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Materials 2016, 9(6), 466; doi:10.3390/ma9060466

Environmentally-Friendly Dense and Porous Geopolymers Using Fly Ash and Rice Husk Ash as Raw Materials

Department of Applied Science and Technology, INSTM Research Unit Polito, Lince Laboratory, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino 10129, Italy
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Academic Editor: Arie van Riessen
Received: 15 May 2016 / Revised: 1 June 2016 / Accepted: 8 June 2016 / Published: 14 June 2016
(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)
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Abstract

This paper assesses the feasibility of two industrial wastes, fly ash (FA) and rice husk ash (RHA), as raw materials for the production of geopolymeric pastes. Three typologies of samples were thus produced: (i) halloysite activated with potassium hydroxide and nanosilica, used as the reference sample (HL-S); (ii) halloysite activated with rice husk ash dissolved into KOH solution (HL-R); (iii) FA activated with the alkaline solution realized with the rice husk ash (FA-R). Dense and porous samples were produced and characterized in terms of mechanical properties and environmental impact. The flexural and compressive strength of HL-R reached about 9 and 43 MPa, respectively. On the contrary, the compressive strength of FA-R is significantly lower than the HL-R one, in spite of a comparable flexural strength being reached. However, when porous samples are concerned, FA-R shows comparable or even higher strength than HL-R. Thus, the current results show that RHA is a valuable alternative to silica nanopowder to prepare the activator solution, to be used either with calcined clay and fly ash feedstock materials. Finally, a preliminary evaluation of the global warming potential (GWP) was performed for the three investigated formulations. With the mix containing FA and RHA-based silica solution, a reduction of about 90% of GWP was achieved with respect to the values obtained for the reference formulation. View Full-Text
Keywords: geopolymers; mechanical properties; microstructure; porosity geopolymers; mechanical properties; microstructure; porosity
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Ziegler, D.; Formia, A.; Tulliani, J.-M.; Palmero, P. Environmentally-Friendly Dense and Porous Geopolymers Using Fly Ash and Rice Husk Ash as Raw Materials. Materials 2016, 9, 466.

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