Corrosion Effect of Rice Husk Ash in Concrete Pore Solution: Response Surface Analysis

Abstract

Background: Corrosion of reinforcement impedes the structural integrity of concrete infrastructures by reducing the flexural, shear and axial strength of concrete, thereby making it structurally weak. Aim: This research assessed the corrosion effect of rice husk as a concrete constituent for the design of long-lasting concrete infrastructures. Materials and Methods: To achieve the aim of this research, rice husk was air-dried for two days and then burnt at a temperature of 600oC. It was used as a partial replacement for cement at 0%, 10%, 20% and 30% replacement of cement. The concrete pore solution was extracted by mechanical means. This was used as the medium to assess the weight loss and calculate the corrosion rate at seventy-two (72) hours interval with a focus on the temperature of the environment. The corrosion inhibition of the steel rebar was determined using the weight loss method. Results: The result was analysed and modelled using a response surface analysis. The optimisation of the corrosion effect was also assessed using the same method. The result of the study revealed that the inhibition efficiency based on the average corrosion rate was -69.54%, which indicates that 5% of rice husk ash does not inhibit corrosion, likewise the other replacements. The corrosion inhibition of 15% replacement with rice husk ash is slightly higher than the control sample. The research revealed that the most favourable replacement in terms of corrosion rate in comparison to the other percentages is 15%. Conclusion: The mathematical model showed that RHA has a positive effect on the corrosion rate of mild steel. This indicates that the higher the RHA, the lower the corrosion rate. The outcome of this research will serve as a guide for concrete users, engineers, corrosion experts and researchers on the use of rice husk ash in concrete production.