Effect of polycarboxylate superplasticiser adsorption on fluidity of cement-clay system

摘要

Clay reduces fluidity and increases fluidity loss of concrete added with polycarboxylate superplasticiser. Sometimes it cuts down concrete durability. Fluidity of clay-cement paste with the addition of polycarboxylate superplasticiser, adsorption amount of polycarboxylate superplasticiser and zeta-potential has been tested to understand the effect of polycarboxylate superplasticiser on cement-clay systems. The results show that cement particles have a smooth surface; there are lots of layered or sheet structure existing on the surface of clay; when the particle size distribution is little different, the specific surface area of clay is 17 times that of cement; it is the reason why polycarboxylate superplasticiser adsorption on clay is much greater than that of cement. Initial adsorption amount and equilibrium adsorption amount of polycarboxylate superplasticiser on clay are 3-4 times that of cement; strong PC adsorption of clay is the main reason why the presence of clay reduces fluidity and increases fluidity loss of cement paste.