The Study On The Developing Law Of Crack In Polymer Modified Cement Concrete Composite Beam

Based on the characteristics of polymer modified cement concrete such as deformation capacity, high tensile strength and good bonding properties with reinforcement, etc, the plain concrete within a restricted range of at the bottom of the ordinary reinforced concrete is replaced with polymer modified cement concrete to form a new type of polymer modified cement concrete composite beam in this paper.A combining method of the theoretical, experimental analysis and finite element analysis were adopted in the work to conduct an exploratory and path-breaking research on the crack load, crack distribution and law of development of these new type of composite beams in order to set a good theoretical and experimental basis for engineering application.The mechanical properties of polymer modified cement concrete are studied in the paper. The result shows that polymer modified cement concrete is with strong deformation capacity, high tensile strength and good bonding properties with steels and concrete.A multi-angle analysis of the law of development of cracks of polymer modified cement concrete is carried out in these papers. From the angle of mechanics of the reinforced concrete structure, the strong deformation capability and high tensile strength of the polymer modified cement concrete can effectively improve the cracking load of reinforced concrete beams and delay the emergence of cracks. From the angle of fracture mechanics and deformation compatibility, the strong deformation capacity of polymer modified cement concrete can slow down the development of cracks after cracking of the composite beams. From the angle of adhesion and co-working of concrete with reinforced, the good bonding properties of polymer modified cement concrete with reinforced ensures better deformation compatibility which can effectively reduce the crack spacing and crack width.The paper focuses on the law of development of cracks in polymer modified cement concrete composite beam. Some important conclusions can be drawn as follows:①Failure characteristics of polymer modified cement concrete composite beams is similar to that of ordinary reinforced concrete beam which is in line with the typical reinforced beam failure characteristics;②Compared with ordinary reinforced concrete beams, the crack distribution of polymer modified cement concrete composite beam is more uniform. The number of crack increases and the crack width and crack spacing decrease. The growth of crack slows down. The distribution of crack is "dense and narrow";③ompared with ordinary concrete beams, the cracking load of polymer modified cement concrete composite beams increase by about30%;④With the same load level, the maximum crack width and average crack width aggregate of modified cement concrete composite beam are significantly smaller than those of ordinary reinforced concrete beams;⑤ith the maximum allowable crack width of0.15mm, the bearing capacity of composite beams increased by up to27%, with the maximum allowable crack width of0.15mm, the bearing capacity of composite beams increased by up to24%.In the paper a finite element study of the law of development of cracks in polymer modified cement concrete composite beam is carried out. The analysis is consistent with the experimental research. The calculations show that the special bonding properties of polymer modified cement concrete and reinforcement help the polymer modified cement concrete around reinforcement in participation of loading. The crack resistance of reinforcement becomes stronger which the effective reduces the reinforcement stress, crack width and stress intensity factor at the crack tip.Through the research of the law of development of cracks in new type of composite beam, a new method for crack control in reinforced concrete structures and also a new direction for the application of polymer modified cement concrete are provided.