A Study of the Penetration of Chloride in Rice-Husk Ash Concrete


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Title: A Study of the Penetration of Chloride in Rice-Husk Ash Concrete

Author(s): A. A. Azevedo, M. 1. C. Martins, and D. C. Dal Molin

Publication: Special Publication

Volume: 202


Appears on pages(s): 379-396

Keywords: chloride ions; concrete durability; mineral admixture; rice husk ash

Date: 8/1/2001

A large number of relatively new reinforced concrete structures may require intervention due to problems affecting their durability. Repair and replacement costs of structures account for a considerable share of the total cost of constructions. Rice-husk ash (RHA) concrete displays lower permeability due to changes in the concrete microstructure, which reduces the vulnerability of this material to the action of aggressive agents. This study assesses concrete durability properties to chloride ions, an aggressive agent. The effect of chloride ions was investigated with tests of compressive strength and chloride penetration. These tests were performed in high initial strength portland cement concrete (CPV-ARI) modified with the addition of rice-husk ash (RHA) and in pozzolanic portland cement concrete (CPIV). The input variables were the water/cimentitious ratio (0.30-0.35-0.45-0.60-0.80) and the contents of the rice-husk ash additions (0%-5%-lo%-IS%/,-20%). Results show that the addition cf rice-husk ash to CPV-ARI concrete had no significant effect on compressive strength properties when compared to the reference concrete. Results for chloride penetration show that the addition of RHA produces an average reduction of 126.6% on the charge passed. Comparative results of RHA CPV-AR1 concrete and CPIV concrete show that the compressive strength performance of the latter is poorer than the former. Chloride penetration results show that CPIV concretes displayed a better performance than CPV-ARI concretes with and without the addition of RHA.