Efficient mix design of alkali activated slag concretes based on packing fraction of ingredients and paste thickness

Bondar, Dali; Nanukuttan, Sreejith; Provis, John L.; Soutsos, Marios

doi:10.1016/j.jclepro.2019.01.332

Cited by 53 publications

(7 citation statements)

References 32 publications

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“…It is known from the literature that the content of water and activating solution strongly affects the workability of the geopolymers: generally, the higher the liquid-to-binder ratio, the higher the workability of the mix [32][33][34][35]. The results of the present study followed the results of the literature, as the consistencies of the three mixes were very different depending on the content of the activating solution and water.…”

Section: Consistency Of the Mortarssupporting

confidence: 83%

The Use of Lightweight Aggregates in Geopolymeric Mortars: The Effect of Liquid Absorption on the Physical/Mechanical Properties of the Mortar

Vasanelli,

Calò,

Cascardi

et al. 2024

Materials

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Geopolymers have been proposed as a green alternative to Portland cement with lowered carbon footprints. In this work, a geopolymeric mortar obtained using waste materials is studied. Fly ash, a waste generated by coal combustion, is used as one of the precursors, and waste glass as lightweight aggregates (LWAs) to improve the thermal performance of the mortar. The experimental study investigates the effect of varying the alkali activating solution (AAS) amount on the workability, compressive strength, and thermal conductivity of the mortar. Indeed, AAS represents the most expensive component in geopolymer production and is the highest contributor to the environmental footprint of these materials. This research starts by observing that LWA absorbs part of the activating solution during mixing, suggesting that only a portion of the solution effectively causes the geopolymerization reactions, the remaining part wetting the aggregates. Three mixes were investigated to clarify these aspects: a reference mix with a solution content calibrated to have a plastic consistency and two others with the activating solution reduced by the amount absorbed by aggregates. In these cases, the reduced workability was solved by adding the aggregates in a saturated surface dry state in one mix and free water in the other. The experimental results evidenced that free water addiction in place of a certain amount of the solution may be an efficient way to improve thermal performance without compromising the resistance of the mortar. The maximum compressive strength reached by the mortars was about 10 MPa at 48 days, a value in line with those of repair mortars. Another finding of the experimental research is that UPV was used to follow the curing stages of materials. Indeed, the instrument was sensitive to microstructural changes in the mortars with time. The field of reference of the research is the rehabilitation of existing buildings, as the geopolymeric mortars were designed for thermal and structural retrofitting.

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Section: Consistency Of the Mortarssupporting

confidence: 83%

The Use of Lightweight Aggregates in Geopolymeric Mortars: The Effect of Liquid Absorption on the Physical/Mechanical Properties of the Mortar

Vasanelli,

Calò,

Cascardi

et al. 2024

Materials

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“…Figure 4 shows the results of water absorption, accessible porosity for water and dry bulk density at the curing age of 28 d. As shown in Figure 4, the mixes made with RA (PC-R1 and PC-R2) obtained higher water absorption and lower dry bulk density than reference concrete made with NA (PC-RER), which may be due to the higher porosity of the RA [61,62]. Recycled aggregates (R1 and R2) showed a lower particle dry bulk density and higher water absorption than NA (Table 1), which is an intrinsic property of recycled aggregates from CDW [20,[63][64][65].…”

Section: Dry Bulk Density Water Absorption and Accessible Porosity Fo...mentioning

confidence: 94%

Accelerated Carbonation of Vibro-Compacted Porous Concrete for Eco-Friendly Precast Elements

et al. 2023

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This research studied the effect of accelerated carbonation in the physical, mechanical and chemical properties of a non-structural vibro-compacted porous concrete made with natural aggregates and two types of recycled aggregates from construction and demolition waste (CDW). Natural aggregates were replaced by recycled aggregates using a volumetric substitution method and the CO2 capture capacity was also calculated. Two hardening environments were used: a carbonation chamber with 5% CO2 and a normal climatic chamber with atmospheric CO2 concentration. The effect of curing times of 1, 3, 7, 14 and 28 days on concrete properties was also analysed. The accelerated carbonation increased the dry bulk density, decreased the accessible porosity water, improved the compressive strength and decreased the setting time to reach a higher mechanical strength. The maximum CO2 capture ratio was achieved with the use of recycled concrete aggregate (52.52 kg/t). Accelerate carbonation conditions led to an increase in carbon capture of 525% compared to curing under atmospheric conditions. Accelerated carbonation of cement-based products containing recycled aggregates from construction and demolition waste is a promising technology for CO2 capture and utilisation and a way to mitigate the effects of climate change, as well as promote the new circular economy paradigm.

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“…Fine aggregate was 4 mm sand. These were combined in a ratio of 48:12:40 according to the procedure outlined in Bondar et al [13]. The bulk specific gravity and water absorption of the aggregates were measured based on BS EN 1097-1 [14] and were 2.66 and 1.92%, respectively.…”

Section: Methodsmentioning

confidence: 99%

External Sulphate Attack on Alkali-Activated Slag and Slag/Fly Ash Concrete

Bondar

Nanukuttan

2022

Buildings

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Two types of alkali-activated material (AAM) concretes were exposed to various sulphate bearing-solutions for over two years. Physical changes to the concrete specimen and chemical changes in the exposure liquid were studied in an attempt to understand how sulphate attack occurs in such binders and the role the mix variables play in offering resistance against such attack. The mix variables of alkali-activated slag concrete (AASC) included water-to-binder ratio, percentage of alkali, and the SiO2/Na2O ratio (silica modulus, Ms); for alkali-activated slag/fly ash (AA-S/F) concrete, the mix variables included slag/fly ash ratio and the SiO2/Na2O ratio. The exposure solutions included water, magnesium sulphate (5%), sodium sulphate (5%), calcium sulphate (0.2%), and two concentrations of sulphuric acid solutions, pH 3 and pH 1. The physical changes studied were length and mass change, visual appearance, and change in compressive strength. The exposure liquids were analysed for change in pH and ionic composition. Findings show that the AA-S/F blend performs better than AASC in sulphate environments, based on strength and change in length. Exposure to water resulted in the most expansion/shrinkage in all mixes studied. An empirical model was proposed for predicting the change in compressive strength for AAS&AA-S/F concretes based on mass gain. Further, a simple performance criterion was put forward for mixes in sulphate environments based on mass gain.

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Efficient mix design of alkali activated slag concretes based on packing fraction of ingredients and paste thickness

Cited by 53 publications

References 32 publications

The Use of Lightweight Aggregates in Geopolymeric Mortars: The Effect of Liquid Absorption on the Physical/Mechanical Properties of the Mortar

The Use of Lightweight Aggregates in Geopolymeric Mortars: The Effect of Liquid Absorption on the Physical/Mechanical Properties of the Mortar

Accelerated Carbonation of Vibro-Compacted Porous Concrete for Eco-Friendly Precast Elements

External Sulphate Attack on Alkali-Activated Slag and Slag/Fly Ash Concrete

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