Preparation And Performance Test Of Hardening Accelerating Type Polycarboxylate Superplasticizer

The hardening accelerating type polycarboxylate superplasticizer can improve the early strength of the concrete,at the same time,it can ensure the concrete with high water-reducing rate,also can speed up the construction progress in engineering.In recent years,China has vigorously promoted and used prefabricated buildings made with hardening accelerating type polycarboxylate superplasticizer.Therefore,the development and use of hardening accelerating type polycarboxylate superplasticizer is of great significance.However,in China,most of the traditional hardening accelerating type water reducing admixture currently use salt which has hardening accelerating function and water reducing admixture in a simple combination,it will be going to cause corrode steel bars and reduce the durability of concrete,and there are many formulas which is uneven,no friendly to environment,large usage and low efficiency.The hardening accelerating type polycarboxylate superplasticizer with many advantages is still in the stage of exploration and research,there are not many domestic mature products,and the market has been occupied by foreign companies for a long time.Therefore,there is an urgent need to develop products with early strength and good water reduction in China.Starting from the point of polymer structure design,the mechanism of water reducing admixture was discussed,and then the small single maleic anhydride-triethanolamine(MA-TEA)monoester with early strength function is synthesized to hardening accelerating type polycarboxylate superplasticizer,Synthesize it with acrylic acid(AA),new modified polyether monomer(GPEG)into hardening accelerating type polycarboxylate superplasticizer,the optimal formulation GR-600 is selected by orthogonal test.Finally,it is applied to cement paste in three different regions,and its water reducing rate and early strength performance are tested.The main research content is as follows:(1)On the one hand,the mechanism of cement hydration is discussed.Triethanolamine has polyhydroxy and nitrogen atoms,which can accelerate the reaction with metal ions in cement,promote hydration and have early and strong function.On the other hand,the water reducing mechanism of polysaccharides is related to the side chain length,main chain length and other spatial configuration and electrostatic repulsion of polysaccharides.(2)Maleic anhydride(MA)and triethanolamine(TEA)were used to prepare small monomer maleic anhydride-triethanolamine monoester(MA-TEA),with hardening accelerating function,Through the orthogonal test method,the best reaction process conditions is: reaction time is 4h,reactant molar ratio n(MA): n(TEA)is 1.05: 1.00,reaction temperature is 110 ?.And the reaction time factor has the greatest influence on the reaction,and the reaction time has the greatest influence on the reaction esterification rate.(3)The modified polyether macromonomer GPEG,triethanolamine maleate monoester(MA-TEA),acrylic acid(AA),ascorbic acid(VC),mercaptopropionic acid(MPA)as main raw materials,preparation hardening accelerating type polycarboxylate superplasticizer(GR-600)by free radical polymerization.Used orthogonal test method to test the performance of 1 day,3 days,7 days,water reduction rate,clean fluidity,find the formula of GR-600.The best formula is 80% for AA,2% for MA-TEA,0.5% for VC,2.0% for MPA,and the usage amount of MA-TEA has the greatest influence on the performance of the formula.(4)Select three representative cements in different regions and use GR-600 to test water reducing rate and hardening accelerating.The results showed that GR-600 water reducing rate could reach 26.4% to 32.4%,the 1 day and 3 day average ratio of compressive strength were 203% and 187%,respectively.The early strength increase is significant and has significant performance advantages.