Study On Preparation And Properties Of New Compensating Shrinkage Concrete

In recent decades,due to the rapid development of market economy,urban road construction has been speeding up,and the amount of concrete has changed rapidly.However,after mixing the concrete,the heat produced in the hydration process of the cementitious material makes the temperature of the system 20-30 degrees higher than the surrounding environment.When the heat of the hydration is not released in time,the concrete will produce temperature difference,drying shrinkage and chemical shrinkage.Tensile stress makes concrete easy to produce shrinkage and crack.Therefore,it is of great practical value to prepare a concrete which can reduce shrinkage.In this paper,a new type of compensating shrinkage concrete was tested.First,the liquid expansive agent in the market was introduced,and the effect of the dosage of liquid expansive agent on the expansion rate and strength of the mortar was studied.It was found that the the liquid expansive agent could increase the expansion rate of the mortar at various ages.With the increase of dosage,the expansion rate increases,and the expansion rate is not obvious when it is beyond a certain range.The liquid expansive agent reduces the strength of the mortar,When the dosage is 0.6%,the decrease of strength is the smallest.At the same time,the effect of cementitious material on the performance of concrete was studied.The effect of cement-reducing rate on the performance,mechanical properties and shrinkage of concrete with different strength grades was studied by adding cement-reducing admixture to concrete.The test results showed that after the addition of the cement-reducing admixture,it can still improve the performance of concrete,increase the workability of concrete,reduce the time loss of slump and extensibility,and reduce the shrinkage of concrete in a certain range.The higher the grade,the more obvious the decrease of the shrinkage rate;in the mechanical properties,the mechanical properties of the concrete are all improved when the cementreducing rate is below 12%,and the suitable range of the cement-reducing rate is 10-12%a new type of compensating shrinkage concrete is prepared by adding liquid expansive agent and cement-reducing agent to increase the initial expansion of concrete by liquid expander and reduce the temperature difference caused by reducing the hydration heat.The working performance,mechanical properties and expansibility of the new type of compensation shrinkage concrete were tested.The results showed that the working performance,the limit expansion rate and the free expansion rate of the concrete were greatly improved when the a cement-reducing agent was mixed with the l liquid expansive agent,and it could make up the expansion of the later contraction.In the mechanical properties,the new type of shrinkage compensating concrete performs best when the glue reduction rate is 10%.At the end of this paper,the durability and Micromorphology of the new compensated shrinkage concrete and ordinary concrete are analyzed.The results show that the new compensation shrinkage concrete is superior to the ordinary concrete in water permeability and frost resistance,and it has obvious improvement on the surface of the micro surface.The experiment determined the preparation method of the best new type of compensating shrinkage concrete: reducing 10% the cement(10% cementreducing rate)of the total cementitious material of concrete,the dosage of cementreducing admixture and liquid expansive agent is 0.6% of the total amount of residual cementitious material of concrete,and adding the reduced cement quality to the sand and stone that the sand rate is constant.In this paper,the cost analysis of a new type of compensated shrinkage concrete is carried out,It has good economic practicality.