Influence of the molar concentration of phosphoric acid solution on the properties of metakaolin-phosphate-based geopolymer cements

By H. K. Tchakouté, C. Rüscher, E. Kamseu, F. Andreola, C. Leonelli. 2017

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Abstract Six different phosphoric acid solutions with molar concentrations 4, 6, 8, 10, 12 and 14 M were prepared by dilution of commercial phosphoric acid in distilled water. The obtained phosphoric acid solutions were used for producing metakaolin-phosphate-based geopolymer cements. These geopolymer cements were obtained by adding each fresh prepared phosphoric acid solution to metakaolin with a mass ratio phosphoric acid solution/metakaolin = 0.80. It was observed in the infrared spectra of phosphoric acid solutions 8, 10, 12 and 14 M, the absorption bands at 875–879 and 949–972 cm − 1 which are assigned to H 2 PO 4 − . The SEM images of geopolymer cements exhibit the presence of berlinite (AlPO 4 ) which is dispersed in the matrix and contributes to enhancing the strength, whereas the geopolymer cements from phosphoric acid solution with 14 M are heterogeneous microstructures. The compressive strength of phosphate-based geopolymer cements was between 36.4 and 93.8 MPa; it increased with increasing the concentration of phosphoric acid solutions up to 10 M. It can be concluded that the most convenient concentration of phosphoric acid solution required for producing phosphate-based geopolymer cements with good mechanical properties is around 10 M.

Subfields: Civil and Structural Engineering, Industrial and Manufacturing Engineering, Materials Chemistry

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