Recycling of Construction Demolition Waste

Kshemendra Nath P, Managing Director Resilient Energy India Private Limited

India is one of the fastest growing economy and is urbanizing rapidly. Over the next 30 years, 53% of the population is expected to be in urban agglomerations. According to the guidelines issued by Ministry of Urban Development (2015), about 303.5 million sq.m. of real estate, covering 25,000 acres of land will need greenfield development and additional 202.3 million sq.m of existing buildings will need to be redeveloped. Prime examples of greenfield development are cities such as Amravati, the proposed new capital of Andhra Pradesh, while the Saifee Burhani Upliftment Project in Mumbai and East Kidwai Nagar in New Delhi are examples of large redevelopment projects.

Construction of infrastructure, particularly in developing countries, is associated with positive externalities, such as livelihood generation and hence desirable. However, rapid growth, particularly unplanned activity, is often associated with increased pollution loads. According to a report by IQAir AirVisual (2019), Indian cities rank amongst the most polluted, with six featuring in the list of top ten. For example, the concentration of Suspended Particulate Matter (SPM) in large metros such as Delhi, Mumbai is routinely in the “Unhealthy” category (100-150) and in “Very Unhealthy” in winter months. One key reason for increasing pollution is the lack of facilities for scientific waste management and capturing of pollutants.

Even though C&D waste is the largest components of the waste stream, it was traditionally ignored. There were several reasons, such as its relatively inert nature, possibility of utilization in refiling and less benign options such as illegal dumping in water bodies or by roadsides. Due to lack of focus, the estimates of total C&D waste generated at city level and across the country are unreliable and vary from 15 million tons to 625 million tons per year (BMTPC, 2018).

The health cost of the pollution has attracted increasing attention of the regulators, judiciary and common man in the recent years. As a result, policy and pragmatic action has gained momentum. Several steps have been initiated such as amendments to the Waste Management Rules in 2016, stricter norms for power plants, launch of new initiatives such as the Swachh Bharat Abhiyaan (Clean India Program), the Namami Gange Program (National Mission for Clean Ganga), amongst others.

C&D Waste Management Rules and Implementation Status
Need for amendment to the waste management rules

The need to scientifically manage C&D waste was first recognized in the Municipal Solid Waste Rules 2000, but with insufficient details i.e. it did not include relevant details, particularly roles and responsibilities as well as lack of incentives and penalties. As a result, they proved inadequate to the challenge. Over the last two decades, lack of C&D waste management facilities appears to have contributed significantly to the environmental damage in various forms. For example, C&D waste dumped along roadsides leads to increased SPM as it tends to degrade over time. Metro cities such as National Capital Region, a centre of construction activity over the last two decades has witnessed increasing level of PM 2.5 concentration in recent years. In some years it crosses 150 µg/m3 in the summer while in the winter it was found to be around 200µg/m3, against the acceptable level of 60 µg/m3. According IIT Kanpur (2016) study, construction and demolition waste combined with batching activities were consistently amongst the largest contributors to the pollution load. Chemicals from dumped debris often leach into the land, particularly during the monsoons, causing land degradation and contamination of ground water. A significant portion of C&D waste tends to be dumped in water channels, natural and manmade drains, leading to clogging and flash floods. Mumbai and Chennai are prime witnesses. According to CAG (Citizen Consumer and Civic Action Group) (2016) study, one of the contributing factors for Chennai floods in 2015 was the mismanagement of C&D waste. Increasing pressure from judiciary, think-tanks and citizen groups created momentum for enactment of C&D Wate Management Rules in 2016.

C&D Waste Management Rules, 2016
Given the increasing pollution load, consequent economic and health costs, a more comprehensive and separate set of regulations for managing various types of waste were enacted in early 2016. These included the Construction and Demolition Waste Management Rules (2016) (in brief C&D Rules 2016), Solid Waste Management Rules (2016), Plastic Waste Management Rules (2016) and E-Waste Management Rules (2016).

These rules embodied several common principles creating an enabling, consistent, and supportive framework for implementation by Urban Local Bodies (ULB). Five most important are outlined here. The first principle emphasized source segregation, in-order to increase recycling and reuse opportunities. A complementary provision, mandating the usage of recovered materials was the second key principle. In case of Municipal Solid Waste (MSW), for example, the rule requires all industrial units within 100 km radius to replace 5% of the fuel requirement with Refuse Derived Fuel. Likewise, the C&D Rules require public construction projects to use 10% to 20% recycled materials. Third, the rules clearly outline the duties of the waste generators, with emphasis on the concept of extended producer responsibility. This approach strengthens the “polluter pays” principle, already enshrined in various orders, by levying and or increasing the fees to be paid by the generators. Fourth, the rules outline the responsibility of various arms of the Government, such as policies to be issued by the State Governments, guidelines to be prepared by the Pollution Control Boards and specific provisions for local authorities such as ensuring availability of land. Last, but not the least, the rules prescribe a timeline for various milestones, most notably for operationalising waste processing facilities. Table-1 below illustrates key provisions of the C&D Rules 2016 in so far as roles and responsibilities of various stakeholders and timelines for key milestones are concerned.

