Rheology of Pastes Containing High-Volume Fly Ash and Their Permeability Because of Calcium Leaching Procedure in Ammonium Chloride Solution

Abstract

Abstract This article presents the findings of a research program that concern the rheology of fresh paste containing high-volume fly ash and its permeability because of calcium leaching procedure after 90 days’ curing. In a fresh state, the combined influence of fly ash content and water addition time on Herschel–Bulkley parameters was investigated. The critical value of fly ash content and water addition time was defined. In a hardened state, ammonium chloride (NH4Cl) was chosen as the accelerate leachant based on the comparison of microscale effect of ammonium nitrate (NH4NO3) and NH4Cl solution as well as leaching mechanism establishment. At specified leaching durations, the leached depth and porosity and permeability coefficient of both sound and deteriorated paste specimens were tested. It was indicated that both the porosity increment and permeability coefficient increment have a linear relation to the square root of leached ratio. Additionally, the velocity of the porosity increment declines with fly ash content, whereas the velocity of permeability coefficient increment declines with fly ash content at first and increases slightly when the fly ash dosage ranges from 40 % to 60 %. It can be concluded that fly ash was effective in improving leaching resistance. Finally, the relevance of fresh and hardened behavior was proposed.