Influence And Mechanism Of SAP On The Properties Of Cement Concrete

The cracking problem of bridge concrete construction is widespread,and with the wide application of high-strength concrete,the cracking problem is intensified,resulting in the inherent shortage of bridge quality,which seriously affects the safety,applicability and durability of the bridge during service.How to improve the prevention technology of bridge concrete construction cracks and ensure the quality of concrete bridge construction has become a technical problem to be solved urgently.Based on the prevention and treatment of shrinkage cracks in bridge concrete,this paper focuses on the characteristics of water absorption and release of superabsorbent resin,studyingits influence on concrete performance and mechanism.At the same time,research on preparation and application technology of high performance concrete based on SAP internal curing is carried out.The research contents and conclusions are as follows:(1)The water absorption ratio of different fineness and different types of super absorbent resin was measured by tea bag method,and the main factors affecting the water absorption of superabsorbent resin were studied.Studies have shown that the main factors affecting the water absorption of superabsorbent resin(SAP)are A(acrylic acid to acrylic acid ratio),F(SAP particle size)and B(acrylic acid neutralization degree);SAP particle size reduction is beneficial to SAP water absorption.The improvement of the magnification;using the saturated calcium hydroxide solution and the cement hydration solution as the test medium,the ratio of acrylamide to acrylic acid is increased to facilitate the absorption of the saturated calcium hydroxide solution and the cement hydration solution.(2)The effects of SAP particle size and dosage on the workability,mechanical properties,volume stability and durability of concrete were studied by experiments.Studies have shown that under the same water consumption conditions(without additional water diversion)the slump of concrete is basically the same by the amount of admixture,and the slump of concrete increases with the increase of SAP content(equivalent SAP particle size).When it is increased,the slump loss is reduced,the gas content is increased,the pressure bleeding is increased,the setting time is prolonged,and the compressive strength,flexural strength and elastic modulus of concrete are reduced.The self-shrinkage,dry shrinkage and plastic cracking performance ofconcrete show a decreasing trend,and the anti-freezing performance and resistance to chloride ion penetration of concrete are significantly improved.Based on the concrete mix ratio of C40 pier,the optimal SAP particle size is 0.4mm,and the optimum SAP content is 0.4% of the cement material quality.(3)The high-performance mechanism of SAP concrete was investigated by SEM,MIP,NMR and integrated thermal methods.Research shows that when SAP is added to concrete,the pores of the gel and small pores increase,the size of large pores and pores decreases,and the pore structure of the concrete is refined.At the same time,the release of water in the later stage of SAP promotes the Secondary hydration of cement and fly ash.When enter the structure of C-S-H increase in the number of Al[4]increases,thereby increasing the Al[4]/Si of the C-S-H gel,increasing the compactness of the slurry,thereby improving the durability of the concrete(4)The application technology of SAP in concrete was studied,and SAP concrete preparation,concrete construction technology and concrete quality inspection technology were formed.This paper based on the external health method to solve the technical problems of shrinkage cracks in bridge concrete,and this paper proposes the control method of the performance of the super-absorbent resin type inner health material and the application method of the internal health technology,and strives to break through the defects of the single external health technology of bridge concrete and promote the new bridge of internal and external health care.The development of concrete health technology and the improvement of concrete bridge construction crack prevention technology have important theoretical and practical significance.