Experimental Study On Wind-blown Sand Erosion Of Concrete Under The Effect Of Salt Soaking Erosion

The central and western Inner Mongolia crosses the northwest and north China. It has complex natural environment. It is an area with frequent sandstorms and a lot of saline soil. The concrete infrastructure such as roads, bridges and houses of the region suffer a lot from saline soil and sandstorm erosion environment for a long time. All soluble salt in saline soil will erode concrete seriously and make the concrete crack. When the wind with sand blows,it will lead to double erosion to the concrete and threaten the duration and safety of the concrete.Saline soil and sandstorm environmental characteristics in the central and western Inner Mongolia are analyzed in this paper. The actual engineering service conditions are simulated according to characteristics of the region’s natural erosion environment. Erosion solutions of different multi-salt concentrations are prepared according to the higher soluble salt content in saline soil for long-term immersion test. Single salt erosion solutions are prepared according to the soluble salt types in multi-salt solution to do check experiments. In addition, the erosion test of concrete samples after long soaking in salt solution were carried out by sediment-air injection method to study the mechanism of erosion and the damage rules of concrete after soaking in different salt solutions under different erosion parameters.This subject is supported by national natural science fund project(Grant no.11162011) and(Grant no. 51468049). Specific content as follows:1. In this paper, a large number of researches are done on the environmental features of the saline soil in the central and western Inner Mongolia, the main types of saline soil in the area, the main ingredients of the soluble salt in the saline soil and how each ingredient damages buildings are analyzed. Meanwhile the characteristics of the sandstorm meteorological environment in this region are analyzed to find proper erosion parameters.2. Multi-salt erosion solutions are prepared according to the main ingredients of the soluble salt and single salt erosion solutions are prepared according to the salt types in the multi-salt solution to do long-term immersion tests. Apparent morphology, mass loss and the intensity attenuation of concrete are analyzed from a macroscopic view at different erosion ages. Furthermore, the corrosion mechanism of concrete is revealed by electron microscope scanning, analysis of EDX spectrum and chemical composition analysis of the concrete microstructure.It is concluded that the corrosion damage of concrete is mainly caused by the salt chemical erosion. Besides, the expansion effect of salt crystallization accelerates the concrete cracking and performance degradation.3. Sediment-air injection method is adopted to carry out the research on erosion resistance of the concrete samples after being soaked in salt solutions under different erosion parameters. The result shows that:(1) The erosion rate of the concrete from the same salt solution increases with the erosion speed.(2) The erosion rate of the concrete from the same salt solution increases with the increase of erosion angles and reaches its top in 90°.(3) The erosion rate of the concrete from the same salt solution increases first and decreases later with the increase of the falling rate of sand. It is obvious within a certain scope.(4) There is a direct relationship between the erosion rate of the concrete under short-term salt corrosion and the surface expansion product. For the concrete under long-term salt corrosion, the erosion rate is related to the extent of its spalling,the erosion resistance ability of the concrete after salt corrosion fades.4. Based on the scanning electron microscopy and three-dimensional microscope are adopted to observe and analysis the facial damage morphology of the concrete, the failure mechanism is sand erosion wear of concrete exist horizontal cutting action and positive impact simultaneously. Under low impact angle, horizontal stress component relatively large, acting on the concrete surface mainly for horizontal cutting action, the concrete surface is given priority to with scratch damage; Under the high impact angle, vertical stress component is relatively large,concrete surface mainly bear the impact of the positive role, destruction is mainly impact crushing effect,leading to concrete surface generate micro cracks, micro cracks expanding cross, cause material brittle fracture and peeling.