Table 1: Key provisions and timelines under the C&D rules 2016
Source: Ministry of Environment, Forest and Climate Change, C&D Management Rules, 2016
Provision under the Rules City with Population
1 Million + 0.5-1.0 Million < 0.5 Million
State Government: Formulation of the C&D waste management policy 12 months 12 months 12 months
Local Authority: Identification of sites for collection and processing facility 18 months 18 months 18 months
Local Authority: Commissioning of the Processing facility 18 months 24 months 36 months
State Pollution Control Boards: Approvals, Monitoring and Reporting 3 times/year 2 times/year 2 times/year
Central Pollution Control Board: Environmental Management Guidelines and Annual Report Once a Year
Complementary regulatory provisions
In addition to the C&D Rules 2016, two complementary regulatory provisions were enacted to C&D Rules 2016. Both relate to the standards for enabling use of recycled materials for various purposes. The Bureau of Indian Standards amended the specification IS 383:2016 for coarse and fine aggregate for concrete (3rd revision) in 2016. The revised specification includes manufactured aggregates produced from other than natural sources for use in the production of concrete for normal structural purposes, including mass concrete works. The revised IS 383: 2016 thus allows use of up to 20% recycled concrete aggregates in Reinforced Concrete (M 25 grade) as coarse or fine aggregate and up to 100% in Lean Concrete (< M 15grade). This modification is consistent with provisions of the National Buildings Code (NBC-CED 46) of India 2005: Part 11 which allows up to 30% replacement of natural aggregates with recycled concrete aggregates.

Results: Assessment of the implementation status
According to the C&D rules 2016, State Pollution Control Boards (SPCBs) should submit reports to Central Pollution Control Board (CPCB) regarding the status and the waste generation data. However, no information is readily available in the public domain. A report by the Niti Aayog, the Government’s think tank, (Strategy for Promoting Processing of Construction and Demolition (C&D) Waste and Utilisation of Recycled Products) dated 5 November 2018 suggests that only two out of fifty-three cities with million plus population have operational facilities. This appears to be somewhat dated information. Available information based on extensive review, triangulating information from multiple sources indicate that the progress till date has been slow, with only six out of thirty-six states and UTs, i.e., about 17%, having either issued a policy or a draft version of the policy for managing C&D waste. The situation is similar at the city level, with only six out of forty-four cities i.e., 15%, having issued bylaws for C&D waste management. Nine out of forty-four i.e., 20% had an operational facility and another ten i.e., less than 25% were in the process of constructing one. Contrast this with the requirement under the C&D Rules 2016 that all cities need to have an operating facility by March 2019. Since there is no information available on most of the other cities, overall compliance to the C&D Rules 2016 may be less than 10%, given that there are about 300 cities with a population of 100,000 and above. There are several reasons for slow progress which we discuss in following sections, along with policy and business enablers required to advance scientific management of C&D waste.

Systematic Assessment of C&D Waste
One of the key bottlenecks in planning and operationalizing C&D waste management facilities relates to the lack of data, quantitative and qualitative. In the absence of data, most ULBs are unable to arrive at proper estimate of the scale, type and logistics required to implement the mandate under the C&D Rules 2016. The Ministry of Environment, Forests and Climate Change (MoEF&CC) and related government agencies such as the Central Pollution Control Board acknowledge that there is no systematic database or reliable estimate of C&D waste in India.

Widely Varying Estimates of C&D waste
Various estimates have been derived by various agencies, official and independent, at different points in time. Data in the table highlights the dilemma in planning and implementing scientific C&D waste management, considering that the difference between the minimum and maximum estimate is over 5000 percent. The situation at the city and town level is even worse, as in most cases, there is simply nothing available.

Table 2: Estimates of quantity of C&D waste from various agencies
Source: CPCB – March 2017 *CSE Report No:3- 2014
Name of the Agency Estimation Year C&D waste (Million MT /annum)
Ministry of Environment & Forest (MoEF&CC) 2010 10-12
Technology Information, Forecasting and Assessment council (TIFAC) 2001 12-15
Central Pollution Control Board (CPCB) 2017 12
Building Material Promotion Council (BMTC) 2013 165-175
Centre for Science and Environment (CSE)* 2014 530
As evident, it is likely that some of the numbers, particularly from the Government agencies above, may be an underestimate of the overall C&D waste quantum. Further, there is a lack of clarity on the methodology adopted by different agencies. To illustrate, CSE used TIFAC guidelines on the amount of waste generated per m2 of construction (40-60 kg per m2), demolition (400-600 kg per m2). and repair (40-60 kg per m2), to arrive at the quantity of waste from construction (50 million tons), demolition (288 million tons) and repair (193 million tons), respectively in 2013, i.e. collectively a total quantity of 530 million tons. On the other hand, TIFAC’s own estimate for 2001 was much smaller i.e. 12-15 MT. Obviously, the rather large difference cannot be explained by the fact that the two estimates were 12 years apart.

