Study On The Performance Of C-FRCM Plate As Multifunctional Exempted Formwork

Carbon fiber reinforced cementitious matrix(C-FRCM plate)which is made of carbon fiber reinforced polymer(CFRP)and cement-based cement it ious materials,can not only for structural reinforcement(SS)to effectively improve the work performance of reinforced concrete,but also can be used as an auxiliary anode used for impressed current cathodic protection(ICCP)to prevent the steel fro m corrosion and ensure the dual protection effect of ICCP-SS system.At the same time,it can participate in the bearing of the structure and has the potent ial to be used in building formwork,which is expected to provide the perfoemance of mult i-functional disassembly formwork.Therefore,this paper conducted a series of experimental studies on C-FRCM plate as a mult i-funct ional detachable template.It not only studies the bending performance of C-FRCM plate,but also studied the evo lution of the interface performance between C-FRCM plate and concrete based on the background of the ICCP-SS system.The main research contents are as follows:Through the three-point bending test of C-FRCM plate,the influence of the content of chopped carbon fiber on the mechanical properties of C-FRCM plate was investigated,and the flexural strength and interlaminar shear strength of C-FRCM plate under different cement-based cement it ious materials were obtained.The results show that:(1)CFRP in the middle of the C-FRCM plate enhances the plasticity o f the cement-based cementitious material,and the increase of the silica fume content also makes the ductilit y of the C-FRCM plate slight ly improved;(2)C-FRCM plate has the best bending resistance when the carbon fiber content is1.2%,and the uniformly dispersed chopped carbon fiber has better cross-linking effect;(3)The cement-based cement it ious material blended with chopped carbo n fiber has good structural reinforcement performance,which can satisfy the function of C-FRCM plate as a free template.Through the pull-off test,the interface-adhesive performance between C-FRCM plate and the concret e under the ICCP-SS system was investigated,and the influence of cement-based cement it ious materials,current densities and electric densit ies on the adhesion relationship were obtained.The cathodic protection effect was verified by electrochemical signal analysis and chloride ion titration results,and the SEM and XRD test were carried out to investigate the degradation mechanism of the auxiliary anode.The results show that:(1)During the 356-days ICCP experiment period,the steel bars inside the specimens with the electric densit y of 20mA/m~2,60mA/m~2 and 100mA/m~2 can be well protected.The impressed current will force chloride ions near the cathode to be transferred to the auxiliary anodes,and the cathodic protection effect is well reflected;(2)The interface between C-FRCM plate and concrete has good bonding performance,and the pull-off strength of the specimens meets the requirements of the current international regulations for structural reinforcement;(3)When the current densit y exceeds 0.9×10~6C/m~2,the pull-off strength of specimens without chopped carbon fiber will significantly decrease with the increase of current density due to the deterioration of the auxiliary anode;(4)The main deterioration of the auxiliary anode does not occur in the matrix material but is caused by the destruction of the carbon fibers in the CFRP;(5)The conductivit y of the chopped carbon fiber can reduce the degree of deterioration of CFRP and ensure that the interface pull-off strength is not affected by the current density.Chopped polypropylene fiber can not slow down the deterioration of CFRP,but its reinforcement mechanism can reduce the degree of interface strength affected by the current density.Through the double-shear test,the interfacial adhesion performance between C-FRCM plate and concrete under the ICCP-SS system was further explored.The influence of the cement-based cement it ious materials,current densities and electric densit ies on the interface were also analyzed,and DIC was used to monitor the whole test process.The results show that:(1)Further proved that the steel reindorcement inside the specimen is well protected when the electric density is20mA/m~2,60mA/m~2 and 100mA/m~2;(2)The main failure mode of the test is the destruciton of CFRP interface in C-FRCM plate,which proves that the interface between C-FRCM plate and the concrete have good working performance;(3)When the current density exceeds 0.9×10~6C/m~2,the shear strength of specimens without chopped carbon fiber and with chopped polypropylene decreased rapid ly with the increase of current densit y due to the deterioration of the auxiliary anode;(4)The conductivity o f the chopped carbon fiber can reduce the degre e of deterioration of CFRP and ensure that the interface shear strength is not affected by the electric densit y;(5)DIC can monitor the destruction process of the who le test specimen in real time,and can observe the development of crack more intuitively.