Effect of recycled coarse aggregate on physical and mechanical properties of concrete

Abstract

Recycling of building waste has become essential process in the construction industry due to the sustainability and economic benefits such as decreasing the waste to landfill, conserving natural resources, and reducing pollution. Large amount of building waste is produced from the construction and demolition process of reinforced concrete (RC) structures. In this paper, the effect of using recycled coarse aggregate (RCA) on the behavior of concrete is experimentally studied. The RCA is prepared by crushing and sieving of waste of standard compression test cubes having a compressive strength ranging between 25 MPa and 30 MPa. The physical and mechanical properties of RCA are experimentally estimated and compared to those of natural coarse aggregate (NCA). A set of 72 standard concrete cubes, cylinders, and beams specimens are made using coarse aggregate replacement ratios (CARR) of 0%, 30%, 50%, and 100%. The specimens are tested to estimate the compressive, splitting, and flexure strengthens at the ages of 7 and 28 days. The study is extended by using the RCA in casting 12 RC columns with CARR similar to those of specimens. The columns are tested in an axial compression test protocol till failure. Crack patterns, failure loads, strains, displacements, and toughness of the tested columns are compared. It is concluded that using a CARR of 30% and 50% and a specific water cement ratio provides better mechanical behavior than that of NCA while the CARR of 100% yields worst mechanical behavior compared to that of NCA.

Torsion Behavior of Recycled Aggregates Concrete Beams With Openings

“…For the compressive behavior of RCA columns, the crack pattern was similar to the column specimen with NCA [13]. The columns' ultimate capacity, stiffness, and maximum displacement were higher for RCA columns with 30 % and 50 % RCA replacement ratios compared with NCA columns, while the 100 % RCA replacement ratio recorded the lowest values [13]. For the shear behavior of beams with RCA without stirrups reinforcement, the crack pattern and failure mode had no major differences between RCA and NCA beams [15].…”

“…By increasing RCA, the torsional strength decreases, and the angle of twist increases. The torque-twist behavior and failure mode of RCA beams were similar to that of NCA beams [12][13][14]. Due to the difference between the densities of RCA and NCA, the mix design require more amount of RCA [14].…”

“…For the flexural behavior of RCA beams, the crack pattern was similar to NCA beams, while the deflection is increased with the increase of the RCA replacement ratio [14]. For the compressive behavior of RCA columns, the crack pattern was similar to the column specimen with NCA [13]. The columns' ultimate capacity, stiffness, and maximum displacement were higher for RCA columns with 30 % and 50 % RCA replacement ratios compared with NCA columns, while the 100 % RCA replacement ratio recorded the lowest values [13].…”

“…The differences in values for the first crack and ultimate torque between RCA and NCA beams were less than 12.5 %, and 7.7 %, respectively [12]. RCA has more water absorption than NCA up to 1246% [13]. In the case of 100 % replacement with RCA, the modulus of elasticity achieved the lowest value of 18 % decrease compared with the NCA beam [12].…”

Research on the Performance of Recycled-Straw Insulating Concrete and Optimization Design of Matching Ratio

“…The physical properties of recycled aggregates from different sources also differ, which can also lead to varying thermal conductivities [24,25]. Miguel et al [26] investigated the thermal conductivity of concrete made from recycled aggregates from different locations.…”