Effect of Dry-Wet Ratio on Properties of Concrete Under Sulfate Attack.

Guo Guo,Yang Yang,Wang Wang,Zhang Zhang

doi:10.3390/ma12172755

Abstract

In order to explore the drying–wetting cycle test method of concrete under sulfate accelerating erosion, the influence of dry–wet time ratio on concrete sulfate erosion was studied. Under the condition of 7 days for one cycle, five different dry–wet time ratios were designed: 1:3, 1:1, 3:1, 5:1, and 10:1. The basic properties such as compressive strength, splitting tensile strength and dynamic elastic modulus of concrete were tested. Scanning electron microscopy (SEM) was used to analyze the microstructure of concrete before and after erosion. The test results show that under the environment of sulfate drying–wetting cycle erosion, the change of mechanical properties of concrete are divided into three stages: ascending period, fluctuating period and rapid descending period. Concrete is subjected to periodic damage process of initial damage followed by filling compaction, cracking, further filling, and cracking again, in that order. Dry–wet ratio has a significant effect on concrete sulfate attack. Under the same drying–wetting cycle period, as the dry–wet ratio increases, the degree of deterioration of concrete by sulfate attack increases first and then decreases. When the dry–wet ratio is 5:1, the deterioration is the most serious.

Highlights

Large amounts of concrete structures are being subjected to the erosion of different salt ions in their service environment [1,2,3]
Can decrease the shrinkage strain of cement mortar, and the generation of ettringite is more effective when α-calcium sulfate hemihydrate (αHH) is substituted into Portland blast-furnace slag cement (PSC) than into ordinary Portland cement (OPC) and is more effective in suppressing the shrinkage strain [7]
Ganjian et al found that SF cement has a lower compressive strength loss rate than ordinary concrete, and has better resistance to dry and wet cycles [19]. He et al carried out a systematic experimental research, and the results showed that the compressive strength of the whole immersion specimen increased slowly, and the compressive strength of the drying and wetting cycle specimen suddenly dropped after a long time of microliter exposure [20]

Summary

Introduction

Large amounts of concrete structures are being subjected to the erosion of different salt ions in their service environment [1,2,3]. The drying process enhances the internal ion concentration of the concrete by evaporation of water, and the volume expansion of the crystalline product can be up to 4 to 5 times [8], thereby enhancing the intensity of ion corrosion. According to related research, drying–wetting cycle environment is the most significant factor in the process of concrete erosion by sulfate, and the degradation rate is much higher than that of long-term immersed concrete [9]. As a consequence, studying the drying–wetting cycle system and its damage mechanism in Materials 2019, 12, 2755; doi:10.3390/ma12172755 www.mdpi.com/journal/materials

Methods

Results

Conclusion