The effects of alkalis and curing regimes on the mechanical strength of metakaolin based cementitious materials with steel slag

The alkali activation of metakaolin is a way of producing high strength cementitious materials. The processing of these materials has been the subject of numerous investigations. This paper investigated the effects of alkali category and curing regimes on the mechanical strength of metakaolin based cementitious materials with steel slag. At the same time, the reaction products characterisation was carried out by means of X-ray diffraction (XRD) and scanning electron microscope (SEM). The results of mechanical strength showed that sodium silicate activated metakaolin based cementitious systems with steel slag has a higher and faster mechanical strength development than the systems activated by NaOH, Na2SO4, gypsum, phosphorus-gypsum, Na2CO3. When the modulus and baume degree of the sodium silicate solution are 1.4 and 41%, respectively, the compressive strength of the cementitious systems is highest and can reach 92.2MPa. Curing temperature is a significant factor for the compressive strengths. It can also be concluded that the steel slag was almost fully dissolved to take part in the alkali activated reaction and be immobilized into the amorphous aluminosilicate matrix shown by means of XRD and SEM.