Effects of slag composition and temperature on the strength performance of slag blended cement mortars in composite chloride-sulphate environments

摘要

Major structures are often located near marine environments which expose them to attack from sea water containing mostly chlorides and sulphates. The compressive and flexural strength properties of ground granulated blast-furnace slag - blended cement specimens were investigated at temperatures of 20 °C and 38 °C, to assess their performances under typical arid and temperate marine climatic conditions. Slags, having Ca/Si ratios of 1.05 and 0.94, were blended with CEM I 52.5R at 30% replacement levels. The performances of the slag-blended cements were compared with CEM I 42.5R. Mortar samples measuring 40mm x 40mm x 160mm were cast using 0.5 water to binder ratio, pre-cured under water before exposure to combined solutions of chloride and sulphate. Compressive and flexural strengths were determined at specified ages of hydration between 1 and 28 days. Also, x-ray diffraction (XRD) and calorimetry analyses were conducted on paste samples to follow the hydration characteristics of the test binders. The results show that flexural strength increased for samples in combined test solution, and further indicated that the relationship between flexural and compressive strengths could be greatly influenced by temperature changes.