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  Scopus ID: 21100926589

Study of the Influence of Na2CO3 and H3PO4 Activators on the Mechanical and Mineralogical Properties of Geopolymer Based on Coal Waste-fly Ash

Hassan Ez-zaki, Saida Ennaji, Ayoub Aziz, Nacer Khachani and Abdeljebbar Diouri

Abstract

This work aims to compare the mechanical and mineralogical properties of coal waste and fly ash based geopolymers obtained in the same conditions using sodium carbonate (Na2CO3) and phosphoric acid (H3PO4) solutions as diverse activators. Na2CO3 solutions with 3.5% and 5% mass ratios were prepared by dissolving Na2CO3 powder (99.9%) in deionized water. On the other hand, three H3PO4 solutions with molar concentrations of 4, 6, and 8 M were prepared by dilution of the commercial H3PO4 (85%) in distilled water. Both types of alkaline and acidic solutions were used to produce geopolymers from the coal waste which is systematically replaced by fly ash (0, 15, 25, and 35 wt.%). The geopolymers were obtained by adding each of the prepared solutions to the blend with a liquid/solid ratio of 0.5 and 0.6 for the alkaline and acid solutions, respectively. The mechanical tests of cubic samples after 28 days of curing showed that the compressive strength of phosphate-based geopolymers is 5.33 MPa while that of alkali-based geopolymers is 5.14 MPa. The strength increases with the increase of the activator concentration. The mineralogical analysis of cured samples after 28 days showed the formation of berlinite (AlPO4) in the structure of the phosphate-based geopolymer which is dispersed in the matrix and contributes to the strength. For alkali geopolymers, X-ray diffraction results showed the existence of Portlandite crystalline phase and the N-A-S-H gel type.

Published on: September 27, 2023
doi: 10.17756/nwj.2023-s2-048
Citation: Ez-zaki H, Ennaji S, Aziz A, Khachani N, Diouri A. 2023. Study of the Influence of Na2CO3 and H3PO4 Activators on the Mechanical and Mineralogical Properties of Geopolymer Based on Coal Waste-fly Ash.NanoWorld J 9(S2): S281-S287.

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