| Based on National Natural Science Foundation of China(51408448) poly carboxylic acid reduction agent and hydroxy carboxylic acid salt corrosion depressant molecular structure coupling mechanism " and hydroxy carboxylic acid salt corrosion depressant molecular structure coupling mechanism "and the National Natural Science Fund Project 51178363" concrete Thaumasite erosion mechanism and protective measures.This article focused on engineering problems by raw clay and other causes of concrete slump loss, by exploring the interaction mechanism of montmorillonite and Polycarboxylate and prepare Polycarboxylate and sustained-Paul collapse agent, through complex retarder, after a lot of testing to find excellent performance slump material system, in the summer high temperatures and under high clay content in the concrete conditions of the amount, after mixed method with the materials used in the concrete mix slump together in order to solve the problem of providing some concrete slump loss method. Details are as follows:By preparing a polycarboxylic acid water reducing agent and a slump, and to study the mechanism of action slump agent slump for the preparation of the material system to provide a theoretical basis, as follows:(1) Synthesis of maleic anhydride, monomethyl maleate, optimum reaction conditions were: reaction time 105 min, the molar ratio of maleic anhydride / methanol 1.1: 1, the choice of concentrated sulfuric acid catalyst, the conversion rate of 84.69%.(2)Analysis of the stability of the slump agents found hydroxyethyl acrylate type slump better stability agent, Paul excellent performance slump standing three months later, maleic anhydride ester type slump single agent in the static Set ester decomposition process into high performance superplasticizer.(3) Determination by NMR spectroscopy and found that the mechanism slump agents by introducing an ester group in the molecular structure, hydration process of hydrolysis of the ester group "slow release" carboxyl group, compared with the superplasticizer, it dispersion properties can be maintained for a long time.2 Through complex superplasticizer, slump agent and retarder, find out the excellent performance slump material system, as follows:(1)Complex slump agent and reducing agent, both good match, especially when incorporated 0.8g JS-3 water reducing agent and 0.2g BT slump optimal effect, the initial fluidity of 210 mm, 1h Fluidity is 240 mm.(2) water reducing agents or retarders slump in cement particles competitive adsorption occurs, resulting in the initial fluidity of cement paste declined slightly, but the loss of inhibition 1h fluidity, which affect the size of Fe2(SO4) 3> SG> STTP.(3) ternary component Paul JS-3-BT- retarder collapse based material excellent performance, particularly in the quality of the components is JS-3(0.8g)-BT(0.2g)- Retarder(0.2g), the initial fluidity of cement paste at 220 ~ 235 mm, 1h fluidity at 240 ~ 255 mm.3 study significantly affected montmorillonite clay minerals paste fluidity, and by studying the adsorption mechanism of polycarboxylate superplasticizer, find suitable material system to suppress the adsorption of water reducer montmorillonite, as follows:(1) When the cement incorporating montmorillonite, dramatically reducing the initial fluidity of cement paste and 1h fluidity and decrease with increasing MMT content increased.(2) When Polycarboxylate montmorillonite or slump agent is incorporated, montmorillonite interlayer spacing increases from 1.51 nm to 1.63 ~ 1.70 nm. And montmorillonite adsorption Polycarboxylate adsorption is much larger than Polycarboxylate cement, resulting in greatly reduced the effective utilization of water reducer, which is the cement paste by large losses cause.(3) When the cement-MMT system while simultaneously incorporated polycarboxylate superplasticizer and retarder, retarder inhibits the adsorption of Polycarboxylate montmorillonite, increasing the initial cement paste fluidity, when inhibited by the loss of paste.(4) A MMT Polycarboxylate adsorption is part Polycarboxylate side chain adsorbed layers of montmorillonite.4 of concrete containing high clay content and high temperature environments, after the slump material doped with a way to solve the concrete slump when the loss is too large problem, as follows:(1) When the concrete high clay content(8%), concrete superplasticizer single agent or slump, slump loss of concrete quickly, 60 min a slump 0mm, no longer have the construction performance. Using superplasticizer- slump agents- retarder slump ternary component materials that can effectively inhibit the concrete slump loss at higher temperatures in summer, you can ensure concrete 60 min slump in 180 mm above, to ensure workability.(2) incorporation slump in two ways to ensure the concrete material 120 min slump in 180 mm or more, to meet the construction requirements. Early slump after blending doped materials should be selected proportion of 70% and 30% or 80% and 20%. |
