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 aggreg ate 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 p harmacology. In this study, the effects of admixtures such as lime, so dium citrate and various superplasticizers on the hydration of perlite -gypsum plaster, perlite-white Portland cement and perlite-blended Por tland cement mixtures were investigated by measurement of flexural and compressive strengths and by DTA-TG. It was found that the addition o f lime caused pozzolanic reactions and, consequently, increased streng th in gypsum plaster-perlite mixtures; however, sodium citrate was fou nd to have negative effects. On the other hand, the use of superplasti cizers in perlite-Portland cement pastes resulted in reduced water/cem ent ratios and an excessive decrease in strength.