| Along with the large-scale urbanization construction and the rapid development of ready-mixed concrete technology in our country, chemical admixture of concrete, especially the high efficiency water reducing agent plays a more and more important role in the industrialization of mass premixed concrete and become an indispensable five Points in the production of ready-mixed concrete because of the improvement for the comprehensive performance of concrete and its production construction way. According to the concrete admixtures branch of China building materials federation, In2007,2009and2011, production of synthetic water reducing agent in our country is2845.4thousand tons,4846.8thousand tons and6453.6thousand tons, Almost all the ready-mixed concrete in Xiamen is mixed with water reducing agent.During recent five years, author’s research group did a lot of research on the quality of partial concrete work in Xiamen and found that90%of built concrete work and under construction concrete work had cracks. The generation of cracks immensely reduces the strength and durability of concrete structures, so the prevention of concrete cracks has become an urgent-needed technical problem in concrete work. The causes of concrete cracks is very complicated, in addition to the structure design, construction, environmental conditions and load stress factors, increasingly complex material composition and the influence of mixture ratio design is also not allowed to be ignored in concrete. Related research shows that: the application of water reducing agent is one reason of shrinkage deformation of concrete and serious cracking phenomenon. Recently people at home and abroad do lots of research on the influence of other components for the concrete shrinkage deformation, but do a little research on the influence of high efficiency water reducer for concrete shrinkage deformation. So, it is necessary to research on this topic.Through the investigation of main ready-mixed concrete production enterprises in Xiamen(such as R&B Sunston, Hua Xin, San Hang, Hua Yue Group),choose four kinds of typical series(FDN, FAS, AS, PC),different brand(Point, HF and so on), different types(BD-A, BD-B) of a total of14kinds of high efficiency water reducing agent as the research object, and has carried out the following work:(1) Breaking limitations that the traditional design of concrete mixture ratio is only considering the working performance and strength, according to the characteristics of raw material and environmental conditions in Xiamen, both considering the working performance of concrete, strength, volume stability and durability, do innovation design of C40concrete mixture ratio in order to achieve the purpose of the prevention and control of concrete early shrinkage deformation.(2) by testing the slump and slump loss during of C40concrete mixture, the different ages compressive strength, DRCM and K, and study on working performance, strength and durability for different high efficiency water reducing agent.(3) Using non-contact displacement measurement method, putting the high efficiency water reducing agent in the ready-mixed concrete under the condition of same water/cement ratio and same mixture ratio so as to study on early shrinkage deformation of the different high efficiency water reducing agent and compile the atlas "the relationship between high efficiency water reducing agent and ready-mixed concrete early shrinkage deformation".(4) Preparing cement paste of different high efficiency water reducing agent and taking samples after3days’maintenance, observing its early hydration condition by scanning electron microscopy with Combination of all kinds of chemical composition and the molecular structure of high efficiency water reducing agent,discussing mechanism of action of different high efficiency water reducing agent. |
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