Experimental Study On The Performance Of Self-compacting Concrete With Polycarboxylate Superplasticizer

This thesis investigates the proportioning and properties of self-compactingconcrete using the polycarboxylate superplasticizer through a large number ofexperiments. From the experiments, the efficiency and the compatibility betweensuperplasticizer and cementitious materials are studied, and the optimizedpolycarboxylate superplasticizer is synthesized on the basis of the related mechanismscontrolling the compatibility. The superplasticizer for steel-tube self-compactingconcrete is mixed using two kinds of polycarboxylic acid water reducing agents andthe optimal portion of each agent is determined through orthogonal experiments. Theacrylic acid, sodium methylacrylsulfonate and hydroxyethyl methacrylate areidentified as the influential factors for the30min fluidity of cement paste and theinfluential factors for60min fluidity of cement paste are the sodium methylacryl-sulfonate and hydroxyethyl methacrylate, acrylamide and peroxide. The identificationof these factors helps to determine the superplasticizer synthesis. The obtainedsuperplasticizer has the advantage of each agent, and is proved to have goodcompatibility through the verification experiments.To reduce the binder content in concrete, mineral admixture including fly ash andslag are used to increase the mechanical strength, decrease the concrete hydration heat,and ameliorate the self-compacting properties. Through orthogonal experiments, theproportioning of self-compacting concrete is determined for w/b ratio, binder contentas well as sand ratio. Through the workability study of the fresh mixture, the mostinfluential factor for slump is identified as the sand ratio of concrete mixture, followedby the dosage of polycarboxylate superplasticizer, and the last is the dosage ofthickener agent. The most influential factor for the slum flow is the thickener, followedby the dosage of polycarboxylate superplasticizer, the sand ratio and the binder content.For the shrinkage tests of the self-compacting concrete, the optimal dosage of theexpansion agent is determined. Due to the limitation of the present expansion agentand the water loss during the curing, the super absorbent polymer (SAP) is added intothe concrete mixture. The SAP can retain free water during the initial stage of themixing and hydration, release free water in the later stage of hydration, and increase the pore water supply. Globally, the SAP can ameliorate the performance of theexpansion agent. An optimal dosage of SAP is determined through orthogonalexperiments and the incompatibility of deformation between the self-compactingconcrete and the steel tube is solved.