Rice husk ash instead of cement? Multi-university study on at RAK

RHA Concrete Specimens-1719483969648
Rice husk ash (RHA), which is rich in silica, has favourable chemistry as supplementary cement-like material for use in concrete.
Image Credit: Supplied

Ras Al Khaimah: As part of quest for substitutes for cement in the construction industry, a group of researchers from 10 universities – including the American University of Ras Al Khaimah (AURAK) — have published a paper that explores the viability of the use of rice husk ash as a partial replacement of cement for the production of sustainable concrete.

Rice husk ash (RHA), which is rich in silica, has favourable chemistry as supplementary cement-like material for use in concrete. The use of RHA in concrete results in its chemical reaction with the hydrates of cement, chiefly Calcium Hydroxide, and forms secondary products that impart strength and stability to the resulting concrete mixture.

The production of concrete is associated with the release of a significant amount of carbon dioxide gas associated with the production of cement, which is one of the main ingredients of concrete. The aim of the study was to reduce the negative environmental impacts associated with the manufacturing of concrete. Environmentalists strongly believe cement must be replaced with a substance with a lower carbon footprint.

Raw Rice Husk-1719483964131
Raw rice husk ash.
Image Credit: Supplied

The study used Machine Learning (ML) techniques to develop prediction models for the compressive strength of RHA concrete, in contrast with the traditional methods which are both expensive and time-consuming. ML approaches are now used in the materials industry for developing efficient predictive models that explicitly incorporate the relationship between response parameters and input factors. The study provides valuable guidance for builders and researchers to estimate the compressive strength of RHA concrete.

In the ongoing second phase of the research (exclusively carried out at AURAK), the effects of RHA as a partial replacement of cement in concrete were investigated in a laboratory experimental program. Cement was replaced at 5 per cent, 10 per cent and 15 per cent (by weight) with RHA for the production of concrete. Important strength and durability characteristics of the resulting concrete mixtures were evaluated in fresh and hardened states at various concrete ages.

Test results showed that the use of RHA as a partial replacement of cement in concrete enhances the later age compressive strength, abrasion resistance, and moisture barrier characteristics of concrete. In addition, an important durability indicator of concrete, namely low drying shrinkage, is significantly improved with the incorporation of RHA as a partial replacement for cement.

Rice husk ash powder-1719483971136
Rice husk ash powder
Image Credit: Supplied

Prof. Stephen Wilhite, Senior Vice President of Academic Affairs and Student Success and Provost, AURAK, said: “We would like to compliment the research team that contributed to this study. It is part of ongoing global attempts by different researchers to find replacements for environmentally harmful materials. The results are encouraging and we are confident that research into the use of rice husk ash as a replacement for cement will continue and potentially boost sustainability in the construction sector.”

Prof. Roz-Ud-Din Nassar from the Department of Civil and Infrastructure Engineering, AURAK, and one of the authors of the paper, said: “As the world struggles to reduce CO2 emissions to save the planet, it is everyone’s duty to contribute to this effort. We are happy that our research makes a strong case for using RHA as a partial replacement for cement in concrete manufacturing. The outcomes of the test results point to the viability of using RHA in concrete for the production of economical, durable, and environmentally-friendly concrete mixtures. Such mixtures represent an important step in the direction of sustainable construction practices.”

Considering cement’s binding properties, the US Geological Survey (USGS) estimates that around 4 billion tons of cement are produced globally each year, accounting for 7 per cent of the total CO2 emissions. To be more precise, 1 ton of cement manufacturing produces 0.9 ton of CO2.

The other universities whose researchers were involved in the first phase of the study were: Najran University, Saudi Arabia; University of Engineering and Technology, Pakistan; Macroview Projects, Australia; Prince Sattam Bin Abdulaziz University, Saudi Arabia; Gulf University for Science and Technology, Kuwait; Silesian University of Technology, Poland; Budapest University of Technology and Economics, Hungary; Luleå University of Technology, Sweden; and Monash University, Malaysia.