Exploring the use of fine surplus silica sand in low CO2emission earth construction

The usage of industries' by-products and recycled materials in construction has become crucial for a sustainable future, as it reduces waste, has economic benefits, and helps to preserve natural resources while lowering CO2emissions. This research explored the possibility of utilizing fine silica sand, a by-product of quarrying, as a construction material aligned with circular economy strategies. Investigating various by-products alongside surplus fine silica sand from Nilsiä district, Finland, the study aimed to identify optimal recipes for stabilized silica sand blocks. The main focus was on experimentally assessing the technical properties of these blocks and evaluating the suitability of silica sand for sustainable rammed earth construction techniques. The filler and aggregates used were silica sand as well as quarry fines, while the binders included bio-based fly ash, bottom ash, green liquor dreg, lime kiln dust and cement. The material’s index properties were measured, and the binders were tested for the flexural and compressive strength. Selected binders, exhibiting strength properties, were incorporated with sand and quarry fines to prepare cylindrical blocks, subsequently subjected to uniaxial compression tests. The comparison of 28 days cured compressive strength of different recipes revealed that samples containing bio-based fly ash with ratios of 1:5 and 1:6 binder to aggregate demonstrated superior rresults, with the best recipe containing a 50%-50% ratio of quarry fines to sand and a binder to aggregate ratio of 1:6,containing fly ash sourced from paper and pulp industry.