Recycled Concrete Aggregate: A Solid Wealth

(Akshay Kaushal(1), Danish Malhotra(2), Jaspreet Singh(3), Leezu Goyal(4) and Vivek Makkar(5))

Guru Nanak Dev Engineering College, Ludhiana, Punjab, India

1.0 Abstract

A comparative analysis of the experimental results of the properties of fresh and hardened concrete with different replacement ratios of natural with recycled coarse aggregate is presented in the paper. Recycled aggregate was made by crushing the waste concrete of laboratory test cubes and precast concrete columns. Five types of concrete mixtures were tested. Concrete made entirely with natural aggregate (NAC) as a control concrete and four types of concrete made with natural fine aggregate and recycled coarse aggregate (0%, 25%, 50%, 75% and 100% replacement withnatural coarse aggregate). 100 specimens were made for the testing of the basic properties of hardened concrete. Load testing of concrete cubes made of the investigated concrete types is also presented in the paper. Regardless of the replacement ratio, recycled aggregate concrete (RAC) had a satisfactory performance, which did not differ significantly from the performance of control concrete in this experimental research. However, for this to be fulfilled, it is necessary to use quality recycled concrete coarse aggregate and to follow the specific rules for design and production of this new concrete type.

2.0 Introduction

Demolition of old and deteriorated buildings and traffic infrastructure, and their substitution with new ones, is a frequent phenomenon today in a large part of the world. The main reasons for this situation are changes of purpose, structural deterioration, rearrangement of a city, expansion of traffic directions and increasing traffic load, natural disasters (earthquake, fire and flood), etc. For example, about 850 milliontons of construction and demolition waste are generated per year, which represent 31% of the total waste generation. The most common method of managing this material has been through its disposal in landfills. In this way, huge deposits of construction waste are created, consequently becoming a special problem of human environment pollution. For this reason, in developed countries, laws have been brought into practice to restrict this waste, in the form of prohibitions or special taxes existing for creating waste areas. On the other hand, production and utilization of concrete is rapidly increasing, which results in increased consumption of natural aggregate as the largest concrete component. This situation leads to a question about the preservation of natural aggregates sources; many countries have placed taxes on the use of virgin aggregates. A possible solution to these problems is to recycle demolished concrete and produce an alternative aggregate for structural concrete in this way. Recycled concrete aggregate (RCA) is generally produced by two-stage crushing of demolished concrete, and screening and removal of contaminants such as reinforcement, paper, wood, plastics and gypsum. Concrete made with such recycled concrete aggregate is called recycled aggregate concrete (RAC). The main purpose of this work is to determine the basic properties of RAC depending on the coarse recycled aggregate content and to compare them to the properties of concrete made with natural aggregate (NAC)—control concrete. Fine recycled aggregate was not considered for RAC production because its application in structural concrete is generally not recommended.

3.0 Estimates of C&D Waste

The divergent government figures promoted Delhi non-profit Center for Science and Environment to do its own calculation. It used data from three agencies. For calculating the C&D waste generated in

2013, it used estimate by Technology Information, Forecasting and Assessment Council (TIFAC), a government of India agency. TIFAC says C&D waste generated during a new construction is 40-60 kg/square meter (sq m), during repairs is 40-50 kg/sq m and during demolition 300-500 kg/sq m.

For determining the built-up area, CSE used McKinsey & Company’s report, which says the total built-up area in India in 2013 was 13.75 billion sq m. Of this, almost 1 billion sq m was constructed in 2013 alone. This would have generated 50 million tonnes of waste. Usually one-third of buildings get repaired every year. This would have added another 193 million tonnes of C&D waste. Assuming 5 percent of buildings undergo large-scale restoration/demolition a year; these would generate 288 million tonnes of waste. The total adds up to 531 million tonnes. To estimate the area needed to dispose of this waste, CSE used calculations done by the Kasturirangan Task Force on Waste to Energy. The report says 400 hectares of landfill is needed to dispose of one million tonnes of waste. According to this formula, India would need a landfill of 8.65 million hectares by 2030 to dispose of its C&D waste.

