Carbonation and Chloride Ions’ Penetration of Alkali-Activated Materials: A Review

Zhang, Xuanhan; Long, Kaidi; Liu, Wei; Li, Lixiao; Long, Wu-Jian

doi:10.3390/molecules25215074

Cited by 25 publications

(9 citation statements)

References 161 publications

(335 reference statements)

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“…In general, in AAMs and geopolymers, fluid penetration through the material occurs due to the presence of an open-pore system [ 12 ]; additionally, the transport mechanisms in these materials are similar to cementitious binders and have been well investigated [ 13 , 14 , 15 ].…”

Section: Introductionmentioning

confidence: 99%

Chloride Ions’ Penetration of Fly Ash and Ground Granulated Blast Furnace Slags-Based Alkali-Activated Mortars

et al. 2021

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Due to the need to reduce the CO2 emissions of mineral binders, researchers are considering the use of alkali-activated materials (AAMs) as an alternative to cementitious binders. The properties of AAMs can be more advantageous than those presented by cementitious binders, and thus they can replace Portland cement binders in some applications. Mechanical tests of AAMs are being conducted on an ongoing basis; however, durability issues related to reinforcing steel in conditions in which steel members interact with chloride ions remain unsolved. In this paper, the precursors for AAM preparations are blends of fly ash (FA) and ground granulated blast-furnace slag (GGBFS) in four slag proportions: 0%, 10%, 30% and 50% expressed as a percent of FA mass. Four alkali-activated mortars were prepared, denominated as AAM 0, AAM 10, AAM 30 and AAM 50, respectively. Their basic physical and mechanical characteristics were investigated, as were their gas transport properties. The nitrogen Cembureau method was applied to determine the permeability of the mortar. The transport properties of the chloride ions were determined using the modified NT BUILD 492 migration test. The comparison of results obtained demonstrated a positive effect of GGBFS addition in terms of an increase in bulk density, permeability, porosity and, at the same time, a reduction in chloride ion penetration. The water absorption tests also provided insight into the open pore structures of mortars. The measurements revealed a strong dependence between fluid transport through the mortars and the water absorption and initial water content of materials.

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Section: Introductionmentioning

confidence: 99%

Chloride Ions’ Penetration of Fly Ash and Ground Granulated Blast Furnace Slags-Based Alkali-Activated Mortars

et al. 2021

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“…It is well known that porosity, pore size distribution, and tortuosity strongly affect mechanical properties and chloride transport in hardened concretes [31,53,54]. Each material was also subjected to a porosity analysis using mercury porosimetry using Poromaster Micromeritics AutoPore IV.…”

Section: Methodsmentioning

confidence: 99%

Mechanical Strength and Chloride Ions’ Penetration of Alkali-Activated Concretes (AAC) with Blended Precursor

et al. 2022

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The purpose of this study was to investigate the properties of hardened alkali-activated concrete, which is considered an eco-friendly alternative to Portland cement concrete. In this paper, the precursors for alkali-activated concrete preparations are blends of fly ash and ground-granulated blast-furnace slag in three slag proportions: 5%, 20%, and 35%, expressed as a percentage of fly ash mass. Thus, three concretes were designed and cast, denominated as AAC5, AAC20, and AAC35. Their physical and mechanical characteristics were investigated at 28 and 180 days, as well as their properties of chloride ion transport. The modified NT BUILD 492 migration test was applied to determine the chloride ions’ penetration of the alkali-activated concretes. Improvement of mechanical strength and resistance to chloride aggression was observed with ground-granulated blast-furnace slag content increase in the compositions of the tested concretes. Mercury intrusion porosimetry tests provided insight into the open pore structures of concretes. A significant decrease in the total pore volume of the concrete and a change in the nature of the pore diameter distribution due to the addition of ground granulated blast furnace slag were demonstrated.

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“…1. After 7 days of exposure to accelerated carbonation, mix S1 exhibited the highest carbonation depth, which can be explained by the lower alkali content than in the mix S2 and the lowest Ms of all three mixes [3,11,12]. Increase in Ms is expected to provide the best performance in terms of carbonation resistance due to the formation of less porous matrix structure [12].…”

Section: Carbonation Depthmentioning

confidence: 97%

“…It is reported that higher alkali content (%Na2O) and higher silica modulus (Ms) of the mix (i.e., SiO2/Na2O) improve the carbonation resistance [3,11,12]. A higher alkali content may result in higher activation degree of the slag, while a higher Ms results in a denser matrix and lower permeability due to slower slag hydration, which in turn results in a more uniform distribution of hydration products [3,6,10].…”

Section: Introductionmentioning

confidence: 99%

Influence of alkali content and silica modulus on the carbonation kinetics of alkali-activated slag concrete

Olivera

Serdar

2022

MATEC Web Conf.

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Carbonation is inevitable process during the service life of concrete structures, where CO2 causes decalcification of the calcium-bearing phases. These changes affect the durability of concrete and accelerate the corrosion of reinforcement. Alkali-activated materials (AAMs) are alternative, cement-free binders based on aluminosilicate rich precursor and alkaline activator. The interest in AAMs increased during the last century, due to the production process with low CO2 footprint comparing to Portland cement (PC) concrete, the possibility to use wide range of industrial by-products as precursors and comparable performance to PC concrete. Despite the extensive research in this field, the carbonation resistance of AAMs needs to be better understood, due to the differences and complexity of binder chemistry compared to PC concrete. The propagation of carbonation process will depend on chemical composition of the precursors and the type and dosage of activators. This paper presents the results of microstructural changes of three alkali-activated concrete mixes after exposure to accelerated carbonation. Ground granulated blast furnace slag was used as a precursor and sodium hydroxide and sodium silicate as activators. Three mixes have constant water to binder ratio and slag content, while alkali content and silica modulus were varied. The carbonation resistance was evaluated by testing carbonation depth after 7 and 28 days of exposure in carbonation chamber. Microstructural changes during carbonation were investigated by thermogravimetric analysis and mercury intrusion porosimetry.

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Carbonation and Chloride Ions’ Penetration of Alkali-Activated Materials: A Review

Cited by 25 publications

References 161 publications

Chloride Ions’ Penetration of Fly Ash and Ground Granulated Blast Furnace Slags-Based Alkali-Activated Mortars

Chloride Ions’ Penetration of Fly Ash and Ground Granulated Blast Furnace Slags-Based Alkali-Activated Mortars

Mechanical Strength and Chloride Ions’ Penetration of Alkali-Activated Concretes (AAC) with Blended Precursor

Influence of alkali content and silica modulus on the carbonation kinetics of alkali-activated slag concrete

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