Effect of various additives on the hydration of perlite-Gypsum plaster and perlite Portland cement pastes

Perlite is a volcanic glass which forms a light-weight cellular aggregate when ground and heated to about 1000 degrees C. It is used in the production of light-weight masonry blocks and concrete in the building industry as well as in insulation, fire protection, agriculture and pharmacology. In this study, the effects of admixtures such as lime, sodium citrate and various superplasticizers on the hydration of perlite-gypsum plaster, perlite-white Portland cement and perlite-blended Portland cement mixtures were investigated by measurement of flexural and compressive strengths and by DTA-TG. It was found that the addition of lime caused pozzolanic reactions and, consequently, increased strength in gypsum plaster-perlite mixtures; however, sodium citrate was found to have negative effects. On the other hand, the use of superplasticizers in perlite-Portland cement pastes resulted in reduced water/cement ratios and an excessive decrease in strength