Research On Synthesis And Performance Of Polyether-type Polycarboxylic Superplasticizer

Compareing with traditional polycarboxylic superplasticizer , polyether-type polycarboxylic have many advantages, such as polymerized by one-step method directly, short production cycle , reduce the production costs and so on, which made it become a worldwide hotspot. At fist, this paper uses allyl polyethylene glycols(APEG), acrylic acid (AA) and maleic anhydride (MA) as experiment materials, got the optimum technological conditions to synthesis polycarboxylic superplasticizer(A-A), based on the orthogoned experiment. Then according to the considerations of molecular design, use Lignin and hydroxypropyl methyl cellulose(HPMC) by means of grafting copolymerization to modify Polyether-type polycarboxylic superplasticizer separately,and got two types of modified polycarboxylic superplasticizer. The influences of synthesis polycarboxylic superplasticizer and the performance of polycarboxylic superplasticizer were researched, through the fluidity of cement paste, water reducing, compressive strength, heat of hydration, IR, SEM, etc.(1) The optimum conditions to synthesis polycarboxylic superplasticizer had been got, at 86℃, dosage of initiator ammonium persulfate (APS) accounts for 4% of the monomer mass; the dropping time of monomers and initiator(APS) is 4.5h and 6.0h respectively; molar ratio of monomers is: APEG:AA:MA=1:4.5:1.2; dosage of chain-transfer agent mercaptoacetic acid(2-M) accounts for 1% of the monomer mass, and got polyether-type polycarboxylic superplasticizer A-A ,A-L,A-Hwith the above conditions.(2) A series of tests of A-A shows, the water reduce rate got to 33.5%; the cement paste lossed 31% for 1h, and the slump loss of 2h got to63%,proved fluidity-retaining abilityis poor, and segregation and bleeding easily;3d, 7d,28d concrete compressive strength improved than benchmark by 115%, 99.4%, 76.5% respectively, which indicated the mechanical properties enhanced significantly; the hydration heat generation reaction delay 6h or so, the highest peak temperature is lower, indicated thermal stability is good, beside SEM photos also proved A-A cement hydration speed was slower.(3) A series of tests of A-L shows, the water reducing rate was28.5%; the cement paste lossed only 4% for 1h,and the slump loss 2h was only 11%;3d,7d,28d concrete compressive strength improved than benchmark by 65.4%, 94.4% ,71.8% respectively, which indicated the mechanical properties enhanced significantly; the hydration heat generation reaction ahead of A-A about 6h; different dosage of lignin affect the Cement hydration obviously. Compared with A-A, A-L has remarkable fluidity-retaining abilities, but the water reducing rate reduced.(4) A series of tests of A-H shows, the water reducing rate was 32.4%; the cement paste lossed only 4% for 1h, and the slump loss rate of 2h was only 26.8%;3d,7d, 28d concrete compressive strength improved than benchmark by 92%, 89% ,82.4% respectively; the curve of hydration heat appeared earlier than A-A. Comparaed with A-A and A-L, the comprehensive property of A-H was more dieal.