Effect of rice husk ash on hydrotechnical concrete behavior

Vietnam is one of the leading rice exporters in the world. Popularly, as other rice producing countries, rice husks from rice processing in this nation are used widely not only in electricity generation and silicon making but also one kind of raw material for various building materials production. This article presents a reusing waste method of Rice Husk Ash (RHA) in Vietnam to improve the behavior of hydrotechnical concrete (HTC), one of the most significant building materials.

In this study, RHA plays a role as a highly active fine mineral additives, containing 88.42% amorphous SiO₂ oxide in component. The combination of RHA and superplasticizer ACE 388 as mineral additives is able to modify the concrete structure. Not only the compressive strength of hydrotechnical concrete at the age of 28 days increase 7.39% (from 11.71 to 19.1%), but also its water resistance rises up to 50% (from the point of 25%) due to compaction of the structure.

The experimental results of permeability of chloride-ion according to standard ASTM C1202-97 (American) show that the HTC patterns containing 10% and 20% RHA by mass of the binder have the average value of electrical energy, respectively 351.18 C and 297 C. While other control samples without RHA have the average value of electrical energy of 1013.22 C. In comparison to the American Concrete Association classification table, these chlorine-ion permeability values of samples HTC-10 and HTC-20 are, precisely, at low level. Therefore, hydraulic concrete, using modified structure from mineral additives of superplasticizer ACE 388 and RHA, is appropriate building material for construction of irrigation works and hydroelectric projects in Vietnam. (paper)