USAGE OF C&D WASTE IN CONCRETE AS A REPLACEMENT OF NATURAL AGGREGATE

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1 USAGE OF C&D WASTE IN CONCRETE AS A REPLACEMENT OF NATURAL AGGREGATE ABSTRACT Nikhil Kaushik & V V Arora National Council for Cement and Building Materials, India Construction and demolition (C&D) waste is defined as the solid waste generated by the construction, repair, alteration or demolition of residential, commercial or institutional buildings and infrastructures such as roads, bridges, dams, tunnels, railways and airports. NCCBM conducted studies on usage of C&D waste as replacement of natural aggregate in concrete. C&D waste was collected from a demolished building in New Delhi and from C&D waste processing plant in Burari, New Delhi. The waste from demolished building was processed (classification in different fractions) at NCCBM. Characterization on physical parameters was done as and the results were found to comply with IS: 383 specifications. Concrete mixes at particular water cement ratio were prepared and checked for their workability, compressive strength and other tests concerning durability of concrete like Rapid chloride Penetrability test, water permeability test etc. Samples were cast using coarse recycled aggregate and fine recycled aggregate as a replacement of natural aggregates at different percentages. Results in terms of Strength, workability and durability tests on certain percentage replacements of coarse and fine recycled aggregate were found to be encouraging for part replacement of Natural Aggregate. 1.0 INTRODUCTION Concrete[1] is the most widely material of construction all over the world. A huge quantity of concrete is consumed by construction industry all over the world. In India, the conventional concrete is produced by using natural sand/crushed sand obtained from different sources. However, due to the increased use of concrete in almost all types of construction works, the demand of natural or river sand has been increased. To meet this demand of construction industry, excessive quarrying of sand from river beds is taking place causing the depletion of sand resources. The scarcity of natural sand due to such heavy demands in growing construction activities have forced to find the suitable substitute. One of the cheapest and the easiest ways of getting substitute for natural sand is by crushing natural stone to get artificial sand of desired size and grade. The promotional use of artificial sand will conserve the natural resources for the sustainable development of the concrete in construction industry. The main reasons for increase of volume of demolition concrete / masonry waste are as follows:- i. Many old buildings, concrete pavements, bridges and other structures have overcome their age and limit of use due to structural deterioration beyond repairs and need to be demolished; ii. The structures, even adequate to use are under demolition because they are not serving the needs in present scenario; iii. New construction for better economic growth; iv. Structures are turned into debris resulting from natural disasters like earthquake, cyclone and floods etc. v. Creation of building waste resulting from manmade disaster/war. The changes in mechanical properties of recycled concrete aggregate are attributed to the patches of cement mortar present after crushing which increases the water absorption,

2 prolongs the mixing time and affect the strength of the recycled aggregate concrete. Mortar present on recycled aggregate varies from 40 to 60% depending upon the size of the aggregates and the water absorption lies between 3 10 percent. Concrete made with higher water absorptive recycled aggregate will have effect on compressive strength, resistance to freezing and thawing, elasticity, creep, shrinkage and workability. Inclusion of recycled aggregate [2] decreased the permeability of concrete mixes. Chloride conductivity increases with increased percentage of recycled aggregate. It also results in decreased workability and loss of slump in a short time. The work on durability is still very limited. In the present study Recycled Concrete is being compared with the normal concrete in terms of strength and certain durability parameters so as to enable use of C&D waste as a part replacement of natural aggregate in concrete. 2.0 INCORPORATION IN SPECIFICATIONS: The specific provisions in different countries are discussed below: IS: 383, included in draft revision. [3] It states that recycled fine and coarse aggregate can be used as replacement of Natural aggregate up to 25% in case of Plain concrete and up to 20% for M20 grade of reinforced concrete. It is not permitted to use recycled aggregate for more than M20 Grade of reinforced concrete. Additional requirements for manufactured aggregate: Sl. No. Characteristics Requirement 1. Total alkali content as Na2O equivalent, percent, Max Sulphate content as SO3, percent, Max Chloride Content, percent, Max Water absorption, percent, Max 10* 5. Specific Gravity 2.1 to 3.2 Higher Water Absorption is permitted subject to pre-wetting (saturation) of aggregate before batching and mixing. European (CEN) Practice EN [4] Physical Properties like Bulk density, water Absorbtion, Freeze thaw Resistance, drying shrinkage, soundness, Alkali silica Reactivity are mandatory similarly chemical Properties like chloride, acid soluble sulphate, sulphur content and carbonate content is mandatory. UK - BS :2006, [5] which is the complementary British Standard to BS EN 206, refers to two types of recycled aggregate: Recycled concrete aggregate (RCA), and Recycled aggregate (RA). RCA is obtained from crushing demolished concrete structures, discarded precast elements and unused hardened concrete. In some modification of EN 12620, BS 8500 stipulates that RCA must be predominantly composed of concrete (at least 83.5 percent) and masonry content not more than 5 percent. Such aggregate can be used in structural concrete having cube strength of concrete 50 MPa. Recycled aggregate concrete containing crushed leftover concrete has no strength limitation provided the aggregate is not contaminated. For concrete cube strengths of 25 to 50 MPa, a maximum of 20 percent replacement of coarse aggregate applies, for designated concrete.

