Compressive Strength and Sulfuric Acid Resistance of Mortars Containing Residual Solids from Concrete Sludge

Abstract

　This study investigates the reuse of residual solids from concrete sludge, dewatered using a filter press technique, which were added to cement mortar mixes in place of JIS standard sand. An ordinary Portland cement mortar was mixed with differing ratios of residual solid (50, 75, and 100 mass%), which produced mortars that had a significantly lower compressive strength than mortar without additives. The compressive strength of mortar mixes containing Type B equivalent cement (which is a 60:40 blend of ordinary Portland cement and blast furnace slag fine powder) combined with differing ratios of residual solids (10, 20, 30, 40, 50, 75, and 100 mass%) was then tested, which showed that compressive strength was not significantly lower in mortar mixes containing up to 40 mass% residual solids when compared to mortar without additives. This may be due to the blast furnace slag activating the residual solids. In the sulfuric acid resistance test, the Type B cement mortar mixes were immersed in 5 and 10 mass% sulfuric acid solutions, with high sulfuric acid resistance shown at a 5 mass% sulfuric acid concentration. These results confirm that the mortar meets the standards of the Japan Sewage Works Agency.