| Research Abstract |
The purpose of this study is to develop new superplasticizer for high-performance concrete such as high-strength concrete and self-compacting concrete. We have applied the comb-like copolymer having graft chain made of polyethylene oxide to newly developed superplasticizer. In this study, we investigated the effect of several factors such as kinds of cement, temperature and mixing condition on the fluidity of cement paste in order to optimize the chemical structure of comb-like copolymer. Moreover, the properties of fresh concrete were also examined in order to verify the results of paste test.
The most important findings are summarized as follows;
(1) The effect of chemical structure of copolymer on the fluidity of paste depended markedly on the kind of main polymer. In case of maleic anhydride based copolymer, the better the fluidity was, the shorter the length of polyethylene oxide chains became. In the opposite, in case of methacrylic based copolymer, the better the fluidity was, the
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longer the length of polyethylene oxide chains became.
(2) The delay of the hydration decreased with an increase in the length of polyoxyethylene graft chain, an the degree of the delay was different depending on the kind of the main chain polymer. In case of maleic anhydride based copolymer, the hydration of alite (3CaO・SiOィイD22ィエD2) in cement inhibited remarkably when the length of polyoxyethylene graft chains was short. On the other hand, in case of methacrylic based copolymer, the hydration of alite was not inhibited significantly, regardless of the length of polyoxyethylene graft chains.
(3) The fluidity of cement paste containing comb-like polymer, of which main chain makes of the methacrylic acid, was not affected easily by the kinds of cement used, temperature and mixing condition.
(4) Fresh concrete indicated the same tendency of the cement paste; the longer the length of graft chains became, the better were the flowability, segregation resistance, passing ability and self-compactability of concrete.
From the results in this study, we conclude that the comb-like methacrylic copolymer with a long graft chain has the best efficient chemical structure in terms of both fluidity and strength development. Thus it is possible that we can produce easily the high performance concrete by using the comb-like methacrylic copolymer with a long graft chain even when the kinds of the cement used, temperature and mixing conditions are varied. Less
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