Effects Of Compounding Polycarboxylate Superplasticizer On Concrete Performance

Polycarboxylate superplasticizer, due to its advantages such as low dosage, highwater reduction and strong maintain slump performance, has been widely applied inproducing commercial concrete. However, when mixed alone with concrete,polycarboxylate superplasticizer often shows poor coordination with cement, and leadsto problems in concrete producing process, such as poor workability and large slumploss, it is difficult to meet the construction requirements. Therefore, polycarboxylatesuperplasticizer is often used together with other admixtures.In this thesis, effect of compounding polycarboxylate superplasticizer on concreteperformance has been systematically studied by experiments, and correspondingconcludes have been reached as following:(1) By compounding polycarboxylate superplasticizer with different retarders, thesetting time of concrete mixture, slump and losses, and compressive strength ofconcrete are studied. Results show that with the increase of sodium citrate, the settingtime is prolonged, whereas the compressive strength of concrete declines. Sodiumgluconate can also prolong the setting time of concrete mixture, but has little effect onthe28d strength of concrete. Both sodium citrate and sodium gluconate have auxiliaryplasticizing effect to concrete, and maintain slump performance of concrete mixture.(2) By compounding polycarboxylate superplasticizer with different air entrainingagents and changing ways of the air entraining, air-content and losses, compressivestrength, and resistance to chloride ion penetration of concrete are studied. With theincrease of degussa or triterpenoid saponins, compressive strength of concrete declines,but air-content increases and the bubbles can easily polymerize and escape. Comparedwith degussa, triterpenoid saponins has a better entraining effect. By changing the wayof air entraining, air loss per hour is reduced, and the bubbles become more stable.When degussa dosage is between0.01‰and0.04‰, or triterpenoid saponins dosage isbetween0.06‰and0.10‰, the resistance to chloride ion permeability of concrete isincreased.(3) Proportion optimization of polycarboxylate superplasticizer and otheradmixtures is studied. Results of comparative experiments of four compound samplesshow that polycarboxylate superplasticizer compounded with degussa, sodiumgluconate and takemoto oil can reach a good coordination with cement, and theconcrete can achieve optimum performance. The best degussa dosage is0.03‰, and the best sodium gluconate is0.06%.The conclusions can provide reference for concrete admixtures mixture ratiodesign.