Evolution of ITZ and its effect on the carbonation depth of concrete under supercritical CO2 condition

Xu, Gang; Yu, Mao-Hong; Li, Rende; Saafi, Mohamed; Ye, Jianqiao

doi:10.1016/j.cemconcomp.2021.104336

Cited by 23 publications

(4 citation statements)

References 71 publications

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“…Mixture T4 presented the smallest carbonation penetration and capillary water absorption with CO 2 penetration decreasing 78.3% with respect to T3. Bao et al [38] noted that capillary absorption had a great effect on concrete durability, even greater than the thickness of the transition zone. Overall, results showed that decreases in mercury intrusion also decreased the carbonation depth and, at a compressive strength of 40 MPa, there was an elevated decrease of CO 2 ingress in concrete.…”

Section: Accelerated Carbonationmentioning

confidence: 99%

Proposed variations in nominal reinforcement cover based on the environmental aggressivity class (EAC) of concrete exposure

Pacheco,

Ehrenbring,

Christ

et al. 2024

Rev. IBRACON Estrut. Mater.

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The physical and chemical protection of steel reinforcement afforded by the cover is a consequence of the quality of the concrete and its thickness, with a long-term impact on durability and service life. This study proposed variations in cover based on environmental aggressivity class (EAC) of exposure considering concretes of prescribed compressive strength classes (C20/C25/C30/C40). To this end, concrete mixtures were subjected to accelerated testing in salt spray chambers or carbonation. Accelerated testing was kept for periods long enough to reach each EAC cover level. Thus, the effect of each EAC, from mild to severe, was determined on the physical and mechanical characteristics of each mixture. It was determined that the required reinforcement cover varied linearly with compressive strength. This denoted the possibility of using more than one class of concrete and cover for each EAC. It should be noted that the difference in required cover became greater when using concrete with a strength class higher than C30. Still, it was noticed that the chloride ions attack s was more severe than carbonation and was, for most of the test cases, the determinant factor in minimum cover thickness to ensure the desired durability.

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Section: Accelerated Carbonationmentioning

confidence: 99%

Proposed variations in nominal reinforcement cover based on the environmental aggressivity class (EAC) of concrete exposure

Pacheco,

Ehrenbring,

Christ

et al. 2024

Rev. IBRACON Estrut. Mater.

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“…Evidently, there is an increase in pores and alterations in pore connectivity. In addition, the MF pores are mainly located within ITZ and unhydrated cementitious material, which is distant from the aggregate [46]. The hydration leads to the densification of ITZ and the hydration of unhydrated material.…”

Section: Evaluation Of Pore Connectivitymentioning

confidence: 99%

Pore Structure Quantification and Fractal Characterization of MSA Mortar Based on 1H Low-Field NMR

Jiang,

He,

Tian

et al. 2024

Fractal Fract

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With the gradual depletion of natural sand due to over-exploitation, alternative building materials, such as manufactured sand aggregate (MSA), have attracted much attention. In order to interpret the evolution of pore structure and fractal characteristics in MSA mortar over long-term water saturation, the 1H low-field nuclear magnetic resonance (LF-NMR) relaxation method was used to investigate the temporal evolution of the pore structure in five single-graded MSA mortars and synthetic-graded mortars with small amplitudes in particle size. MSA presents a fresh rock interface characterized by a scarcity of pores, which significantly reduces the porosity of the mortar. The surface-to-volume ratio (SVR) is employed for characterizing the MSA gradation. Through an analysis of parameters, such as total porosity, pore gradation, pore connectivity, and pore fractal dimension of mortar, a correlation model between pore structure parameters and aggregate SVR is constructed. The fractal characteristics of pores and their variations are discussed under three kinds of pore gradations, and the correlation model between fractal dimension and porosity is established. These results demonstrate the high impermeability and outstanding corrosion resistance of synthetic-graded mortar. The fractal model of the pore structure evolution of MSA mortar has a guiding effect on the pore distribution evolution and engineering permeability evaluation of MSA mortar in engineering.

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“…Many studies have been conducted to characterize the microstructure of the ITZ in concrete using different tools such as scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) [ 10 , 11 ]. These tools have been widely applied to identify the microstructural gradients through the ITZ in concrete [ 12 , 13 ]. However, the aforementioned techniques are limited because the local mechanical properties across the ITZ cannot be quantified using the SEM and EDX.…”

Section: Introductionmentioning

confidence: 99%

Study of the Interfacial Transition Zone Characteristics of Geopolymer and Conventional Concretes

Alanazi

2022

Gels

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The properties and performance of geopolymer at different length scales have been intensively studied, but only limited studies on geopolymer have investigated the zone located between paste and aggregates, which is called the interfacial transition zone (ITZ). The microstructure of ITZ and its nanomechanical properties in geopolymer concrete are examined in this study. Fly ash-based geopolymer has great potential to be an alternative to traditional concrete. To this end, scanning electron microscopy (SEM) and nanoindentation tests were performed to investigate the microstructural characteristics and nanomechanical properties of the ITZ, and the results were compared with the ITZ of traditional concrete. Results show that traditional concrete demonstrated a weak ITZ with pores and microcracks, while the geopolymer concrete microstructure did not present weak ITZs in the vicinity of aggregates. More pores and crack were observed in the ITZ in traditional concrete. Further, a considerable amount of fly ash particles, that appear to be unreacted or partially reacted in the matrix phase, was observed. Based on the nanoindentation results, 58% of the microstructure is composed of unreacted or partially reacted fly ash particles. The results of nano- and microscale tests will enhance the understanding of how concrete behaves and performs at large scales.

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Evolution of ITZ and its effect on the carbonation depth of concrete under supercritical CO2 condition

Cited by 23 publications

References 71 publications

Proposed variations in nominal reinforcement cover based on the environmental aggressivity class (EAC) of concrete exposure

Proposed variations in nominal reinforcement cover based on the environmental aggressivity class (EAC) of concrete exposure

Pore Structure Quantification and Fractal Characterization of MSA Mortar Based on 1H Low-Field NMR

Study of the Interfacial Transition Zone Characteristics of Geopolymer and Conventional Concretes

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