Ziming Wang;Huiqun Li;Xiao Liu;
<正>The demand for polycarboxylate superplasticizer(PCE) applied in construction increases quickly with the development of construction industry.Polycarboxylate superplasticizer provides excellent workability,compressive strength and durability of concrete.Functional polycarboxylate superplasticizers were developed and used to solve the specific problems in construction.The slow-release polycarboxylate superplasticizer can release its dispersion gradually that it could provide concrete a poor initial slump and rises slowly in 1 or 2 hours and reaches the maximum slump.The slow-release characteristic of polycarboxylate superplasticizer avoid the bleeding of fresh concrete and present good workability in the process of construction.It can also reduce the evaporation of mix water during long-distance transport and prevent slump loss in a certain extent.Slow-release PCE was studied according to the adsorb process of molecule.The experiment made unsaturated carboxylic acid ester a substitute for unsaturated carboxylic acid and lessened the quality of initial adsorb molecules.The molecule adsorbed gradually onto the cement particles after the carboxylic acid ester hydrolyzed in the alkaline environment of cement paste. Four different carboxylic acid esters were selected as target comonomers and synthesized to slow-release PCE with different characteristic.The samples were test by cement paste fluidity and concrete slump.The slow-release PCE provide a good slow adsorption and it has been proved by the total organic carbon test. Originality The flowability and its maintenance tend to be more important in application of concrete using slump retaining PCE in construction.The concrete is required to have a high initial slump as well as the maintaining performance.The slow-release PCE provides a poor dispersion at the beginning and increases gradually over time,and performs a small initial slump and grows to a maximum slump after mixed. Unsaturated carboxylic acid ester was made a substitution for unsaturated carboxylic acid in the preparing of slow-release PCE,and the initial adsorption of PCE molecules was reduced on cement particles.The carboxylic acid ester hydrolysis and produces carboxylic acid in the alkaline environment of cement paste after mix with concrete gradually,and thus there are would be enough PCE molecules remained in the solution to adsorb onto the cement particles constantly which can achieve the slow-release function finally.
slow-release;;polycarhoxylate superplasticizer;;carboxylic acid derivatives;;hydrolyze
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