The feasibility of using kaolins activated at T = 550 degrees C to synthesize geopolymers has been assessed, opening the way for utilizing low-grade kaolins containing sulfates. The effects of temperature (in the range 40-90 degrees C) and time (in the range 1-19 h) of curing, as well as of a secondary drying treatment on compressive strength and linear shrinkage of geopolymers have been studied by experimental design technique using a high-quality kaolin as starting material. Geopolymers characterized by high strength (>60 MPa) and low shrinkage (<1%) have been obtained when long curing times are applied at T<65 degrees C, while the oven-drying treatment is demonstrated not to improve geopolymer performances. Geopolymers synthesized starting from an alunite-bearing kaolin activated at 550 degrees C and cured at the conditions suggested by the statistical model showed good compressive strength and shrinkage. All geopolymers have been characterized by thermal analysis, X-ray powder diffraction and infrared spectroscopy. (C) 2015 Elsevier B.V. All rights reserved.

Geopolymers from low-T activated kaolin: Implications for the use of alunite-bearing raw materials

Tarantino S;Zema M
2015

Abstract

The feasibility of using kaolins activated at T = 550 degrees C to synthesize geopolymers has been assessed, opening the way for utilizing low-grade kaolins containing sulfates. The effects of temperature (in the range 40-90 degrees C) and time (in the range 1-19 h) of curing, as well as of a secondary drying treatment on compressive strength and linear shrinkage of geopolymers have been studied by experimental design technique using a high-quality kaolin as starting material. Geopolymers characterized by high strength (>60 MPa) and low shrinkage (<1%) have been obtained when long curing times are applied at T<65 degrees C, while the oven-drying treatment is demonstrated not to improve geopolymer performances. Geopolymers synthesized starting from an alunite-bearing kaolin activated at 550 degrees C and cured at the conditions suggested by the statistical model showed good compressive strength and shrinkage. All geopolymers have been characterized by thermal analysis, X-ray powder diffraction and infrared spectroscopy. (C) 2015 Elsevier B.V. All rights reserved.
2015
Istituto di Geoscienze e Georisorse - IGG - Sede Pisa
geopolymers
metakaolin
compressive strength
shrinkage
curing
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/295194
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