Corrosion Resistance Properties Of Non-dispersible Underwater Concrete In Saline Soil Environment

In saline soil environment,the use of cast-in-place concrete piles in transmission line projects is facing not only the loss of cement slurry when concrete is poured underwater,but also the erosion of corrosive ions such as Cl^-,SO₄^2-.In order to solve this problem,a series of studies have been carried out based on the State Grid Corporation’s scientific and technological project"Key Technologies for Anti-Corrosion of Cast-in-place Pile Foundation of Transmission Line Engineering in Strong Corrosion Environment"（GCB51201603093）.This paper mainly studied the influence of ground granulated blast furnace slag（GGBS）on the fluidity and anti-dispersion performance of non-dispersible underwater concrete and the influence of ground granulated blast furnace slag and water-binder ratio on non-dispersible underwater concrete compressive strength and anti-corrosion coefficient in the environment of sulfate(SO₄^2-,20000mg/L),chloride（Cl^-,50000mg/L）and compound salt(SO₄^2-,20000mg/L+Cl^-,50000mg/L).By means of SEM test,XRD test,TG-DTG test and FT-IR test,corrosion mechanism of non-dispersible underwater concrete in saline soil environment was studied.The main results are as follows:（1）Basic properties of non-dispersible underwater concrete:ground granulated blast furnace slag can significantly improve the fluidity of fresh non-dispersible underwater concrete,but significantly reduce the anti-dispersive performance of concrete.When addition of ground granulated blast furnace slag content was 20%,40%and 60%,the slump of non-dispersible underwater concrete at 120 s increased by 6%,13%and 15%and the suspended matter content increased by10%,23%and 105%.（2）Sulfate corrosion resistance of non-dispersible underwater concrete:in sulfate environment,the compressive strength of concrete with water-binder ratio of 0.50 and 0.40decreased by19%and 7%respectively when test age was 360 days.When the water-binder ratio was 0.45 and the addition of ground granulated blast furnace slag was 20%,40%and60%,the compressive strength increased by 13.2%,23.5%and 25.7%respectively,and the corrosion resistance coefficient reached 0.9,0.92 and 0.94,respectively.Reducing water-binder ratio and adding ground granulated blast furnace slag could obviously improve sulfate resistance of non-dispersible underwater concrete.The optimum content of ground granulated blast furnace slag is 60%.The corrosion products of underwater non-dispersible concrete in sulfate environment were both ettringite and gypsum.Addition of ground granulated blast furnace slag was able to reduce the production of ettringite and gypsum.（3）Chloride corrosion resistance of non-dispersible underwater concrete:The compressive strength of non-dispersible underwater concrete won’t be affected by chloride.The corrosion resistance coefficient of concrete in chloride environment was between 0.95and 1.0.The water-binder ratio and the content of granulated blast furnace slag powder had no effect on the corrosion resistance coefficient.Friedel’s salt was produced in non-dispersibleunderwater concrete under chloride environment.Addition of ground granulated blast furnace slag could increase by the content of Friedel’s salt.（4）Compound salt corrosion resistance of non-dispersible underwater concrete:when water-binder ratio was 0.50 and 0.40 and test ages was 360 days,the compressive strength of concrete decreased by 13%and 4%respectively in compound salt environment.The compressive strength of non-dispersible underwater concrete with water-binder ratio of 0.45increased by 8.7%,16%and 18.7%respectively and the corrosion resistance coefficient increased by 0.07,0.07 and 0.11 after adding 20%,40%and 60%ground granulated blast furnace slag.Reducing water-binder ratio and adding ground granulated blast furnace slag can obviously improved compound salt resistance of non-dispersible underwater concrete.The optimum content of ground granulated blast furnace slag is 60%.The corrosion of non-dispersible underwater concrete in compound salt environment is weaker than sulfate environment,but stronger than chloride environment.The corrosion products include ettringite,gypsum and Friedel’s salt.The existence of Cl^-could weaken the corrosion of SO₄^2-to concrete.