Study On The Mechanism Of Early Cracking For The Big Fluidity Of Concrete Pavement

Refers to large fluidity concrete mixture slump value in more than 160 mm of concrete, it is a new direction for the development of concrete research.As admixture and mineral admixtures in recent years the development of applied research, the fluidity of concrete at home and abroad research has made great progress.Will be big fluidity concrete for road engineering, paving concrete can reduce the labor intensity and workload, save energy, reduce noise and protect the environment, improve the construction progress, increase the uniformity of concrete pavement the plate.But its liquidity also produced some negative effects, such as the early shrinkage cracking phenomenon is more serious, lead to greater fluidity concrete pavement of the actual use fixed number of year can not meet the design life requirements.So the big fluidity of concrete pavement early cracking mechanism is very important.At first, this paper preliminary discusses the big fluidity of concrete pavement cracks causes and control measures, and then through the orthogonal experiment, in a slump, 7 d, 28 d flexural, compressive strength as the evaluation index, mixture ratio design, optimizing large fluidity pavement concrete mixture ratio design parameters, test showed that water consumption is the key factors influencing the big fluidity concrete workability, water/cement ratio is greater fluidity concrete flexural strength of the key factors.According to the mixture ratio of water/cement ratio, sand ratio and dosage of fly ash to the early cracking of concrete factors influencing test, the test data show that with the increase of dosage of fly ash, the big fluidity of cracking unit area total area increased after decreased first, adding a certain amount of fly ash in concrete can effectively reduce the craze, with the increase of sand ratio, large fluidity the early cracking of concrete increases gradually, with the increase of water cement ratio, large flow of the early cracking of concrete has increased dramatically.Then causes the nature of the early cracking of concrete is the concrete internal temperature gradient and moisture gradient, systematically analyzes the changing rule of concrete temperature field and humidity field and temperature stress and shrinkage stress of numerical calculation method.Finally through finite element analysis software MIDAS to big fluidity of concrete pavement slab temperature stress and shrinkage stress of numerical calculation, analysis the influence law of the early cracking of concrete, and the calculation results of temperature stress and shrinkage stress superposition on the fluidity of concrete pavement early cracking of risk judgment.