Another aspect worth highlighting is the fact that the CSE estimate is based entirely on buildings constructed. Hence, it appears, that waste from construction of infrastructure projects such as highways and from the Ready Mixed Concrete plants is not included. Given the scale of large infrastructure projects and 60 million-meter-cube of RMC produced annually, the possibility that CSE may have also underestimated cannot be ruled out. The more important point being the need for a transparent and objective assessment of the quantity of waste. At city or town level, another detail which is required for planning and design is the characterisation of the waste in terms of its constituents. The available data on the constituents of C&D waste in India is in Table 3 below.

Table 3: Estimate of constituents of C&D waste from various agencies (%)
Source: *ICI Guidelines 2013 # BMTPC Ready Reckoner Oct 2018
Constituent  TIFAC
Estimate (2001)
MCD Survey* Estimate (2004)  BMTPC#
Estimate (2018) 
Soil/Sand, Gravel 36 43 26
Bitumen 2    
Metal 5   6
Masonry/Bricks 31 35 32
Concrete 23 35 28
Wood 2   3
Others 1 7 5
Total 100 100 100
The TIFAC estimate in Table 3 are average numbers for the country whereas the MCD (Municipal Corporation of Delhi) estimate is for Delhi and the BMTPC estimate is for urban areas in North India. The absence of data on characterization of waste is often a barrier in designing an optimum plant and strategy. It leads to multiple distortions, depending on the context. For example, lack of interest by bidders in the tendering process, higher prices due to increased risk perception and inability to operate or a costly renovation, after the plant has been operationalized.

With the above backdrop, a systematic assessment of C&D waste generated in Goa was developed by the SINTEF team comprising of the author as part of work under the C&D WIN project.

C&D-WIN project
SINTEF AS, an independent research organisation based out of Norway is supporting Indian organizations under a program funded by the Royal Norwegian Embassy. This program, titled “Treatment and recycling of construction and demolition waste in India (C&D-WIN)” enables joint activities to provide assistance to CPWD, Urban Local Bodies and private sector entities in India towards safe, scientific treatment and utilisation of C&D waste.

As a part of the C&D-WIN activities, SINTEF and Goa Waste Management Corporation (GWMC) entered into a MoU to focus on C&D waste management. The aspiration of Goa is to develop, operate and maintain a world class C&D waste management facility towards the principle of circular economy, to enhance environment sustainability of its sensitive ecosystem. The overall objective of the Project is to implement safe, scientific treatment and utilisation of C&D waste in Goa.

Methodology and Process for Systematic assessment of C&D waste in Goa
As with the rest of the country, neither the urban local bodies in Goa nor the State Pollution Control Board (GPCB) had readily available authentic data on the volume or the composition of the C&D waste generated in Goa Therefore, after deliberations with stakeholders, it was agreed that the best possible method to estimate the volume and stream of waste generation from C&D activities was to derive the same from the three main streams of C&D waste. These three streams included construction activity, demolition activity and refurbishment of hotel rooms, a large sector requiring frequent renovation and hence significant contributor to overall C&D waste in Goa.

As a starting point in the data collection drive, more than 40 key stakeholders of the Goa construction industry were identified, and meetings conducted. This included three ULBs, the planning departments (TCP and Planning and Development Authority – North and South Goa), various Government development agencies such as Goa Industrial Development Corporation (GIDC), Goa Tourism Development Corp, Goa State Infrastructure Development Corporation, Goa Public Works Department, Goa Pollution Control Board, Indian Navy-Western command, Leading engineering contractors such as Larsen and Toubro and Dilip Buildcon Ltd, real estate developers such as Adwalpalkar constructions and Nanu group of companies, architects such as Devari and associates and Effective architectural solutions key players in the hotel industry Taj group of hotels and Novotel, Building material suppliers such as Cement companies, RMC suppliers, Concrete pavers and blocks manufacturers and suppliers of vitrified and ceramic tiles, demolition contractors and debris transporters.

Detailed discussions with key individuals and organisations provided an understanding of the construction market of Goa, type of building materials used and construction practices in urban and rural areas of Goa, the current and the potential areas for future growth, the demolition methods and disposal means for the debris. The location of the RMC and precast companies and the waste generated at the plant and supply site was mapped to identify the volume and the geographical distribution of the waste. A detailed list of all hotel units in Goa, with their location, from the single room facilities to the large 500 room hotels was collected and their cycle of refurbishment studied, along with the composition of the waste generated per square metre of refurbishment. Builders, architects and contractors were consulted to obtain an accurate estimate of the average waste generated in the construction phase of different building materials, from concrete and blocks to plumbing materials, electrical cables, packing materials, bathroom fittings and accessories. The discussions with the demolition contractors and the debris transporters provided critical inputs on the demolition process, composition of the debris, the peak season for demolition activities, transportation and disposal means adopted, including prices charged.

Results and Key Findings
As mentioned above, the methodology adopted for estimation of waste was to analyse three separate streams i.e. construction, demolition and hotel renovation, to arrive at the overall waste quantity and its likely composition.

