Abstract:
The corrosion behavior of reinforced concrete containing various proportion of admixtures (Rice Husk Ash and Brewers Dried Grain Ash), as replacement for ordinary portland cement in concrete mixes were studied. The admixtures were produced by controlled burning of Rice Husk and Brewers Dried Grain using a basket burner. X-ray Diffraction (XRD) spectroscopy was performed on the ashes to determine their chemical composition and texture (crystalline or amorphous). Concrete samples were made by substituting portland cement with ashes up to 50 weight percent. Test samples for compressive strength test were prepared by casting concrete in a wooden mould of dimension 100 mm × 100 mm. Corrosion test samples were prepared by centrally placing the reinforcing steels in moulds filled with different concrete mixtures, leaving 15mm protrusion for electrical connections. The corrosion test samples were partially immersed in sea water sample to simulate chloride induced corrosion of the rebar. Sea water samples were collected from coastal environment (Lagos bar Beach, Lagos, Nigeria). The test blocks were connected in parallel to a D.C rectifier set at 6 V to accentuate the rate of corrosion. The amount of current flowing between the bars was measured using an ammeter that was placed in each circuit. Corrosion potential was determined at intervals of 2 days for a period of 28 days after the initial 28 days of conditioning. The results showed that concrete made with rice husk ash as a partial substitute of ordinary Portland cement up to 30% by weight of ordinary Portland cement has superior corrosion resistance compared to conventional concrete. Likewise, Brewers dried grain ash up to 20% partial substitution of ordinary Portland cement has superior corrosion resistance compared to conventional concrete. It is concluded that rice husk ash possesses a superior performance characteristics compared to brewers dried grain ash as ordinary Portland cement substitute