Table 1. Government Estimates

Estimate Year C&D Waste (million tonnes per year)Urban Development Ministry 2000 10-12

Technology Information, Forecasting and Assessment Council

2001 12-15

Union Environment Ministry 2010 10-12Center for Science And Environment

(CSE)2013 531

4.0 Solid wealth

India is a churning out construction and demolition debris at an incredible pace. With landfills overflowing and building material becoming scarce, country needs a policy to recycle the waste. India needs a landfill size of West Bengal to dump 21,630 million tons of construction & demolition waste it will generate from repair and demolition of old buildings and from new ones between 2005 to 2030. CSE finds ring alarm bell at a time when urban area across the country are witnessing a real estate boom, and the new government plans to create 100 smart cities as a part of its development agenda.

Unfortunately, there is no up-to-date official data on the magnitude of the problem. On February 6, replying to a question rose in RajyaSabha; the Minister of Urban Development (MOUD) said there is no current estimate on the amount of C&D waste generated in the country.Worse, the handful of the government estimate available for C&D wastes are at variance with each other and fail to capture the real picture. Considering this in 2000, estimate by MOUD showed that India generated 10 to 20 million tons of C&D waste a year. A decade later, a report by Union Ministry of Environment & Forest (MOEF) gave the same estimate.One can think of only one reason for this incongruous government data: most of the C&D waste generated in the country is unaccounted for.

With landfills overflowing with garbage and in the absence of policy to regulate C&D waste disposal, developers, including government agencies, dump the waste in low lying or watershed areas, roadsides and even on vacant plots and fields. In fact, disappearance of urban water bodies and wet lands in urban areas can be attributed to illegal dumping of C&D waste. In most cases, real estate developers deliberately do this to reclaim eco-sensitive area for real estate. In Mumbai, builders dump C&D waste in coastal mangroves and creeks. In Delhi, the Yamuna flood plain is the favourite dumping ground.

Recently the Delhi Metro Rail Corporation faced the fury of a National Green Tribunal for choking the Yamuna flood plains with C&D waste.

The situation is equally worrisome in neighbouring Gurgaon which saw a private real estate boom in 2000s that is continued to this day. Developers regularly dump on vacant plots, water bodies and low lying areas of eco-sensitive Aravalli Hills. Frustrated by inaction of municipal aurthourities, malba hatao group, a Gurgaon based, citizen-driven initiative fighting for a comprehensive policy on drives and recycling of C&D waste, approach the National Green Tribunal in October 2013. A map from Tribunal has elicited action from Municipal Corporation of Gurgaon. “The municipal aurthourities has notified four villages for dumping C&D waste”, say Ruchika Sethi, member of the group. Sethi, who is steering the case in the Tribunal and holding consultations with corporations, sales,“ The authorities were planning to issue notifications to penalize the builders who fail to transfer their C&D waste to the dumping areas. They delayed it because of 2014 general elections. ”

But dumping urban waste in villages may lead to protest by residents and results in Thiruvananthapuram like situation. The municipal body plan to set up plant to recycle the waste in Aravalli Hills. This may do more than good to the environment.

4.1 Initiatives in India

In some cities, local authorities tried to fix the problem. The municipal corporation of Chandigarh is possibly the first urban local body in the country to have a launched scheme for C&D waste management. Under the decade-old scheme, residents can dial MCC’s helpline number for C&D waste removal and the debris gets collected within 48 hours. “We have identified 4 to 5 sites across the city where the malba (C&D waste) is dumped. We also use the inert waste to cover up the garbage in our landfills,”says Vivek Pratap Singh, commissioner of MCC. However, he admits that most of the C&D waste doesn’t reach the designated dumping sites. Developers use the waste to reclaim low-lying area around Chandigarh.

The Municipal Corporation of Greater Mumbai (MCGM) framed the Construction and Demolition Waste (Management and Disposal) Rules in 2006 after realizing that more than one-third of the waste it was collecting was the C&D waste generated by its ever expanding real estate and infrastructure sectors. Poor implementation of the rules means illegal dumping of C&D waste continues unabated. Builders have even started charging customers for disposing off debris. “My contractor sends someone to collect malba,” says Kamini Baghchi of Andheri who is getting her house repaired. “He charges extra for that.”

