Rapid screening tests for supplementary cementitious materials: past and future

Rapid screening tests for supplementary cementitious materials (SCMs) have been in use for over 150 years. Over the years a multitude of methods have been put forward to predict the strength development of SCM blended mortars and concrete. This paper summarizes and rationalizes the main approaches and then applies them to a selection of materials that cover a broad range of SCMs, both pozzolanic and hydraulic. Included are siliceous fly ash, blast furnace slag, natural pozzolan, metakaolin and an inert quartz filler. The selected test methods are the Chapelle test, the Frattini test, active silica and alumina extractions, a dissolution rate test, and a new calorimetry-based test. The results are compared, interpreted and discussed in view of their aim of predicting the compressive strength development. Finally, a new test method is proposed that relates the cumulative heat of the SCM reaction in a simplified model system to the compressive strength development in standardized mortars. The new method is practical, repeatable and applicable to a wide range of SCMs (both pozzolanic and hydraulic), it furthermore reduces the experiment duration by a factor of 10 and correlates well to the compressive strength development of blended cement mortar bars.