Effect Of Molecular Structure Of Polycarboxylate Superplasticizer On Corrosion Resistance Performance Of Concrete In Tropical Marine Climate Area

How to build concrete buildings with excellent durability has become the most important problem which is faced by the concrete industry today. Hainan province is located in tropical marine climate area, the climate here is influenced by two terrible natural environments, tropical environments and marine environments. And the specific characteristic of this area is high temperature, high humidity and high radiation. With the evaporation of seawater, relative content of chloride ions is high in the air and other corrosive medium, such as oxygen, water vapor and ultraviolet radiation is more activity in this area. Therefore, it is important to improve the chloride ion penetration resistance and sulfate resistance of concrete in Hainan Province.Polycarboxylate superplasticizer (PCE) is one kind of concrete water reducer which is most widely used and researched currently. The mechanism of its molecular structure effect on the durability of concrete research has been reported rarely. In this thesis, different series of carboxylic groups, sulfonate groups and side chains of PCE were synthesized respectively. Study on the effect of PCE on the performance of cement paste, the chloride ion penetration resistance and sulfate resistance of concrete under the tropical marine climate, from the molecular structure level. And further exploration of mechanism is exhibited.For series of different carboxylic groups, the short side chain ester PCE, short side chain PCE and long side chain PCE had been studied. Results showed that, the optimal paste fluidity and fluidity loss ratio could be got by acid ester(ether) ratio of both ester and ether PCE with short side chains are2.5:1. It was need acid ether ratio of3.5:1to get the optimal paste fluidity for ether PCE with long side chains, and the optimal fluidity loss ratio also can be got by the acid ether ratio of2.5:1. The results of apparent viscosity in20?is consistent with the fluidity test, when the temperature raised to40?, the apparent viscosity of high acid ether (ester) PCE showed the tendency of first increased and then decreased. As for sulfate resistance, PCE with short side chains had worse sulfate resistance property under lower ester (ether) ratio. But for PCE with long side chains, sulfate resistance property decreased under the higher ether ratio. There was no significant effect of different ester (ether) ratios of ester PCE with short side chains on chloride ion penetration resistance property. And for the ether PCE, good chloride ion penetration resistance property could be got under higher ratio of acid ether ratio. From the internal structure of concrete, there was no significant laws for esters PCE with short side chains in the changes of pore structure parameters. The porosity was decreased by the increasing of acid ether ratio of ester PCE with long side chains, while for the ester PCE with short side chains, the porosity was increased with the acid ether ratio increased and the narrowpore conent was decreased with the acid ether ratio increased.For series of different sulfonate groups, the results show that, with the amount of sodium methacrylate (MAS) increased, its fluidity, fluidity loss and apparent viscosity were reduced after the first increase, the optimum property was obtained by the content of MAS is0.32. With the temperature increased, the increase of apparent viscosity for PCE with high MAS contents was less than the PCE with low MAS contents. There is not much impact on sulfate resistance property with the MAS contents increased, but for chloride ion penetration resistance property, it would be reduced by the increasing of MAS contents.For series of different side chains, results showed that, paste fluidity was improved and the loss rate was reduced by10%of carboxylic groups replaced by ester groups in PCE. The properties of PCEs which both have long chains and short chains is between the performance of PCEs which are only have long side chains or short side chains. Paste fluidity was increased, the loss ratio and the apparent viscosity were decreased with the growth of side chains length, and especially the one with long side chains PO block PCE had most obvious effect change. Paste apparent viscosity increased with the temperature rise to40?, but the presence of high content ester groups in PCE could reduce the paste apparent viscosity at high temperature. Corrosion resistance results show that, with shorter ether PCE side chains, concrete porosity decreased, the corrosion resistance performance became better. Both the replacement of carboxylic groups by ester groups and bringing in the side chain with PO block in are conducive to improving chloride ion penetration resistance of concrete, but the exist of ester groups made the fresh concrete in poor workability which contribute to reduce the sulfate resistance property. For the PCEs both had long chains and short chains, no matter what type they were, its concretes were porosity compared to the concretes with PCEs which are only have long side chains or short side chains. So the PCEs both had long chains and short chains weren't conducive to the corrosion resistance of concrete. At the same time, there was connection between the corrosion resistance of concrete with PCEs and the apparent viscosity of paste with PCEs, the corrosion resistance of concrete got better with the apparent viscosity of paste increased.