Research On The Synergestic Effect Of Polycarboxylate Superplasticizer And Hardening Accelerants

Superplasticizer for concrete has gotten rapid development in recent years and the polycarboxylate based superrplasticizer has become the trend of research and application in the 21'st century. At present, the conventional hardening accelerating and water reducing admixtures usually adopt the 2nd generation water reducing admixture, for example naphthalene based superplasticizer as the basis , and cooperate with hardening accelerants at the same time,so they often contain chloride ion or sulfate ion, and high alkali content which lead a potential risk to the durability of the concrete constructions and can't adapt to the demand of green and high performance concrete. While the known matching principles between naphthalene based superplasticizer and hardening accelerants are not suitable to the polycarboxylate superplasticizer any more, the research work concerning the matching principles between polycarboxylate superplasticizer and hardening accelerants should be conducted to make a better understanding of the synergestic effect between them, and expected to develop a new type admixture which has outstanding performance of water reducing and high early strength properties.In this project, the related performances of three kinds of polycarboxylate superplasticizer are tested and two of them are chosen as the basis, namely PCE-A and PCE-H, for further study because of their different outstanding characteristics. The synergistic effect between polycarboxylate superplasticizer and hardening accelerants was systematically studied and test resultss prove that the polycarboxylate superplasticizer and some accelerators have excellent synergistic effect. Through orthogonal test between the two kind of polycarboxylate superplasticizer and hardening accelerants, two optimal proportions are selected. In the concrete test, PCE-A(A) and PCE-H(A) with proper dose antifoam agent all have high water reducing rate of more than 20%, and compressive strength ratio to the blank specimen amount to more than 300% for 12h and 1 day age , 200% for 3 days age, 120% for 28 days age, other performance datas also meet or exceed the state criterion of the first class product and the imported product of some international company.The two developed tentative admixtures in this project have high water reducing capability and excellent hardening accelerating effect , furthermore they are chloride free and sulfate free and low alkali content, thus minimize the possibility of steel corrosion and the alkali-aggregate reaction and improve the durability of steel bar reinforced concrete structure.