Correlations between pozzolanic evaluation methods, electrical conductivity and chemical shrinkage test

Abstract

The use of pozzolans is one of the main strategies of the cement industry to reduce the CO2 emissions; however, one barrier to increase the use of pozzolans is the local availability. Rapid pozzolanic evaluation methods can facilitate the search for new pozzolanic materials and their quality control. The pozzolanic activities of eleven materials which include two class f fly ash, two silica fumes, metakaolin, ground granulated blast furnace slag, ground glass, sugar cane bagasse ash and three natural pozzolans were evaluated with two types of ordinary Portland cement and calcium hydroxide (CH). The strength activity index (mortar mixtures at 7 and 28 days of age), the Chapelle test (10.57 g/L CH and 4 g/L pozzolan suspension at 80 °C for 16 h), chemical shrinkage (cement pastes with 10 or 20% of pozzolan at 60 °C for 3 days) and a proposed electrical conductivity method (800 mg/L CH and 302.7 mg/L pozzolan suspension) were compared. Simple and multivariable linear regression analysis were employed to identify possible correlations between methods and physicochemical characteristics of materials. Only a significant correlation (R2=0.84) was found between the CH consumption of Chapelle and the loss of conductivity of conductivity tests. Based on this finding, the proposed conductivity method may be useful for estimate the CH consumption of the Chapelle method.