| The acceleration of China’s urbanization process places extremely high demands on urban areas and urban-rural transportation.Rail transit has its own unique advantages in terms of speed and passenger capacity.Subway operation mileage accounts for the vast majority of rail transportation operation mileage.The subway project is closely linked to people’s lives,facilitating the travel of citizens,and strengthening the geographical connection of the entire city.The Metro Engineering Department is in an environment rich in stray currents and groundwater,and it is of engineering significance to study the corrosion of cement-based materials in metro engineering under stray currents.In this paper,the corrosion of cement-based materials under stray current composed of direct current is studied.This paper mainly studies the corrosion of cement-based materials under stray current from the aspects of stray current voltage,different water-binder ratio,different fly ash content and silica fume content.The main contents and conclusions of this article are as follows:1.The presence of stray current accelerates the dissolution of cement-based materials.The existence of stray current makes an electrolysis cell formed between stray current,water and cement-based materials,and an electrolytic reaction occurs.The test piece is placed in the environment of an electrolytic cell formed by stray current,and the movement of ions will be accelerated and directional movement,which will affect the calcium dissolution.After stray current is applied,the solution on the cathode side of the test piece will become turbid with white precipitate.After passing the stray current,compared with the test piece without stray current,there will be white precipitation on the cathode side of the test piece,and the compressive strength of the test piece also drops significantly.At the same time,stray current electrolysis aqueous solution will find bubbles on both sides of the test piece.2.The effect of stray current voltage and cement-based material water-binder ratio on the cement-based material corrosion under stray current.Cathodic dissolution and compressive strength of the test piece were used to measure the change of cement-based material dissolution under different ages of stray current.After passing the stray current,the strength of the specimen showed a downward trend.The magnitude of the stray current voltage can affect the dissolution of calcium ions,which in turn affects the compressive strength of the test piece.It also reflects from the concentration of Ca2+ in the cathode side of the test piece and the quality of the exudate on the cathode side of the test piece.After passing the stray current for 120d,the compressive strength of the specimen with a stray current voltage of 60 V decreased the most,which was 13.7%lower than that of the specimen in hydrostatic corrosion;by limiting the magnitude of the stray current,the stray current to the cement can be fundamentally reduced.Corrosion damage of the base material.After 120 days of stray current,the compressive strength of water-cement ratio 0.50 specimens only decreased by 3.7%,and the compressive strength of water-cement ratio(0.60)decreased more.3.Effect of different fly ash content and silica fume content on the cement-based material corrosion under stray current.From the perspective of the Ca2+ concentration on the cathode side of the test piece and the quality of the exudate on the cathode side of the test piece,the presence of stray current will accelerate the calcium in the test piece.The performance is not the same.After passing stray current for 120d,the compressive strength of the test piece with 10%silica fume is 1.6%higher than that without the silica fume.The samples without silica fume decreased by 7.0%and 5.1%respectively.After passing stray current for 120 days,the compressive strength of the specimens with 5%,10%,and 15%decreased by 30.0%,24.7%,and 26.7%,respectively,compared with the specimen without fly ash. |
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