EFFECT OF THERMAL-TREATMENT OF RICE HUSK ASH ON THE SURFACE-PROPERTIES OF HYDRATED LIME-RICE HUSK ASH BINDERS

Rice husk ash fired at different temperatures, 450, 700 and 1000 degre es C, was mixed with different concentrations of lime (molar lime/sili ca ash ratio of 0.2, 0.5 and 1.0). Each dry mixture was first ground a nd hydrated in the suspension form (water/solid ratio = 10) for variou s time intervals within the range of 1 to 365 days. The surface proper ties of the unhydrated and hydrated samples were studied by means of n itrogen adsorption measurements. The results indicated that the surfac e areas and total pore volumes of unhydrated solid mixtures and hydrat ed lime-rice husk ash samples, prepared with lime/silica ash ratio of 1.0, decrease with increasing firing temperature of rice husk ash. The effect of varying the lime/silica ash ratio of the solid mixture on t he surface area and pore structure was fully discussed. The results of surface area and pore volume measurements could also be related to th e crystal structure of silica produced from rice husk ash.