Environmental Factor and Concentration of Cl- and OH- in Mortars

The concentration of free hydroxyl ions in pore solutions of mortars is studied, and the effects of hot environment on these ions are reported. The influence of fly‐ash addition is observed and discussed. Fog curing decreases free ${\mathrm{OH}}^{-}$ ions in cement mortar. Fly‐ash mortar retains free ${\mathrm{OH}}^{-}$ ions more satisfactorily. A further decrease in ${\mathrm{OH}}^{-}$ concentration is observed as a consequence of exposure to hot environment. Initially well‐cured fly‐ash/cement mortar performs better in this respect than cement mortar. The ratio of ${\mathrm{Cl}}^{-}$ to ${\mathrm{OH}}^{-}$ in mortars that include ${\mathrm{Cl}}^{-}$ ions increases sharply as a result of hot environment. Fly‐ash inclusion is also beneficial in this situation. Nevertheless a large increase in the ${\mathrm{Cl}}^{-}$‐to‐${\mathrm{OH}}^{-}$ ratio is still recorded as a result of hot weather application. The results of this study indicate the importance of applying a suitable curing regime when the concrete contains fly‐ash and/or is exposed to hot weather. The results are relevant to studies concerned with corrosion protection of steel reinforcement in concrete. More importantly they are of particular relevance to the understanding and prevention of the phenomenon of extensive reinforcement corrosion occurrence in hot weather environment.