Effects of use of alkaline mixing waters on engineering properties of cement mortars

In this study, the effect of pH level of mixing water on physical, mechanical and microstructure properties of cementitious mixtures was examined. In order to adjust the pH level of mixing water, various ratios of NaOH were added to ultra-pure water. Therefore, in total, six different mixing waters were obtained including the reference mixing water, pH10, pH11, pH12, pH13 and pH14. Mortar samples were produced using the obtained mixing waters with CEM I 42.5R Portland cement, then physical and mechanical properties of the cement mortars were determined on the 7th, 14th, 28th and 90th days. In addition, microstructure properties of the cement mortar specimens were determined after the 28days curing period. Porosity measurements by mercury intrusion porosimetry were also examined after the 28days cure periods. At the end of study, it was determined that the alkaline mixing waters (up to pH13) have positive effects on the compressive strength and workability of the cement mortars. The best result was obtained with pH12 mixing waters.