Preparation And Properties Of Early - Strength Polycarboxylate Composite Water Reducing Agent

Polycarboxylate superplasticizer, not only performing high water reducing rate but also being environmentally friendly in the process of production, has been widely used in the field of concrete engineering. Early strength polycarboxylate superplasticizer can significantly improve the performance and the early strength of concrete, which accelerates the progress of the project, improves production efficiency and saves energy consumption. The development and utilization of early strength polycarboxylate superplasticizer shows important and practical impact on the development of economy and society in our country. However, the research on the preparation of polymer is still in the exploratory stage, and there is a lack of information of the design of molecular structure to realize the early strength of polycarboxylate superplasticizer in our country. There are few mature products, and the early strength performance of most polycarboxylate superplasticizer is not ideal. The conventional early strength compounding polycarboxylate superplasticizer was obtained by compounding the naphthalene superplasticizer with early strength agent. It not only increases the possibility of corrosion of steel but also reduces the durability of concrete structures, and it is not environmentally friendly and a waste of material.The object of the study is to prepare a new type of polycarboxylate superplasticizer with early strength properties from the perspective of molecular structure design, and further research focuses on the compound of early strength polycarboxylate superplasticizer with early strength agent, then the early strength type compound polycarboxylate superplasticizer was prepared. The main research contents and the results include the following aspects:(1)The polycarboxylate superplasticizer was synthesized with isoamyl alcohol polyoxyethylene ether(TPEG), acrylic(AA) and sodium methylallyl sulfonate(SMAS), by free-radicalcopolymerization. According to the performance test results of polycarboxylate superplasticizer, the optimal prescription is made certain by holistic consideration. The optimal molecular weight of TPEG was 3800, the optimum molar ratio of SMAS and AA to TPEG is 10.0, the optimum molar ratio of AA to SMAS is 8.0, the dosage of APS was 1.5%, and the reaction time was 3 h. The performance of PS-C1 polycarboxylate superplasticizer is similar to commercial ones. FTIR test results show that the PS-C1 polycarboxylate superplasticizer owns hydroxyl, carboxyl, ether bond, sulfonic acid group and other features of functional groups, and it performs well in copolymerization effect.(2)The early strength polycarboxylate superplasticizer was synthesized by grafting it with small molecular groups of early strong function in the PS-C1 polycarboxylate superplasticizer through orthogonal test. According to the results of polycarboxylate superplasticizer, the optimal prescription is made certain by holistic consideration. The optimum molar ratio of SMAS and AA to TPEG is 8.0, the optimum molar ratio of AA to SMAS is 10.0, the dosages of MAE and AM were 2% and 1%. Compared with commercial polycarboxylate superplasticizer, the early strength polycarboxylate superplasticizer prepared under optimal prescription shows higher water-reducing, dispersibility and excellent early strength. FTIR test results show that the expected functional group is introduced into the structure of BS-C3 early strength polycarboxylate superplasticizer and the copolymerization effect is excellent.(3)Organic(triethanolamine) and inorganic(calcium nitrate, sodium sulfate)early strength agents were compounded with early strength polycarboxylate superplasticizer(BS-C3) by orthogonal test. According to the performance test results of polycarboxylate superplasticizer, the optimal prescription is made certain by holistic consideration. The dosages of triethanolamine, calcium nitrate and sodium sulfate were respectively 0.02%, 0.04% and 0.02%. Compared with BS-C3 polycarboxylate superplasticizer, commercial HSD4 and QL-P3 polycarboxylate superplasticizer, the early strength of concrete using early strength compound polycarboxylate superplasticizer prepared under optimal prescription was respectively increased by 11.03%, 13.77% and 26.90%. Compared with BS-C3 polycarboxylate superplasticizer, the dispersibility of early strength compound almost remains unchanged. Compared with HSD4 and QL-P3 commercial polycarboxylate superplasticizer, the dispersibility of early strength compound was respectively increased by 17.65% and 10.00%. The early strength compound polycarboxylate superplasticizer shows high water reducing rate, excellent dispersing performance, and it can significantly improve the early strength of the concrete.