3 RA may contain masonry up to 100 percent. Because the potential composition of recycled aggregate (RA) is so wide, additional specification clauses may be required on a case by case basis. In particular, a project specification should include maximum acid soluble sulphate, method for determining the alkali content, ASR reactivity and any limitations on use in concrete. Recycled aggregate (RA) is limited to concrete cube strength of 20 MPa. Similarly Other Countries like USA, Germany, Norway, Japan etc. are also using C&D waste as a replacement of natural aggregate. 3.0 C&D Waste Plant in Delhi The collection and transportation of C&D waste started on 24 Jul 2009 and processing at the plant commenced on 29 Dec 2009.In the processing facility, IL&FS Environmental Infrastructure & Services Ltd (IEISL) is collecting 500 tonne per day (TPD) of C&D waste from three designated zones of the Delhi i.e. Karolbagh, Sadar - Paharganj and City. The C&D waste is thereafter being recycled into aggregates at the waste management facility, which is in turn converted to Ready Mix Concrete (RMC), pavement blocks, kerb stones and concrete bricks. The waste collected consists of percent soil. Containers and skips were placed at the designated collection points for enabling private and public waste generators to store C&D waste. Collection is based on information provided by the MCD staff regarding the area from where the C&D waste is to be picked up. The recycling process at the central processing unit consists of the following steps: Fig 1: Material is Transported Through Conveyor Belts 4.0 EXPERIMENTAL DATA 4.1 Materials: Aggregates: a) Natural Coarse aggregate with a maximum nominal size of 20mm and Fine aggregate confirming to Zone III as per IS-383 was used. b) Construction and Demolition waste: C&D waste was collected from a demolished building in New Delhi and from C&D waste processing plant in Burari, New Delhi. The waste from demolished building was processed (classification in different fractions) at NCCBM. The properties of aggregates are listed in Table 1, 2, 3, 4 and 5. Table 1: Properties of Natural Aggregates

4 Property Fine Aggregate Coarse Aggregate 20 mm 10 mm Specific gravity Water absorption Sieve Analysis Cumulative Percentage Passing 20mm mm mm mm mm µ µ µ Silt Content, By wt 2.1 Impact Value, % 20 Crushing Value, % 18 Los Angeles Abrasion, % 23 Soundness, Na2SO4, % Elongation Index, % 14 Flakiness Index % 5 CBD, kg/l LBD, kg/l Table 2: Physical Properties of C&D waste from demolished building Property Recycled Fine Aggregate Coarse Aggregate 20 mm 10 mm Specific gravity Water absorption Sieve Analysis Cumulative Percentage Passing 20mm mm mm mm mm µ µ µ Silt Content, By wt 8.0 Impact Value, % 34 Crushing Value, % 36 Los Angeles Abrasion, % 47 Soundness, Na2SO4, % Elongation Index, % 23 Flakiness Index % 7 CBD, kg/l LBD, kg/l Mortar Content 61% 24% 45%

