The Study Of Synthesis Of Polycarboxylic Superplasticizer And Its Compatibility And Adaptability On Cement

Polycarboxylate-type water reducer has the following advantages such as lowdosage, strong dispersity, controllable molecular structure, environmental protection,and so on. Hence, it becomes the development direction and the research hotspot ofconcrete admixture.The present paper through the design of polycarboxylate-type water reducermolecular, many functional groups such as polyoxyethylene ether, carboxyl, sulfonicacid group are introduced into the molecular structure; we use water solution freeradical copolymerization method to synthesize PC-1and PC-2two kinds of waterreducer in experiment,APEG、MPEG with AA and MAS are employed as reactionraw materials, H₂O₂（30%）is employed as redox system, we research the influence ofdifferent factors such as the ratio of reaction monomers, molecular weight ofpolyether monomer, dosage of initiator and chain transfer agent, reaction temperature,polymerization time, polymerization concentration on the performance of waterreducer, and determine the optimal synthetic process.The optimal synthetic process of PC-1is reaction temperature65℃,polymerization concentration60%, polymerization time3.5h, dosage of initiator1.6%,chain transfer agent1.5%, n（AA）: n（APEG）:n（MAS）=4.2:1:0.3; the optimalsynthetic process of PC-2is reaction temperature60℃, polymerization concentration60%, polymerization time3.5h, dosage of initiator1.6%, chain transfer agent1.5%, n（AA）: n（MPEG）:n（MAS）=3.9:1:0.2. and we analyse the molecular weight andits distribution of synthetic products by GPC, according to the results, the averagemolecular weight and its distribution of PC-1is2.04×10⁴and3.93, respectively; theaverage molecular weight and its distribution of PC-2is2.61×10⁴and3.87,respectively. We also analyse the purified products by IR and NMR, and molecularstructure was characterized.We carried on the test of net cement slurry fluidity that contain syntheticproducts, test of different cement mortar water reducing rate, test of hardened concretemechanical properties, and the test of hardened concrete durability. According to theresults, when the amount of synthetic products is0.2wt%, the fluidity of net cementslurry that add optimal PC-1will reach285mm; the fluidity of net cement slurry thatadd optimal PC-2will reach295mm; on the premise of the same content, the waterreducing rate of synthetic products in the slag Portland cement is highest, and havegood adaptability; the mechanical properties and durability of concrete that containsynthetic products is greatly improved, when the dosage of synthetic products is 0.25%, water cement ratio is0.33, age of concrete is7d, compressive strength willreach around50MPa, flexural strength will reach around6MPa, compressive strengthand flexural strength increased by40%and44%; age of concrete is28d, compressivestrength will reach around60MPa, flexural strength will reach around6.8MPa,compressive strength and flexural strength increased by47%and48%.With theincrease of synthetic products the frost-resistance, impermeability and contractility ofhardened concrete improved significantly; we analyse the internal pore structure, poresize distribution, interface of hydration products and stone of hardened concrete bySEM. According to the results, when we add water reducer to concrete, pore size issmaller, distribution will more uniform, cement stone structure is more closely, andproviding the basis for the theory analysis of mechanical properties and durability ofhardened concrete.