National Council For Cement And Building Materials, a premium government R&D facility based at Ballabgarh , has carried out studies that say fine aggregate from recycled C&D waste be considered for use as part replacement of natural fine aggregates (sand ). But durability studies will take at least one more year to conclude.

Central Building Research Institute, based in Roorkee, says the quality of aggregate would depend on the quality of source. Tests on 10 beams, with 100 percent recycled concrete aggregate have shown promising results. Further research is under way to establish the optimum percentage of replacement.

Central Road Research Institute, based in Delhi, has conducted multiple studies and is upbeat about the prospect of using recycled C&D waste in making concrete roads. It is willing to provide guidelines for use of C&D waste in road construction.

4.2 Policy void

Proactive measures by these cities have failed because there is no policy at the national or state level to tackle the waste.C&D waste finds only a brief mention in schedule III of the Municipal Solid Waste (Management and Handling) Rules, 2000. MOUD’s Manual on Municipal Solid Waste (Management and Handling) Rules, 2000, offers a basic guideline on handling C&D waste. These guidelines are not binding on developers or government development agencies.

In 2009, MOEF constituted a Working Sub-Group on Construction and Demolition Waste to evolve a mechanism for management of solid waste. The sub-group made several recommendations, which include developing institutional mechanism for waste collection, reusing and reprocessing the waste; segregation of C&D waste at source; imposing charges on waste generators; formulating standards for C&D waste and amending the Municipal Solid Waste Rules. MOEF’s proposed amendments in the rules in 2013 did not include the Working Sub-Group’s recommendations. Instead, it is now drafting separate rules for managing C&D waste, Construction and Demolition waste (Management and Handling) Rules 2014.

4.3 Is it really a waste?

Of late, there have been sporadic initiatives in India to recycle C&D waste into aggregates for making ready-mix-concrete, pavement blocks and concrete bricks. In 2009, the Municipal Corporation of Delhi, in collaboration with IL&FS Environmental Infrastructure & Services Ltd (IEISL),set up a C&D waste recycling project in Burari. “The recycling plant has a capacity to recycle 500 tonnes of C&D waste a day, but it receives 1200-1400 tonnes daily”, says N B Mazumdar, technical advisor to IEISL.

A similar initiative was undertaken by Mumbai-based non-profit Youth for Unity and Voluntary Action (YUVA) and the City and Industrial Development Corporation in 1999 in Navi Mumbai. Over 1500 tonnes of C&D waste was recycled under the project during 2002-06. These initiatives have, however, failed to take off. While the YUVA project ended in 2009, IEISL plant finds no takers for its blocks and pavers.

5.0 Complicated standards

Officials involved with the projects blame the failure on the construction products standards of the Bureau of Indian Standards (BIS) that do not mention recycled C&D waste as a “suitable building material”.

IS: 383-1970, the BIS for aggregates (sand and stone used for making concrete), stipulates that concrete can be made only with “naturally accessed material”. Construction agencies cite this rule to avoid using recycled waste. “The interpretation is inaccurate”, says Sunil Soni, director general of BIS, adding that BIS permits the use of aggregates, other than natural aggregates, in concrete under the standard IS: 456-2000. The text of IS:456-2000 code, however, does not include the word “recycled”, dissuades developers from using recycling C&D waste. In fact, through it allows using “broken brickbats”, a major component of C&D waste, builders play safe and prefer buying fresh bricks and then break them to make brickbats. Some experts say there is an urgent need to set standards for C&D waste. But Soni says framing new standards is a long process and will take time. Since BIS does not prohibit using any new material in the absence of standards, he suggests that authorities can take the initiative and permit recycled material. “This is allowed under the National Building Code,” he says.

