Research On Microstructure And Properties Of Internal Curing Concrete

High performance and long life are the development direction of concrete materials research. The higher degree of cement fineness, lower water to binder ratio, as well as the application of super plasticizer in the modern cementitious system shorten the time interval between initial and final setting process and accelerate the initial micro-structure formation, which produced lots of grown-in defects due to the inconsistent deformation of various composition. This lead to some discount of cement properties, especially the durability performance.Our work is based on the technology innovation project of China State Construction ENGRG. CORP. LTD(CSCEC), and innovatively offers a new way of preparing concrete internal curing materials, which is a composite preparation technology of inorganic multi-porous absorbent material and organic super absorbent polymer. The water absorption and release characteristics of inorganic multi-porous fine lightweight aggregate and super absorbent polymer, as well as their influence on internal relative humidity and autogenous shrinkage of concrete are studied to determine the mix design method of high strength concrete with composite internal curing materials. This solved the problem that lower efficiency only doped with norganic multi-porous fine lightweight aggregate, also that lower concrete strength only with super absorbent polymer.Also the long-term mechanical properties and its variation laws had been studied. The results showed that the concrete under internal curing conditions had higher increase rate of later rstrength. Moreover, the influence of internal curing on the later strength of the concrete with lower w/o was particularly prominent. The anti-crack performance and durability properties of concrete with internal curing were systematically studied. The durability test showed that, comparing with standard concrete, the addition of internal-curing material could improve the anti-crack performance, enhance the frost resistance and anti-carbonization, but the influence on the anti-permeability was not significant.The improvement mechanisms of internal curing on the later strength and durability had been studied with the research results of concrete micro structure,like SEM, MIP etc. The results showed that, under the internal curing condition, the concrete had higher fly ash hydration reaction degree, thinnerpaste stone pore, and less porosity. This was the critical reason of later strength increase and better durability. The high performance concrete design and preparation idea of self-healing technology of original crack in the interface transition zone (ITZ) was proposed innovatively.Also we mastered the commercialization of production and construction technology; developed the vector preparation technology which ensured the even desperation of internal-curing material. This technology had been successfully applied on the wuhan Mo'er city and yintai dazhi jiayuan project, which achieved significant social and economic benefits.