Evaluation of rheological properties of sustainable self-compacting recycled aggregate concrete produced by two-stage mixing approach

Abstract

The rheological properties such as static yield stress (τ0s), dynamic yield stress (τ0d), and plastic viscosity (μ) play an important role in controlling the fresh state activities of self-compacting concrete (SCC). In the present investigation, these rheological parameters of self-compacting recycled aggregate concrete (SCRAC) prepared by two-stage mixing approach (TSMA) are determined as a function of recycled coarse aggregate (RCA) percentage. Five types of samples are prepared for this purpose: M1 (0% RCA), M2 (25% RCA), M3 (50% RCA), M4 (75% RCA), and M5 (100% RCA). The static yield stress is determined by a well-accepted static yield stress formula; whereas, the dynamic yield stress and plastic viscosity are determined by Reiner-Riwlin theory in conjunction with the Bingham and modified Bingham models. The values of τ0s, τ0d, and μ are observed to increase with the increase in RCA%. This is due to the increase in internal friction between the particles. However, the influence is less in the proposed TSMA. Various conventional fresh properties of SCC of the same mixes are evaluated and the correlations between the conventional fresh properties and rheological properties have been established. Finally, the compressive strength of the samples is reported and a plausible model is developed to elucidate the mechanism based on the various characterizations including X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM). The study found that the proposed TSMA is an effective approach for improving the rheological and mechanical properties of SCRAC.