Self-healing Behavior Of Cementitious Composites And Mechanical Property Of Cementitious Materials-BFRP Bar Composited Structure

The cracking of concrete may cause a series of durability problems.However,the conventional repair methods are time-consuming and laborious;also do not have a good effect.Fiber reinforced cementitious composites(ECC),as a kind of strain-hardening,crack-controlling and self-healing material,together with FRP bars,that is known for its high tensile strength and stainless propertity,are becoming excellent substitute materials for traditional reinforced concrete structures.To study the tensile and self-healing properties of ECC,as well as the mechanical behavior of ECC-BFRP bar beam,relevant experimental studies were carried out.Tensile tests were carried out to determine the tensile properties of ECC materials,and then the self-healing behaviors of ECCs were evaluated on the basis of strength recovery,anti-permeability recovery and crack width reduction.Finally,mechanical and self-healing behavior of ECC-BFRP bar composited beams was tested.The results show that the slag can improve the material's compactness,which correspondingly decreases its permeability.A material with fly ash,silica fume,slag,metakaolin,and PVA-fiber of 2%volume presents the greatest tensile property with an ultimate strain of 2.2%and ultimate tensile strength of 3.86 MPa.In addition,it also shows the best self-healing behavior.The tensile strength of this self-healed material can reach 117%of its initial pre-loading tensile strength after a wet-dry cycle curing for 28 days.In consider of the self-healing performance and the practical operability,wet-dry cycle is considered as a best curing condition for ECC materials.Besides,the initial crack width has a dominant influence on the self-healing ratio.Cracks with a-width less than 50 ?m can be healed significantly,while those over 150 ?m are not healed obviously.The self-healing effect decreases with the increase of crack width,when it is between 50 ?m and 150?m.The flexural capacity of the reinforced concrete beam is increased by 10%,when using ECC to replace 70mm of the tension zone at the bottom and replacing common carbon steel with BFRP bars with a same section area,comparing to that of BFRP bars concrete beam.In addition,the stiffness of the beam is increased obviously.The deflection of the beam decreases by about 20%.The stiffness of the beam recoveries obviously,when the beam is preloaded to 50kN and then cured in wet-dry cycle environment for 28 days.The self-healing of micro-cracks is also observed.