Bio-treatment of Fly Ash

Fly ash, a waste product from coal combustion, is posing disposal problem all over the world. It is being used in various civil engineering works such as in embankment works and fill materials, etc. The strength of fly ash is very much less compared to the natural soils and hence needs to be improved. A relatively new method of injecting bacteria to bind the soil particles known as Microbial Induced Calcite Precipitation (MICP) was proven to be very effective in the stabilization of poorly graded sands. In the present study, an attempt is made to study the effects of bio-treatment of fly ash using the Sporosarcina Pasteurii to promote calcite precipitation from urea hydrolysis. Single staged injection was adopted for introducing bacteria into the fly ash. A standard bacterial cell concentration and varied urea-calcium chloride were adopted for treating fly ash specimens. Unconfined Compression Strength tests (UCS) revealed an increase in strength ranged from 41.19 to 183.31 kPa. Approximately one order of magnitude reduction in the coefficient of permeability values was observed.