Characterization and value-added application of low-quality concrete waste based recycled aggregates

Abstract

An enormous amount of construction and demolition waste (CDW) is generated as a result of the renovation/maintenance/demolition activities of buildings. Since they are often considered to be of low-quality and there are unawareness and reluctance of the importance of effective recovery, CDW-based materials are frequently either downcycled as road base fillers or disposed of directly to landfills. To address this issue, this study concentrated on the characterization of different originated low-quality concrete waste (CW)-based recycled concrete aggregates (RCA) and assessment of their effective recycling performance with the purpose of utilizing in value-added applications. CWs of unknown origin were collected from three different demolition sites and subjected to crushing-sieving procedures to obtain fine and coarse RCAs. Firstly, the original materials utilized in the manufacturing of RCAs were identified by analyzing their physical properties and chemical composition. Secondly, the selected RCAs were utilized in the development of Portland cement (PC) concrete produced with different PC dosages and different RCA replacement ratios. Special attention was given to adjusting the slump values of the mixtures in the range of 100–150 mm by using superplasticizer, while the water content for all mixtures was kept constant. The specimens were mechanically analyzed with various testing protocols such as slump tests, 7- and 28-day compressive and splitting-tensile strength tests. According to the results, an increment in compressive and splitting-tensile strength was seen with increasing RCA ratio at low and medium PC dosages and higher w/c ratios, on the other hand, the opposite behavior was noted at high PC dosage. The maximum performance was obtained from the mixture produced with 100% RCA and medium PC dosage with 47.3 MPa compressive strength and 4.27 MPa splitting-tensile strength. Consequently, the findings of the study demonstrated that RCAs can be successfully utilized in value-added applications such as incorporating green concrete production.