The Deterioration of Cement Mortar under the Coupled Conditions of Stray Current and Sulfate

摘要

Subway engineering often suffers varieties of corroding environments. This article investigatedthe effects of stray current and external sulfate coupled conditions on the deteriorationof cement mortar. The cement mortar specimens suffered from one-dimensional sulfateattack. Simultaneously, a direct current electric field was applied to both ends of the specimento simulate stray current. By contrast, a group of mortar specimens was immersed inthe same concentration of sodium sulfate (Na_2SO_4) solution. In order to investigate theeffect of stray current on the sulfate attack of cement mortar, the compressive strengthof specimens was tested. In addition, the sulfate ions profile in the cement mortar specimenwas tested. Corrosion products and the microstructure of specimens were investigatedusing x-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electronmicroscope. Experimental results showed that stray current could exacerbate strengthdegradation and accelerate the sulfate ions’ migration into the cement mortar, which ledto the number of total sulfate ions and free sulfate ions at the same depth beinghigher than that of the immersion group, and quantities of corrosion products (gypsumand ettringite) were also higher than those of the immersion group. In a word, the straycurrent aggravated the sulfate attack of cement mortar. Therefore, the durability of cementmortar exposed to the stray current and sulfate coupled conditions should be given moreattention.