Experimental Study on Mechanical Properties of High-Ductility Concrete against Combined Sulfate Attack and Dry-Wet Cycles.

Lingling Li,Junping Shi,Jialiang Kou

doi:10.3390/ma14144035

Abstract

Concrete will deteriorate and damage under sulfate attack.In order to study the degradation characteristics of HDC under sulfate attack, the mechanical properties of high-ductility concrete (HDC) were investigated using the uniaxial compressive strength test of HDC specimens soaked in different concentrations of sulfate solution and subjected to different times of dry–wet cycles. The variations in the compressive strength, loss rate of compressive strength, and the max compressive strength under the action of sulfate attack and dry–wet cycles were analyzed. The analytical expressions of damage variables were given. SEM was used to observe the microstructure of the sample, and the microdamage mechanism of the HDC was explored. The deterioration of the HDC was found to be the result of the combined action of sulfate attack and dry–wet cycles and was caused by physical attack and chemical attack. PVA prevented the rapid development of deterioration. On the basis of the change of compressive strength, the damage variable was established to quantitatively describe the degree of damage to HDC. The experimental results showed that with the increase in the number of dry–wet cycles, the compressive strength of HDC generally increased first and then decreased. As the concentration of the sulfate solution increased, the loss rate of the compressive strength of HDC generally increased and the max compressive strength gradually decreased. With the increase inthe number of dry–wet cycles, HDC first showed self-compacting characteristics and then gradually became destroyed. Compared with ordinary concrete (OC), HDC is superior to OC in sulfate resistance and dry–wet cycles. This study provided a test basis for the engineering application of HDC in sulfate attack and dry–wet cycles environment.

Highlights

At present, the most widely used building material in the world is concrete, which is recognized by the engineering community as the material with the most stable compressive strength and safety performance
After 30 dry–wet cycles and before 90 dry–wet cycles, the compressive strength of high-ductility concrete (HDC) slowly decreased under the 5% sulfate solution, the compressive strength of HDC first decreased and increased under the 10% sulfate solution, and the compressive strength of HDC decreased under saturated sulfate solution
After 105 dry–wet cycles, the compressive strength of HDC quickly decreased under the 5% sulfate solution, and the compressive strengths dropped significantly under 10% and saturated sulfate solution, mainly due to a large amount of cracking caused by a large amount of SO42− chemical reaction with HDC hydrate

Summary

Introduction

The most widely used building material in the world is concrete, which is recognized by the engineering community as the material with the most stable compressive strength and safety performance. In the sulfate attack and dry– wet cycle environment, concrete is eroded to varying degrees; the volume expansion of erosion products causes micro-cracks at different levels inside the concrete, and the internal structure is gradually damaged, which eventually leads to a decrease in the bearing capacity of the component, a shortened service life and even severe disasters [1,2,3,4]. The soil and water in these areas contain different concentrations of sulfate, which causes dissimilar degrees of erosion to bridges, dams, and houses. The fluctuating levels of rivers and groundwater with seasonal changes subject concrete to a dry–wet cycle environment, thereby exacerbating the erosion and damage degree of bridges, dams, and houses and seriously affecting their normal service life. It is of practical significance to study the mechanical properties of concrete under the combined action of sulfate attack and dry–wet cycles

Methods

Results

Conclusion