The Research On Resistance To Dry-wet Cycling And Corrosion Of Alkali-activated Slag/Fly Ash Cements

As a new type of cement, alkali-activated cement has received extensiveattention with its excellent performance. A large amount of experiments have shownthat alkali-activated cement has many advantages, such as rapid development ofearly strength, high final strength and eximious durability. But there are also somedisadvantages, such as high drying shrinkage and being carbonated easily in the dryenvironment. Alkali-activated cement is a mixture of some type of complex andchangeable elements. Curing condition, the kind of activator, alkali content and thetype of cementitious material have great influence on its performance and durability.In particular, the composition of slag and fly ash in different producing areas islikely to be different, which makes it difficult to research the performance anddurability of alkali-activated cement. The research on performance and durabilityis not enough and systemic.This paper presents an investigation into the performance and durability ofalkali-activated slag/fly ash blend cement including strength development, resistanceto dry-wet cycling, acid and sulfate. After compared with Portland cement, thedifference properties between these two kinds of cement are analyzed andsummarized.The results showed that under the condition of appropriate mixture proportion,the strength of alkali-activated cement is much higher than Portland cement. Thetype and character of activators had great effect on strength of alkali-activatedslag/fly ash blend cements. The higher the amount of fly ash was, the lower the finalstrength of cement was. In the range of0to1.5, the higher the modulus of waterglass was, the higher the final strength of cement was. The durability of resistance toacid and sulfate of alkali-activated cement is better than Portland cement, the typeand character of activator had great influence on durability of alkali-activatedslag/fly ash cements. The higher the amount of fly ash was, the lower the porosityand permeability of cement was. Corrosion ionic was difficult to penetrate into theinterior of concrete, so it has better durability of resistance to dry-wet cycling, acidand sulfate. But if the amount of fly ash is too high, a small amount of slag wasunable to form dense structure after activated by alkaline, then porosity becamelarge and compressive strength, durability of resistance to dry-wet cycling, acid andsulfate became lower. In the range of0to1.5, the higher the modulus of water glass was, the more compact of cement structure was. And then the durability of resistanceto dry-wet cycling, acid and sulfate was better.