A comparison of test methods to assess the strength potential of plain and blended supplementary cementitious materials

Abstract

This paper studies the effectiveness of various test methods to measure the reactivity of combinations of supplementary cementitious materials (SCMs). While several test methods that quantify the reactivity of individual SCMs are available, the advent of ternary cements necessitates the testing of not just the individual SCMs, but also their combinations. The study was carried out on fly ash (FA), slag, calcined clay, limestone (LS) and their blends. Various standardised and non-standardised test methods, that measure the physical and chemical characteristics of SCMs were studied. The measurements from these test methods were compared to the 28-day compressive strength of cement mortars, partially replaced by the respective SCMs or their blends. It was observed that most of the test methods that are used for individual SCMs are also suitable for use with the blends of SCMs. In this way, the compatibility of the two SCMs being blended can also be tested. It was found that test methods that measure the consumption of calcium hydroxide (CH) are not suitable for testing SCMs and blends containing slag. Methods involving the measurement of heat of hydration and bound water are more suitable for such SCMs. It was also seen that the reliability of simple indirect test methods is similar to other more sophisticated test methods.