Environmentally sustainable use of sandstone slurry in self-compacting concrete

Dried sandstone slurry (DSS) is generated during mining and processing of stone and is accounted as man-made hazardous waste material, contaminating the environment in nearby areas. The use of DSS in self-compacting concrete (SCC) was studied by partially substituting pozzolana Portland cement at different percentages. This represents the recycling element of the 3 R's of the environment (reduce, reuse and recycle). Mechanical and permeability properties were evaluated and the microstructure of SCC analysed with respect to a control mixture which is without sandstone slurry. Mechanical and permeability parameters were found to relate each other. With increased replacement of DSS, the porosity and hence the sorptivity coefficient of SCC also increased and its compressive strength decreased. The higher porosity caused a significant increment in the depth of carbonation. Scanning electron microscope (SEM) and X-ray diffraction (XRD) showed decreased calcium-silicate-hydrate (C-S-H) gel formation as the replacement percentage of DSS increased. This, along with the increased porosity and permeability, degraded the mechanical properties of SCC. The rapidly developing construction sector in India must meet the following indispensable criteria: low environmental impact at improved structural performance, economy and speed of construction. Utilization of sandstone waste is highly recommended from the above viewpoint.