Partical Combination Of Fine Powder Effect On Performance Of Cement And Concrete

In the cement concrete the fine powder grain composition's design needs to consider two aspects: Pellet stack and hydration speed. Reasonably designing the particle combination of fine powder, may compound the high performance cement and the material admixture of high performance concretes, and is advantageous in the cement concrete performance enhancement.This article discusses the effect of powder on cement and concrete, through researching particle size distribution, activity of powder of superfine fly ash, slag and fly ash grade one, and the compound with clinker and cement.The experimental results indicated: when the fine powder component (less than three kinds), the fine powder close stack degree plays the major effect role to the hydromass dense degree, the cement substance and the concretes compressive strength enhances along with the close stack degree rises; But regarding the fine powder with many component, the powder packing degree is not the most important influence to intensity,"Synergistic effect"among different components become the influence to concrete performance. Through the experimental study, this article obtains the best proportion, superfine fly ash and slag according to 5:5 compounds with 50% clinker. As the single component admixture, the superfine fly ash which provides more fine-grains having good activity may cause the fine powder stack to be closer in the concretes. Superfine fly ash will modify the performance of fresh concrete, although it reduces the early strength of concretes, but obviously enhances the later strength specially 28 day later. The best substitution quantity is 30%. Studying the influence of compound admixture over concrete, obtains solutions as follow:"Synergistic effect"raises the fine powder hydrated speed, enhances the performance of fresh concrete and the early and later strength of harden concrete comparing with the concrete composing of single component admixture and the one without admixture. But because of admixture, the shrinkage of concrete will slightly rise within the earliest 10 days. The best compound admixture ratio is superfine fly ash and slag according to 3:7, the best mixing quantity is 30%.