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Polycarboxylic Superplasticizers and Their Mechanism
Author: LiPing
Tutor: ZhangFuQiang
School: Hebei University of Technology
Course: Polymer Chemistry and Physics
Keywords: Polycarboxylate Superplasticizer Paste fluidity Dispersion mechanism Hydrodynamic radius Adsorption amount
CLC: TU528.042.2
Type: Master's thesis
Year: 2010
Downloads: 172
Quote: 0
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Abstract
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Polycarboxylate superplasticizer has a high water reducing rate advantage of the collapse of high security, high enhanced cement adaptability and safety and environmental protection, increasing attention has been widespread concern. Article with a molecular weight of 1100 and 600, methoxy polyethylene glycol, synthetic large monomer methoxy polyethylene glycol methacrylate ester (MPEGMA), studied the MPEGMA / AA / MAA / AMPS Copolymers, performance , the mechanism of the adsorption characteristics of the cement particles. Methoxy polyethylene glycol, and methyl methacrylate was prepared by the transesterification MPEGMA again with other monomers by aqueous solution to adjust the copolymerization of a comb-type structure is prepared efficient polycarboxylate based superplasticizer (PC), and used FTIR spectra of their structure. Detailed study of a large monomer structure, feeding mode, the amount of initiator, acrylic pre-degree, MPEGMA1100/MPEGMA600 molar ratio AA / MAA molar ratio and neutralizing reagents and other factors that impact on the fluidity of cement paste. In addition, research PEG branched composed of cement mortar strength as well as the impact of the hydration process. The results show that the synergistic effect exists between the long-chain branched and short branched PEG, short branched-chain PEG improve the superplasticizer in the adsorption force of the cement surface and the stability of the adsorption, the long-chain branched PEG provides a larger steric The combination of both can better ensure adsorption and steric stabilization, when MPEGMA1100/MPEGMA600 molar ratio is 1:0.2, the superplasticizer of dispersibility and dispersion stability. When the the MPEGMA1100/MPEGMA600 molar ratio is 1:0.2, the AA / MAA molar ratio of 1:1, the APS molar amount of 5%, and ethanolamine, the better the dispersing performance of the superplasticizer: fold solid ash 0.3%, 0.29 when the water-cement ratio, cement fluidity of up to 330mm, and 120min after still 220mm flow. The continuous use of ultrasonic detection test signal characterization of the mortar microstructure throughout the development process, to explore the impact of superplasticizer on the hydration process of cement mortar. The results show that contains the length of PEG branched superplasticizer better able to extend the initial and final setting time, delaying the exothermic cement mortar and to more effectively ensure the cement mortar 3d, 7d, 28d The compressive strength and flexural strength, much better than a single PEG branched superplasticizer SNF, also showed good dispersion properties aluminate cement. Measured by light scattering experiments average hydrodynamic radius of the PC in the simulated cement pore solution and the mean square radius of 256.4 nm and 118.7nm. The results showed that the PC is formed in the surface of the cement particles similar core-shell structure of the aggregate, its steric hindrance help to improve the dispersion stability of the superplasticizer. Use of total organic carbon was measured limit adsorption amount of superplasticizer on cement 2mg / g. PC gathered in different ionic strength of the solution changes in body size and adsorption entropy change of the cement particles showed a weak effect of superplasticizer intensity response soft material properties.
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CLC: > Industrial Technology > Building Science > Building Materials > Non-metallic materials > Concrete and concrete products > General issues > Raw materials and auxiliary materials > Admixtures > Superplasticizer
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