Alkali activation of blended cements containing oil shale ash

The influence of using different types of alkali activators namely: sodium sulphate, sodium silicate, sodium carbonate and sodium hydroxide on the hydration characteristics and physic-mechanical properties of special blended cement systems containing oil shale ash were investigated. Compressive strength values of the blended cement pastes containing 10% oil shale ash I and 30% oil shale ash II in absence of activators about 83–80% of Portland cement paste respectively. The addition of various alkali-activators to the same two mixes improves the mechanical strength of both cement mixes. The various cement alkali-activators used in this study followed this order (major to minor) with respect to the mechanical strengths Na2SO4 > Na2SiO3 > Na2CO3 > NaOH. The results showed that SAII would have better pozzolanic properties than SAI referring to chemical composition and the degree of crystalinity and these findings were confirmed by DTA, XRD and SEM.