Use of foundry silica-dust in manufacturing economical self-consolidating concrete

Abstract

This paper presents results of an experimental work conducted on the use of foundry silica-dust in self-consolidating concrete (SCC). A control SCC mixture was made, in which ASTM C 618 Class C fly ash constituted 40 mass% of the total cementitious materials. Three more SCC mixtures were made using silica-dust obtained from an iron foundry, collected by a high-efficiency baghouse. Silica-dust was used to replace 10%, 20%, and 30% of fly ash at a 1:2 (fly ash to foundry dust) ratio by mass. The extra amount of foundry dust was treated as very fine sand. Use of foundry dust in SCC resulted in high air content (7–10%), possibly due to reaction between foundry dust and the particular chemical admixtures used. With the increase in foundry dust content containing iron, the color of concrete changed to dark gray or black. At 30% replacement of fly ash with foundry silica-dust, the demand for high-range water-reducing admixture (HRWRA) increased. As the foundry dust content increased, the demand for viscosity-modifying admixture (VMA) decreased. It was concluded that foundry silica-dust material could be used in producing economical SCC.