Influence of Metakaolin on Resistivity of Cement Mortar to Magnesium Chloride Solution

An experimental study for the resistance of mortar paste specimens incorporating 0, 5, 10, 15, 20, 25, and 30% metakaolin (Mk, produced by firing kaolin at 820°C for 2 h) to the magnesium chloride solution was reported. Results confirmed that mortar specimens with a high replacement level of metakaolin showed higher resistance to magnesium solution. The reduction of calcium hydroxide and the increase of secondary calcium silicate hydrate (CSH) in the cement matrix results from the pozzolanic reaction of Mk. The compressive strength values of the blended ordinary portland cement (OPC) mortars specimens improved relative to those containing no Mk, up to 25% by weight OPC substitution, and then decreased up to 30% by weight Mk. Scanning electron microscope microstructures indicate a good improvement for the matrix structure of the blended cement mortars, in which a denser structure was observed.