Sulfate Resistance and Life Prediction of Uhpc in Western Saline Soil Environment

Abstract

Ultra-high-performance concrete (UHPC) used in western saline soil environments undergoes accelerated durability degradation as a result of wet-dry cycles, corrosive salt ions, extreme temperatures, and freeze-thaw cycles. This study, based on an investigation of the characteristics of typical western saline soil environments, developed a laboratory erosion simulation protocol tailored to mimic these conditions. The study examined the sulfate attack resistance of UHPC under this protocol and analyzed the degradation mechanisms associated with variations in water-cement ratios, silica fume content, and fiber types. Wiener degradation theory was applied to predict the lifespan of various UHPC mixtures in this environment. The results indicate that UHPC demonstrates minimal performance degradation under erosion simulation conditions when the water-cement ratio is 0.20, silica fume content is 26%, and steel fibers are used. After 240 days of erosion, UHPC specimens reinforced with PVA fibers exhibited reductions in compressive strength, flexural strength, and equivalent flexural toughness of 7.79%, 35.48%, and 42.01%, respectively, with the relative dynamic modulus of elasticity declining to 97.29%. These reductions were significantly more pronounced compared to those in specimens reinforced with steel fibers. Phase composition and micro-structural analyses revealed that the primary sulfate attack products in UHPC were ettringite and gypsum, in addition to the physical crystallization of anhydrous sodium sulfate. The expansion caused by these erosion products, combined with crystallization stress from salt precipitation, resulted in the formation of detrimental pores and micro-cracks within the UHPC. A reliability function curve based on compressive strength effectively modeled the degradation process of UHPC under these conditions, projecting a potential durability lifespan of over 70 years in western saline soil environments.

Keywords: Ultra-High Performance Concrete, western saline soil environment, erosion simulation system, sulfate attack resistance, Wiener stochastic process, life prediction