Study On SO₄^2- Transport-corrosion Law In Concrete Under High Water Pressure

The water pressure of corrosion solution on the outer side of the structure will increase gradually in the concrete building with the increasing of the underground depth.Therefore,the concrete structure must face the high water pressure and corrosion solution,two kinds of coexisting concrete are liable to produce damage under unavoidable external conditions.In this paper,short-term transmission test and long-term overall corrosion test are carried out for underground concrete structure considering the water head pressure and the concentration of corrosion solution.The main factors considered in the test include: the water-cement ratio(0.4,0.5,0.6)of concrete;the high water pressure(1.2 MPA,2.4 MPA,3.6 MPA)in the presence of corrosive solution;the different transfer time caused by the different water-cement ratio and water pressure;Continuous high water pressure(10d,20 d,30d and 40d).The sulfate ion content at different heights of concrete is analyzed,and the mathematical models of ion content and time,water cement ratio,water pressure at different depths are established.In order to be able to test the working condition of high water pressure,the standard impermeable instrument was used in this test,and the standard impermeable test block was poured.The transmission time of concrete with different water-cement ratio is different under different water pressure by using standard impermeable apparatus.Firstly,based on the time of complete penetration under the same working condition,it is divided into four time periods to study the depth of penetration and the concentration of sulfate ion in each time period,the experimental results show that water pressure plays a leading role in the three factors of water cement ratio,water pressure and seepage time.The greater the water pressure is,the shorter the time of complete penetration into concrete is,the higher the sulfate content entering the concrete in a certain time,the higher the sulfate ion content at different depths,and the higher the water cement ratio,the shorter the time of fully penetrating the concrete under the same water pressure,the higher the content of sulfate ion at different depth.Finally,the transport rate model of high water pressure and water cement ratio is established based on the sulfate ion content at different depths.The corrosion test under high water pressure is the main method,and the minimum time is 10 days under high water pressure.On this basis,the sulfate solution will permeate through the concrete completely.Combined with ultrasonic velocity and sulfate ion content,this paper studies the Change Law under various working conditions with different durative permeation time,water pressure and water cement ratio.The results show that under high water pressure,the corrosion degree of sulfate to concrete is much higher than that under soaking and so on.High water pressure is still the dominant factor,followed by continuous penetration time and water-cement ratio.The change rule of sulfate ion content was proved by XRF and energy spectrum analysis.Under other conditions,the higher the water pressure,the higher the ion content at the same place,and the longer the duration,the higher the ion content at the same place.The paper has 56 graphs,24 tables,80 references.