Investigation of Chloride Diffusion for High-Performance Concrete Containing Fly Ash, Microsilica, and Chemical Admixtures

This study was carried out to evaluate the influence of addition of fly ash, microsilica (MS) and calcium nitrite solution (CN) on chloride diffusion of high-performance concrete. The concentrations of chloride ions penetrating specimens through diffusion were measured periodically, up to 1 year, by using an electronic ion/PH meter. When the diffusion flux reached a steady state, the diffusion coefficients of all mixes were calculated based on Fick's first law The test results demonstrated that the 25 percent addition of fly ash by weight of cement improved the mix's resistance to chloride diffusion: The improvement was especially evident when 25 percent of fly ash and 10 percent of MS by weight of cement were added into the mt together However, the addition of CN into the mix resulted in deterioration in improvement of resistance to chloride diffusion enhanced by the incorporation of fly ash and MS. Through the mercury intrusion porosimetry test the influence of CN on chloride diffusion is studied further The results showed that the addition of CN leads to the increase of micropore diameter. Therefore, CN should be adopted cautiously in the practical engineering in which higher resistance to chloride diffusion is required.