The Performance of Concrete Made with Secondary Products—Recycled Coarse Aggregates, Recycled Cement Mortar, and Fly Ash–Slag Mix (original) (raw)
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Physical properties and mechanical behaviour of concrete made with recycled aggregates and fly ash
This paper investigates the behaviour of concrete made with recycled constituents. The synergistic use of recycled concrete aggregates and fly ash is addressed. Twelve different concrete mixes were prepared, sampled and tested. Stable correlations emerged between replacement ratios and concrete properties. The suitability of these concretes for structural applications was clearly proved. a b s t r a c t Enhancing the environmental sustainability of human activities and industrial processes is a common challenge in various branches of modern research and technology. Being characterised by a huge demand of both energy and raw materials and by a significant contribution to the global emissions of greenhouse gases (GHGs), the construction industry is fully concerned by this challenge. Particularly, since concrete is the most widely used construction material, several solutions are nowadays under investigation to reduce the environmental impact of its production processes. They often consist of partially replacing ''natural'' constituents (i.e. aggregates, cement, water, fibres) with recycled ones, in view of the twofold objective of reducing both the demand of raw materials and the amount of waste to be disposed in land-fills. However, the formulation of reliable relationships between the main physical and mechanical properties of concrete produced with the aforementioned recycled constituents is still considered as an open issue. This paper is a contribution to such topic. The results of a wide experimental campaign carried out on concretes made using recycled concrete aggregates (RCAs) and fly-ash (FA) in partial substitution of natural aggregates (NAs) and cement (C) are presented and discussed herein. Particularly, concretes charac-terised by variable water–binder ratios and produced with different percentages of RCA and variable the content of FA have been tested. Test results have allowed estimating the time evolution of the compres-sive strength, as well as the tensile strength at 28 days, along with some relevant physical properties, such as permeability and resistance to chloride ion penetration. The feasibility of producing structural concrete made with even significant amounts of the aforementioned recycled constituents and industrial by-products clearly emerges from the experimental results.
Concrete is the single largest manufactured material in the world. The use of recycled materials in construction is an issue of great importance. Utilization of Recycled Aggregates (RA), Ground Granulated Blast Furnace Slag (GGBFS) and fly ash in concrete addresses this issue. In this project, strength, durability of Recycled Aggregate Concrete (RAC) with GGBFS was studied. M-50 grade concrete with 0.30 w/c ratio and maximum size of 16mm course aggregate was used for this study. Totally 16 mix combinations were prepared for this study with different replacements of Recycled aggregate (0%, 25%, 50%, and 100%) and GGBFS (0%, 20%, 30%, and 40%). Compressive & Tensile tests were conducted at 7, 14, and 28 days to study the strength characteristics and Sorptivity test were conducted to examine the durability characteristics. It was found that the replacements of Natural Aggregate (NA) and cement with Recycled aggregate and GGBFS respectively, significantly decrease both the compressive and tensile strength and cement with GGBFS replacement increases the resistance against permeability. Based on experimental results it was concluded that 40% replacement of GGBFS and 50% replacement of RA give satisfactory results and it is recommended for reinforced concrete works with proper mix design
International Journal for Science and Advance Research In Technology ISSN : 2395-1052, 2017
The work audits the feasibility of demolished concrete as partial substitute of natural coarse aggregate respectively. In initial stage, same optimum ratio of cement is added with partly replaced natural coarse aggregate (NCA) with recycled concrete aggregate (RCA) in concrete. For test intent, recycled aggregates were accessed from crushed concrete cubes of grade M25 in laboratory. Variant composition of natural coarse aggregate and recycled aggregate adopted and test samples from this matrix were prepared for the same test as mentioned above. Observations reveal, combination of 90% NCA and 10% RCA in ratio, leads to adequate results.
STUDIES ON STRUCTURAL BEHAVIOUR OF RECYCLED AGGREGATE CONCRETE WITH WASTE CLAY TILES AND FLY ASH
This paper studied the possibility of using waste materials such as clay tiles and fly ash as substitute for coarse aggregate and cement respectively in concrete. Experimental studies were conducted on fresh and hardened concrete made with partial replacement of crushed granite coarse aggregate with broken tile and cement with fly ash. The experimental results showed that 20% and 30% tile aggregate concrete (TAC) attains 82% and 75% compressive strength of natural aggregate concrete (NAC). The replacement of cement with 25% of fly ash further reduces the strength in the initial age and at the later age, the strength gets improved and it attains 85% and 79% compressive strength of NAC for 20% and 30% tile aggregate concrete (TAC) respectively. The same scenario was found in tensile and flexural strength of tile aggregate admixed concrete. Hence these waste materials could be used in concrete within the limits of the results as obtained in the present experimental study
Effect of Recycled Aggregate and Fly Ash in Concrete
Waste arising from construction and demolition constitutes one of the largest waste streams within the developed and developing nations. The rapid growth in construction and depleting natural resources demands the recycling and reusing technology to be adopted in construction field. The use of recycled coarse aggregate (RCA) and fly ash (FA) is one of theapproaches towards this need.Use of RCA and FA in concrete can be useful for environmental protection and economical terms. In this experimental study the natural coarse aggregate (NCA) is replaced with RCA at different percentage and the mechanical strength of concrete is tested. In addition the FA is introduced as replacement of Cement.The objective of present study is to determine the sustainability of RCA as an alternate material to NCA and to compare the workability, density and compressive strength result using FA. The mix designing is done for water cement ratio 0.5. Cubes are casted by replacing virgin aggregate and cement with 10%, 20%, 30%, 40% RCA and FA and compressive strength is checked. Obtained results are then used to establish an empirical relationship between the strength of concrete by using percentage of RCA and percentage of FA. Results shows that RCA and FA up to 30% can be used for making concrete.
