Hydration process of rice husk ash cement paste and its corrosion resistance of embedded steel bar

Thermogravimetric analysis and electrical resistivity were used to determine the hydration process of cement paste with rice husk ash (RHA) (0–15%) and water-cement ratio of 0.4 in this work. X-ray diffraction (XRD) method and scanning electron microscopy (SEM) were used to survey crystal composition and microstructures of specimens cured for 3 h, 1 d, 7 d and 28 d. Finally, electrical parameters (electrical resistance and AC impedance spectroscopy) of steel bars reinforced cement paste were investigated to study the effect of RHA on the corrosion resistance. Results showed that RHA could affect the cement hydration by hydration promotion and pozzolanic effect. The evaluation function for electrical resistivity and curing ages fitted well with linear increasing function. The addition of RHA higher than 5 % demonstrated a decreasing role in the electrical resistivity of cement paste at earlier curing ages (3–7 d). Meanwhile, when at later curing ages (7–28 d) the result was the opposite. Moreover, RHA demonstrated positive effects on corrosion resistance of steel bars in cement paste.