Study on the Sulfate Resistance and Drying Shrinkage of Mortars Containing Scoria as a Cement Replacement

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Use of blended cements is growing rapidly in the construction industry due to economical, ecological and technical benefits. Syria is relatively rich in volcanic scoria. In the study, three types of cement were prepared; one plain Portland cement CEM I (control) and two blended cements: CEM II/A-P and CEM II/B-P (EN 197-1), each of them with three replacement levels of scoria: (10%, 15%, 20%) and (25%, 30%, 35%), respectively. Evaluation of sulfate resistance of mortars containing scoria-based cements was performed in accordance with ASTM C1012. Length measurements were performed up to 52 weeks after immersing the specimens into 5% Na2SO4 solution. Drying shrinkage has been evaluated using mortar bar method in accordance with ASTM C596. Lengths of mortar bars subjected to drying shrinkage were measured periodically up to 360 days. SRPC cement was employed for comparison in both tests. Test results revealed that the increase of scoria significantly improves the sulfate resistance of mortars. The expansion of scoria-based mortar bars decreased with the increase of scoria replacement level. Further, according to the expansion test results, CEM II/B-P can be used instead of SRPC in sulfate-bearing environments. The results of drying shrinkage showed that the CEM II/B-P-based mortar bars exhibited greater contraction when compared to the control mortar, especially at early ages. However, the long-term drying shrinkage of mortars was not influenced much by the addition of volcanic scoria.