Influence Mechanism Of Clay On The Performance Of Polycarboxylate Superplasticizer And Control Measures

Polycarboxylate superplasticizer (PCE) has become an important component in theproduction of high performance concrete. With the enlargement of the application area,it was found that the concrete raw materials have obvious effect on the performanceof polycarboxylate superplasticizer, especially the existance of clay in aggregate. Inthis case, the sensitivity of polycarboxylate superplasticizer to clay has greatlyrestricted its generalization and application. Based on systemic theory and practiceresearch, the inhibition mechanism of clay mineral to polycarboxylate superplasticizerwas discussed and the solving measures was proposed.Through analysis to the clay elemental composition and phase composition inaggregate in several regions around the country, the mineral composition and relativecontent in clay mineral was obtained, and then single clay mineral as representativewas picked up. Combined with the performance tests including cement paste, cementmortar and concrete test, the influence and critical content of different clay mineral tothe function of polycarboxylate superplasticizer were identified. What’s more, theinterlayer spacing d(001)and expansibility of clay under different conditions weremeasured through X-ray diffraction analysis. Compared with the molecular size ofpolycarboxylate superplasticizer, the mechanism which the clay mineral causes thepolycarboxylate superplasticizer out of work was put forward.In this dissertation, a series of linear chain polycarboxylic polymer was synthetized,and the effect of combining the linear chain polymer with the polycarboxylatesuperplasticizer to reduce the clay sensitivity was investigated. The results show thatthe cement paste rheological property can be improved effectively with the linearpolycarboxylic polymer in certain molecular weight and molecular structure, and thesensitivity of PCE to clay can be reduced significantly. In addition, the preparationmethod to get the excellent performance of linear chain polymer was obtained bychanging monomer mole ratio, adjusting the molecular weight regulator and initiatordosage and optimizing the synthetic technology. When adding the linear polymer intothe concrete system which contains the clay mineral, the clay particle with thenegative charge will preferentially adsorb the linear polymer into its surface orinterlamination, thus protect the PCE molecules not to be adsorbed and destructed. Inthe end, the adverse effects of clay to PCE will be offset.