Effects of foreign substances in cement mortar mixing water Available to Purchase

This study examined the effects of magnesium sulfate and sodium sulfide on fresh and hardened cement mortar. Two 410 kg/m³ dosed mortars were produced (water/cement ratios of 0·63 and 0·72). Sulfate salt solutions were prepared in different concentrations and used as mixing water. Solutions of magnesium sulfate and sodium sulfide and reference mortars were prepared with 1 l of mixing and drinking water, respectively. Mortars were produced in 26 (2 × 13) different mixtures. From each mixture, eight samples were produced for shrinkage and other tests. The workable life of the mortars was determined by vibratory table experiments. Experiments were conducted using a Vicat apparatus to determine the effects of the tested chemical substances on setting duration. For each mixture, six samples were held in water at a temperature of 20 ± 2°C until the day of testing. Bending and compression tests were then performed on samples aged 7, 28 and 90 d (two samples per age). For shrinkage tests, size changes of the two samples were measured until the 90th day of holding in a controlled environment (21°C and 55%–65% humidity). The effects of sulfate salts on fresh and hardened concrete mixes were analysed. The results revealed that magnesium sulfate was the most detrimental, but also showed that sodium sulfide increased the compressive strength.