Study On Stray Current Corrosion Behavior Of Steel In Fiber Reinforced Cement-based Materials Containing Waste Ceramics

Rail transit has been widely used in some large cities with its advantages of fast speed and large passenger capacity to alleviate urban traffic congestion and elevate the travel experience.However,the stray currents generated during the severe of the rail transit system often cause serious stray current corrosion to the steel bars in the surrounding underground components,and it is tough to repair or replace after corrosion damage.Fiber-reinforced cementitious materials can reduce rust expansion and cracking caused by metal components’ corrosion and improve structures’ durability.At the same time,incorporating ceramic waste in fiber-reinforced cementitious materials can reduce their energy consumption,in line with sustainable development strategies.In this thesis,the stray current corrosion behavior of steel bars in cementitious materials reinforced with waste ceramic fibers is studied,and the main work and research results are as follows:(1)Cement-based specimens with different ceramic powder substitution rates(0%,5%,10%,20%,30%)and different polyvinyl alcohol(PVA)fiber volume content(1%,1.3%,1.6%,1.9%,2.2%)were designed,and the ordinary river sand was replaced with ceramic sand.After 180 days’ curing time,the corrosion of specimens at different corrosion durations(0 h,24 h,48 h)was tested.The results show that the anti-stray current corrosion performance of specimens first increases and then decreases with the rise in the replacement rate of ceramic powder.When the replacement rate of ceramic powder was 0% and 5%,the volume content of PVA fiber had little effect on the anti-stray current corrosion performance of the test block.When the replacement rate of ceramic powder is 10%,the anti-stray recent corrosion performance of the test block fluctuates significantly with the increase of PVA fiber volume.When the replacement rate of ceramic powder is 20% and 30%,the anti-stray current corrosion performance of the test block first increases and then decreases with the increase of PVA fiber volume.The internal steel bars of the test block with a replacement rate of 20% ceramic powder and a magnitude of 1.6% PVA fiber had the largest resistance to stray current corrosion.The steel bars inside the test block with a replacement rate of 0% ceramic powder and a volume of 1% PVA fiber had the worst resistance to stray current corrosion.(2)Based on electrochemical impedance spectroscopy and linear polarization method,the Nyquist curve and polarization curve of the test block under different corrosion times were tested,and the charge transfer resistance,self-corrosion potential,polarization resistance,and corrosion current density of the internal steel bar of the test block were obtained by fitting.The results show that with the increase of corrosion time,the diameter of the capacitive arc decreases,and the position of the high and low-frequency intersection points shifts to the left.The charge transfer resistance and polarization resistance decrease,the self-corrosion potential shifts negatively,and the corrosion current density increases.(3)Based on the theory of elasticity and fracture mechanics,the relationship between cement-based materials with different PVA fiber volume content(0%,0.3%,0.6%,0.9%,1.2%,1.5%)and corrosion cracking time was established based on the mathematical model obtained by previous research.The enhancement effect of fiber incorporation was analyzed.The results show that with the increase of PVA fiber volume,the corrosion cracking time of cement-based materials first increases and then decreases.When the volume content of PVA fiber is 1.2%,the crack resistance of cement-based materials is the strongest.Incorporating PVA fiber can significantly prolong the corrosion cracking time of cement-based materials.The cracking time of specimens with PVA fiber volume content of 0.3%,0.6%,0.9%,1.2%,and 1.5% is1.83 times,2.75 times,2.97 times,3.87 times,and 3.54 times that of specimens without fiber,respectively.(4)The specimen with a replacement rate of ceramic powder of 10% was selected to apply a waterproof coating on the surface and compared with the uncoated samples,and the critical role of the coating on stray current corrosion protection was studied.The results show that the waterproof coating can effectively prevent the corrosive medium from entering the inside of the test block and contacting the steel bar,thereby reducing the stray current corrosion influence of the steel bar inside the test block.Before the coating fails,the longer the corrosion time,the more pronounced the layer’s protective effect on the steel bar.