Scale-up effects in alkali-activated soil blocks

Alkali activation is a novel method of soil stabilisation, which could be used for the production of compressed blocks as walling materials. Given that much of the fundamental research into the chemical behaviour of this process has been done for small specimens, there is a knowledge gap over the potential effects of increasing specimen size. In this study, blocks were made from a mix of soil, sand and sodium hydroxide solution using a manual block press. Their phase composition and microstructure were investigated using powder X-ray diffraction and scanning electron microscopy; drying behaviour and compressive strength were also measured. No major microstructural or phase differences were found between the central and edge regions of the blocks. Longer curing time had little effect on phase formation and microstructure, but resulted in increased compressive strength. There are no fundamental chemical issues obstructing the scale-up of this stabilisation method, but further research should focus on the measurement of properties in line with building standards and eliminating hazards in the manufacturing process.