Compressive Constitutive Relationships Of Coral Aggregate Concrete And Bond Behavior With FRP Bars

Coral aggregate concrete is a typical marine aggregate concrete utilizing the local coral rock instead of traditional aggregates.Using local coral rock aggregates in marine construction can substantially reduce the costs and shorten the construction period.To have a better understanding of the mechanical properties of coral aggregate concrete and promote its application in practical engineering,constitutive models of coral aggregate concrete under different loading conditions were developed,including uniaxial compression and triaxial loading.Moreover,the bond-slip behavior between fiber-reinforced polymer bars and coral aggregate concrete were also experimentally studied.First,the properties of coral aggregates and coral aggregate concrete were briefly introduced based on literature review and experimental data,including the properties of coral debris as aggregates,the microstructure of coral aggregates,the mechanical properties and durability of coral aggregate concrete,and the microstructure of interface transition zone.Then the compression behaviors of coral aggregate concrete under uniaxial loading were investigated comparing with lightweight aggregate concrete and ordinary aggregate concrete.The results indicated that the uniaxial compression behaviors of coral aggregate concrete show great brittleness and were different from those of ordinary aggregate concrete but similar to those of lightweight aggregate concrete,for coral rock aggregates are porous and have lower strength than ordinary aggregates.Based on the test data obtained from this research as well as collected from literatures,a stress-strain model was proposed for coral aggregate concrete under uniaxial compression.Subsequently,triaxial tests were performed to 19 coral aggregate concrete specimens to study its mechanical behaviors under triaxial compression.The investigated variables include concrete type,concrete strength,lateral pressure and principal stress ratios.Under triaxial compression,the internal damage of the concrete is the crushing of aggregates instead of damage at the cement-aggregate interface.The crushing of aggregates results in macroscopic defects inside the concrete,which further leads to the premature destruction of cement stones.The test results agree with a failure criterion proposed for lightweight aggregate concrete well.To understand the interaction between fiber-reinforced polymer bars and coral aggregate concrete,27 pull-out tests were conducted to investigate the bond-slip behavior.Three typical failure modes of specimens were presented: concrete cover splitting,pull-out with damage in concrete,layer of rebar peeling off.Various failures can be attributed to different concrete strength,cover thickness,rebar geometry and surface treatment.A two-branch model is developed to describe the bond stress-slip curves.Moreover,interface mechanics analysises are conducted.Combined with the multiaxial failure criterion of CAC,the analysis approach can be used to determine the characteristic bond strengthes of CAC-FRP bars,...