Research On Early-age Plastic Shrinkage And Cracking Of Green High Durable Concrete

In the 21st century, the cement concrete is still the most important sructural materials of the civil engineering, which durability is significantly concerned in the engineering domain both home and aboard. Early-age plastic shrinkage is main reason of the plastic cracking of high performance concrete, and is also a common problem occurred with the high performance concrete. Concrete's early-age plastic cracking accelerates the concrete's deterioration process, and affects the formation and development of the later cracking, and affects the concrete's durability.Therefore, many scholars in different countries have begun to research the concrete deeply and widely on the early-age mechanics performance, the liquidation principles and the environment factors. Meanwhile, most of the tests are stressed upon the some certain concrete's special characteristics, and different researchers adopt different test method, and therefore it is hard to compare their research conclusions. And they lack effective test means and system analysis about principles of the early-age plastic shrinkage, so these researches on the concrete's early-age plastic shrinkage and cracking are not done well. There are still not many researches especially aimed on the high durability concrete's, made with the high content mineral admixture, Superplasticizer, expansion agent and hybrid fibers, early-age plastic shrinkage and cracking.In the dissertation, based on the relationship and the formation mechanism of the high performance concrete's plastic shrinkage and cracking, tests of the restricted shrinkage with slab are taken. Superplastcizer admixture, expansion agent and hybrid fibers and the assembly with different proportion of these materials are adopted in this research. The preparation technology of green high durable concrete is optimized according to this research. During the process of this research, fractal estimation is made to the concrete's early-age plastic shrinkage leaks, and also the expansion agent's compensation mechanism, the fiber's restraint mechanism and the integrative polyphyletic restraint mechanism. And conclusions are made in this dissertation:(1)Developed a technology of producing GHDC materials with the small early-age shrinkage. Integrated utilizing the technologies of expansion agent's compensation and fiber's restraint to the cracking is an important technical method to produce low shrink and high anti-crack concrete materials.(2)The affection to the early-age anti-crack performance of the expansion agent to the polypropylene fiber is related to the type of the water-reduction agent. The hybrid affection of the high effective polyocarboxy acid water-reduction agent with the aluminate expansion agent is better than that of the naphthalene water-reduction agent with AEA.(3) Combined AEA and polycarboxylate type superplastieizers is the effective measure to enhance the plastic shrinkage and cracking resistance of GHDC.(4) The length, width and area of single crack coincide with the cracking fractal dimension.The higher the fractal dimension,the longer the crack and the wider the aera.(5) The total area of Cracking coincide with the cracking fractal dimension,and the craking aera is proportional to the fractal dimension. the higher the fractal dimension,the larger the total aera.(6)Through the SEM of GHDC we can find: Combined concrete expansion egent Compensation contraction and polycarboxylate type superplastieizers is the effective measure to enhance the plastic shrinkage and cracking resistance of GHDC. Then it is Greatly increasing the durability of concrete.