Effect of magnesium concentration vs. pure water attack on the leaching kinetics and mechanical properties of low-carbon cementitious pastes

Abstract

With the increasing use of mineral additions to partially replace Portland cement, reaction mechanisms and the effects of chemical attack on material properties change. A recent study examined magnesium attack on a model low-carbon cementitious paste, but the influence of Mg concentration on the observed mechanisms remains unclear. To investigate this, a low-carbon model cementitious paste was exposed to 5 and 50 mmol/L MgCl₂ solutions for few months, as well as in pure water, to assess its impact on leaching kinetics and mechanical properties. The increase in MgCl₂ concentration, leads to a comparable phenomenology, only the deterioration rate increases with higher Mg levels. When immersed in pure water, the Ca leaching of the paste is more progressive, and the degraded depth is slightly lower than that of magnesium attack. Immersion in pure water appears to generate larger pores compared to magnesium attack and a higher reduction in E_PSIM is observed.