STRENGTH PROPERTIES OF CLAYEY SILT-FLY ASH-CEMENT MIXTURES BASED ON LABORATORY TESTING

Soil stabilization is usually based on reactions between clay and chemical agents. The pozzolanic reaction products lead to strength development. In the present study, a laboratory testing programme was undertaken to investigate the strength properties of a clayey silt soil mixed with class F fly ash and cement. Fly ash was mixed in different proportions up to 90% by mass of the soil. Cement content varied up to 2% of the combined mass of soil and fly ash. Proctor compaction and unconfined compressive strength tests were conducted on soil-fly ash and soil-fly ash-cement mixtures. Compaction results indicate that the addition of fly ash has a significant effect on the maximum dry density and optimum moisture content of the soil-fly ash mixes. Compression results of the average of three specimens show that the addition of fly ash plays an important role in the development of strength of the soil-fly ash mixes. The addition of a little amount of cement to the soil-fly ash mixes leads to a further increase of unconfined compressive strength and can satisfy the strength requirement criteria for subgrade as well as sub-base construction of low-volume roads. The replacement of the clayey silt soil by up to 35% fly ash content gives the optimum mix.