Microstructure as a key parameter for understanding chloride ingress in alkali-activated mortars

Runci, Antonino; Provis, John L.; Serdar, Marijana

doi:10.1016/j.cemconcomp.2022.104818

Cited by 24 publications

(8 citation statements)

References 61 publications

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“…The coarser pore structure of AASF, when slag was substituted by metakaolin, was consistent with the findings from previous literature [9]. The introduction of MK into the system promoted the transformation of the gel phase from C-A-S-H gel into N-A-S-H gel, which had a poorer space-filling capacity than C-A-S-H gel [33]. As a result, a distinct peak at 0.5 µm was present in mixture MK10, which was also related to the lower degree of reaction of AASF when MK was added.…”

Section: The Pore Structure Of Aasf Pastessupporting

confidence: 90%

Effect of Activator and Mineral Admixtures on the Autogenous Shrinkage of Alkali-Activated Slag/Fly Ash

Ma,

Gong,

et al. 2023

Sustainability

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The high autogenous shrinkage of alkali-activated fly ash/slag (AASF) poses a significant concern for the widespread application of AASF in structural engineering. The present study compares the efficacy of activator and mineral admixtures in mitigating the autogenous shrinkage of AASF, and discusses the underlying mechanism. The results show that the use of activators with a lower silicate modulus and a lower sodium content, as well as incorporating metakaolin (MK) or silica fume, can reduce the autogenous shrinkage of AAMs. These approaches delay the appearance of the second exothermic peak, which corresponds to the later formation of C-A-S-H gels and slower development of capillary pressure. The inclusion of MK not only retards the reaction but also facilitates the formation of N-A-S-H gels, resulting in a coarse pore structure and reduced water consumption. The use of the activator with a lower silicate modulus (reduced from 1.5 to 1.0) leads to a higher internal relative humidity and the reduced pore volume of silt-shaped and ink-bottle pores (2–50 nm) in AASF, thereby reducing the autogenous shrinkage without significant strength reduction.

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Section: The Pore Structure Of Aasf Pastessupporting

confidence: 90%

Effect of Activator and Mineral Admixtures on the Autogenous Shrinkage of Alkali-Activated Slag/Fly Ash

Ma,

Gong,

et al. 2023

Sustainability

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“…The results of testing physical, mechanical and durability properties of the mortar used are shortly presented in Table 4. These properties were analysed in more detail in a previous paper by the authors [34]. It can be seen that FN9 has a poor resistance to penetration of chloride anions compared to OPC and other binders [35], while SN3 and BN3 provide high protection to chloride penetration despite their relatively high water contents [36,37].…”

Section: Mortar Characterizationmentioning

confidence: 99%

Revealing corrosion parameters of steel in alkali-activated materials

2023

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“…The salt ponding test, following NT Build 443, is a widely recognized procedure for evaluating the chloride permeability of concrete [ 2 , 8 , 30 , 36 , 42 , 43 , 49 ]. This test assesses the ability of concrete to resist the penetration of chloride ions, which is crucial for the durability and longevity of concrete structures, especially in harsh environmental conditions [ 32 ].…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Additionally, it is established that the NT Build 492 and NT Build 443 test methods were suitable approaches for determining the chloride diffusion coefficient in mortars containing blended cement. Furthermore, a separate investigation [ 43 ] also employed both NT Build 443 and NT Build 492 methods to assess how microstructural properties impact the chloride diffusion resistance of alkali-activated materials. The findings indicated that both quantifying reaction products and establishing a correlation between chloride penetration and pore surface area suggested that physical chloride adsorption on the surfaces of C-A-S-H/N-A-S-H gels took precedence over chemical chloride binding.…”

Section: Introductionmentioning

confidence: 99%

Effect of Carbon Nanotubes on Chloride Diffusion, Strength, and Microstructure of Ultra-High Performance Concrete

Rafieizonooz,

Kim,

Kim

et al. 2024

Materials

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This study delved into the integration of carbon nanotubes (CNTs) in Ultra-High Performance Concrete (UHPC), exploring aspects such as mechanical properties, microstructure analysis, accelerated chloride penetration, and life service prediction. A dispersed CNT solution (0.025 to 0.075 wt%) was employed, along with a superplasticizer, to ensure high flowability in the UHPC slurry. In addition, the combination of high-strength functional artificial lightweight aggregate (ALA) and micro hollow spheres (MHS) was utilized as a replacement for fine aggregate to not only reduce the weight of the concrete but also to increase its mechanical performance. Experimental findings unveiled that an increased concentration of CNT in CNT1 (0.025%) and CNT2 (0.05%) blends led to a marginal improvement in compressive strength compared to the control mix. Conversely, the CNT3 (0.075%) mixture exhibited a reduction in compressive strength with a rising CNT content as an admixture. SEM analysis depicted that the heightened concentration of CNTs as an admixture induced the formation of nanoscale bridges within the concrete matrix. Ponding test results indicated that, for all samples, the effective chloride transport coefficient remained below the standard limitation of 1.00 × 10−12 m2/s, signifying acceptable performance in the ponding test for all samples. The life service prediction outcomes affirmed that, across various environmental scenarios, CNT1 and CNT2 mixtures consistently demonstrated superior performance compared to all other mixtures.

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Microstructure as a key parameter for understanding chloride ingress in alkali-activated mortars

Cited by 24 publications

References 61 publications

Effect of Activator and Mineral Admixtures on the Autogenous Shrinkage of Alkali-Activated Slag/Fly Ash

Effect of Activator and Mineral Admixtures on the Autogenous Shrinkage of Alkali-Activated Slag/Fly Ash

Revealing corrosion parameters of steel in alkali-activated materials

Effect of Carbon Nanotubes on Chloride Diffusion, Strength, and Microstructure of Ultra-High Performance Concrete

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