Experimental Study on the Mechanical Properties of Alkali-Activated Slag Porous Concrete

Alkali-activated concretes with slag base as new materials could be used to achieve a healthy environment without pollutants such as greenhouse gases and to solve the problems of water shortage and groundwater resources and use by-products produced during the processing of materials such as iron, steel and copper alloys for construction projects. On the other hand, porous concretes have economic and environmental potentials such as preventing flooding, increasing groundwater reserves, decreasing the flow of surface water. Slag-based alkaliactivated concretes have been synthesized by natural pozzolans and industrial wastes such as sodium silicate with alkaline silicate and alkali hydroxide solutions. In the current study, the performance of alkali-activated porous concrete with the different amounts of sodium hydroxide molarity and the ratio of sodium hydroxide to sodium silicate has been investigated in terms of mechanical properties such as compressive strength. The flexibility and permeability of the specimens were also investigated. The tests have been performed on 9 series of samples with three values of 8, 12 and 16 Molar of sodium hydroxide and three ratios of sodium silicate to sodium hydroxide 1, 2 and 3 under curing times of 7, 14 and 28 days. The test results show that the alkali-activated porous concrete indicated a higher initial strength compared to conventional porous concretes. The compressive strength at curing time of 14 days and flexural strength at curing time of 7 days were about 75% of its strength at curing time of 28 days which is significant. The compressive and flexural strengths have been increased with the increasing of molarity and the ratio of sodium silicate to sodium hydroxide about 20 to 25% and 9 to 13%, respectively. However, the permeability decreases with the increasing of molarity of sodium hydroxide solution or the ratio of sodium silicate to sodium hydroxide.