Ijraset Journal For Research in Applied Science and Engineering Technology
Authors: Dev Anand Pandey, Dr. Hemant Sood
DOI Link: https://doi.org/10.22214/ijraset.2023.54280
Certificate: View Certificate
The world has, by now, identified the seriousness and challenges regarding the sustainability of resources amid major environmental concerns that are part of modern problems today. The construction industry all over the world has been explicitly using concrete owing to its quality, strength, and adaptability to various construction needs and situations. However, in the last few decades, increased awareness, legislation, and global initiatives to combat pollution, energy consumption, waste disposal, and global warming have pushed industries, researchers, engineers, and other stakeholders to substitute virgin materials with alternative construction materials. Construction and demolition account for about 30% of the total solid waste generated worldwide. The top ten countries including India and China which are contributing heavily to this waste stream, together generating about 2.5 billion metric tonnes every year. The C&D waste poses a significant strain on landfill sites, contributes to energy waste, and adds additional costs for its disposal. However, through careful sorting, processing, and recycling processes, a significant chunk of it can be reused and help minimise environmental impact. The work presented here involves fractional replacement of C&D waste aggregates viz., RCA and RA in amounts ranging from 05-25% as coarse and fine aggregates, respectively. Most of the previous works have not aimed at higher grades like M35 and M40, which form the subject matter of this paper. Several tests were conducted to estimate the fresh and hardened state properties of concrete, most important being compressive and tensile strength as well as slump test for workability.
I. INTRODUCTION
Concrete is by far, the most used construction material worldwide. There are so many factors which makes concrete almost irreplaceable as construction material anytime soon. Concrete is a highly durable material that can withstand heavy loads and resist the effects of weathering, erosion, and chemical attacks. Concrete is versatile material with ability to be moulded and cast in any shape and size, the local availability of constituent materials also makes it cost effective. It has high thermal mass, good fire resistance and better sound insulation and acoustic comfort. Every year, about 12 billion tonnes of concrete is produced world over, which amounts to per capita consumption of 1 m3, hardly any material would reach anywhere near this number, in terms of production. The annual demand for concrete is expected to exceed 18 billion tonnes by 2050. With such huge demand forecast, it is vital to look for sustainable practices to balance environmental impacts associated with the extraction and manufacturing of its components, as well as carbon emissions from cement production. China is the largest producer and consumer of concrete, followed by India and the United States and unarguably these are the chief contributors to construction related waste. These wastes can be managed with sustainable mindset by incorporating recycled materials such as aggregates coming from Construction and Demolition (C&D) waste and other industrial waste by-products which causes considerable nuisance for municipal authorities and put pressure on landfill sites for disposal, such practices can relax the demand for virgin resources to a good extent and reduce carbon footprint of the associated processes.
A. Construction And Demolition Waste.
Construction and Demolition waste is largely composed of materials which comes from debris from demolished structures, waste generated from construction and renovation projects, road construction and repairs, construction of bridges and other infrastructure works. C&D materials generally include concrete, asphalt, wood, metals, gypsum, plastics, and reclaimed building materials. Rapid construction is often viewed as an indicator of improving lifestyle and economic growth.
Recycling of waste developed as a concept in late 20th century, since then efforts are being taken to use recycled aggregates (RA) to produce recycled aggregate concrete (RAC). The absence of proper recycling facilities, inconsistent government policies and regulations, quality issues in recycled aggregates, impurities, and contamination etc. are proven limitations for the use of it on large scale, maybe this is why it has not gained popularity except in works of minor importance such as base and sub-base course in road construction, as filler in foundation work and sanitary structures. However, recent studies have shown that these recycled aggregates have enough potential to be reused in conventional concrete grades with replaced component ranging from anything between 0-100%.
