Mechanical Properties of Recycled Concrete Aggregate for Medium-Quality Structural Concrete
With increased attention to the construction industry’s environmental impact, research has turned to investigating ways to decrease these effects. Concrete production, use and sustainability are areas where researchers seek to lessen the construction industry’s environmental impact.
Abstract
The use of recycled coarse aggregate (RCA) has a high potential to significantly reduce the environmental impact of construction projects as well as the cost of construction materials. Reusing RCA in concrete mixes as a partial or full replacement of fine or coarse aggregate would be a more effective action in supporting and protecting the environment and reducing construction and demolition waste. This research reports the evaluation of medium-quality concrete properties incorporating RCA. Concrete cylinders, prisms, and cubes, as well as reinforced concrete (RC) beams, are prepared with different replacements of the RCA (25%, 50%, 75%, and 100%). The workability, mechanical properties, and reinforcement bond of cured concrete are examined at different ages. Moreover, microscopic analysis for the recycled concrete is presented to investigate the bond between the cement paste, the used aggregates, and the interfacial transition zone (ITZ). The effect of the stainless-steel fibers, crumb rubber, and CFRP laminates on the mechanical properties of recycled concrete aggregate is explored.
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Rubberized concrete is widely used in construction by utilizing the advantages of partially replacing fine or coarse aggregate with rubber to enhance several properties of concrete and provide an environmentally friendly solution. This paper experimentally explores the influence of utilizing crumb rubber (CR) as an alternate coarse aggregate in concrete. Concrete specimens were prepared with different percentages of rubber (0%, 5%, 10%, 15%, and 20%). Additionally, other parameters, such as freezing–thawing cycles, temperature, and stainless steel fibers (SSFs), were investigated. The workability of fresh concrete and the compression properties of hardened concrete were examined. Reductions in the mechanical properties of rubberized concrete were obtained. The compressive strength reductions ranged between 13% and 50%, based on the percentage of CR in the concrete mix. However, a lesser unit weight and higher toughness were obtained relative to conventional concrete. The average unit weight decreased by 1.3%, 2.5%, 3.4%, and 5.7% of the control mixture when 5%, 10%, 15%, and 20% of the CR were incorporated into the concrete mixtures, respectively. Regression models to predict the compressive strength and unit weight of concrete with CR were developed. In addition, a life cycle cost analysis (LCCA) to identify and quantify the possible benefits of using CR in concrete mixes was carried out. Using rubberized concrete mixtures for thin whitetopping offered a slightly lower net present value compared to the ordinary concrete mix.
