Fly ash based lightweight aggregates incorporating clay binders

This study focuses on the strength characterization of artificial fly ash aggregates produced from a pelletization process. Additionally, to improve the stability and strength properties of fly ash aggregates clay binders such as bentonite and metakaolin are added during the production. Physical properties such as specific gravity, bulk density, water absorption, gradation and individual crushing strength of aggregates are determined. The faster hardening of fresh aggregates is envisaged with the addition alkali activator in the binder. Fly ash aggregates are then cured in different environmental conditions such as controlled humidity curing at 40% RH and 35oC, hot air oven curing at two different temperatures 50oC and 100oC. Porosity of fly ash aggregates is found to be reduced with the addition of binder material as a result of good agglomeration with fly ash. Also, the production efficiency of fly ash aggregates is found to be dependent on the binary blends of fly ash with clay binders and the concentration of alkali activator added to the fly ash. The test results also indicate that a maximum crushing strength of 17.97 MPa can be obtained in the case of fly ash aggregates subjected to hot air oven curing at 100oC.