B. C&D Waste: Indian Scenario
A detailed study was carried out to know the exact amount of C&D waste generated in India, it was done by Technology Information, Forecasting and Assessment Council, TIFAC. Overall C&D waste output was approximately 13-15 million tonnes for the year 2000. Several findings reported in this study is highlighted through the following points:
It also gave rule of thumb for C&D waste generation for different types of construction and repair work. However, as per C&D Waste Management Rules 2016, the C&D waste generated can be assumed to be 25% of total municipal solid waste, total output lying between 10-750 million tonnes per year as reported by different government agencies, this figure could be a gross underestimate given the absence of special measures to collect C&D waste separately. As per Annual report on Solid Waste Management 2020-2021 in conformance with Solid Waste Management (SWM) Rules 2016, about 50% of waste is recycled and 18.4% goes to landfills. The load on landfills seems to be decreasing due to improved collection efficiency. The policy roadblocks and economic viability are slowly giving way for better data accumulation and inclusion of C&D waste in construction industry.
IS 383 which only allowed for ‘naturally sourced’ virgin materials for aggregates got revised in 2016 and allowed for usage of C&D waste in conventional concrete mix with certain limits. The latest stipulations in IS 383 allows for use of recycled aggregates with 25% replacement limit in plain concrete, 20% in RCC mixes of M25 and below grades, with up to 100% replacement in lean concretes of grades smaller than M15. Similar changes were incorporated in other technical institution such as National Building Code of India (NBC) which added a chapter on ‘sustainability’ and made certain provisions to allow recycled aggregates to replace natural aggregates.
II. LITTERATURE SURVEY
III. EXPERIMENTAL ARRANGEMENT
A. Materials
Cement is the most basic material in concrete production, it acts as a binder and imparts strength. In this study OPC 43 Grade cement was used which complies with IS 8112: 1989. Several properties of concrete such as setting times, fineness, consistency etc. are used to judge the quality of cement, these tests were carried out to ascertain quality of cement, properties, and test results are listed in Table I.
We have taken fine aggregates which are part of demolished concrete structure, it was subjected to cleaning with running water and manually sorted for impurities, it is labelled as recycled fine aggregate (RFA). Sieve analysis was carried out and based on fineness modulus it falls into Zone III, control mix i.e., a reference mix was designed with natural river sand having nominal size of 4.75 mm.
In this study, coarse aggregates of 10 mm and 20 mm were chosen and combined grading was done to work out the proportion in which they need to be mixed, sieve analysis was done to match the grading requirements given in IS 383:2016 and recycled concrete aggregate (RCA) was used substituted with natural coarse aggregates; the recycled aggregates were sourced from a local construction waste processing plant in Chandigarh. Physical properties of coarse and fine aggregate are listed in Table II.
Table I : Physical Properties of OPC 43 Grade Cement
Physical Properties |
Test Results |
IS 8112-1989 Stipulations |
% Fineness (90 µm IS Sieve) |
4.25 |
?10 |
Soundness (mm) Le Chatelier’s Method |
1.20 |
?10 |
Normal Consistency (%) |
31 |
- |
Initial Setting Time (mins.) |
220 |
≥ 30 |
Final Setting Time (mins.) |
335 |
≤ 600 |
Specific Gravity (Le Chatelier’s Method) |
3.15 |
- |
Table II : Physical Properties of Fine & Coarse Aggregates
Properties |
Fine Aggregates |
Coarse Aggregates |
Admixture (Conplast SP430G8) |
||
Natural Fine Aggregate |
Recycled Aggregate (RA) |
Natural Coarse Aggregate |
Recycled Concrete Aggregate (RCA) |
||
Maximum Size (mm) |
4.75 |
4.75 |
20 |
20 |
- |
Bulk Density (loose) in kg/m3 |
1656 |
1435 |
1480 |
1155 |
- |
Bulk Density (compacted) in kg/m3 |
1865 |
1600 |
1570 |
1316 |
- |
Specific Gravity |
2.60 |
2.63 |
2.65 |
2.45 |
1.24 |
Free Moisture (%) |
1.55 |
1.38 |
0.30 |
2.25 |
- |
Water Absorption (%) |
14.6 |
16.3 |
0.34 |
5.065 |
- |
B. Water
The various limits of impurities to be allowed in water used for mixing the ingredients of concrete are given in IS 456:2000 and samples used in our study have been made with clean source of potable water at room temperature for mixing and curing and conforms to IS 456 limits.
