Synthesis And Properties Of Shrinkage Reducing Polycarboxylate Superplasticizer With High Performance

One of the indispensable components of modern concrete is chemical admixtures,especially polycarboxylate superplasticizer,whose excellent water reducing and dispersing properties have played a huge role in engineering construction.However,the commonly used polycarboxylate superplasticizer are not effective in solving the shrinkage and cracking that occurs in concrete under harsh construction conditions,and the use of shrinkage reducing admixtures can reduce the shrinkage and cracking of concrete.The use of shrinkage reducers can reduce the shrinkage and cracking of concrete.However,the cost of producing the admixture with current technology is huge and the demand for the admixture in construction is also high,which can put a lot of economic pressure on the construction unit.Therefore,this experimental study makes use of characteristics of polycarboxylate superplasticizer molecular structure with programming and wide application to introduce the shrinkage reducing components to synthesize shrinkage reducing functional shrinkage reducing polycarboxylate superplasticizer（SRPC-1）,so that it has good shrinkage reducing effect while maintaining water reducing dispersion.The use of SRPC-1 can reduce the pressure on construction cost while ensuring the quality of the project.The main elements are as follows:（1）Preparation and flowability study of polycarboxylate superplasticizer（PCE3）:methallyl polyoxyethylene ether(TPEG₂₄₀₀)and acrylic acid（AA）were used as reactants to produce PCE3 under specific experimental conditions.The optimum process was determined experimentally:n（AA）:n(TPEG₂₄₀₀)of 3:1,a monomer concentration of 30%,a mass of initiator as a percentage of monomer mass of 1.0%,a reaction temperature of 80°C and a drop-in time of 1.0 h.Under these conditions,a polycarboxylate superplasticizer（PCE3）with good compatibility with cement was successfully prepared.PCE3 has a high water reduction rate and can save a lot of water resources in engineering construction.The polycarboxylate superplasticizer（PCE3）has a high water reduction rate and can save a lot of water in construction.Moreover,the polycarboxylate superplasticizer（PCE3）can achieve a net cement flow rate of 252 mm,which solves the problem of cement flow loss caused by long time transportation of cement.（2）Preparation,structural characterization and performance study of shrinkage reducing polycarboxylate superplasticizer（SRPC-1）:three alcohols,polyethylene glycol PEG₆₀₀,polyethylene glycol monomethyl ether and dipropylene glycol monomethyl ether,were selected for esterification reaction with the carboxylic acid group in the polycarboxylate superplasticizer,and SRPC-1 was synthesized by combining water-reducing and shrinkage reduction.FTIR test results show that the shrinkage reduction group is modified by chemical grafting onto the polycarboxylate superplasticizer.Zeta potential tests were carried out to observe the changes in the surface potential of the cement particles,and scanning electron microscopy was carried out to observe the microstructure of cementitious sand samples at 28 d.The results showed that the surface tension of SRPC-1 in saturated lime water solution was 35.8m N/m,which was lower than that of the commercially available water reducing agent PCE1（45.2 m N/m）and PCE2（54.1 m N/m）,and also lower than that of the home-made polycarboxylate superplasticizer PCE3（45.2 m N/m）.The surface tension of PCE3（45.7 m N/m）was also lower than that of the home-made polycarboxylate superplasticizer（PCE3）.This provides a theoretical basis and direction for the future synthesis and application of SRPC-1 in engineering.（3）Testing of shrinkage reducing polycarboxylate superplasticizer（SRPC-1）in cementitious sand:Using Dalian Tianrui cement as the base test material,the water reduction rate test,dry shrinkage rate test and mechanical strength test of cementitious sand were conducted to understand its dispersion performance,shrinkage reduction performance and mechanical strength performance.A comparison of the water reduction,shrinkage reduction and compressive strength of the samples showed that SRPC-1 had a high shrinkage reduction of 23%at 28 d and a water reduction of 38%as well as a 101.4%increase in the compressive strength of the cementitious sand.Overall,the synthetic SRPC-1 has outstanding performance in reducing water consumption in construction and shrinkage and cracking in concrete.