Effect of silica modulus on the geopolymerization activity of natural pozzolans

Firdous, Rafia; Stephan, Dietmar

doi:10.1016/j.conbuildmat.2019.05.161

Cited by 61 publications

(50 citation statements)

References 35 publications

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“…In other words, this increase provided less degradation of the foam bubbles, thus forming a less dense paste with a greater and, consequently, less resistance to compression. This effect may be related to the decrease in the degree of geopolymer reaction when the silica modulus is increased [22,56]. The relationship between dry and saturated densities with the silica modulus can be seen in Fig.…”

Section: Resultsmentioning

confidence: 93%

Evaluation of the properties of a foamed geopolymer developed with different types of metakaolin

et al. 2021

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The physical and mechanical properties of foamed geopolymers were determined. The geopolymers were made with two different metakaolins (from Metacaulim do Brasil -MB, and Pantano Grande/RS -MPG) as precursors, with NaOH and Na 2 SiO 3 as activators, and with the addition of foam, which was produced with the foaming agent diethanolamide of coconut fatty acid with a minimum of 80% concentration. Also, two times (2.5 and 4 h) were used for the calcination of MPG at 750 °C. The results showed that all factors (precursors type, alkali content, silica modulus, and foam content) had a significant influence on the response variables, which presented the following variations: compressive strength of 0.36 to 3.23 MPa; thermal conductivity from 0.22 to 0.42 W/(m.K); saturated bulk density from 1176 to 1364 kg/m 3 ; dry bulk density of 619 to 864 kg/m 3 ; air void from 46.4% to 62.5%; and water absorption from 55.7% to 95.4%. It was also concluded that the precursor type was the factor that had the most influence on the properties of foamed geopolymers, with MPG calcined for 4 h being the best, as greater compressive strength and low thermal conductivity were obtained.

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Section: Resultsmentioning

confidence: 93%

Evaluation of the properties of a foamed geopolymer developed with different types of metakaolin

et al. 2021

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“…In general, high-ratio silicates are most suitable for chemical bonding because the siliceous portion of the silicate reacts with the cations. A low-ratio modulus, that is, <2.0, should only be used if the alkaline activation in the mixture is insufficient [ 91 ].…”

Section: Alkaline Activation Of Natural Volcanic Ashesmentioning

confidence: 99%

Volcanic Ash as a Sustainable Binder Material: An Extensive Review

2021

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The construction industry is affected by the constant growth in the populations of urban areas. The demand for cement production has an increasing environmental impact, and there are urgent demands for alternative sustainable solutions. Volcanic ash (VA) is an abundant low-cost material that, because of its chemical composition and amorphous atomic structure, has been considered as a suitable material to replace Portland cement clinker for use as a binder in cement production. In the last decade, there has been interest in using alkali-activated VA material as an alternative material to replace ordinary Portland cement. In this way, a valuable product may be derived from a currently under-utilized material. Additionally, alkali-activated VA-based materials may be suitable for building applications because of their good densification behaviour, mechanical properties and low porosity. This article describes the most relevant findings from researchers around the world on the role of the chemical composition and mineral contents of VA on reactivity during the alkali-activation reaction; the effect of synthesis factors, which include the concentration of the alkaline activator, the solution-to-binder ratio and the curing conditions, on the properties of alkali-activated VA-based materials; and the mechanical performance and durability properties of these materials.

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“…Remarkably, only 6.67 features (factors effecting the properties) are used on average to represent the composition of the material. The level of detail of the data considered is thus low relative to the complexity of alternative binders, as the properties of AAB are depended on several factors and the wide characteristics of aluminosilicate precursors and alkaline activators directly impact the properties of resultant AAB [8].…”

Section: Literature Reviewmentioning

confidence: 99%

“…Natural or artificial pozzolans, including granulated blast furnace slag, fly ash, metakaolin, or natural pozzolans, can be used as aluminosilicate sources [7]. However, the nature, chemical and mineralogical composition of the aluminosilicate precursor affect the properties of the resultant binder, such as fresh and hardened characteristics [8]. On the one hand, the wide variety of precursors available for the synthesis of AAB/GP makes them a suitable alternative binder for many applications.…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, such large variations in the precursor composition make it difficult to draw general valid rules to synthesize these binders with the expected properties. Moreover, the type and concentration of alkaline solution impact the reactivity of the aluminosilicate precursors used for AAB/GP [8]. Several publications have shown the potential of granulated blast furnace slag and fly ash as a precursor for AAB/GP [5].…”

Section: Introductionmentioning

confidence: 99%

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Sequential learning to accelerate discovery of alkali-activated binders

et al. 2021

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Alkali-activated binders (AAB) can provide a clean alternative to conventional cement in terms of CO2 emissions. However, as yet there are no sufficiently accurate material models to effectively predict the AAB properties, thus making optimal mix design highly costly and reducing the attractiveness of such binders. This work adopts sequential learning (SL) in high-dimensional material spaces (consisting of composition and processing data) to find AABs that exhibit desired properties. The SL approach combines machine learning models and feedback from real experiments. For this purpose, 131 data points were collected from different publications. The data sources are described in detail, and the differences between the binders are discussed. The sought-after target property is the compressive strength of the binders after 28 days. The success is benchmarked in terms of the number of experiments required to find materials with the desired strength. The influence of some constraints was systematically analyzed, e.g., the possibility to parallelize the experiments, the influence of the chosen algorithm and the size of the training data set. The results show the advantage of SL, i.e., the amount of data required can potentially be reduced by at least one order of magnitude compared to traditional machine learning models, while at the same time exploiting highly complex information. This brings applications in laboratory practice within reach.

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Effect of silica modulus on the geopolymerization activity of natural pozzolans

Cited by 61 publications

References 35 publications

Evaluation of the properties of a foamed geopolymer developed with different types of metakaolin

Evaluation of the properties of a foamed geopolymer developed with different types of metakaolin

Volcanic Ash as a Sustainable Binder Material: An Extensive Review

Sequential learning to accelerate discovery of alkali-activated binders

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