An alternative thermal method for identification of pozzolanic activity in Ca(OH)2/pozzolan pastes

Pozzolans play an important role in the industry of cement and concrete. They increase the mechanical strength of cement matrices and can be used to decrease the amount of cement in concrete mixtures, thus decreasing the final economic and environmental cost of production; also, as some of them are byproducts of industrial processes (such as silica fume and fly ash) and their use can be seen as a solution for some residues, that otherwise would be disposed as a waste. Pozzolans fixate the Ca(OH)(2) generated during cement's hydration reactions to form calcium silicate hydrates (C-S-H), calcium aluminate hydrates (C-A-H), or calcium aluminosilicate hydrates (C-A-S-H), depending on the nature of the pozzolan. Traditionally, the pozzolanic activity is identified using the Ca(OH)(2) fixation percentage which is quantified by thermogravimetric (TG) analysis, using the mass loss due to the Ca(OH)(2) dehydroxylation around 500 A degrees C. An alternative method to identify pozzolanic activity at lower temperatures using a standard issue moisture analyzer (MA) is presented in this paper, using the mass loss due to hydrate's dehydration generated by pozzolans in the pozzolanic reaction. Samples of Ca(OH)(2) blended with different pozzolans were prepared and tested at different hydration ages. Using TG analysis and an MA, a good correlation was found between the total mass loss of the same sample, using the two methods at the same temperature. It was concluded that the MA method can be considered a less expensive and less time-consuming alternative to identify pozzolanic activity of siliceous or aluminosiliceous materials.