The Central Public Works Department (CPWD), for instance, can revise its schedule of rates (SOR is a document that determines the price of construction materials used by government agencies) to incorporate recycled C&D waste in the list of building materials. Since CPWD’s SOR serves as the base document for the state SORs, any change in the CPWD document will get readily incorporated in the state SORs. CPWD, however, has been sceptical about recycled C&D waste and does not allow its use in construction. Early this year, it informed Parliament that “C&D waste having no salvage value is disposed of at approved dumping sites as per Municipal rules”. It has also not responded to appeals by the Environment Pollution Control Authority for suggesting how to promote the use of C&D waste.

To eliminate skepticism regarding the suitability of C&D waste, BIS has gone out of its way and constituted a panel to formulate a list of aggregates from other than natural sources.It has already held two meetings within three months this year, something unheard of in BIS where technical meeting are usually held once a year. To avoid delay, BIS has decided to incorporate provisions allowing recycled C&D waste as aggregates under IS: 383-1970. “The amendment would automatically allow the use of recycled C&D waste in all products made out of concrete and reduce the need of subsequent amendments in other standards,” says Kurian. BIS is considering allowing up to 20 percent recycled concrete aggregates as replacement of natural aggregates. The percentage of replacement could be increased in future as and when new research data becomes available.

To determine these checks, BIS requires technical studies by government agencies on suitability of recycled C&D waste as replacement of natural aggregates in concrete. These studies need to be independently carried out by multiple agencies to avoid biases or flaws.

5.1 Fixing the gaps

At a time when sand is becoming scarce and bricks expensive, fixing standards of C&D waste will tilt the market dynamics in its favour. But its potential cannot be fully tapped until the country expands its capacity to recycle the waste and introduces a comprehensive management policy. The Municipal Corporation of Delhi, the only municipality in the country to have recycling C&D waste plant, has not been able to set up more recycling plants. Since 2011, the Gurgaon municipal authority has been claiming on its website that the city will have two to three C&D recycling plants.

They can also learn from the land –constrained Hong Kong which has stringent rules for C&D waste. It charges builders for generating C&D waste. Even if a builder utilizes 100 percent of C&D waste, he has to pay HK$27( 126)pertonne. The charges spike up to HK $125 ( 1000) per tonne if the₹ ₹ developer sends 50 percent of waste generated to landfill. The generation of C&D waste reduced to 60 percent in the first year of implementation of the rule in 2006. The government uses the revenue to run, maintain and subsidies C&D waste recycling centers. Instead of demolishing structures, builders now dismantle them to salvage the construction material.

To make this possible in India, MOEF also needs to hasten the foundation of construction and Demolition Waste (management and Handling) Rules, 2014. It needs to set up a system to support cities in collecting and recycling C&D waste. Given the magnitude of environment destruction associated with construction material, promotion of alternatives and recycling of waste is not matter of choice but necessity.

6.0 Objective

The objective of this study was to develop concepts for the reutilization of construction materials, including waste debris, by means of recycling into other components that are useful in construction. This study:

(1) Identified the primary opportunities, constraints, and means to divert C&D debris from the solid waste stream,

(2) Identified waste concrete as construction material from existing facilities that may be directly salvaged or reused without substantial alteration or reprocessing.

7.0 Basic Properties of Concrete with Recycled Concrete Aggregate

When demolished concrete is crushed, a certain amount of mortar and cement paste from the original concrete remains attached to stone particles in recycled aggregate. This attached mortar is the main reason for the lower quality of RCA compared to natural aggregate (NA). RCA compared to NA has following properties:

1. Increased water absorption.2. Decreased bulk density3. Decreased specific gravity4. Increased abrasion loss 5. Increased crushability6. Decreased compressive strength

Technology of RAC production is different from the production procedure for concrete with natural aggregate. To obtain the desired workability of RAC it is necessary to add a certain amount of water to saturate recycled aggregate before or during mixing, if no water-reducing admixture is applied. One option is to first saturate recycled aggregate to the condition - water saturated surface dry, and the other is to use dried recycled aggregate and to add the additional water quantity during mixing. The additional water quantity is calculated on the basis of recycled aggregate water absorption in prescribed time.

