Improvement of CFG Pile Corrosion Resistance Capability in the Application of Wu-Guang Passenger Transport Special Railway

With Chinese economy speedup since late 1990s, it was required that large numbers of construction of civil engineering projects, and passenger transport special railway was the results of economic development. CFG (cement fly ash gravel) is one of groundwork reinforced methods widely used in civil engineering. And CFG was also applied in the construction of Wu-Guang passenger transport special railway. However, according to field investigation, it was found that groundwater in Haudu to Shaoguan in Gunagdong province containing lots of sulphate, which can result in corrosion damage of underground CFG pile. Therefore, in order to improve service life of CFG pile, it is necessary to increase the capability of CFG corrosion resistance. In this paper, influence of compositive materials such as water to binder rate ( w/b ), fly ash to cement rate (F/C) and quantity of cement on mass change of CFG in sulfate sodium solution, permeability coefficient and compressive strength of CFG were studied. Results show that with the increase of w/c, mass of CFG increase quickly first and then keep steadily. The increase of F/C and cementious addition in CFG can decreases the mass increase rate of CFG effectively. The increase of w/c and cementious addition increase permeability coefficient of CFG. And there exits an optimal F/C (1.0–1.2) in CFG , making permeability coefficient of CFG decrease to the least at 28 day ages. When CFG is immerged in water and sulfate solution respectively, the compressive strength of CFG immerged in sulfate solution is higher than that immerged in water at 28 day ages. With w/c , F/C and cementious addition increasing, the compressive strength of CFG decreases. There are acicular ettringite crystals in CFG after immerged in sulfate solution.