The production of high-performance self-compacting concrete using recycled concrete aggregates and steel waste tyre fibres

Abstract

Globally, rapid urbanisation has led to greater demands for concrete constituents. Consequently, a sustainable approach towards infrastructure is crucial. The integration of waste in concrete can be beneficial towards mitigating the overexploitation of natural resources while converting waste to a resource. This study investigates high-performance self-compacting concrete (SCC) performance containing two sources of waste as constituents, namely recycled concrete aggregates (RCA) and steel waste tyre fibres (SWTF) concerning rheology in the fresh state, early age and hardened state characteristics. A total of six mixes containing different SWTF dosages and RCA proportions were tested. The natural coarse and fine aggregate replacement percentages for the initial four mixes were 100% and 50%, respectively, with SWTF dosages ranging from 0 kg/m3 to 30 kg/m3. In addition, the remaining mixes had the same coarse RCA content of 100% while a natural fine aggregate percentage replacement of 0% and 100%, respectively, with an SWTF dosage of 20 kg/m3 was used. The results obtained through various standardised testing indicated that the addition of SWTF recorded a reduction in the SCC workability with time, mainly the passing ability. A decrease in SCC viscosity with an increase in yield stresses proportional to the addition of SWTF was also noticed using the rheometer. Although the SCC performance levels reduced, as expected, the SCC maintained certain flow characteristics. In assessing the early age characteristics using an environmental chamber, a decrease in plastic shrinkage crack width as opposed to an increase in time of occurrence, proportional to the addition of SWTF, was noted. Furthermore, with an increase in SWTF dosage, an increase in the age of cracking under restrained shrinkage was recorded using the ring test. A decrease in density and compressive strength was recorded with an increase in both SWTF dosage and RCA content in terms of hardened state characteristics. With the addition of SWTF, the flexural peak load and the tensile splitting strength increased up to a particular fibre dosage, whereas the flexural toughness increased with higher SWTF dosages.