5 Table 3: Chemical Properties of C&D waste of Demolished Building in Delhi Sl. No Characteristic RCA RFA Requirement as per IS 383 Total Alkali Content as Na2O 1 equivalent, % Max, 0.3% 2 Sulphate Content as SO3, % Max, 0.02% 3 Chloride Content, % Max, 0.04% Table 4: Physical Properties of C&D waste from C&D waste Plant Property Recycled Fine Aggregate Coarse Aggregate 20 mm 10 mm Specific gravity Water absorption Sieve Analysis Cumulative Percentage Passing 20mm mm mm mm mm µ µ µ Silt Content, By wt 9.8 Impact Value, % 25 Crushing Value, % 29 Los Angeles Abrasion, % 35 Soundness, Na2SO4, % Elongation Index, % 14 Flakiness Index % 3 CBD, kg/l LBD, kg/l Mortar Content 52% 20% 42% Table 5: Chemical Properties of C&D Waste of C&D waste Plant, Burari, Delhi Sl. No Characteristic RCA RFA Requirement as per IS Total Alkali Content as Na2O equivalent, % Max, 0.3% 2 Sulphate Content as SO3, % Max, 0.02% 3 Chloride Content, % Max, 0.04%

6 4.1.2 Cementitious material: PPC was used for casting of concrete samples. Table 6: Physical and Chemical Characteristics of Cement PHYSICAL PROPERTIES PPC Fineness Blaine s (m 2 /kg) 356 Soundness Autoclave 0.06 Soundness Le Chatelier 2 Setting Time Initial (min.) 155 Setting Time Initial (max.) 215 Compressive Strength, 72±1 hrs, Mpa 24.5 Compressive Strength, 168±2 hrs, Mpa 32 Compressive Strength, 672±4 hrs, Mpa 43 Specific gravity 2.89 CHEMICAL PROPERTIES Loss of Ignition (LOI) 2.74 Silica (SiO 2) 32.2 Iron Oxide (Fe 2O 3) 3.57 Aluminium Oxide (Al 2O 3) Calcium Oxide (CaO) Magnesium Oxide (MgO) 1.35 Sulphate (SO 3) 2.15 Alkalies Na 2O 0.89 K 2O 0.53 Chloride (Cl) 0.05 IR Mix design details: Concrete mixes prepared with PPC Cement at w/c ratio of 0.55 and were checked for their workability, Compressive Strength, flexure strength and durability properties. Natural aggregate was replaced by Recycled aggregate of both the sources at various percentages upto 100%. The mix design details of specimens are given below. The Adjustment was made in mixing water to correct the water Absorbtion of aggregates. The laboratory conditions of temperature and relative humidity were monitored during the curing i.e. 27±2 o C and relative humidity 65±5. Sl. No. Table 7: Concrete Mix Design Details W/C Mix Constituents Fine Cement Cement Content (Kg/m 3 ) Water Conten t (Kg/m 3 ) Dose of Admixture % by weight of Cement Aggregate as % of Total Aggregate by weight - strength of concrete (N/mm 2 ) Exposure Condition: Moderate PPC

7 5.0 RESULTS 5.1 Results on Fresh Concrete is being Mentioned Below: Specime n ID Replace ment, % Workabi -lity in terms of slump (mm) Air Conten t, % Specime n ID Replacement, % Workability In terms of slump (mm) Air Conten t, % M1NS M1NS M1R M1X M1R M1X M1R M1X M1R M1X M1D M1Y M1D M1Y M1D M1Y M1D M1Y Note: 1. D: Recycled fine aggregate from demolished building, R: Recycled Fine Aggregate from C&D waste plant, Burari, Delhi. 2. Y: Recycled Coarse aggregate from demolished building, X: Recycled Coarse Aggregate from C&D waste plant, Burari, Delhi. 5.2 Results on Hardened Concrete:- a) Results for Replacement of recycled fine aggregate with natural fine aggregate. Specimen ID Replacement Compressive Strength (MPa) Flexure Strength (MPa) M1NS M1R M1R M1R M1R M1D M1D M1D M1D Specimen ID Replacement RCPT, Coulomb s Drying Shrinkage Water Permeability (mm) Modulus of Elasticity (Mpa) M1NS M1R M1R M1R

