Abstract

The macroscopic mechanical properties and frost resistance durability of concrete are closely related to the changes in the internal pore structure. In this study, the two-dimensional and three-dimensional ICT (Industrial Computerized Tomography) pore characteristics of C30 concrete specimens before and after freezing and thawing in clean water, 5 wt.% NaCl, 5 wt.% CaCl2, and 5 wt.% CH3COOK solution environments are obtained through concrete frost resistance durability test and ICT scanning technology. The effects of pore structure changes on concrete frost resistance, durability, and compressive strength mechanical properties after freezing and thawing cycles in different salt solution environments are analyzed. This paper provides new means and ideas for the study of concrete pores. The results show that with the increase in the freezing and thawing times, the concrete porosity, two-dimensional pore area, three-dimensional pore volume, and pore number generally increase in any solution environment, resulting in the loss of concrete compressive strength, mortar spalling, and the decrease in the relative dynamic elastic modulus. Among them, the CH3COOK solution has the least influence on the concrete pore changes; the NaCl solution has the greatest influence on the change in the concrete internal porosity. The damage of CaCl2 solution to concrete is second only to the NaCl solution, followed by clean water. The increase in the concrete internal porosity from high to low is NaCl, CaCl2, clean water, and CH3COOK. The change in the pore volume of 0.1 to 1 mm3 after the freeze–thaw cycle is the main factor for reducing concrete strength. The test results have certain guiding value for the selection of deicing salt in engineering.

Highlights

  • Deicing salt can effectively reduce the freezing point and realize the effect of melting ice and snow to alleviate the traffic pressure caused by snow in winter

  • The changes in the mass loss rate and the relative dynamic elastic modulus reflect the intuitive state of concrete, and the change in the compressive strength reflects the strength loss of concrete after the freeze-thaw cycles

  • The relative dynamic elastic modulus and compressive strength are negatively correlated with the number of freeze-thaw cycles

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Summary

Introduction

Deicing salt can effectively reduce the freezing point and realize the effect of melting ice and snow to alleviate the traffic pressure caused by snow in winter. The test results show that the mechanical properties of concrete significantly decrease with the increase in the freezing and thawing cycle They believed that the change in the micro-structure of the salt freezing environment is the main factor for the decrease in the mechanical properties of concrete. There is a lack of research on the influence of the change in internal pore characteristics of concrete after salt freezing with different deicing salt solutions on its working performance. The relationship between pore characteristics and concrete working performance under different salt freezing environments is investigated to further study concrete damage mechanisms by salt freezing

Test Materials
Test Scheme and Concrete Durability Processing
The Data Processing of ICT
Test Results and Analysis
Two-Dimensional Pore Structure Characteristics
Three-Dimensional Pore Structure Characteristics
Effect of Salt Solution on the Pore Structure of Concrete
Effect of Pore Change on the Compressive Strength of Concrete
Conclusions
Full Text
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