Publications Internationales

Permanent URI for this collectionhttps://dspace.univ-boumerdes.dz/handle/123456789/13

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Author: search.filters.author.Irekti, AmarSubject: search.filters.subject.Geopolymer

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    Mechanical performance of metakaolin-based geopolymer mortar blended with multi-walled carbon nanotubes
    (Elsevier, 2022) Oualit, Mehena; Irekti, Amar
    In recent decades, the cement industry has been viewed as a major environmental problem mainly due to carbon dioxide CO2 emissions during the production of Portland Cement (PC). Among the solutions to this problem is to replace Portland cement-based materials with alkali-activated materials. Metakaolin-based geopolymer mortars are currently considered a serious alternative to ordinary Portland cement mortar due to its various advantages. The present experimental study aims to develop metakaolin-based geopolymer mortars reinforced with multi-walled carbon nanotubes (MWCNTs). The content of MWCNTs incorporated was 0.1; 0.2; 0.3, and 0.4 wt%, respectively, with respect to the mass of metakaolin. A mixture without the addition of carbon nanotubes was also prepared and used as a reference (control sample). The alkaline activation of metakaolin was carried out using aqueous sodium silicate solution having a molar ratio (SiO2/Na2O) equal to 1.77. Mechanical characterization of the hardened samples was performed after curing for 3, 7 and 28 days. The results indicate that the incorporation of multi-walled carbon nanotubes in the geopolymer matrices improves compressive strength. Microscopic analysis has shown that these carbon nanotubes contribute to the densification of the geopolymer matrix and give rise to crack bridging mechanisms. The highest value of the compressive strength was recorded using an alkali silicate content equal to 8 (expressed as a percentage of Na2O) combined with 0.2% of multi-walled carbon nanotubes in the geopolymer mortar. The integral absolute error (IAE) calculated on the compressive strength values at different curing ages are all within an acceptable range (0–10%)
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    Strength and setting times of Metakaolin-Cement-Based geopolymer pastes
    (2017) Oualit, Mehena; Irekti, Amar; Jauberthie, Raoul
    The objective of this research is, in a first time, to synthesize geopolymer materials from two types of activator concentrated solutions prepared respectively with two different bases (NaOH and KOH). These solutions have been mixed thereafter with a kaolin previously heated under 550°C in order to obtain geopolymers samples, while optimizing the Si/Al ratio. Secondly, the influence of the partial substitution of metakaolin by a Portland cement has been studied in order to reduce the curing time of geo-polymer pastes. Thereafter, mechanical properties of the specimens at hardened state, notably the compressive strengths and the resistances on traction are investigated. The results showed that the use of the activator solution containing KOH during the preparation of the activator solution increases the solubility between KOH and silica gel. However, the solution based on sodium hydroxide (NaOH) promotes obtaining better mechanical resistances in the geopolymer materials. Otherwise, the partial substitution of metakaolin by Portland cement (PC) reduces the setting time of pastes and improves the mechanical resistances of hardened specimens but to a certain percentage before inverse effect appears. Finally, recommendations and perspectives are proposed in relation with the used raw materials and the mechanical performances of the geo-polymers materials found