Effects of Sodium Sulfate Attack on Concrete Incorporated with Drying-Wetting Cycles

Fang Liu,Zhanping You,Xu Yang,Rui Xiong,Peerapong Jitsangiam

doi:10.1155/2021/5393504

Abstract

It has been widely observed that sulfate attack can damage the durability of concrete. This research investigated the mass loss and damage degree of concrete under sodium sulfate attack incorporated with drying-wetting cycles. The impact factors, including water-binder ratio, solution concentration of sodium sulfate, fly ash content, curing time, and drying-wetting cycle system, were observed to influence the sodium sulfate attack by the mass loss rate and damage degree at regular time intervals. Also, the hydrates of sulfate-attacked samples were analyzed using X-ray diffraction. Results indicated that a high water-binder and high-concentration sodium sulfate solution could accelerate the transportation of sulfate ion inside the concrete and the deterioration degree of concrete. Appropriate fly ash and longer curing time can effectively improve the internal pore structure of concrete to reduce the sulfate corrosion damage. The sulfate ion erosion and deterioration degree of the concrete are synchronously intensified along with the increase of the baking-immersing time ratio. The trend of the predicted life for concrete is basically consistent with the damage evolution result, indicating the feasibility of the Weibull distribution model to predict the service life of concrete under sodium sulfate attack incorporated with drying-wetting cycles.

Highlights

External sulfate attack on concrete is a complex interaction between sulfate and the concrete, including physical, chemical, and mechanical processes, leading to the decrease of concrete durability [1, 2]
Influence by Water-Binder Ratio on the Mass Loss Rate. e variation of the mass loss rate of concrete with different water-binder ratios is shown in Figure 2. e change law of the mass loss rate of concrete specimen N10G1R35 over the number of drying-wetting cycles can be divided into two stages: accelerated decline in the first stage and slow rise in the second stage. e change law of the mass loss rate of concrete specimen N10G1 over the number of drying-wetting cycles can be divided into two stages: accelerated decline and decline. e change law of the mass loss rate of concrete specimen N10G1R45 over the number of drying-wetting cycles can be divided into three stages: accelerated decline, decline, and rise
The effect of sodium sulfate attack on concrete incorporated with drying-wetting cycles was investigated

Summary

Introduction

External sulfate attack on concrete is a complex interaction between sulfate and the concrete, including physical, chemical, and mechanical processes, leading to the decrease of concrete durability [1, 2]. E.g., concrete piers of sea-crossing bridges in tidal zones and port docks in splash zones, concrete structures have to be simultaneously subjected to the combined effects of dryingwetting cycles and sulfate attack. Under the action of drying-wetting cycles and sulfate attack, concrete is chemically corroded and accompanied by physical corrosion [11]. E transmission of sulfate ions (SO2−4) in concrete can be divided into the wetting state and drying state. After the Na2SO4 solution is adsorbed, on the surface of the concrete specimens, physically and chemically, sulfate ions enter the interior of the concrete with moisture due to capillary action. After being saturated in the solution, sulfate ions migrate into deeper parts of the concrete due to the diffusion effect caused by the concentration gradient. Reactions between the cement hydration products and sulfate ions

Objectives

Results

Conclusion