Research on the Effect of Salt Erosion on the Performance of UHPC in Western Saline Soil Environments

Saline soil environments contain large amounts of erosion salts such as sulfates and chloride salts， which will have an important impact on the performance of UHPC. In this paper， an environmental erosion simulation system for western saline soils was formulated， and indoor accelerated erosion tests were designed to explore the performance degradation laws of UHPC under sulfate erosion and sulfate-chloride composite erosion. Microscopic testing methods such as XRD， TG-DTG， SEM and MIP revealed the degradation mechanism of UHPC under different salt erosion conditions. The results showed that after 240 d of sulfate-chloride composite erosion， the surface of the specimen appeared to flake off， and more holes were produced and a large number of salt crystals were precipitated. Compared with the uneroded specimen， its compressive strength， flexural strength， equivalent bending toughness and relative dynamic elastic modulus were reduced by 7.36%， 25.49%， 10.87%， and 97.83%， respectively. At the end of composite salt erosion， the characteristic peaks of ettringite and gypsum in the specimen were stronger than those under sulfate erosion condition， and a large number of needle-like ettringite crystals were formed inside， and the expansion stress generated led to the appearance of more penetrating cracks and connected pores inside the structure. After composite salt erosion， the proportion of harmful pores such as capillary pores and macropores increased， while the number of gel pores decreased relatively， which had a greater impact on the pore structure than the sulfate-eroded specimen.