Fly ash-based boroaluminosilicate geopolymers: Experimental and molecular simulations

Bagheri, Ali; Nazari, Ali; Rajeev, Pathmanathan; Duan, Wenhui

doi:10.1016/j.ceramint.2016.12.020

Cited by 58 publications

(17 citation statements)

References 25 publications

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“…The decrease in the compressive strength of the pastes with sucrose, borax and the commercial retarder was 37%, 46% and 14%, respectively with reference to the paste without retarder. Previous studies also reported a decrease in compressive strength of “two-part” geopolymer when sucrose or borax was used as the retarder [44,45,67].…”

Section: Resultsmentioning

confidence: 99%

Efficiency of Different Superplasticizers and Retarders on Properties of ‘One-Part’ Fly Ash-Slag Blended Geopolymers with Different Activators

2019

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Currently, there are a very limited number of studies on the effect of admixtures on properties of ‘one-part’ geopolymers. This paper reports the effects of different superplasticizers and retarders on fresh and hardened properties of one-part fly ash-slag blended geopolymers made by different solid activators. Two different grades of sodium silicate, namely anhydrous sodium metasilicate powder (nSiO2/nNa2O = 0.9) and GD Grade sodium silicate powder (nSiO2/nNa2O = 2.0) were used as the solid activators. Five different commercially available superplasticizers, including three modified polycarboxylate-based superplasticizers (denoted as PC1, PC2, and PC3) and two naphthalene-based superplasticizers (denoted as N1 and N2), as well as three different retarders, including sucrose, anhydrous borax and a commercially available retarder, were investigated. Workability, setting time and compressive strength of the mixtures without and with addition of each ‘individual’ admixture were measured. The results showed the effect of admixtures on the properties of the one-part geopolymers significantly depended on the type of solid activator and the type of admixture used. When GD Grade sodium silicate powder was used as the solid activator, all investigated admixtures not only had no positive effect on the workability and setting time, but also significantly reduced the compressive strength of the mixture. However, when anhydrous sodium metasilicate powder was used as the solid activator, the PC1 and sucrose were the best performing superplasticizer and retarder, respectively, causing no reduction in the compressive strength, but significant increase in the workability (up to + 72%) and setting time (up to + 111%), respectively as compared to the mixture with no admixture. In addition, the results also showed that addition of ‘combined’ admixtures (i.e., PC1 in the presence of sucrose) significantly increased the workability (up to + 39%) and setting time (up to + 141%), but slightly reduced the compressive strength (−16%) of the mixture activated by anhydrous sodium metasilicate powder, as compared to the mixture with no admixture.

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Section: Resultsmentioning

confidence: 99%

Efficiency of Different Superplasticizers and Retarders on Properties of ‘One-Part’ Fly Ash-Slag Blended Geopolymers with Different Activators

2019

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“…It is present in nature in many kinds of minerals, and its main salts (borates) are not considered toxic substances [ 21 ]. There have been some studies regarding geopolymers with the addition of various boron compounds, such as borax, anhydrous borax, boric acid, amorphous and crystalline lithium tetraborate, and colemanite [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. Boron may also be introduced to a geopolymer matrix when the raw aluminosilicate material contains this element.…”

Section: Introductionmentioning

confidence: 99%

Immobilization of Heavy Metals in Boroaluminosilicate Geopolymers

et al. 2021

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Boroaluminosilicate geopolymers were used for the immobilization of heavy metals. Then, their mechanical properties, phase composition, structure, and microstructure were investigated. The addition of borax and boric acid did not induce the formation of any crystalline phases. Boron was incorporated into the geopolymeric network and caused the formation of N–B–A–S–H (hydrated sodium boroaluminosilicate) gel. In the range of a B/Al molar ratio of 0.015–0.075, the compressive strength slightly increased (from 16.1 to 18.7 MPa), while at a ratio of 0.150, the compressive strength decreased (to 12 MPa). Heavy metals (lead and nickel) were added as nitrate salts. The loss of the strength of the geopolymers induced by heavy metals was limited by the presence of boron. However, it caused an increase in heavy metal leaching. Despite this, heavy metals were almost entirely immobilized (with immobilization rates of >99.8% in the case of lead and >99.99% in the case of nickel). The lower immobilization rate of lead was due to the formation of macroscopic crystalline inclusions of PbO·xH2O, which was vulnerable to leaching.

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“…Hence, changing the composition of alkaline activator of geopolymers in order to introduce new binders has been the topic of many types of research. [19][20][21][22][23] Many efforts have been made to substitute the silicon and aluminium atoms of the geopolymer matrix with other elements. Boron-based geopolymer is one of them that was introduced in previous studies.…”

Section: Introductionmentioning

confidence: 99%

Formulation of mix design for 3D printing of geopolymers: a machine learning approach

Bagheri

Crémona

2020

Mater. Adv.

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Fly ash-based boroaluminosilicate geopolymers: Experimental and molecular simulations

Cited by 58 publications

References 25 publications

Efficiency of Different Superplasticizers and Retarders on Properties of ‘One-Part’ Fly Ash-Slag Blended Geopolymers with Different Activators

Efficiency of Different Superplasticizers and Retarders on Properties of ‘One-Part’ Fly Ash-Slag Blended Geopolymers with Different Activators

Immobilization of Heavy Metals in Boroaluminosilicate Geopolymers

Formulation of mix design for 3D printing of geopolymers: a machine learning approach

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