The feasibility of using a high volume of non-clinker binders in self-compacting concrete related to its basic engineering properties

Abstract

This paper presents the results of an investigation aimed at producing and evaluating self-compacting concrete (SCC) made with high volumes of non-clinker binders. Ordinary Portland cement (OPC) was partially replaced with 60% of fly ash, 60% of slag or 30% of fly ash and 30% of slag. The paste volume was maintained at 0.34 m3/m3 to the explicit comparison of the effect of the mineral addition on SCC properties. The experiments examined the properties important for the civil engineering application of SCC. Hence, the setting time, workability, stability, density, water absorption, the development of the compressive and tensile strength and the modulus of elasticity over time were investigated. The tested thermal properties of concrete included the measurement of the hydration heat, the determination of apparent activation energy, and the thermal conductivity. Free and restrained shrinkage was measured, and the shrinkage cracking susceptibility was assessed. Test results indicated that using a high volume of fly ash in SCC significantly decreases its 28-day compressive strength. At the same time, fly ash revealed the best effect on improving the thermal and shrinkage properties of concrete. Slag replacement was found to be the most effective considering the concrete strength and maintaining the improvement of thermal and shrinkage properties. Furthermore, the results showed that the synergistic effect of fly ash and slag sustained the advantageous aspects of using fly ash, such as beneficial thermal and shrinkage properties, with the simultaneous much better mechanical properties compared to using only fly ash as OPC replacement in SCC.