Waste from construction activity
The starting point for this stream was the data from Town and Country Planning (TCP) Department, which levies a one-time tax on all construction projects with a size exceeding 100 square metres. This data was collected along with similar data for the industrial buildings from GIDC. The data was classified under residential, commercial, and industrial categories for analysis purposes, as materials used vary by the type of structure. The data was also segregated on geographic basis i.e. by each of the twelve Talukas in the state.

In addition to the waste generated at the site during construction, waste is also generated in the supply chain of the Ready Mixed Concrete (RMC) industry, an essential input to most large structures. Goa has an annual production of 330,000 m3 of concrete, from thirteen plants located in the state. On an average, the waste generated in these plants is approximately 1.5 to 2 percent of the total production. This includes the spilled concrete during batching, rejects due to technical, placement, and workability related issues, crushed concrete cubes used for testing, chipped off concrete from the build up inside the plant mixer and truck mixer. This waste was estimated to be 32 MT/day based on the current production volume and mapped to each Taluka, based on the geographic location of each plant.

Based on the estimate of waste generated during the construction phase for different categories, and aggregating the waste generated from the RMC plants, the total waste generated from construction activity was estimated to be 266 MT per day. Its composition for each Taluka is presented in Table 4 below.

Table 4: Construction waste volume and its composition (Taluka-wise, MT per day)
Source: Author’s calculations
Location Concrete Concrete blocks Laterite stones Tiles/ Granite Aerated concrete Paver block Cement Mortar PoP/ Gypsum Other Total
Tiswadi 8.9 14.5 5.3 3.2 5 1.6 6.7 0.5 0.4 46
Bardez 27.3 27.4 8.6 6.4 10.8 3 12.2 0.9 0.7 97.3
Salcete 9.8 9.6 13.2 2.7 4.6 1.4 5.5 0.3 0.3 47.5
Marmugao 13.7 2.7 0.5 0.3 0.6 0.8 1 0.1 0.1 19.7
Ponda 9.6 4.1 1.7 0.6 0.8 0.6 1.7 0.1 0.1 19.3
Pernem 0.5 0.6 1 0.1 0.1 0.1 0.4 0.02 0.02 3
Bicholim 4.3 2 1.7 0.5 0.6 0.2 1.4 0.1 0.1 10.8
Sattari 0.4 0.2 0.5 0.1 0 0 0.2 0.01 0.01 1.4
Quepem 2.5 1.7 3.2 0.6 0.2 0.2 1.5 0.1 0.1 10.2
Sanguem 1.7 0.5 0.4 0 0 0 0.3 0.01 0.01 3
Dharbandora 0.1 0 0.1 0 0 0 0 0 0 0.2
Canacona 2.6 1.3 1.9 0.6 0.4 0.1 1.1 0.1 0.04 8.1
Total 81.5 64.6 38.2 15.2 23 8.1 32.1 2.1 1.7 266
Waste from demolition activity
Majority of the demolition activity in Goa is directly linked to the tourism industry which is located along the coast. Within the demolition, waste from hotel refurbishment was estimated separately and is presented in the next sub-section. The peak of the demolition activity, during which about two-thirds of the waste generated, occurs between June and September, coinciding with the monsoon off-peak season for tourism. There was limited evidence of systematic de-construction being adopted during demolition of buildings. In most cases, the demolition was carried out using an excavator, the resultant waste being a mixture of concrete, mud, laterite, and gypsum. There are two main types of buildings demolished in Goa viz. the Mangalore roof tiled buildings and the concrete roofed ones. The Mangalore tiles themselves however do not form a significant part of the waste stream as they are salvaged and removed before demolition. Table 7 below summarises the volume of waste per square metre of demolition and the typical composition of the waste in percentage.

Table 5: Composition of the C&D waste from demolition of different type of structures
Source: Based on anecdotal evidence collected from demolition contractors and debris transporters in Goa.
Type of Construction Average MT/m2 Laterite / Mud Concrete Mortar Tiles and Bathroom fittings Gypsum / PoP
Mangalore Tile Roofed 1.6 65% 3% 24% 5% 3%
Concrete Roofed 2 52% 20% 21% 4% 3%
Total waste generated from demolition activities, other than hotel refurbishments, was estimated to be 250 MT per day. Table 8 below summarises the Taluka-wise waste generated from demolition in different parts of the state along with its composition during a typical year.

