Direct synthesis of construction material from low-quality sand reacted with KOH and ethanol

Abstract

A strong construction material was synthesised directly from low-quality sand (defined as the sand that particle size smaller than 250 μm) via the sol–gel method with ethanol as the solvent. Appropriate KOH content and ethanol concentration could improve the reaction degree and promote the compressive strength. The main results indicated that the specimen with 50 mass% KOH and 80 v/v% EtOH had the highest strength (>25 MPa) with the lowest porosity (5.79%). The high strength was attributed to microcline and tetraethoxysilane formation. Microcline was formed due to the dissolution and reorganization of Si-O-Si(Al) bonds in the raw sand, leading to a more homogenous structure and the decrease in the porosity. Formed tetraethoxysilane was a good consolidate, which could function as glue to further increase the strength. The carbon emission of the sand-based material in the construction phase was 233 kg CO2 eq/m2, which could be greatly reduced after reusing waste solution and utilizing waste heat. Therefore, a tough construction material was synthesised, which can partially substitute concrete, thus addressing the problem of insufficient concrete raw materials.