Study On Corrosion Behavior Of Reinforcing Steel In SHCC Materials With Multiple Cracks

In today's society,concrete has been widely used in various types of construction,durability has become the focus of C ivil Engineering as an important performance of concrete.Strain Hardening Cement—based Composite?SHCC?is featured with its strain-hardening and multi-crack characteristic under the action of load.Therefore,SHCC has a broad application prospect in the control of structure cracks and improve the durability and so on.This paper makes a systematic study on the durability of SHCC in many ways.The main research contents and results as follows:?1?Through three point bending test to study the crack characteristics of ordinary reinforced-mortar and reinforced –SHCC.The results are as follow: ordinary reinforced mortar specimens only have 1² cracks,the width between 0.05mm⁰.12 mm,but each reinforced-SHCC specimens has 12 cracks in average and the width between 0.01mm⁰.04 mm.Reinforced-SHCC showed good multiple crack characteristics.?2?The corrosion state of steel bars in different chloride corrosion cycles was studied by means of half cell potential method and electrochemical impedance spectroscopy method.The results are as follow: Compared with ordinary reinforced mortar specimens,reinforced-SHCC with multiple fine cracks can significantly reduce the erosion rate of chloride ion and slow down the corrosion process of steel bar.The EIS result show that the radius of curvature of the Nyquist curve and the polarization resistance of reinforced bar obtained by fitting the curve will become smaller with the increase of corrosion.The unidirectional penetration of chloride ions leads to more serious corrosion in the lower surface of the steel bar than on the surface.?3?Effect of silane coating on concrete waterproof was studied by chloride corrosion experimentcarried out on reinforced-SHCC specimens with different silane coating amount.The results are as follow:the steel bar in the specimen without waterproof treatment is soon to be corroded.The potential mutation period of specimen with waterproof is prolonged obvious ly and the waterproof effect is positively correlated with silane coating amount.?4?The influences of different factors on crack healing were studied through the measurement of crack width and water absorption in ordinary reinforced-mortar and reinforced –SHCC,analysis of components of self healing products by electron microscope scanning technique.The experiment results are as follow:effects of different influencing factors on the degree of crack self healing:?1?water cement ratio:0.6>0.4;?2?curing time:7days>28days>60days>90days;?3?curing system:saturated calcium hydroxide solution>maintained in fresh water>standard curing;?4?crack width:0⁴0 um>above 40 um.The self healing products are mainly composed of hydrated calcium silicate ?Ca?OH?2 and the 2 generatio n and air CO₂ reaction CaCO₃.