Abstract

The use of blended cements incorporating supplementary cementing materials and cements with low C₃A content is becoming common to prevent the deterioration of concrete structures subjected to aggressive environments. This paper presents the results of an investigation on the performance of finely ground volcanic scoria (VS) based ASTM Type I and Type V (low C₃A) blended cement concrete mixtures with varying immersion period of up to 48 months in environments characterized by the presence of mixed magnesium-sodium sulfates. The concrete mixtures comprise a combination of two Portland cements (Type I and Type V) and two VS based blended cements with two water-to-binder ratio of 0.35 and 0.45. Background experiments (in addition to strength and fresh properties) including X-ray diffraction (XRD), Differential scanning calorimetry (DSC), mercury intrusion porosimetry (MIP) and rapid chloride permeability (RCP) were conducted on all concrete mixtures to determine phase composition, pozzolanic activity, porosity and chloride ion resistance. Deterioration of concrete due to mixed sulfate attack and corrosion of reinforcing steel were evaluated by assessing concrete weight loss and measuring corrosion potentials and polarization resistance at periodic intervals throughout the immersion period of 48 months. Plain (Type I/V) cement concretes, irrespective of their C₃A content performed better  in terms of deterioration and corrosion resistance compared to Type I/V VS based blended cement concrete mixtures in mixed sulfate environment.

Keywords: volcanic scoria, sulfate attack, blended cement concrete, corrosion/deterioration