Rice husk ash used in cement mixture

SAN FERNANDO, La Union – Amid the rising cost of construction materials, a Filipino scientist here has tapped the potential of rice husk ash as supplementary material in cement paste and concrete.

Marshal Calica, a researcher at the Saint Louis College here, said rice husk ash could be used as “admixture” in cement paste and concrete because it contains silica, a compound that serves as cement “binder.”

Calica said 10 percent of commercial cement could be replaced with rice husk ash.

“Replacing 10 percent of cement with rice husk ash does not mean sacrificing the strength of concrete,” he said.

Calica said the main parameter in the design of concrete structure is compressive strength of the concrete.

Calica’s study, entitled “Influence of Rice Husk Ash as Supplementary Material in Cement Paste and Concrete,” was one of the finalists in the second Ilocos Consortium for Industry and Energy Research and Development (ICIERD) R&D competition.

Calica said people could save P20 for every P200 worth of cement bag with the use of rice husk ash.

Calica said the product is not yet available in the market because he lacks the equipment to produce a huge quantity of rice husk ash.

“Hardened concretes with up to 10 percent of rice husk as partial replacement are considered moderate strength concrete or structural concrete and can be used for structural work,” he said.

Concrete with 20 percent rice husk ash is considered low-strength concrete and can be utilized for non-structural concrete works, he said.

Calica said the presence of rice husk ash in cement paste influences the normal consistency of the cement paste mixture.

“Rice husk ash is the influencing factor causing the cement paste to absorb large amount of water,” he said.

The setting time of the cement paste mixture is affected by the presence of rice husk ash as partial replacement of ordinary cement, he said.

Initial setting time is 108 minutes for cement with rice husk ash, and 212 minutes for cement without it.