Journal ArticleDOI
Rational utilization of volcanic ashes based on factors affecting their alkaline activation
TLDR
In this paper, the authors evaluated the criteria that affect the characteristics of both volcanic ashes and their alkaline activated products, hence their rational utilization, and showed that volcanic ashes could be used either for geopolymer synthesis or as filler.Abstract:
The present study evaluates the criteria that affect the characteristics of both volcanic ashes and their alkaline activated products, hence their rational utilization. To that end, five samples of volcanic ash were examined chemically, mineralogically and physically whereas certain characteristics of their alkaline activated products were determined. In order to elucidate the relationship between the characteristics of volcanic ashes and the products of their alkaline activation, mechanical strength, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) of geopolymer specimens aged 14 days were examined. Volcanic ashes with large amount of amorphous phase (18.2–42.5% by mass) led to geopolymers with compressive strengths of 3.1–12.6 MPa. As for volcanic ashes with small amount of amorphous phase (10.2–12.5% by mass), alkaline activation at 80 °C led to geopolymers with compressive strength of 1.0–4.1 MPa. The results obtained showed that volcanic ashes could be used either for geopolymer synthesis or as filler. The classification depended mostly on the amount and the SiO2/Al2O3 molar ratio of amorphous phase.read more
Citations
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The past and future of sustainable concrete: A critical review and new strategies on cement-based materials
Jorge de Brito,Rawaz Kurda +1 more
TL;DR: A global and extensive review is made here to provide an overall view of concrete sustainability in all possible paths and to open the minds of the readers to the vastly unexplored world of “green concrete”.
Journal ArticleDOI
Natural pozzolan based geopolymers: A review on mechanical, microstructural and durability characteristics
TL;DR: In this article, a review paper summarizes the mechanical and durability characteristics as well as the microstructural properties of natural pozzolan based geopolymers and their potential as binding material.
Journal ArticleDOI
Enhancing the reactivity of aluminosilicate materials toward geopolymer synthesis
L.N. Tchadjié,Stephen O. Ekolu +1 more
TL;DR: A comprehensive review of the main methods used to alter the reactivity of aluminosilicate materials for geopolymer synthesis is presented in this article, which consists of mechanical, thermal, physical separation and chemical activation, of which mechanical activation is the most commonly employed technique.
Journal ArticleDOI
Review on the use of volcanic ashes for engineering applications
Patrick N. Lemougna,Kaituo Wang,Qing Tang,Aubin Nzeugang Nzeukou,Ndigui Billong,U. Chinje Melo,Xuemin Cui +6 more
TL;DR: In this paper, a review summarizes the main interesting research outcomes on volcanic ashes in the fields of cements and concretes, geopolymers, ceramics, low grade refractory materials, lunar soil simulants and adsorbents.
Journal ArticleDOI
Natural volcanic pozzolans as an available raw material for alkali-activated materials in the foreseeable future: A review
TL;DR: In this paper, the most important findings about mechanical performance and durability reported by researchers at a global level are presented and described, and a constructive analysis is carried out in order to establish the future challenges and opportunities to carry out a technological transition of these advances (industrial application) in countries rich in materials derived from volcanic activity.
References
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Journal ArticleDOI
Composition and Microstructure of Alkali Activated Fly Ash Binder: Effect of the Activator
TL;DR: In this paper, the relationship between the mineralogical and microstructural characteristics of activated fly ash mortars and its mechanical properties has been established, and the results of the investigation show that in all cases (whatever the activator used) the main reaction product formed is an alkaline aluminosilicate gel, with low-ordered crystalline structure.
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Kinetics of geopolymerization: Role of Al2O3 and SiO2
TL;DR: In this article, the early stage reaction kinetics of metakaolin/sodium silicate and sodium hydroxide geopolymer system were investigated, and the setting and early strength development characteristics, and associated mineral and microstructural phase development of mixtures containing varying SiO 2 /Al 2 O 3 ratios, cured at 40°C for up to 72h, were carefully studied.
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Characterisation of fly ashes. Potential reactivity as alkaline cements
TL;DR: In this article, a representative group of Spanish fly ashes has been characterised in order to determine its capacity for being alkali activated and give place to a material with cementitious properties.
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Alkali activation of fly ash: Effect of the SiO2/Na2O ratio Part I: FTIR study
TL;DR: In this paper, the main reaction products formed in alkali activated fly ash systems have been studied by using Infrared Spectroscopy, and it has been shown that there is an asymmetric stretching band associated with that aluminosilicate-type gel, which can be interpreted in terms of that gel showing two different types of Si-O bonds: bridge and terminal bonds.
Journal ArticleDOI
Effect of SiO2 and Al2O3 on the setting and hardening of high calcium fly ash-based geopolymer systems
Prinya Chindaprasirt,Pre De Silva,Kwesi Sagoe-Crentsil,Kwesi Sagoe-Crentsil,Sakonwan Hanjitsuwan +4 more
TL;DR: In this paper, the effect of varying silica and alumina contents on setting, phase development, and physical properties of high calcium fly ash (ASTM Class C) geopolymers was investigated by adjusting SiO2/Al2O3 ratio of the starting mix, via series of mixes formulated with varying SiO 2 or Al2O 3 contents to achieve Si O 2/Al 2O3 in the range 2.87-4.79.