Mechanical properties and compressive constitutive relation of solid waste-based concrete activated by soda residue-carbide slag

Abstract

The resource utilization of solid wastes such as soda residue (SR), carbide slag (CS), and iron tailings was improved in this study, which combined iron tailings aggregate to prepare the solid waste-based concrete (SCT) based on the previously developed SR-CS co-activated blast furnace slag-fly ash binder. Considering various factors such as composition of binder, water-binder ratio, and aggregate type, the development rule of mechanical properties of SCT was revealed through the tests of cube compressive strength (fcu), axial compressive strength (fcp), splitting tensile strength (fct), flexural strength (fcf), ultrasonic pulse velocity (UPV), and the compressive constitutive relationship was established through the compressive stress–strain test. The results demonstrated that the early compressive strength of SCT was slightly low, which could be improved through suitable heat curing (60-75℃@12 h) and would not produce an unfavorable effect on its late strength. SCT exhibited excellent axial compressive, tensile, and flexural strengths, where the 28d values fcp, fct, and fcf were 86.8 ± 3.2%, 11.5 ± 0.8%, and 14.7 ± 0.7% of fcu, i.e., higher than that of Portland cement concrete (PCC) with the same grade. The 28d UPV of SCT was 3.677–4.311 km/s, indicating good compactness; thus, SCT could be defined as high-quality concrete. SCT had a relatively longer plastic section during uniaxial compression and showed significant brittleness after peak stress. Its elastic modulus (13.12–19.13 GPa) was positively correlated with compressive strength (20.3–34.4 MPa) and was lower than that of PCC with the same grade. The prediction model of fcu, its quantitative relationships with fcp, fct, and fcf, and the constitutive relationship under uniaxial compression were established by statistical regression, which agreed with the test results. Overall, SCT showed a little discrepancy in mechanical properties compared with the regular aggregate concrete with the same binder.