The Influence of Rice Husk Ash Addition on the Properties of Metakaolin-Based Geopolymers
Paulo H. R. Borges1, *, Vitor A. Nunes1, Tulio H. Panzera2, Giorgio Schileo3, Antonio Feteira3
1 Department of Civil Engineering, Federal Centre for Technological Education of Minas Gerais, Av. Amazonas 7675, 30510-000, Belo Horizonte, Brazil
2 Department of Mechanical Engineering, Federal University of São João del Rei, São João Del Rei, Brazil
3 Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield, S1 1WB, UK
This paper investigates the replacement of metakaolin (MK) with rice husk ash (RHA) in the production of alkali-activated binders or geopolymers. The influence of the RHA addition on compressive and flexural strength, as well as water absorption and apparent porosity were determined, in terms of the percentage of RHA in the mixture and molar ratios of the mixes. Fourier Transform Infrared (FTIR) spectroscopy and Energy Dispersive spectroscopy (EDS) were carried out to assess the changes in the microstructure of the geopolymer matrices with the RHA addition. Results have shown that RHA may be a supplementary precursor for geopolymers. The composition of the geopolymer matrices containing 0-40% RHA is very similar, which indicates that the additional Si provided by RHA is not incorporated to the geopolymer matrix. In addition, geopolymers with RHA content higher than 40% present a plastic behavior, characterized by extremely low strength and high deformation, which can be attributed to the formation of silica gel in formulations containing variable Si/Al ratio.
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* Address correspondence to this authors at the Department of Civil Engineering, Federal Centre for Technological Education of Minas Gerais, Av. Amazonas 7675, 30510-000, Belo Horizonte, Brazil; Tel: +55 31 3319 6826; E-mail: email@example.com