Table 6: Demolition waste volume and its composition (Taluka-wise, MT per day)
Source: Author’s calculations
Taluka Major Town/City Laterite / Bricks Mortar Concrete Ceramic/ Tiles Gypsum Total in MT/Day
Bardez Calangute, Candolim 37.7 14.3 7.8 3.2 2 65
Tiswadi Panjim 43.5 16.5 9 3.8 2.3 75
Marmugao Vasco 31.9 12.1 6.6 2.8 1.7 55
Salcete Madgao 31.9 12.1 6.6 2.8 1.7 55
Total   145 55 30 12.5 7.5 250
% of Total   58 22 12 5 3  
Waste generated from refurbishment of hotel rooms
There are 1686 hotel units in Goa with 30,720 rooms. The franchise of global chains typically undertakes mandatory renovation every 5-7-years, where all rooms in a hotel are refurbished. On the other hand, large Indian chains, such as the Taj Group, which are more conservative and maybe have better maintenance practices, typically manage to extend the refurbishment cycle to 8-10 years. In case of small units, refurbishment of rooms is usually linked to ownership change. A standard hotel room typically generates 1 MT of waste during refurbishment. The waste composition is fifty percent cement mortar, twenty two percent ceramic tiles, bathroom fittings and remaining twenty eight percent Gypsum. For this estimation, an annual volume of waste from refurbishments of hotel rooms, a period of 7 years was assumed on a linear scale of generation. The total volume of waste thus calculated from refurbishments to be approximately 10 MT per day and its composition is presented in Table7 below.

Table 7: Refurbishment waste volume and its composition (MT per day)
Source: Author’s calculations
Waste type Daily Generation
Cement Mortar 5.00
Tiles and Bathroom accessories 2.30
Gypsum board and Plaster of Paris 2.85
Total 10.15
Total C&D waste and its composition
Based on the above three streams, the total volume of C&D waste generated in Goa was arrived at to be 266 MT/day, 250 MT/day and 10 MT/day, respectively from construction, demolition and hotel refurbishment activity, collectively adding to appropriately 525 MT/day. Construction practices specific to Goa were carefully considered while estimating the waste volume and its composition. For example, while bricks constitute a major share of the waste composition in many parts of the country, it is rarely used in Goa, laterite stones being the most preferred option, followed by concrete blocks. Ceramic tiles and bathroom fittings constitute a considerable share of the waste stream in Goa as different from other parts of the country, which is due to many hotels undertaking frequent renovation. This information provides a practical input to the recycling agency for designing the plant and more importantly for identifying recycling opportunities after treatment. The excavated soil was generally used at the site itself for back-filling and for practical purposes not included as its quantity was insignificant. The overall waste composition for Goa is presented in Table 8 below.

Table 8: Composition of C&D Waste in Goa
Source: Author’s calculations
Material Waste Generated
(MT per day)
Proportion
(% of the total)
Concrete 110 21
Concrete blocks + Pavers 95 18
Cement Mortar 90 17
Laterite stone / Mud 185 35
Tiles 30 5.7
Gypsum / PoP 13 2.5
Others 2 0.3
Total 525 100
This ground-up approach provides a detailed understanding of the waste generation and is significantly better for making informed decisions. To illustrate, the waste generated is estimated Taluka-wise, thereby providing a critical input for siting the recycling facility and transfer stations, thereby ensuring optimization of transportation. Further, understanding of the waste stream generated during construction and key development zones is a key input for the source segregation strategy.

Based on the future re-development plans, the composition of waste arising from the demolition activity can be analysed using the above approach. Overall, treatment and recycling projects can benefit significantly by adopting a scientific approach to assess the quantity and composition of the C&D waste. It is however pertinent to note the dynamic nature of the construction, demolition industry and consequent flexibility required to incorporate new strategies and approaches.

Recycling Opportunities in the Construction Industry
Construction is expanding rapidly in the country. For example, the Building Materials and Technology Promotion Council (2018) estimates that in the current year, India will require 380 Million MT of cement, 400 million cubic metres of aggregates and 600 billion bricks. Courts and regulators have been forced to take a stand against illegal mining, common in many parts of the country. As a result, river sand as fine aggregates have been banned from construction and so is the use of kiln bricks due to the over-use of topsoil. Sources of natural aggregates, especially those in proximity of major cities, sites of major construction activities, are depleting fast. Anecdotal evidence suggests that this has resulted in significant increase of the average distance of transporting these materials, maybe as much as 50% in some cases over the last decade. Thus, traditional building materials are increasingly scarce, costlier and therefore the need to think about sustainable solutions to meet the increasing demand.

Annually, 40 billion MT of aggregates are extracted globally, making it the second largest extracted resource in the world. To put this into perspective, the aggregates extracted annually is 9 times that of crude oil. Sand and aggregates, once considered an unlimited resource not very long ago, are depleting rapidly. Hence, countries across the globe have focussed on recycling C&D waste to use them as aggregates in construction. The recycled products are generally classified into two types, Recycled Concrete Aggregates (RCA) which is predominantly product of demolished concrete and Recycled Aggregates (RA), which is predominantly demolished concrete which may include masonry and asphalt.

According to the European standard EN 206:2013, up to 50% replacement of natural coarse aggregates by recycled concrete aggregates in concrete is possible, depending on the characteristics of the RCA and the environmental class for the concrete (ICJ Jan 2020). International evidence suggests that across the globe, many countries have made progress in the use of recycled materials in construction (ICI -2013). In Norway, the Sorumsand High School project, completed in 2003, half of the concrete used in the building was from recycled aggregates and 37 percent of the natural coarse aggregates were replaced by recycled concrete aggregates. The project was implemented as a demonstration project in collaboration with the local county authority (ICJ Sep 2019).

