The structure formation features of gypsum-lime composite binders for non-autoclaved aerated concrete

The crystalline phases of hydration products of the gypsum-lime binder were identified using XRD analysis. The physical and chemical regularities of the structure formation processes in the model system “gypsum – quicklime – metakaolin – amorphous silica – water – borax” were established. The influence of the quicklime type and gypsum binder brand on the morphology and the size of the calcium sulfate dihydrate crystals were investigated. The relationship between processesof the structure formation of composite gypsum-lime binders under normal hardeningconditions and the physical and mechanical characteristics of the stone was established.

The influence of sodium carboxymethylcellulose and sodium chloride on the precipitation of calcium sulfate dihydrate

The inhibition of gypsum was investigated at 25C in aqueous 0,7 and 1,5 mol/l NaCl solutions by so- dium carboxymethylcellulose (CMC-1000, with the degree of polymerization of 1000 units).The efficiency of inhibition was estimated from measurements of the calcium concentration in the supersaturated calcium sulfate solutions (0,15 mol/l) during the precipitation process by the standard procedure of complexometric titration. It was observed that the presence of NaCl exhibits synergistic effect on the performance of CMC-1000. In the presence of CMC-1000 at 0,5 g/l inhibitor concentration and sodium chloride at 0,7 mol/l concentration induction time, preceding the formation of the gypsum, increases from 100 (without NaCl) to 630 min. Induction times at 0,1 g/l CMC-1000 and sodium chloride at 0,7 and 1,5 mol/l concentrations are 60 and 32 min respectively. The results of X- ray powder diffraction indicated that dihydrate calcium sulfate and sodium chloride present in solid phase.

Geometrical Constraints of Thermal Dehydration of β-Calcium Sulfate Hemihydrate Induced by Self-Generated Water Vapor

The thermal dehydration of calcium sulfate dihydrate exhibits complex reaction behavior, in which the reaction pathway and kinetics vary depending on water vapor pressure (p(H2O)) applied as the atmospheric condition...