Influence of MK-based admixtures on the early hydration, pore structure and compressive strength of steam curing mortars

Abstract

Prestressed high-strength concrete (PHC) pipe piles are one of the most widely used concrete elements in building foundation construction. In this study, the effects of material composition on the compressive strength development, early hydration and pore structure of PHC were investigated by a series of analytical techniques. Supplementary cementitious materials, namely metakaolin (MK), granulated ground blast-furnace slag (GGBFS) and limestone powder (L.S) were used to prepare cement pastes and mortars under steam curing condition to improve early compressive strength. Finally the mortar containing 10% MK and 10% L.S was prepared, with the compressive strength up to 89 MPa at 1 day and 93 MPa at 7 days. The effects of the blended mineral admixtures on the early hydration and microstructure of steam cured pastes and mortars were investigated by XRD, TGDTC and MIP. The results showed that the mineral admixtures could consume Ca (OH)2 owing to pozzolanic reaction and promote concrete hydration, which led to the improvement of the properties of hydration products and optimization of pore structure and pore size distribution.