Abstract:
Rice husk ash (RHA) is a fine agricultural by-product and commonly the brick industry in
Sri Lanka produces a significant amount of RHA as a waste. Similarly, Fly Ash (FA) is
resulted as a byproduct of coal power plants (CPP). In Sri Lanka, Nuraichcholai CPP
generates about 200,000 MT/year of FA. Previous studies have reported that both RHA
and FA have pozzolanic reactivity. Cement-Based Grout (CBG) used in geotechnical and
other engineering aspects is expensive since the cost of Portland cement and grout
additives. Therefore, the present study aimed to introduce RHA and FA to the CBG as a
partial replacement for cement. FA and RHA samples were collected from Nuraichcholai
CPP and brick industrial sites respectively. After initial purification, 63-150 µm sieve
fraction of both FA and RHA were selected. Cement, FA, and RHA were thoroughly
mixed in a small grinder to prepare different grout mixtures. Initially, phase analysis for
FA and RHA was conducted by X-ray Diffraction (XRD). Before the solidification, each
grout mixture was analysed with the Standard Flow Cone (FC) test and then Compression
Strength (CS) test during the curing period of 7th, 28th, and 45th days was conducted. XRD
analysis has shown that FA and RHA have the crystalline and amorphous form of SiO2
respectively. FC efflux time in each combination is in the rage of 14.1-17.5 sec. (FC
efflux time < 15 sec. ASTM-C939-02). FC efflux time has increased with the increment
of RHA amount. This may due to the porous nature of RHA, which tends to reduce the
quantity of free water and increase water demand. Except for the FA+cement combination
others have CS less than 20 MPa (CS > 20 MPa BSEN 12390-3:2002). The increment of
RHA tends to decrease the CS. Hence, the application of FA as an additive for CBG is
favourable than the RHA or combination of FA+RHA.
Keywords: Rice husk ash, Fly ash, Cement-Based Grout, Compressive Strength