Germany has also made considerable progress in advancing the use of recycled materials. Through a combination of high landfill charges, widespread use of recycled aggregates in roads and parking lots and preferential procurement of recycled products by local authorities, the recovery rate in Germany is now approximately 95 percent. The market for recycled concrete in Germany is primarily in road construction as lays and drainage material. DIN 1045 permits up to 25% RCA in structural concrete of cube strength 37.5 MPa in dry or low humidity environments.

In the United States, regulatory issues vary from state to state, but the major use of recycled concrete aggregates is in road sub-base. Up to 100% replacement of coarse aggregate is allowed in all non-structural concrete up to 20MPa. For structural applications, ASTM C94/C94-11 b 55, allows replacement of 20-25 percent of coarse aggregates in higher grades of concrete.

In the United Kingdom, use of RCA does not have strength limitation for concrete, provided there is no contamination. For cube strengths of 25 to 50 MPa, a maximum of 20 percent replacement of coarse aggregates is permitted in designated concrete. RA is for unreinforced concrete limited to strength of 20 MPa. According to the European aggregates association, UEPG, most of recycled aggregates find their uses as base layer materials in road and infrastructure works, representing up to 20% of the total of this demand in Europe (ICJ Sep 2019). Many leading countries such as Japan, Australia, South Korea also have similar guidelines that encourage use of aggregates from recycling of C&D waste in concrete, both structural and non-structural.

In India, as mentioned earlier, the Bureau of Indian Standards amended the Indian Standards for Aggregates in Concrete (IS 383) in 2016 to allow use of upto 20% recycled concrete aggregates in Reinforced Concrete (M 25 grade) as coarse or fine aggregate and upto 100% in Lean Concrete (< M 15grade). The standards classify the recycled aggregates into two categories i.e. Recycled Concrete Aggregates (RCA) and Recycled Aggregates (RA). This is a welcome development that will provide the necessary impetus for the Indian construction industry to use recycled products from C&D wastes in both structural and non-structural works. There is a viewpoint that the replacement limits can be enhanced without compromising the quality of concrete, but the current limits suggested in IS 383 should be viewed more as a starting point. Given that it is rare to find buildings using even the current limits and therefore limited data on actual experience, it is difficult to make a case for enhancing limits without necessary evidence. The onus is thus on the construction industry to embrace this opportunity to develop templates and necessary confidence to convince the BIS Committee for enhancing upper limit for use of recycled concrete aggregates. For developing the required confidence and garnering support, the industry needs to demonstrate continuous use of recycled aggregates, documentation of data and verifiable results on a continuous basis, over a period. In addition, work on addressing consumer confidence, mindset issues and environmental sensitization will also facilitate and enable a case for higher limits.

In the current scenario, recycled aggregates, both fine and coarse, can be effectively used in multiple applications such as:

Concrete
BIS permits the use of RCA as both coarse and fine aggregates up to 20% in reinforced concrete in grades up to M25 and up to 25% replacement in plain concrete. Further, it allows 100% use of both RCA and RA in lean concrete below M15 though RA is permitted only in the form of coarse aggregate. This is a major step in promoting the use of recycled aggregates in concrete. Although use in higher grades is currently not permissible, it must be noted that more than 50% of the concrete made in the country is grade M25 and below. Hence there is significant potential for using recycled aggregates within the current regulations. To further encourage and enhance use of RCA in concrete, it is important to test the properties of RCA. Compared to natural aggregates, the water absorption values of RCA are typically higher and exhibits greater variability. This is due to the presence of hydrated cement paste in the RCA. There is a resultant decrease in the specific gravity and increased porosity leading to higher water absorption. Both these properties (specific gravity and water absorption) have an impact on the concrete behaviour and therefore, the mix design has to be suitably modified while using RCA. Other characteristics that need to be monitored are the permissible values for free chlorides and sulphate. Thus, a proper testing regime, preferably through a third-party testing agency needs to be implemented to enhance transparency and confidence of all market players.

Precast Concrete Products
One of the most common and effective use of recycled aggregates is in the pre-cast concrete industry, especially for the concrete blocks, bricks and pavers. As mentioned previously, India will require an estimated 600 billion number of concrete blocks and bricks annually. Since these applications are non-structural in nature, recycled aggregates can completely replace natural aggregates. Many existing C&D processing plants also have concrete blocks and paver manufacturing activities co-existing to manufacture value-added products ensuring seamless consumption of the recycled aggregates. Other pre-cast products that can be produced are concrete floor and wall tiles, kerb stones, concrete fence posts, drain covers, garden furniture, benches and a host of related concrete products.

Granular Sub-Base for Roads
Recycled aggregates are an excellent replacement for natural aggregates in the construction of sub-base for roads. The crushing characteristics of hardened concrete are similar to natural rock and are not significantly affected by the grade or quality of the original concrete. Recycled concrete aggregates produced from original concrete can be expected to pass the same tests required of conventional aggregates. RCA can be used in granular sub-base and lean concrete sub-base. For example, as per IL&FS Environment (2017), the Delhi Development Authority has used close to 5 lakh MT of recycled aggregates as sub-base for roads. Indian Road Congress has permitted the use of produce of C&D waste processing and has issued IRC: 121-2017 “Guidelines for use of construction and demolition waste in road sector”.

