Deformational behavior of self-compacting concrete containing recycled aggregate, slag cement and green powders under compression and bending: Description and prediction adjustment

Abstract

The high fine-aggregate content of Self-Compacting Concrete (SCC) means that its deformational behavior differs from that of vibrated concrete. SCC performance is further altered when industrial by-products are used as raw materials in those fractions. In this paper, the aim is to analyze and to model the deformational behavior under compression and bending of SCC containing 100% coarse and 0%, 50%, and 100% fine Recycled Aggregate (RA), limestone and RA green aggregate powders sized 0/0.5 mm, and Ground Granulated Blast-furnace Slag (GGBS) cement. After the fresh and mechanical characterization of the 18 SCC mixes that were produced, their compressive stress-strain and bending load-deflection curves were determined by continuously recording the applied load and the strain/deflection values of the SCC test specimens. 100% coarse RA yielded deformability levels in accordance with international standards, while higher fine RA contents increased deformation under compression and reduced it under flexural stress. SCC stiffness increased when GGBS was added, due to the adjustment of the proportion of cementitious matrix, while the use of limestone powder and, especially, RA powder had the opposite effect. Both compressive strain and flexural deflection were underestimated with existing theoretical models. However, the incorporation in the models of both exponential correction coefficients, dependent on the fine RA content, and partial adjustment coefficients, dependent on the types of cement and aggregate powder, produced optimal fits with the experimental stress-strain and load-deflection curves. In view of the deformational behavior, which was successfully modelled with maximum deviations of ±10%, fine RA may be used in combination with GGBS and limestone powder, although it is recommended that fine RA should not exceed proportions of 50%.