Feraidon Ataie, program coordinator, Concrete Industry Management Program, CSU Chico

This research project had three main goals: to investigate the long-term durability of concrete containing rice hull ash, to study the impact of rice hull ash on admixtures for concrete, and to compare the performance of rice hull ash with that of other supplementary cementitious materials such as silica fume, metakaolin, and slag.

Work began on this project at Chico State in July 2018. Rice hulls were obtained from a local rice company, soaked in water for a day and then dried. The hulls were then burned in a ceramic kiln to produce rice hull ash. The ash was ground in a laboratory mill to produce a powder. The same procedure was used to prepare rice straw ash.

Mortar samples containing 10% rice hull ash were made and compressive strength was to be measured at seven, 28, and 91 days. Initial results were compared to samples containing no rice hull ash. The heat of hydration also was measured with an isothermal calorimeter.

Before the experiments could be completed, however, smoke from the Camp Fire in nearby Paradise closed the Chico State campus and the ongoing experimental procedures were discontinued. Most of the experiments will be repeated in 2019.

Nonetheless, initial data obtained prior to the Camp Fire, showed that adding rice hull ash in concrete increases strength but reduces concrete workability.