C. Chemical Admixture
Conplast SP430G8 was used in the experimental investigation for both the grades. This admixture is to produce pumpable concrete and high-grade concrete of M30 & above by substantial reduction in water resulting in low permeability and high early strength. Also, it helps in producing high workability concrete requiring little or no vibration during placing. Its dosage was fixed as 0.5% by weight of cement as stipulated in the mix design.
D. Design Mix details of M35 Grade of Concrete
The mix proportions were worked out for the two grades as per IS 10262:2009 and IS 456:2000 and details are tabulated in Table III and IV.
Table III : Mix Design details of M35 Grade Concrete
Grade M35 |
|||
Cement |
Fine Aggregate |
Coarse Aggregate |
Water |
420 |
607.1 |
1222.9 |
159.6 |
1 |
1.45 |
2.91 |
0.38 |
E. Design Mix details of M40 Grade of Concrete
Table IV : Mix Design details of M40 Grade Concrete
Grade M40 |
|||
Cement |
Fine Aggregate |
Coarse Aggregate |
Water |
435 |
587.7 |
1216.2 |
165.6 |
1 |
1.35 |
2.80 |
0.35 |
F. Replacement Details-Sample Matrix
IV. RESULTS AND DISCUSSION
The experimental programme was designed to determine the fresh and hardened characteristics of concrete mixes. The results obtained at the end of various tests conducted are presented here. Two control mixes of M35 and M40 were prepared and then the recycled aggregates were replaced in different percentages equally spaced from one another. The impacts of replacing aggregates on different concrete properties are studied through tests such as workability and density estimation for the fresh properties and compressive strength, splitting tensile strength and flexural tensile strength for matured state of concrete.
A. Workability
The ease of mixing of control mix and concrete prepared with replaced recycled aggregates of both the grades are evaluated using slump test in conformance with IS 1199:1959.
Slump Test: The slump test is most used procedure for measuring the consistency or workability of fresh concrete. The test determines the degree of deformation the concrete undergoes under its own weight after being placed in a cylindrical mould and then removed. The slump test signifies the consistency of various batches of concrete. The shape of the concrete slumps provides information about the workability and quality of the concrete. Since this test is so simple to execute, right from measurement and the apparatus used, this test is being used since last 100 years . The slump cone's shape demonstrates concrete’s workability and it is suitable for low to high workabilities.
Initially, the inner surface of the mould was cleaned and oiled. The non-porous base plate was then covered with a mould, which was then filled with approximately four layers of prepared concrete mixture. Each layer was tamped with 25 strokes, and excess concrete was removed by slowly lifting it upward in a vertical direction. The slump was then known by measuring the height difference between the mould and the highest point of the test specimen mixture.
There are many other tests available to check the workability of concrete such as Compaction Factor Test, Vee Bee Test, Flow Table Test etc which are relatively sophisticated and is suitable for various ranges of workability. For example, a mix with low and very low workability can be better handled and measured using Vee-Bee Test.
Similar trend in variation in the values of splitting tensile strength was observed. The percentage change from the level of control mix as recorded during test conducted is -18.85%, -15.56%, -8.9%, -20.58%, -30.81% corresponding to 5, 10, 15, 20, 25% RL. The percentage change recorded in the values of flexural strength of the samples corresponding to replaced C&D waste as against the control mix is -2.15%, +6.48%, +10.27%, -3.77%, -3.75 % respectively.
