Synthesis And Performances Study Of Functional Polycarboxylate Superplasticizer

Superplasticizer is one of the most studied and the most widely used concrete admixtures.Since its publication,after decades of development,it has been developed from the first-generation lignin-type superplasticizer,the second generation of naphthalene-type superplasticizer developed to the latest third-generation polycarboxylate superplasticizer,which has poured innumerable efforts of scientists.Compared with the first generation and the second generation of superplasticizer,polycarboxylate superplasticizer has become the research focus of the concrete admixture industry due to its low dosage,excellent dispensability and structure design ability.Not only that,in our country's environmental problems have become increasingly serious today,the environmental protection of polycarboxylate superplasticizer make it become superstar of superplasticizer industry.Compared with other types of superplasticizers,polycarboxylate superplasticizer,has many advantages,but there are many problems have arisen in the its whole development process,such as temperature sensitivity,poor adaptability to the material,few polymerizable monomers,unstable performance(for example,the slump maintenance is poor,lack of early strength)and other disadvantages urgently need to be further explored by researchers.In this dissertation,two different types of polycarboxylate superplasticizer's monomers APL and PHS were developed to solve the problems in the performance of polycarboxylate superplasticizers.The APL and PHS were introduced into the main chain of polycarboxylate superplasticizer by means of radical polymerization,the functional polycarboxylate superplasticizer APL-PCE and PHS-PCE were synthesized,the main work is as follows.1.Acryloyl chloride and alanine are used as raw materials to synthesize a novel polycarboxylate superplasticizer monomer APL by amidation reaction,and then used the novel polycarboxylate superplasticizer monomer APL,AA,TPEG-2400 as monomers,synthesized the slump retention type polycarboxylate superplasticizer APL-PCE successfully by free radical polymerization,and then the fluidity of cement paste was used as an indicator to explore the best synthesis conditions from the reaction temperature,the initiator's dosage,the dosage of chain transfer and the dosage of APL 's dosage respectively.The results showed that when the molar ratio of TPEG-2400 to acrylic acid is 1:3,the reaction temperature is 65?,the reaction time(dropping time)is 120mins,the dosage of chain transfer agent is 0.4wt.%,the dosage of hydrogen peroxide was 1.6wt.%,the mass ratio of hydrogen peroxide to ascorbic acid was 3:1,and the dosage of APL was 6wt.%.The APL-PCE had the best dispersing performance and the fluidity of cement paste could reach 330mm,and the fluidity loss is only 30mm within 90 mins,followed by the selection of Xuyan high railway C50 beam concrete ratio to do the stones to compare the performance of concrete,The results showed that the water reduction rate of APL-PCE is 3.4 percentage points higher than that of the common commercial polycarboxylate superplasticizer,and its stability is inferior to that of common commercial polycarboxylate superplasticizer in the process of making C50 beam concrete.It was found that its bleeding rate was higher than that of common commercial polycarboxylate superplasticizer,and eventually resulted in extending the setting time and late strength was wake.And then when we decrease the dosage of APL-PCE in the concrete of the C50 beam,it was found that the bleeding rate meets the requirements of the C50 beam concrete,and its slump retention is significantly enhanced.2.PHS was grafted to the main chain of polycarboxylate superplasticizer by free radical polymerization,and the early-strength type polycarboxylate superplasticizer PHS-PCE was synthesized successfully.And the effect of synthesis conditions on the strength of concrete at 3 days,7 days and 28 days was investigated by orthogonal experiment from four factors level n(AA + PHS)/n(TPEG),n(AA)/n(PHS),the dosage of H2O2/wt.%and the dosage of chain transfer agent/wt.%so as to determine the best synthesis conditions.The results of orthogonal experiment showed that when the dosage of H2O2 was 1.2wt.%and the dosage of H2O2 was 1.0wt.%,the ratio of n(AA+ PHS)/n(TPEG)=7.0,n(AA)/n(PHS)=3.0,the PHS-PCE has the best comprehensive performance.The strength of concrete for 3 days can reach 42.9MPa,the strength of concrete for 7 days can reach 53.9MPa,and the strength of concrete for 3 days can reach 59.8MPa.