Alkali-activated fly ash foams for narrow-trench reinstatement

Unlike with traditional earthfill, materials used in the reinstatement of narrow-trenching must satisfy certain engineering properties. Otherwise, the ongoing traffic and environ- mental condition will damage the trench, degrade the road pavement and damage the service-lines that were installed. This report identifies eight mixtures using Fly Ash as the alumino-silicate precursor to prepare alkali-activated foams, cast to densities between 600 and 1100 kg/m3. These systems were examined for their mechanical performance, dimensional stability, and bond with the asphalt substrate. The hardened foams were first tested for their strength, modulus of elasticity, and Poisson?s ratio. This was followed by evaluating their drying shrinkage and their coefficient of thermal expansion. Lastly, these mixtures were cast against asphalt concrete to assess both slant shear and flexural bond strength. The test outcomes were used to rank the mixtures with an analytical hierarchy process. The results show that the mixtures at the median density (800 kg/m3) offer the most promise and substantial benefit accrues from fibre reinforcement.

Automated summary

This report investigates eight mixtures using Fly Ash as the alumino-silicate precursor to prepare alkali-activated foams, with densities between 600 and 1100 kg/m3. The mechanical performance, dimensional stability, and bond with asphalt substrate were evaluated. The results show that mixtures at the median density of 800 kg/m3 show the most promise, with substantial benefits from fiber reinforcement.