Analysis And Prevention On Non-loaded Crack Of Early Concrete

Concrete is one kind of non-isotropic composition material, and its physical mechanics performance is related to the composition material's respective performance. The formation of the non-loaded crack at early time also have close relationship with the physical mechanics performance of concrete at the same time. Related performance parameter,such as shrinkage,contraction equivalent temperature difference,elasticity coefficient,limit stretch value,relaxation coefficient and so on,are frequently involved in computation of stress.Stress of non-loaded crack involves temperature stress,contraction stress and self-constraint,about which the study is concentrating to the solution of temperature field and stress on theory,and how to select material reasonably, control and monitor efficiently on practice. These are problems refer to many aspects factors,such as structural design,construction environment and so on.Structural simulation analysis is to simulate the structure condition of concrete at construction time and lifetime by unify the geometry shape and structure condition of the structure,with the result the construction plan can be defined,and the formation of crack can be analysed, such as the reinforcement measure. Finite element analysis of temperature field and stress sield at the early time of massive concrete is done in this paper. Influencing rule of environment temperature and placing temperature on stress,and the best interval time of placement in layers are also discussed.The universal existence of early crack will bring mach adverse effect to regular service,but crack is inherent quality,so the controlling measures usually said is refer to macroscopic crack's control,which is the prevention and processing of crack,and reduce crack width to harmless scope for reliability,applicability and durability. Generally speaking,crack comes from the overtake of tensile stress or shrinkage strain,so the efficient measures to controll early cracks are unite the structure design and construction organically,and make the increment rate of the early unti-tensile stress and limit extend value grow more quickly than the tensile strength and elasticity modulus.