Study On Frost Resistance Of SFRC With Steel Fiber Length-Diameter Ratio

In the severe cold area,the hydraulic structures such as bridges have been in the water-melting and freezing conditions for a long time,which makes the freeze-thaw damage become the main failure mode of the concrete structure,which seriously affects the safety and durability of the structural buildings.Based on the research on the anti-freeze performance of steel fiber aspect ratio to SFRC in the Datu River Bridge of Yakang Expressway,the paper studies the effect of steel fiber aspect ratio on the frost resistance of C40 concrete and the mechanical properties after freezing and thawing.The numerical simulation was carried out using ANSYS to investigate the critical aspect ratio.According to the experimental research and simulation analysis,the main work of the thesis is as follows:(1)Based on the engineering mix ratio of steel fiber content of 0.75%,the SFRC with fiber length to diameter ratio of 0,30,40,50,60 was tested for freeze-thaw cycle.The mass loss and dynamic elastic modulus of the concrete were measured every 25 times for the number of freeze-thaw cycles,and the freeze-thaw damage variables were fitted according to the test data.The results show that as the aspect ratio of fiber increases,the antifreeze performance of concrete increases.Before the number of cycles of 100 freeze-thaw cycles,no significant freeze-thaw damage occurred in each group of concrete,and the loss of mass loss and relative dynamic elastic modulus was small.As the number of freeze-thaw cycles increased,the phenomenon of concrete spalling became more obvious.Loss and relative dynamic modulus loss are also gradually increasing.The concrete loss of the A-0 group with the long diameter ratio of 0 is the largest,and the loss of the concrete of the A-4 group with the length to diameter ratio of 60 is the smallest and the loss rate of the A-3 group with the aspect ratio of 50 is similar.(2)The mechanical properties of SFRC with length-to-diameter ratios of 0,30,40,50,60 were tested.The compressive strength and flexural strength after 50,100,150,200,and300 freeze-thaw cycles were studied and the SFRC resistances of different fiber aspect ratios were drawn.The relationship between compressive strength,flexural strength and number of freeze-thaw cycles.The results show that the mechanical properties of SFRC decrease with the increase of the number of freeze-thaw cycles.Before the number of cycles of 100freeze-thaw cycles,the compressive strength and flexural strength of each group of concrete did not change much.As the number of freeze-thaw cycles increased,the compressivestrength and flexural strength began to decrease significantly.The A-0 group with the aspect ratio of 0 has the largest strength loss,and the A-3 group with the aspect ratio of 50 has the smallest loss and is similar to the loss of the A-4 group with the aspect ratio of 60.(3)Using the ANSYS finite element model,the effects of the aspect ratio 50,55,60,65,70,75 on SFRC are further explored on the basis of experiments.The results show that the aspect ratio is best at 60.