Experimental Research On Cracking And Bond Properties Of Concrete

In this paper, the cracking and bond properties of concrete had been researched. Theresearch of concrete cracking is concentrate mainly on cracking test method; theresearch of bond properties of concrete includes two parts: the bond propertiesbetween fiber concrete and bar, the bond properties between fiber concrete and oldconcrete.1) To solve the problems that cracking location of traditional ring test is random andcracking sensitivity of the test is bad, outside-square inside-circle eccentric constraintmethod is proposed. First, outside-square inside-circle specimens are analyzed byANSYS finite element analysis software. Result shows that the eccentricity ofinside-circle leads to the only section of maximum stress, and the greater theeccentricity, the bigger the section stress; while the eccentricity reaches a certainvalue, the maximum stress appears in the outer edge of the specimen. Second, themethod is proved by cement paste and mortar experiments, experimental results are inaccordance with theoretical analysis. So this method can predict the cracking location,and accelerate the cracking of specimen.2) The bond properties between basalt fiber concrete and deformed bar had beenresearched by comparative analysis. There were two kinds of fiber length, and fourkinds of volume fraction. The plain concrete without basalt fiber was designed forcomparison. The bond stress vs. slip curves were obtained by center pull-out test, andthe test results indicate that when basalt fiber is added to concrete, the bond strengthbetween basalt fiber concrete and deformed bar has the tendency of reduction, thecorresponding slip of ultimate bond strength increases. Under the same volumefraction, the ultimate bond strength corresponding to18mm fiber is greater than thecorresponding value of6mm fiber. While volume fraction of basalt fiber is controlledreasonably, the decline of bond strength can be improved. In addition, the formula ofultimate bond strength is obtained by analyzing the data.3) The bond properties between basalt fiber concrete and old concrete had beenresearched by comparative analysis too. There were two kinds of fiber length, and twokinds of volume fraction. The plain concrete without basalt fiber and whole specimenwere designed for comparison. Adhesive bending strength was obtained by bending test, and the test results indicate that the adhesive bending strength (1d) ofrapid hardening cement concrete adhesive specimen is already high, when basalt fiberis added to concrete, the strength increases further. Adding basalt fiber into concretecan increase the bending strength of adhesive specimen and whole specimenobservably, and the strength increased with increasing content of basalt fibers. Underthe same volume fraction, adhesive bending strength corresponding to18mm fiber isgreater than the corresponding value of6mm fiber. In addition, bending test andsimple analysis was also done for adhesive specimens whose adhesive section isunder bending moment and shear force.