Pavement Concrete with Air-Cooled Blast Furnace Slag and Dolomite as Coarse Aggregates

Abstract

This study evaluated the effects of substituting natural coarse aggregate (dolomite) with air-cooled blast furnace slag (ACBFS) on the strength and durability properties of pavement concretes. The scope of the study included evaluation and analysis of four types of concrete subjected to three deicers [calcium chloride (CaCl 2 ), magnesium chloride (MgCl 2 ), and sodium chloride (NaCl)] while undergoing freeze–thaw (FT) exposure. Of the four types of concrete mixtures, two were prepared with ACBFS and two with natural dolomite as coarse aggregate. For each aggregate type, one mixture was produced with Type 1 portland cement, while the second one was produced with a binder composed of Type 1 cement and Class C fly ash (20% replacement by weight). Fresh properties of concrete tested included slump, unit weight, and total air content, while compressive and flexural strengths were measured for hardened concrete. Durability of concrete exposed to FT was assessed by periodically measuring dynamic modulus of elasticity of concrete and average depth of chloride penetration. Concrete with ACBFS aggregates developed slightly higher (~6%) compressive strength but lower (~15%) flexural strength than did concrete with natural dolomite. Periodic measurements of dynamic modulus of elasticity and visual observations of test specimens showed that of the three deicers used, the CaCl 2 was the most aggressive, followed by MgCl 2 and NaCl. In regard to resistance to the FT cycles in the presence of deicers, fly ash concretes (with either ACBFS or dolomite as coarse aggregate) showed better performance than did corresponding plain cement concretes.