Chloride Ion Corrosion Pattern and Mathematical Model for C60 High-Strength Concrete after Freeze-Thawing Cycles

Yan Li,Hai Pu,Jiong Zhu,Chao Ma,Lian-Ying Zhang,Ming Li,Bing Li,Chunyang Zhang

doi:10.1155/2021/5523499

Abstract

In this study, the porosities of C60 high-strength concrete after 0, 30, 60, and 90 freeze-thaw cycles determined via the water retention method are 1.30%, 3.65%, 5.14%, and 7.34%, respectively. Furthermore, a mathematical model of porosity varying with the number of freeze-thaw cycles is established. Using an artificial environment simulation experimental system and the natural diffusion method, the chloride diffusion law of C60 high-strength concrete after 0, 30, 60, and 90 freeze-thaw cycles is obtained. The corresponding diffusion coefficients are calculated based on the experimental results and Fick’s law, where 0.3431 × 10−12, 0.5288 × 10−12, and 0.6712 × 10−12, and 0.8930 × 10−12 m2/s are obtained, respectively, and a mathematical model of diffusion coefficient with freeze-thawing is established. Transport control equations comprising solution flow and solute migration control equations are established for chloride ions in concrete after freeze-thawing cycles. The equations consider the effects of freeze-thawing, solution pressure, solution concentration, solution density, convection, mechanical dispersion, and chemisorption on chloride ion transport in concrete. Using COMSOL numerical software, the transport control equations for chloride ions are solved using a real concrete numerical model, and the chloride ion corrosion process in concrete after freeze-thaw cycles is simulated. The simulation results are consistent with the experimental values.

Highlights

With the continuous increase in energy demand, mineral resources extraction has gradually shifted to deeper strata, and the development depth of vertical shafts has increased along with the increase in the cross-sectional size of the shaft [1,2,3,4,5,6,7,8,9,10,11,12]
As the freezing shaft lining is generally cast on site, pouring concrete will produce a large amount of heat of hydration, and the heat of hydration will contribute to part of the freezing lining temperature
Sulfate has a certain corrosive and destructive effect on concrete materials, and the intrusion of chloride ions accelerates the rusting of reinforcing steel bars, thereby affecting the stability of the structure; this is closely associated with the durability problem of concrete structures and materials [33,34,35,36,37]

Summary

Introduction

With the continuous increase in energy demand, mineral resources extraction has gradually shifted to deeper strata, and the development depth of vertical shafts has increased along with the increase in the cross-sectional size of the shaft [1,2,3,4,5,6,7,8,9,10,11,12]. With the increase in mining depth, high-strength and high-performance concrete materials such as C60 and C70 have been used for freezing shaft lining, and many scholars have conducted relevant studies [20,21,22,23,24]. Many scholars have investigated the effect of temperature on the rupture of vertical shaft lining [20,21,22,23,24,25,26,27,28,29,30,31,32]. Reinforced concrete structures for freezing shaft lining are affected by temperature and stress fields and are susceptible to the Advances in Civil Engineering corrosive effects of the subsurface environment. Sulfate has a certain corrosive and destructive effect on concrete materials, and the intrusion of chloride ions accelerates the rusting of reinforcing steel bars, thereby affecting the stability of the structure; this is closely associated with the durability problem of concrete structures and materials [33,34,35,36,37]

Objectives

Results

Conclusion