Other applications
Approximately half of the output from a C&D recycling facility is loose soil and mixed brick base, which typically has low demand. It is important that these products are also gainfully utilised to enhance sustainability and plant viability. Some applications for loose soil include gardening and landscaping, brick chippings to be used as drainage substrate for green covering and brick sand for tennis courts and other sports facilities. Being bulk of the output, finding long-term sustainable applications for such products will be one of the factors in ensuring success of the recycling facility.

Selection of Technology
Achieving technical and financial viability of C&D treatment and recycling facilities is a significant challenge because of reasons such as lack of data, constrained availability of land in urban areas, significant illegal dumping, lack of understanding of environmental damage and limited willingness to pay. There are three interrelated aspects requiring data and analysis i.e. selection of technology, business model and location. We discuss these in the following paras.

Technology Options and Selection
There are three main considerations driving the selection of the technology. First, whether recycling is feasible on a construction site in a standalone mode or alternatively is land available to develop a stationary facility. Second, the quantum and the nature of waste being generated. Third, the distance between major waste generating locations and the proposed recycling project site.

Based on these three considerations, a choice between two main types of technologies needs to be made. The two options are. (a) mobile crushers of different types which can be placed in-situ and (b) integrated stationary processing plants capable of washing, crushing, and segregating different types of waste. For all large-scale, green-field and redevelopment projects, in-situ mobile units are relevant. There are several reasons for this solution. First, it maximizes opportunities for recycling and reuse as the developer can integrate it in the demolition plan. Second, it minimizes transportation, thereby reducing cost and equally importantly, carbon emissions. Third, mobile units can be moved from one project to another and hence provide a flexible solution.

For recycling of C&D waste at city or town level, the wet processing integrated plants are appropriate in most cases the nature of the incoming waste stream is heterogenous. In larger cities, particularly where significant infrastructure projects such as metro development, new airports or greenfield townships are being planned, it will be useful to provide an additional crushing option as significant quantity of demolished concrete waste can be expected, particularly till the time mobile units become more prevalent.

An additional option that should be evaluated as part of the technology selection is the machinery for value added products such as manufacturing bricks, paver blocks etc. should be considered because the demand for recycled materials such as sand and aggregates may be inadequate. This evaluation will require understanding of the market for raw materials such as sand, aggregates, and soil. A commitment from the State and ULB to off-take a certain minimum quantity, say 30 percent, of the value-added products for development projects have a potential to significantly bolster the financial viability.

Quality Control and Testing
Ensuring quality control is critical to build confidence of the construction industry for addressing the mindset barrier. Systematic quality control will also establish a case for increasing the limits under the standards. Quality control calls for investment by establishing an in-house laboratory facility to perform basic tests, such as water absorption, specific gravity, testing for deleterious materials like chlorides and sulphates and sieve-analysis. A testing system with documented procedure for taking representative samples, frequency of testing and periodic certification by external third-party needs to be adopted. Further, capacity development of plant managers, operators and labour is required to enhance their understanding of the technical aspects and to develop customer orientation.

SINTEF Pilot projects of C&D waste recycling in India
Godrej Construction Materials; Mumbai


The Construction Materials business under Godrej Construction operates an RMC plant, a crushing unit for dry recycling of concrete debris and a fully automated concrete block and pavers manufacturing plant in Vikhroli, Mumbai. The recycling plant has a capacity of 300 TPD and the blocks and pavers plant have the capacity to produce 36,000 solid blocks per day and 54,000 Pavers per day. Marketed under the Godrej Tuff brand, these blocks and pavers are produced totally with recycled aggregates from Construction and Demolition waste. The objective of the project is to demostrate the added value of using concrete blocks with recycled aggregates. This means to document the technical performance of the pilot in each stage – from the source of the demolition to the placing of the blocks and evaluate the net green house gas emission for concrete pavement products by including the natural CO2-binding in the Environmental Product Declaration (EPD) by life cycle analysis.

The project, using a third-party testing house, systematically covered sampling, testing and documenting each stage of the whole cycle of demolition, recycling, block making and laying the recycled concrete block back into the prestigious Mumbai Metro construction project in the Aarey-Goregaon (E) station building. This also included testing a concrete block made with the recycled concrete in the SINTEF lab in Norway for evaluating the CO2 binding properties and the resultant positive impact on lowering the carbon footprint. The project report is currently being analysed and compiled for publication.

L&T – CIDCO Housing project, Ulwe, Navi Mumbai.
L&T has bagged the contract from CIDCO to construct 23,432 dwelling units at various locations in Navi Mumbai. This project, under the Pradhan Mantri Awas Yojana (PMAY) envisages construction of dwellings for the Economically Weaker Section (EWS) and Low-Income Group (LIG). A large part of this project is precast concrete and L&T has set up a PEB factory at Ulwe, Navi Mumbai where the precast concrete would be produced. Recycled concrete aggregates was proposed to be used for the PEB Grade slab (M 20) and for lean concrete (M 10).

