Influence of hydrothermal condition on the physico-mechanical, phase composition and microstructure of autoclaved granulated slag—ground sand mixes using an industrial lime-rich sludge as an activator

The sludge used in this study is a solid waste material produced during the manufacture of acetylene gas. Acetylene gas is produced from the hydrolysis of calcium carbide to form acetylene gas and calcium hydroxide (sludge). On storage, the sludge converted partially to calcium carbonate, which is disposed of by pouring into rivers or dumping into wasteland. Due to the severe environmental pollution problem, it is essential to utilise these waste by-products in the field of building materials. This investigation aimed to study the effect of hydrothermal conditioning on the physico-mechanical, phase composition and microstructure of the autoclaved products made of granulated slag, ground sand and industrial lime-rich sludge as an activator. The hydrothermal specimens were tested for their compressive strength and hydration kinetics (combined water, free lime and free silica contents) as well as the phase composition of the formed hydrates. The changes in phase composition of the specimens were investigated by X-ray diffraction, scanning electron microscopy and combining of differential thermal analysis with differential thermal gravimetry.