus of elasticityThe modulus of elasticity for RAC has been reported to be in the range of 50–70% the

normal concrete (Oliveira et al., 1996; Ajdukiewicz and Kliszczewicz, 2002; Rao, 2005)depending on the water–cement ratio and the replacement level of RA. However, moreexperimental data is required in this area, before conclusive results can be drawn especiallyin applications of RAC where the modulus of elasticity or the stress-strain behavior, is acritical parameter.

4.2.5. Creep and shrinkageThe use of RA in concrete induces a large shrinkage due to the high absorption of these

aggregates. Some studies by show that in RAC at the age of 90 days, the shrinkage couldbe about 0.55–0.8 mm/m, whereas the comparable value for NAC is only about 0.30 mm/m(Katz, 2003).

However, the test results for creep in normal laboratory conditions are not so clear, thoughsome studies have shown the tendency to be reversed, i.e. the creep after 1 year is about20% lower than concrete with NA (Ajdukiewicz and Kliszczewicz, 2002). Though morework is needed in the area, it appears that the overall behavior of RAC and NAC may becomparable when viewing the combined effect of shrinkage and creep.


4.3. Durability of hardened RAC

Durability studies have been done to better understand the effect of using differentqualities of RA on the properties of the RAC. Though, some studies have shown that RACis significantly more permeable than NA concretes, it should also be noted that the durabilityproperties can be improved by using flyash, condensed silica fume, etc. Some of the resultsavailable in literature are discussed in the following paragraphs.

4.3.1. CarbonationOn the basis of carbonation test done after 6 months of curing, the carbonation depth

of the recycled concrete has been found to be 1.3–2.5 times greater than that of thereference concrete (Crentsil et al., 2001; Levy Salomon and Paulo, 2004). It is seenthat for the same water-binder ratio, the carbonation depths of RAC are slightly higherthan that of NAC (Otsuki et al., 2003). This increase in the carbonation depth could beattributed to increased permeability of the RAC on account of the presence old mortaradhering to the original aggregate, and the old interfacial transition zone (ITZ) betweenthem.

4.3.2. Freezing and thawing resistanceThere is no common opinion in the literature as far as the frost resistance of RAC is

concerned. In a study where the effect of mortar content adhering to the aggregate on thefreezing and thawing resistance of RAC was studied, it was found that provided the qualityof the concrete rubble is good, the adhering mortar may not adversely affect the performanceof RAC (Gokce et al., 2004). In another study it was found that the freezing and thawingresistance of RAC using RA made from non-air-entrained concrete was quite poor, thoughthe RAC met the requirements of air entrainment. On the other hand, the concretes madewith the recycled coarse aggregates originated from air-entrained concretes were highlyfrost resistant (Salem and Burdette, 1998; Zaharieva et al., 2004). The likely shortcomingsin the performance of RAC to freezing and thawing can be attributed to the pore structure ofthe previously hardened cement paste that adheres to the surface of the recycled aggregate.This porous matrix absorbs water during mixing, increasing the water-cement ratio of thepaste.

5. Barriers in promoting use of RA and RAC

Acceptability of recycled material is hampered due to a poor image associated withrecycling activity, and lack of confidence in a finished product made from recycled mate-rial. Cost of disposal of waste from construction industry to landfill has a direct bearingon recycling operations. Low dumping costs in developing countries also acts as a bar-rier to recycling activities. Imposition of charge on sanitary landfill can induce buildersand owners to divert the waste for recycling. Some of these issues act as barriers inpromoting more widespread use of recycled aggregate and concrete made with recycledaggregate.


5.1. Lack of appropriately located recycling facilities

Construction and demolition waste is generated in small quantities at locations whichcould be widely separated. Therefore, portable equipment is needed, which can be usedand set up close to a demolition site. Transporting waste over large distances makes theproposition of using C&D waste uneconomical. Lack of such plants is a major barrierfor ‘Newcomers’ in the field of C&D waste management. Commissioning of appropriatelylocated recycling crusher units in a pilot plant can help in lowering barriers against recyclingof construction & demolition waste.

5.2. Absence of appropriate technology

There are very few commercially viable technologies for recycling construction anddemolition wastes, and methods that can be used to crush C&D waste on a commercialscale are urgently required. In fact, when the technology is established, other issues suchas quality control of raw material and finished product, etc. can be taken up.

5.3. Lack of awareness

Lack of awareness towards recycling possibilities and environmental implications ofusing only fresh mined aggregates are the main barriers due to which C&D waste is disposedonly in landfills. Creating awareness and dissemination of information relating to the abovebarriers and the properties of concrete made with recycled aggregate are essential to mobilizepublic opinion and instill confidence in favor of the recycling option. There is a need to createa market for recycled products by involving the construction industry and encouraging themto use recycled materials in projects.

5.4. Lack of government support

A lack of government support and commitment towards development of recycling indus-try is often seen. Developing appropriate policy supported by proper regulatory frameworkcan provide necessary impetus. It will also help in data compilation, documentation andcontrol over disposal of waste material.

5.5. Lack of proper standards

Apart from the specifications of RILEM (RILEM, 1994), JIS and those used in HongKong, only very limited codal specifications/standards regarding use of recycled aggregatesare available. In fact, use of concrete with 100% recycled coarse aggregate for lower gradeapplications is allowed in Hong Kong, though for higher grade applications (above M35concrete), only 20% replacement is allowed, and the concrete can be used for generalapplications, except in water retaining structures. In Japan, JIS has drafted a TechnicalReport, TRA 0006 “Recycled Concrete Using Recycled Aggregate” to promote the useof concrete made with recycled aggregate. Development of relevant standards for recycledmaterials would provide producers with targets and users an assurance of quality of material.


Standards formulated in the above mentioned countries can be a guideline for developmentof specifications.

6. Concluding remarks

Use of recycled aggregates in concrete provides a promising solution to the problem ofC&D waste management. Based on a survey of production and utilization of RA in RAC,and the properties of RA and RAC discussed in this paper, it is clear that RAC can be usedin lower end applications of concrete. With tailor made pilot studies, RA can be used formaking normal structural concrete with the addition of flyash, condensed silica fume, etc.Greater efforts are needed in the direction of creating awareness, and relevant specificationsto clearly demarcate areas where RAC can be safely used.

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Use of Aggregates From Recycled Construction and Demolition Waste in Concrete

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