Study On Polyether Type And Modified Starch Composite Superplasticizer

The dispersion of polycarboxylate superplasticizer for cement was based on their molecular structure. Study on the relationship between the molecular structure of ether polycarboxylate superplasticizer and the water-reducing effect, and preparation of carboxymethyl starch complex ether polycarboxylate superplasticizer. The main contents and results include the following aspects:(1)To modified polyether macromonomer(APEG)、acrylic acid(AA) and propylene sulfonate (AS) as raw materials, oxidize-reduction initiator, through orthogonal experiments and single factor experiments, the optimum conditions of synthesis obtained as follows: polymerization temperature was65℃, so the polymerization time4.5h, the molar ratio of monomer was APEG:AA:AS=2:5:0.4, the best amount of initiator was O0.55%, R0.155%of total quality of monomers. IR spectrum of the polymer proved that the product was desired, under the conditions of this experiment, the best average molecular mass distribution of superplasticizer was in the range of18000-22000.(2)Taking viscosity of carboxymethyl starch solution as evaluation criteria, selecting a amylase(in an amount of1%by mass of the starch) to degradate the carboxymethyl starch; Using stability of complex superplasticizer solution as criteria, we obtained that carboxymethyl starch degradated for at least4h and solids content less than20%, the solution could be stably stored; Through orthogonal experiments, optimum conditions of complex superplasticizer got as follows:in the conditions of carboxymethyl starch degradation temperature was75℃, the degradation time was4hours, the synthesis temperature was65℃, the synthesis time was4.5hours, the solid content of20%of the theoretical, the mass ratio of monomer as follows:APEG:CMS=9:1, Total mass:AA=6:1, Total mass:AS=96:1(Total mass=mAPEG+mcMs), the best amount of initiator was O0.30%, R0.10%of total quality of monomers, the compound superplasticizer has good dispersion. (3)Discussed the water-reducing mechanism of superplasticizer by surface tension and cement hydration experiments, the results showed that:ether superplasticizer has no significant effect on the solution surface tension, it’s a non-air-entraining type water reducing agent, complex superplasticizer can reduce the surface tension of20mN/m at dosage of0.9%, with some bleed air resistance, and consistent of bleed isolation "ball" theoretical description. These two types of water-reducing agent can significantly slow the hydration time, hindering the formation of hydration products, thus improving the dispersion stabilityof the paste.(4)The cement content of saturated experimental results showed that saturated content of these two types superplasticizer were about0.3%; Derived from the reducing agent dispersion performance comparison tests, when the content was0.37%, complex ether superplasticizer has a better performance than the commercially product polycarboxylate and ether superplasticizer, has a good performance of slump.