The Influence Study Of Four Series,Different Types Of Water-reducing Agent On The Shrinkage Deformation Of Concrete

The generation of early cracks in concrete not only reduces the bearing capacity of the structure,but also greatly deteriorates the durability of the concrete and shortens the service life of the building.Chemical admixtures have become an indispensable"fifth component" of concrete,with superplasticizers being the most widely used.At present,the research on the effect of water-reducing agent on the performance of concrete is focused on workability,mechanical properties,durability and so on.There are few studies on the effect of water-reducing agent on shrinkage deformation of concrete,and there is no conclusion.This study selected four series(polycarboxylate,naphthalene,aliphatic,and sulfamate)and different types(standard,retarder,and early strength)of water reducers.The following research work was carried out:(1)Using the same workability and testing strength requirements,keeping the water-binder ratio and sand rate unchanged,designing a new idea of concrete mix ratio with "reducing agent type + dosage" as the test variable;meeting the design goal through trial matching The optimal dosage of each water-reducing agent is to determine the test mix ratio of the ten groups of concrete,and to draw the evaluation map of the effect of different types of water-reducing agent on the workability and mechanical properties of the concrete.(2)The non-contact displacement method was adopted to track and measure the shrinkage deformation rate of the ten groups of concrete specimens at the 7-day age,and the shrinkage deformation rules of the concrete with four series and different types of water-reducing agent were obtained;combined with the results of microscopic test analysis,the The Mechanism of Different Types of Water Reducing Agents on Shrinkage Deformation of Concrete in Early Age.(3)Based on the test results of early age concrete shrinkage,six kinds of numerical methods were used to carry out regression analysis of the test results.By comparing the residual square of the model and the residual square after adjusting the degree of freedom,the shrinkage of the concrete was determined.Based on the prediction model,the shrinkage deformation rate of concrete with different types of water-reducer concrete at the age of 28 days was deduced,and the importance of concrete shrinkage and crack prevention at early age was verified.And the necessity of considering the non-load deformation in the concrete structure design specification is discussed.Through the above studies,it has been found that polycarboxylate-based superplasticizers can play an active role in improving the workability,mechanical properties,and volume stability of concrete,and are the most used superplasticizers;sulfamate salts The effect of high-range water-reducing agent on the performance of concrete in all aspects also has a positive effect,but the effect is inferior to polycarboxylic acid-based high performance water-reducing agent;naphthalene-based and aliphatic-based superplasticizer has no significant effect on the workability and mechanical properties of concrete.However,it obviously increases the shrinkage of the concrete and is not recommended for use in concrete production.The results of this study provided a reference for the rational selection of water reducer for concrete design and effective prevention and control of cracking of concrete.