The feasibility of using a muffle furnace and a balance to determine the calcium hydroxide (Ca(OH) 2 ) consumption of supplementary cementitious materials (SCMs) in model systems was investigated. SCMs were mixed with Ca(OH) 2 in an alkaline solution and, after mixing, the paste was sealed inside a 50 °C oven for curing until testing. The chemically bound water and Ca(OH) 2 consumption were determined using the furnace at two fixed temperatures and the results were compared with those from the thermogravimetric analysis. The protocol of the furnace test was optimized based on thermogravimetric analysis results. While further testing is needed, initial results demonstrated the validity of the method, and suggest that it is able to differentiate inert, latent hydraulic, and pozzolanic materials using reactivity thresholds for the chemically bound water and the Ca(OH) 2 consumption. This new test could be used for rapid and low-cost screening of novel SCMs.