Experimental Investigation on Mechanical Properties and Ions Transmission Law of Concrete under Capillary Action in Water Level Fluctuating Environment

Abstract

Concrete structures partially immersed in seawater will be subjected to severe chloride and sulfate erosion under the capillary and diffusion actions. Nevertheless, the present studies only discuss the capillary action in a static water level environment, without considering the capillary action in a water level fluctuating environment. In this paper, the mechanical properties and ions transmission law of concrete under the capillary and diffusion actions in water level fluctuating environment were investigated through a series of indoor exposure tests. Three erosion solutions were set to study the interaction effects of chloride, sulfate, and magnesium within concrete. Based on the compressive strength tests, the mechanical properties of concrete in a water level fluctuating environment were explored. The natural diffusion tests were carried out to research the sulfate and chloride transmission law within concrete above and in the water level fluctuating zone (WLFZ). Scanning electronic microscopy (SEM), X-ray diffractometer (XRD), and mercury injection porosimeter (MIP) measurements were conducted to analyze the microstructures at various zones of concrete under different erosion solutions. The results show that the concrete partially immersed in WLFZ suffers from severe sulfate attack on mechanical properties due to the dual influences of sulfate chemical and physical crystallization attack. The chloride concentration within concrete above WLFZ is significantly higher under the capillary action. The sulfate concentration within concrete above WLFZ is lower because of the chemical binding of sulfate within concrete. The higher porosity and more capillary pores exist in concrete above WLFZ due to the carbonization and water evaporation. By decreasing the porosity of concrete, sulfate will inhibit the chloride transmission and magnesium will restrain the sulfate and chloride transmission. The transmission mechanisms of erosion ions within concrete above WLFZ consist of vertical transmission under the capillary action and lateral transmission under the diffusion action and water evaporation.