The Influence Of Clay Content On The Properties Of Concrete With Polycarboxylic Superplasticizer

Polycarboxylic superplasticizer(PC)has become an indispensable component of high performance concrete, and it is the development direction and major research focus of concrete admixtures. Clay content brings great negative effects for concrete with PC. Existing researchs on the influence of clay content on the properties of concrete with PC are mostly concerned about the workability and compressive strength of concrete. This paper systematiclly studied on the influence of clay content on the properties of low, medium and high strength concrete with PC. It provides theoretical basises and technical support that will improve and solve the negative effects that clay content brings to the concrete with PC.Chose modified poly-ether(TPEG2400), acrylic acid(AA), sodium methyl allylsulfonate(SMAS) as monomer, synthesized with initiator ammonium persulfater(APS) and mercaptopropionic acidadical(MPA), obtained PC which had high dispersion and low slump loss.Studied on the influence of clay content on the properties of C25, C40 and C70 concrete with PC. The results indicated as follows:(1)Workability: the most impact on workability of C25 and C40 concrete, and the less impact on C70 concrete. From the perspective of clay content of adsorption capacity on different concentration PC, explained the reason for the different influence of clay content on the workability of C25, C40, C70 concrete.(2)Compressive strength: when clay content were more than 1%, 3% and 7%, the compressive strength of C70 concrete, C40 concrete and C25 concrete didn’t satisfy design strength. The sensitivity of the clay content on C70 and C40 were much greater than C25 concrete.(3)Shrinkage: the influence of clay content on shrinkage of C25, C40 and C70 concrete were similar, clay content had little effect for shrinkage of 1 day concrete, it can reduce shrinkage of 3 day and 7 day concrete, after 14 day concrete shrinkage was increased. Early shrinkage of concrete decrease due to clay adsording water, improving humidity of concrete, then concrete shrinkage increase that mainly related to autogenous shrinkage and porosity of concrete.(4)Durability: The influence of clay content on concrete durability leaded to a certain negative correlation with concrete strength grade, the influence of the clay content on concrete chlorine ion penetration resistance and carbonation resistance of C25 and C40 were much greater than C70 concrete. This phenomenon was related with the concrete structure, porosity and alkalinity.