Effect Of Super Absorbent Polymer On Mechanical Properties Of Machine-made Sand Concrete And Research On The Effect Of Frost Resistance

With the increasing depletion of river sand resources in my country,machine-made sand has gradually been promoted in engineering.Compared with river sand,excessive stone powder will be produced in the production process of machine-made sand.Studies have shown that too much stone powder will increase the shrinkage and cracking of con-crete,resulting in a series of problems such as the decline of concrete mechanical proper-ties and durability.Therefore,reasonable control of stone powder content is of great sig-nificance.With the development of high-performance curing technology in the 21st century,super absorbent resin(SAP)provides a new idea for solving problems such as concrete cracking and durability.Therefore,At the National Natural Science Foundation of China"Research on the durability improvement technology and design theory of marine pre-stressed concrete structures(51778272)"is found,this paper studied the effects of SAP and stone powder on the strength and Freeze-thaw of artificial sand.The strength prediction model and freeze-thaw damage model of machine-made sand concrete are established re-spectively.The main work is as follows:1.Study on the mechanical properties of SAP internal curing mechanism sand con-crete.The effects of SAP and stone powder on the compressive strength,flexural strength,axial compressive strength and splitting tensile strength of machine-made sand concrete were studied from the two levels of single admixture and compound admixture.The study found that SAP and stone powder improved the compressive strength and splitting tensile strength of manufactured sand concrete at all ages,and the effect was the best when 0.08%SAP and 9%stone powder were mixed together,compared with the reference group,the intensity at 3d,7d and 28d was increased by 29.44%,11.59%and 14.43%;the splitting tensile strength at 3d age would be reduced by adding SAP and stone powder,the splitting tensile strength at 7d and 28d age is obviously improved,and the the optimal mixture of0.16%and 3%stone powder is 15.88%and 22.35%higher than that of the reference group;The influence of flexural strength and axial compressive strength is similar to that of split-ting tensile strength.When 0.16%SAP and 6%stone powder are mixed together,the im-provement effect is the best,and its 28d age strength is increased by 34.55%and 11.76%compared with the benchmark group.2.Research on the strength prediction model of SAP internal curing mechanism sand concrete.Combined with the test data of compressive strength,Matlab software was used to establish the strength prediction model of SAP internal curing manufactured sand con-crete based on BP neural network is established,and the defects of the BP network model are optimized by genetic algorithm(GA).The results show that:1)The BP network model has high fitting accuracy,its R~2 reaches 0.95622,and the maximum error is within 4MPa,which can better reflect the SAP internal curing mechanism sand concrete compression resistance;2)GA effectively optimizes the defects of the BP neural network model,and the accuracy of the model is greatly improved,and its average error is only 40%of the BP neural network model.3.Study on the frost resistance of SAP internal curing mechanism sand concrete.The effects of SAP and stone powder on the appearance,mass loss rate,relative dynamic elastic modulus,compressive strength loss rate and flexural strength loss rate of machine-made sand concrete were studied using the same dosage and method as the mechanical properties test.The study found that SAP and stone powder can significantly improve the frost re-sistance of manufactured sand concrete.When 0.16%SAP is mixed with 6%stone powder,the concrete has the best frost resistance effect.After 200 times of freezing and thawing,the quality lost only 0.5%,the relative dynamic elastic modulus reaches 96.2%,and the loss rate of compressive and flexural strength is 7.3%and 12.16%.4.Combined with the data of relative dynamic elastic modulus,a freeze-thaw damage model based on Weibull distribution function was established.It is found by fitting that:There is a high fitting accuracy between the fitted curve and the actual value,and the cor-relation coefficient R~2 is above 0.94.