Characteristics of metakaolin-lime sludge phosphogypsum system as a building material

This study aimed to investigate the use of some industrial solid wastes materials in fabrication of building materials. The solid wastes used in this investigation were phosphogypsum and lime sludge. Kaolinite and phosphogypsum were first activated at 800°C for 2 hours. Metakaolin, lime sludge and phosphoanhydrite were mixed in different ratios by weight. The water/ solid ratios of the blended pastes were used corresponding to their water of consistency. Curing of blended pastes was done under water as well as in water vapor at 75°C. The change of phases is determined by using a differential scanning calorimeter. The blended paste containing 60% metakaolin, 20% lime sludge and 20% phosphoanhydrite possesses higher values of compressive strength than those of other blends at all ages and methods of curing.