By Mary Charlotte Fresco
MediaCore, STII

What had long been regarded as waste and disposable could be the unexpected answer to the problems of house builders and engineers harried by rising costs of construction materials.

Such hope is built on a model house made out of ordinary Portland cement bonded with rice hull ash (RHA) and lime.  The RHA-lime house is one of the three model houses constructed using indigenous materials, which to this day stands steady and tough since completed in 1987 alongside the University of the Philippines Film Center in Diliman, Quezon City.

The RHA -lime served as additive to cement sand bricks or hallow blocks used for the exterior and interior walls of the model house.

UP Building Research Service Director Nathaniel B. Diola said that the study on the use of RHA-lime in building construction was confined to small non-bearing block types since the materials are designed to benefit low-income families.

According to Diola, various studies have been conducted to determine the resistance of the materials to fire, weevil, and mould.           

“The results are indeed promising, “ says Diola while citing how the locally produced materials withstood harsh weather condition and other corrosive elements like mould and vermin as attested by many consumers and adoptors.

 UP BRS researcher Roberto Soriano also explained that the materials went through and passed load-bearing test for small block types of houses.

The technology sparked interest from local construction engineers and architects impressed by the results of studies that verified RHA performance as potential substitute for silica fume, an important binding material of pozzolan or cement.

Adoption of such kind of locally produced technology should be maximized and sustained given the fact that resources are renewable, environment friendly, and in great abundance, Diola added.

Latest statistics show that more than 150,000,000 metric tons of rice hulls are generated each year throughout the world.

However, Mr. Soriano admitted that the use of rice hull for building houses is no longer a new technology as it is becoming popular even in developed countries.

A study conducted by Dr. Paul A. Olivier of Louisiana's engineering, separation and recycling department showed that rice hulls have the lowest percentage of total digestible nutrients (less than 10%) of all cereal by-products.  This would mean that rice hull has resilient quality to resist moisture penetration and fungal activities.   

Dr. Olivier explained in a paper that rice hull has an unusual high percentage of silica and crude fiber that gives the hull a very tough elastic property.

One basic consideration in building homes, no matter how big or small, is the materials' resistance to fire.

“Anyone who has tried to set fire to rice hulls understands how difficult they are to burn, since air cannot flow freely through a pile of rice hulls to provide the oxygen needed to initiate and sustain rapid combustion, “, Dr. Olivier explained.

The Department of Science and Technology-Philippine Council for Industry and Energy Research and Development, which funded the study recently turned over the model houses to UP BRS.   Each model house has a floor area of 39 square meters.

The turnover ceremony coincided with the launching of UP BRS's Compendium of Indigenous Building Materials and Technologies, a database containing results of research and development works over the years on indigenous building materials and technologies and their performances and applications.