Understanding of the deterioration characteristic of concrete exposed to external sulfate attack: Insight into mesoscopic pore structures

Zhang, Zhongya; Zhou, Jianting; Yang, Jun; Zou, Yang; Wang, Zongshan

doi:10.1016/j.conbuildmat.2020.119932

Cited by 69 publications

(14 citation statements)

References 31 publications

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“…Change in the compressive strength and elasticity modulus are also used as important indicators. In addition to the above-mentioned test methods, other approaches use techniques like microstructural analysis and chemical analysis (NMR, SEM/EDX; XRD and XRF) to study the formation of ettringite, gypsum and thaumasite in the pores of the attacked specimens [ 60 , 61 , 62 , 63 ]. Moreover, other techniques are used by researchers to obtain further information on the progress of ESA on cementitious materials [ 46 , 59 ].…”

Section: Overview Of the Existing Test Methodsmentioning

confidence: 99%

A Critical Review of Existing Test-Methods for External Sulfate Attack

et al. 2022

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External sulfate attack (ESA) of cementitious materials has been studied worldwide for a very long time. This physical/chemical interaction between sulfate ions and the cement hardened elements affects the long-term durability of concrete structures: cracking, spalling or strength loss of concrete structures. To study these damaging phenomena, some standardized and non-standardized accelerated aging tests are used to evaluate the performance of cements in sulfate-rich environments. However, these existing methods do not adequately predict field performance and some shortcomings or deficiencies still exist: change of degradation mechanisms when using high concentrations of sulfate, variable boundary conditions and small specimens compared to the real concrete structures. In this work, a critical review of some existing test methods and foreign national standard methods for ESA are presented, analyzed, and discussed. This results in some proposed recommendations for improving these methods to meet the needs of structure managers.

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Section: Overview Of the Existing Test Methodsmentioning

confidence: 99%

A Critical Review of Existing Test-Methods for External Sulfate Attack

et al. 2022

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“…The remaining specimens were maintained in saturated Ca(OH) 2 solution as a reference. The dried specimens were partially immersed in a 5% Na 2 SO 4 solution for 80 days (the solution was replaced once 15 days to keep the concentration constant [ 24 ]) with an immersion depth of 5 cm. During this period, some partially immersed specimens were placed in an air environment while the remaining partially immersed specimens were placed in a sealed environment chamber with ≥95% nitrogen gas.…”

Section: Methodsmentioning

confidence: 99%

The Damage Performance of Uncarbonated Limestone Cement Pastes Partially Exposed to Na2SO4 Solution

Cui

Pei²,

Huang

et al. 2022

Materials

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Pore structure and composition of cement paste are the main two factors in controlling the sulfate attack on concrete, but the influence of carbonization on pore structure and composition is often ignored in sulfate attack. Therefore, will the damage performance of concrete partially exposed to sulfate solution be different avoiding the alterations of pore structure and composition due to carbonation? In this paper, the cement pastes were partially immersed in 5 wt. % sodium sulfate solution, with N2 as protective gas to avoid carbonation (20 ± 1°C, RH 65 ± 5%). Pore structures of cements were changed by introducing different contents of limestone powders (0 wt. %, 10 wt. %, 20 wt. %, and 30 wt. %) into cement pastes. The damage performance of the specimens was studied by 1H NMR, XRD and SEM. The results showed that the immersion zone of pure cement paste under N2 atmosphere remained intact while serious damage occurred in the evaporation zone. However, the damage of cement + limestone powders pastes appeared in the immersion zone rather than in the evaporation zone and cement pastes containing more limestone were more severely damaged. Compositional analysis suggested that the damage of the evaporation zone or the immersion zone was solely caused by chemical attack where substantial amount of gypsums and ettringites were filled in the pore volumes. Introduction of limestone powders led to the increase of the pore sizes and porosity of cement pastes, causing the damage occurred in the immersion zone not in the evaporation zone.

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“…Pore structures exist in aggregates, cementitious materials, and interface transition zones and can be divided into primary and secondary pores. The internal pore structure possesses the characteristics of large morphological differences, disorderly distribution, and wide pore size coverage, which significantly impact the strength, deformation, and durability of concrete (Luna-Galiano et al, 2016;Zhang et al, 2020;Liu et al, 2021;Chen et al, 2022;Ren et al, 2022). However, not all pore structures adversely affect concrete performance.…”

Section: Influence Mechanism Of Pore Distribution On Mechanical Stren...mentioning

confidence: 99%

The mechanical properties of concrete in water environment: A review

Wang

Sun

et al. 2022

Front. Mater.

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The service performance of concrete structures in a water environment differs from that in a normal environment. An accurate evaluation of the mechanical properties and service status of wet concrete is related to the reliable design and safe operation of concrete structures, e.g., hydraulics, marine engineering, bridges, and tunnels. To promote the application of new and high-performance concrete to complex water environments and grasp the future development trend, the research progress on the service performance of concrete in water environments was reviewed worldwide. Starting from the internal water content of concrete, the existing research is combed, the influence of water content, water pressure, and loading rate on the static and dynamic characteristics of concrete in a water environment is summarized, and the influence mechanism is analyzed. The literature review demonstrates that the static compressive strength of wet concrete is lower than that of dry concrete; however, the elastic modulus improves. With an increase in the strain rate, the compressive strength of wet and dry concretes improves, and the rate sensitivity of the wet concrete is greater than that of the normal concrete. Pore structure characteristics mainly affect the static strength of the wet concrete. The improvement in the dynamic strength of the wet concrete is caused by the combined effect of the concrete rate sensitivity, “Stefan” effect, and water pressure.

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Understanding of the deterioration characteristic of concrete exposed to external sulfate attack: Insight into mesoscopic pore structures

Cited by 69 publications

References 31 publications

A Critical Review of Existing Test-Methods for External Sulfate Attack

A Critical Review of Existing Test-Methods for External Sulfate Attack

The Damage Performance of Uncarbonated Limestone Cement Pastes Partially Exposed to Na2SO4 Solution

The mechanical properties of concrete in water environment: A review

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