Effect of Using Kaolin and Ground-Granulated Blast-Furnace Slag on Green Concrete Properties
Cement production causes pollution to the environment and the surrounding society especially at Helwan and Suez cities (Egypt) due to the emission of CO2 gas resulting from fuel combustion in cement factories. The research studies the implementation of supplementary cementitious materials (SCM), namely, kaolin (KA) and ground-granulated blast-furnace slag (GGBS), into concrete as a partial replacement of cement and evaluates their effect on concrete mechanical behavior. The study consists of two parts; part I includes activating KA thermally at 750 °C for 3 h to produce metakaolin (MK) and activating GGBS by alkaline solution of 10 molar-concentrated KOH and K2SiO3 with a ratio of 1:2.5, respectively, then investigating their replacing effect on the compressive strength of cement mortars at 3, 7, and 28 days. In part II, the best replacement percentages in terms of compressive strength are selected, and their effects on concrete mechanical behavior at 56 days are investigated. The results showed that 10% MK replacement significantly improves concrete mechanical behavior at 28 days. Moreover, 30% GGBS replacement can be used in production of concrete of 25~35 MPa.