Concrete Incorporating Rice-Husk Ash: Compressive Strength and Chloride-Ion Penetrability

This report deals with the evaluation of the performance in concrete of an Indian sample of rice-husk that was burnt in an industrial furnace in Ontario and ground at the CANMET laboratories. This exploratory study was performed under contract with DCR Phoenix Development Corporation Ltd. Ottawa and is divided in two parts.

The first part deals with determining the optimum grinding time of the RHA in order to produce a highly-reactive product with a minimum energy of grinding. The performance of the RHA in concrete forms part II of the study. The results show that the rice-husk ash sample used in this study is principally composed of SiO2 -90.7 %- contains 4.7% loss on ignition and a relatively high K2O content of 2.2 %. The RHA ground for the optimum grinding time -140 seconds in a pulverizer with a capacity of 30 g- has a median particle size of ~ 8 µm a water requirement of ~ 104% and a pozzolanic activity index of ~ 100% in the mortar used for determining the pozzolanic activity of the RHA. The results also show that in general for similar W/CM -0.40- the replacement of 7.5 to 12.5% of the portland cement by the RHA did not affect significantly the compressive strength but improved significantly the resistance to the chloride-ion penetrability of the concrete with and without the entrained air.

Includes tables and figures detailing the study results.

Technical Report Author: Nabil Bouzoubaa, Benoit Fournier