Properties and performance of metakaolin pozzolanic cement pastes

Cement industry produces the 7% of the global CO2 emission. The most effective way to decrease CO2 emission of cement industry is the substitution of a proportion of cement with supplementary cementing materials. Metakaolin (MK) is a silica-based product that, on reaction with Ca(OH)(2) (CH), produces C-S-H gel at ambient temperature. MK also contains alumina that reacts with CH to produce additional alumina-containing phases, including C(4)AH(13), C(2)ASH(8) and C(3)AH(6). The aim of our research is to investigate the effect of MK up to 20 mass% substitutions of OPC on the hydration characteristics of MK-blended cement pastes. The physico-chemical properties of the hardened cement pastes were studied up to 90 days of hydration. The hydration products of some selected samples were investigated using XRD, DTA and TG techniques. The results indicated that substitution of up to 20 mass% OPC by MK as a pozzolanic materials resulted in an increase in the standard water of consistency, acceleration of the initial setting times, high compressive strength values at earlier ages and improvement of the mechanical, durability properties as well as performance of MK pozzolanic cement pastes.