8 M1R M1D M1D M1D M1D Note: D: Recycled fine aggregate from demolished building, R: Recycled Fine Aggregate from C&D waste plant, Burari, Delhi b) Results for Replacement of recycled Coarse aggregate with natural Coarse aggregate. Specimen ID Replacement Compressive Strength (MPa) Flexure Strength (MPa) M1NS M1X M1X M1X M1X M1Y M1Y M1Y M1Y Specimen ID Replacement RCPT, Coulomb s Drying Shrinkage Water Permeability (mm) Modulus of Elasticity (Mpa) M1NS M1X M1X M1X M1X M1Y M1Y M1Y M1Y Note: Y: Recycled Coarse aggregate from demolished building, X: Recycled Coarse Aggregate from C&D waste, Burari, Delhi 6.0 DISCUSSIONS ON TEST RESULTS: Properties related to Fresh Concrete: Workability in terms of slump and Air Content were measured on fresh concrete. Due to mortar present on the surface of aggregate the workability and air content decreases. The same trend was observed in fine recycled aggregate replacement in which the mortar percentage was 61% and 52% respectively for two different sources of aggregate. In case of recycled coarse aggregate there was marginal change in workability but the air content increases.

9 Basic engineering properties of concrete such as compressive strength, flexural strength and modulus of elasticity: Based on the results obtained, the compressive strength and flexural strength of concrete made with recycled Fine aggregate increases at all ages up to 50% replacement with natural fine aggregate. In case of recycled coarse aggregate up to 25% replacement with natural coarse aggregate, flexure and compressive strength increases at all ages. Similarly the static modulus of elasticity of concrete increases up to 50% replacement of recycled fine aggregate and 25% replacement of recycled coarse aggregate, this is similar to trend observed in compressive strength. The reduction in strength at higher percentages of replacement can be due to the fact that RCA is weaker than the normal aggregate as seen from results from impact, crushing and abrasion values. The increase in strength at lower percentages can be due to improvement of grading & better packing. Properties related to Penetrability/Permeability such as Water permeability and RCPT: The penetrability in terms of charge passed was increasing with increase in recycled coarse and fine aggregate and varying between 1237 to 2755 coulombs and as per [2] the durability properties decreased. Water Penetration depth was decreasing with increase in recycled fine aggregate replacement, but concrete made with recycled coarse aggregate exhibits different behaviour, in that case the water penetration depth increases with increase in recycled coarse aggregate. Drying Shrinkage: Due to higher water absorption of recycled aggregate, the drying shrinkage of concrete increases with increase in recycled aggregate as compared to natural aggregate. Drying Shrinkage varies from to 0.035, i.e. the shrinkage gets doubled when using 100% recycled coarse aggregate in concrete as comparing to % of natural aggregate. 7.0 CONCLUSION:- a) Workability and Air Content: In case of recycled fine aggregate, with increase in percentage of recycled fines the workability and air content decreases in the concrete mix. Cohesiveness of the mix increases. In case of recycled coarse aggregate replacement there was no marginal change in workability but the air content increases slightly with the increase in recycled coarse aggregate. b) Compressive strength, Flexural strength and Young s Modulus: In case of recycled fine aggregate strength parameters and E-modulus increases up to 50% replacement with natural sand. However, in recycled coarse aggregate these parameters increases up to 25 % replacement of natural aggregate. c) RCPT, drying shrinkage and Water Permeability: Chloride Penetration and drying Shrinkage increases with increase in percentage of recycled aggregate. However, water permeability decreases with increase in percentage of recycled aggregate. 8.0 ACKNOWLEDGEMENT The authors would like to acknowledge the Management of C&D Waste Plant, Burari for providing the recycled coarse and fine aggregate for conducting the study as well as the laboratory technical assistants concerned for their assistance in carrying out the research. 9.0 REFERENCES 1. Mirjana Malešev, Vlastimir Radonjanin and Snežana Marinković Recycled Concrete as Aggregate for Structural Concrete Production 2. F.T. Olorunsogoa, N. Padayacheeb, Performance of recycled aggregate concrete monitored by

10 durability indexes, Cement and Concrete Research, Vol.32 (2002) IS:383, Draft Revision, Coarse and Fine Aggregates for Concrete Specification. 4. EN Aggregates for Concrete. 5. BS :2006, Specifications for constituent Materials for Concrete.