| Lightweight aggregate concrete has the advantages of light weight,high strength,good fire resistance and good seismic performance.Compared with the traditional concrete,it has obvious advantages.Because the reinforced concrete members in the north area are often destroyed by freezing and thawing.Therefore,it is of great engineering value to study the change law of the bond behavior between steel bar and ceramsite concrete after freeze-thaw cycles.The purpose of this research is to determine the change of bond properties between steel bar and ceramsite concrete after freezing and thawing,and to obtain the law of the change of bond performance following freeze-thaw cycles.It provides a theoretical basis for durability design of external wall panels,beams or plates of fabricated buildings.The main contents of the study include:(1)Experiments were carried out to analyze the influence of steel bar material(BFRP bars are basalt fiber composite bars,reinforced bar,epoxy coated steel bar),concrete strength(LC25,LC30,LC35),freeze-thaw cycles(0 times,15 times,30 times,50 times)on the bond performance between steel bar and ceramsite concrete core pulling specimens.108 specimens were designed and manufactured through center pull test.The bond slip curves were obtained.The test results were collated,and the influence rules of various factors on the bond and anchorage properties of the drawing specimens were analyzed.(2)The BFRP bar ceramsite concrete specimens are mainly pull-out failure and splitting failure in the freeze-thaw environment.The specimens of the reinforced bar and the epoxy coated steel bar show splitting failure after freeze-thaw cycles.The ultimate bond strength of the reinforced bar specimens is the largest,that of the epoxy coated steel bar is the second,and the BFRP bar specimen is the smallest.The ultimate bond strength of the BFRP bar specimen is 8.95MPa when it is not freeze-thaw.The ultimate bond strength of the specimen is 14.52MPa,and the ultimate bond strength of the epoxy coated steel bar is 12.85MPa..With the increase of freeze-thaw cycles,the bond strength of the center drawn specimens decreases gradually,among which the BFRP bar specimens are the largest,the epoxy coated steel bars are the second,and the reinforced bar specimens are the least.After 50 times of freeze-thaw cycles,the BFRP bar specimens are reduced by 42.57%.The specimen of the reinforced bar is reduced by 38.22%,and the epoxy coated steel bar is reduced by 39.77%.Therefore,the higher strength of the ceramsite concrete specimen is lower than that of the freeze-thaw cycle.(3)The expression of bond strength of three kinds of steel bars under material condition is summarized and verified,which can provide reference for theoretical analysis and subsequent research of bond performance test. |
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