8.0 Experimental Investigation

The aim of this investigation is to compare the basic properties of control concrete (concrete made with natural aggregate) and the properties of concrete made with different contents of recycled aggregate. Mixture proportions of the tested concrete types were determined in accordance to the following conditions:

Same cement content. Same workability after 30 min. Same maximum grain size (20 mm). Same grain size distribution for aggregate mixture. Same type and quantity of fine aggregate. Variable type but same quantity of coarse aggregate. Same w/c ratio.

The type and quantity of coarse aggregate were varied in the following way:

1. The first concrete mix had 100% of natural river coarse aggregate (R0), control mixture

2. The second concrete mix had 75% of natural river coarse aggregate and 25% of recycled coarse aggregate (R25)

3. The third concrete mix had 50% of recycled coarse aggregate (R50).4. The fourth concrete mix had 25% of natural river coarse aggregate and 75% of recycled

coarse aggregate (R75).5. The fifth concrete mix had 100% of recycled coarse aggregate (R100).

The following properties of concrete were selected for testing:

Workability (slump test) immediately after mixing Bulk density of fresh concrete Water absorption (at age of 28 days) Wear resistance (at age of 28 days) Compressive strength(at age of 28 days)

Table 2.Seive Analysis for Recycled Coarse Aggregate

10 mm 20 mm

Sieve sizeIn mm

% passing % passing(permissible limits

as per IS 383)

% passing % passing(permissible limits

as per IS 383)40 - - 100 10020 - - 99.8 85-100

12.5 100 100 - -10 99.8 85-100 6.6 0-20

4.75 11 0-20 0.8 0-5

Table 3.Other Test Results of Recycled Coarse Aggregates

S.No. Parameters Value Permissible limits as per IS 3831. Specific Gravity 2.17 -2. Water Absorption(%age) 6.7 -3. Crushing Value (%age) 36.1 454. Impact Value (%age) 34.9 455. LA-Abrasion (%age) 50.9 456. Soundness(%age loss) 4.1 12 (with Na2SO4 solution)7. Elongation Index 21.1 -

Table 4.Test results –– Compressive strength of Concrete mixes with Replacement of NaturalAgg. With Recycled ConcreteAgg.( 4.5-20 mm fraction only)

Aggregate (4.5-20 mm) Aggregate (<4.5mm) Compressive Strength (N/mm2)

Slump (mm)

Normal Aggregate

%age

Replacement%age

Normal aggregate

%age

Replacement%age

7 days 28 Days 90 Days

100 0 100 0 37 41 46 80

75 25 100 0 34 41 47 90

50 50 100 0 35 41 44 80

25 75 100 0 32 37 41 90

0 100 100 0 17 29 34 100

9.0 Conclusions

Construction and Demolished waste can be recycled to make coarse and fine aggregate (sand) for selective use in concrete.

Air voids and Water absorption is high in recycled C&D waste aggregates. Large variations in type of waste, needs to be carefully segregated before processing for

effective utilization. Even with increased replacement of fine orcoarse aggregate with recycled concrete

aggregates, there is no significant difference in slump value. With increased recycled coarse aggregate the strength gets reduced with the increasing

content of recycled fine aggregate the compressive strength is increased. It was found that 75% replacement of normal aggregate shows good results which are

comparable to control mix at 3-Day, 7-Day and 28-day.

10.0 References

IS: 2386 (Part I, III, IV & V) – 1963, Methods of Test for Aggregates for Concrete.

IS: 5514- 1996, Specifications for apparatus used in Le-Chatelier Test.

IS: 383 -1970, Specifications of coarse and fine aggregate from natural sources for concrete.

M.S. Shetty(2005) – Concrete Technology Theory And Practice.

M. Heeralal, P. Rathish Kumar, Y.V. Rao and V. Tulasi Shiva Kalyan, A study on the utilization of recycled concrete aggregates (RCA) in bituminous concrete.

Katrina McNeil and Thomas H-K Kang, Recycled Concrete Aggregates: A Review, International Journal of Concrete Structures and Materials Vol.7, No.1, pp.61–69, March 2013.