Partial replacement of cement with rice husk ash in concrete production: an exploratory cost-benefit analysis for low-income communities

Cement is an important construction material in concrete production; however, it is expensive and unaffordable for many low-income and rural communities in developing countries. Rice husk is a by-product from the rice mill process, with an approximate ratio of 200 kg rice husk per one tonne of rice produced. This experimental study aimed to investigate the integrity of concrete produced in Zambia using rice husk ash (RHA) to partially replace cement. The primary goal was to carry out a cost–benefit analysis on the use of RHA in concrete. RHA was used to partially replace cement with ratios of 10 %, 20 % and 30 %. The 20 % cement replacement mix produced the optimum 18 MPa concrete strength results at a 0.5 water/binder ratio. This translated in cost reduction of concrete by 12.5 %, which is particularly significant for higher concrete volumes. The produced concrete is suitable for lightly loaded structures, such as foundation footings, surface beds and walkways to benefit low-income communities. The study further concluded that the RHA based concrete was more cost-efficient in structures that were close to areas of rice production due to reduced RHA transportation costs.