It is imperative to note from this study that recycled aggregates have quality issues even when sourced from highly mechanised sorting and cleaning process. The surface imperfections result in decreased strengths as we increase the percentage of replacement to the control mix, however average strength mostly lies between characteristic and target strength . The fresh and hardened properties of concrete both seems to indicate that at higher grades such as M35 and M40 which are standard grades as per IS 456 and are dense enough and needs careful supervision both during design and casting. During mix design process, effort was taken to limit w/c ratio to as low as practically feasible. The compressive strength, split tensile strength and flexural strength have all shown a similar trend of strength variation that as soon the control mix is replaced with recycled aggregates, there is dip in values which starts rising gradually till 15% RL and it starts decreasing from 15 to 25% RL, the greatest fall recorded from 20 to 25% RL. From observations at the time of casting, such decrease at 25% RL was quite apparent as the workability, appearance and surface finish of the concrete were decreasing rapidly. From our study, it is therefore concluded that the ideal level of replacement at these grades with chosen recycled aggregates lies at 15% RL as at this point, peak strength is achieved. It was also concluded, based on experience that coarse aggregates contribute more to strength than fine aggregates as fine aggregates have large surface area, so there should be greater cohesion and hydration reactions occurring on its surface but since the aggregate was already subjected to loads before and contains impurities on it surface hence it hampers the strength development appreciably. Also, the water absorption of recycled aggregates is higher and requires at least 10-15% more water to not hamper the workability, fine aggregates being porous absorbs most of it and this may necessitate use of admixtures. Therefore, the quality and source of recycled aggregates play a vital role in overall performance of such recycled concrete. Use of recycled fine aggregate (RFA) can be substituted with other alternatives like Industrial by-products (IBP) such as blast furnace slag, wood ash (WA), waste foundry sand (WFS), etc. and effect of such material in conjunction with recycled coarse aggregate can be studied. Results of this study can be conveniently used for future studies on C&D waste (recycled coarse and recycled fine aggregates) concrete.
[1] Andreu, G., & Miren, E. (2014). Experimental analysis of properties of high performance recycled aggregate concrete. Construction and Building Materials, 52, 227–235. https://doi.org/10.1016/j.conbuildmat.2013.11.054 [2] Bravo, M., De Brito, J., Pontes, J., & Evangelista, L. (2015). Durability performance of concrete with recycled aggregates from construction and demolition waste plants. Construction and Building Materials, 77, 357–369. https://doi.org/10.1016/j.conbuildmat.2014.12.103 [3] Duan, Z. H., & Poon, C. S. (2014). Properties of recycled aggregate concrete made with recycled aggregates with different amounts of old adhered mortars. Materials and Design, 58, 19–29. https://doi.org/10.1016/j.matdes.2014.01.044 [4] Etxeberria, M., Vázquez, E., Marí, A., & Barra, M. (2007). Influence of amount of recycled coarse aggregates and production process on properties of recycled aggregate concrete. Cement and Concrete Research, 37(5), 735–742. https://doi.org/10.1016/j.cemconres.2007.02.002 [5] Khatib, J. M. (2005). Properties of concrete incorporating fine recycled aggregate. Cement and Concrete Research, 35(4), 763–769. https://doi.org/10.1016/j.cemconres.2004.06.017 [6] Rao, A., Jha, K. N., & Misra, S. (2007). Use of aggregates from recycled construction and demolition waste in concrete. Resources, Conservation and Recycling, 50(1), 71–81. https://doi.org/10.1016/j.resconrec.2006.05.010 [7] Yang, C.?;, Hs, C., & Ashour, A. F. (2008). Influence of Type and Replacement Level of Recycled Aggregates on Concrete Properties. In ACI Materials Journal (Vol. 105, Issue 3). http://hdl.handle.net/10454/7768 [8] Report on Construction and Demolition waste generation in India by Technology Information, Forecasting and Assessment Council (TIFAC), New Delhi in 2001. [9] Solid Waste Management Rules, S.O. 1357(E), 2016 published by Ministry of Environment, Forest and Climate Change, Government of India, New Delhi. [10] C&D Waste Management Rules 2016 published by Ministry of Environment, Forest and Climate Change, Government of India, New Delhi.
Copyright © 2023 Dev Anand Pandey, Dr. Hemant Sood. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Paper Id : IJRASET54280
Publish Date : 2023-06-20
ISSN : 2321-9653
Publisher Name : IJRASET
DOI Link : Click Here