Use of Recycled Aggregate and Fly Ash in Concrete Pavement
American Journal of Engineering and Applied Sciences, 2011
Problem statement: Recycled materials aggregate from the demolished concrete structures and fly ash from burning coal shows the possible application as structural and non structural components in concrete structures. This research aims to evaluate the feasibility of using concrete containing recycled concrete aggregate and fly ash in concrete pavement. Approach: Two water cement ratio (0.45 and 0.55) the compressive strength, modulus of electricity and flexural strength for concrete with recycled aggregate and fly ash with 0, 25% replacing cement in mass were considered. Results: The material properties of recycled aggregate concrete with fly ash indicate comparable results with that of concrete with natural aggregate and without fly ash. Conclusion/Recommendations: The recycled materials could be used in concrete pavement and it will promote the sustainability of concrete.
KnE engineering, 2020
This study investigates the possible effects of incorporating different industry wastes during manufacturing of concrete, with percentages ranging from 0% to 30%, and assesses the influence of these combinations (mineral additions and recycled aggregates) on the properties of a recycled concrete comprised of these two main constituents products. Recycled concrete samples with different combinations of mineral additions at various dosages were used to determine these properties in the fresh and hardened states. The "Design-expert" methodology was used to analyse the results after 7, 14 and 28 days, identifying correlations and the effects of the different variables. The results obtained showed the advantageous effect of incorporating the pozzolana and slag into the concrete mixture at dosages of 15% and 30%, they also demonstrated the low optimal percentage of marble fillers of 5%. These findings suggest that replacing clinker with industrial waste could limit the dust and CO 2 emissions into the atmosphere during concrete manufacture, offering environmental advantages as well as conserving the natural resources of aggregate recovery from C&D wastes.
Use of recycled concrete aggregate in fly-ash concrete
Construction and Building Materials, 2011
Nowadays, environmentally friendly building is becoming a crucial issue in construction industry. The course towards sustainable concrete involves mainly minimizing the environmental impact of concrete production by substituting virgin mineral materials by recycled ones as well as reducing the global CO 2 emissions. The approach adopted here includes a large substitution of natural coarse aggregates (NA) by recycled concrete aggregates (RCA) obtained from crushed concrete debris, as well as the use of 30% fly ash (FA) as a partial substitute of Portland cement for FA concrete production. Previous study by the authors has revealed the potential of using coarse RCA to produce concrete with a similar 28-day design strength to that obtained when using natural aggregates. This paper discusses the effect of both partial and full replacement of natural coarse aggregates by coarse RCA in a fly ash concrete. Engineering properties and durability performance have been examined on both concrete types (Portland cement and fly ash) for mixes designed with various proportions of the RCA (0%, 30%, 50% and 100%) by mass. The results obtained showed that while embedding high amount of the RCA could lower the resistance to chloride penetration and carbonation of concrete still comparable design strength to that of the control mix might be achieved.
Mechanical Properties of Concrete with Recycled Concrete Aggregate and Fly Ash
Recycling, 2021
Recycled concrete aggregate (RCA) collected from the demolition of old reinforced concrete structures can be reused to prepare structural and non-structural concrete, thereby protecting the environment by preserving natural resources. This study explores RCA’s use, collected from the crushed concrete of different building projects in Riyadh, to manufacture fresh self-compacting concrete (SCC) and investigate its properties in the fresh and hardened state. Four SCC mixes were prepared by replacing natural aggregate (NA) with RCA at 0%, 25%, 50%, and 75% replacement levels. The water-cement (w/c) ratio was maintained constant at 0.38 for all the mixes. Slump Flow, J-ring, and V-funnel tests were performed on the SCC mixes in the fresh state, and the compressive strength of hardened concrete was determined after seven, 14, and 28 days. Water absorption and split tensile tests were also carried out for all the mixes. The findings revealed that it is possible to reach compressive strengt...
A Study on the Behaviour of Recycled Aggregate Concrete with Plastic Waste and Fly Ash
Concrete plays a vital role with in the development of infrastructure globally. Certain amount of cement can be replaced with fly ash which aids the usage of less cement content in the concrete mix. Natural aggregates can be replaced with RAC to make it more vulnerable and eco-friendly. From past studies it is known that use of recycled concrete aggregates might reduce the strength. To compensate this strength reduction PET were employed. PET fibers can be obtained from as bottles and containers. In the present experimental investigation, concrete having compressive strength 40 MPa used. Fly ash proportion in concrete kept constant as 25%. The coarse aggregate replaced with RCA are 0, 25, 50, 75, 100 percentages with natural aggregates. PET is added 1% of the total weight of the cement. Various tests are carried out by casting different mix proportions of cubes, cylinders and beam prisms to perform compressive strength, split tensile strength and flexural strength for 7 and 28 days. This project aims to know the usage of fly ash, recycled aggregates and PET fibers will give similar strength.