Demolished concrete from Mumbai Metro project, Line no:5, Thane city was recycled at Metrro waste handling Private Limited plant at Kalyan Phatta, set up for the Thane Municipal Corporation. It was decided to use RCA fine aggregates A detailed sampling and testing schedule was prepared beforehand and testing of the recycled aggregates were conducted at a third-party laboratory before dispatch. Based on the physical properties of the RCA, the mix design was suitably modified. RCA was used at 100 percent for lean concrete, while 50% of the fine aggregate was replaced with RCA for grade slab concrete (M 20).

A total of 268 MT of RCA was supplied to the site and close to 500 m3 of concrete produced. 150.5 m3 of M 10 lean concrete and 342.55 m3 of Grade slab concrete M 20 was produced with this RCA. The concrete was cohesive and the compressive strength was comparable to the concrete produced with fine aggregate from natural stone.

Conclusion
Scientific management of C&D waste is a key challenge for reducing environmental risks such as air pollution, land degradation and ground water contamination. The current state of play suggests that stakeholders at the federal level are more aware and have issued new policies, regulations and introduced programs. At the city level, there has been limited progress and several barriers still exist. India’s rapid urbanisation will lead to an exponential increase in the volumes of the C&D waste generated and resource shortage for construction. To quote John F Kennedy, “when written in Chinese, the word ‘crisis’ is composed of two characters, one represents danger and the other represents opportunity”. The parallel is striking. C&D waste poses a real danger to the environment as we have seen earlier, but when treated and converted to recycled materials it also provides an opportunity to reduce the extraction and use of virgin aggregates, that are depleting rapidly. Effective policy setting, enforcement of regulatory provisions, capacity building and scientific waste management practices are powerful tools available with us to achieve the twin objectives. It must also be mentioned here that there have been some “islands of excellence” in India in the area of recycling C&D waste effectively and utilising in construction, the prime examples being IL&FS facilities in Delhi and Godrej in Mumbai, where recycled concrete aggregates is being successfully used in manufacturing high quality concrete blocks and pavers. The research analysed technical and financial options to develop business models based on principles of polluter pays, risk mitigation and market linked prices. An optimal business model can be selected based on a range of scenarios presented. Continued role of state and ULBs through policy enablers and capacity development were identified as other critical success factors.

References
Indian Concrete Journal; “Policies and Business Strategies for C&D waste management in India” Kshemendra Nath P, Gaurav Bhatiani: Aug 2020

Building Materials and Technology Promotion Council (2018) Utilisation of Recycled Produce of Construction & Demolition Waste - Ready Reckoner. Available at : http://164.100.228.143:8080/sbm/content/writereaddata/C&D%20Waste_Ready_Reckoner_BMTPC_SBM.pdf (accessed on 10 May 2020)

Central Pollution Control Board – Guidelines on Environmental Management of Construction and Demolition (C&D) Wastes – (Prepared in compliance of Rule 10, Sub rule 1 (a) of C&D Waste Management Rules 2016); CPCB – March 2017

Centre for Science and Environment (2014) Report 03. Available at: https://cdn.cseindia.org/userfiles/construction-and-demolition-waste (Accessed on 12 May 2020)

Citizen consumer and civic Action Group (2016) Citizen’s report on the 2015 floods in Chennai. Available at: https://www.cag.org.in/sites/default/files/database/4._wfc_citizensreportv4.pdf (accessed 27 September, 2019)

Indian Concrete Institute – Guidelines on Recycling, Use and Management of C&D wastes; Report of the Technical Committee (ICI/TC/05) – Oct 2013.

Indian Concrete Journal; “Use of recycled aggregates – Full scale demonstration”; Christian J Engelsen, Jacob Mehus-Sep 2019.

Indian Concrete Journal; “Construction and Demolition waste recycling in Europe – Long-term trends and challenges ahead”; Vincent Basuyau – Jan 2020.

IIT Kanpur (2016) Comprehensive Study on Air Pollution and Green House Gases (GHGs) in Delhi. Available at: http://cerca.iitd.ac.in/files/reports/IITK%20study%202016.pdf (accessed 27 September, 2019)

IL&FS Environmental Infrastructure & Services Limited – (IEISL) Presentation in the SINTEF-CPWD Workshop on C&D Waste Management, Delhi; 28 November 2017.

IQAir AirVisual (2019) 2019 World Air Quality Report Region & City PM2.5 Ranking. Available at: https://www.airvisual.com/world-most-polluted-cities?continent=&country=&state=&page=1&perPage=50&cities=(accessed on 01 June, 2020)

Ministry of Urban Development (2015) Smart Cities Mission Statement & Guidelines. Available at: http://smartcities.gov.in/upload/uploadfiles/files/SmartCityGuidelines(1).pdf (accessed 10 September, 2019)
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