Crack Control And Crack Prevention Of Mass Concrete Structure

A big technical problem for mass concrete structures during pouring is how to control crack expansion . Releasing steam heat from the mass concrete structures while solidifying leads to produce the temperature change and contraction. They cause the corresponding stresses which are the main factors to from crack in the mass concrete structures. It is obvious for crack to destroy the completeness , anti-water and water-tolerant behavior of the structures and to become a hidden peril of the structures. Thus, crack control must be considered while a mass concrete structure is in construction.The paper presents a solution method for the transient temperature field, in which the finite element method or the finite difference method is used to get discrete structure , and the finite difference method is used to get discrete time in order to simplify the transient thermal conductive equations as a set of linear equations as a set of linear equations at different moment. Separating the whole process of reduction in temperature into several time sections in which change in temperature is to be assumed as linear the total disparity in temperature including the disparity due to equivalent contraction can be obtained. Considering creep influence can also be derived. If their summation is over the tensile strength of the concrete, the crack would exist in the structures.As practical engineering examples the paper has shown the analyses on crack control in two mass concrete structures by use of the procedure mentioned above, in which the transient temperature fields were obtained from the results by the finite difference method or the temperature curves measured in construction. The results are the same as happened in engineering . No crack happened in practice and in calculation. The involving date calculated could be used by the designers and technicians. The paper also mentioned some measures on crack prevention.