Design and characterization of Cameroonian pegmatite-calcined clay binary mortars via geopolymerisation

In this work, geopolymer binders obtained from a mixture of Cameroonian pegmatite and type 1/ 1 calcined clays (metakaolin and metahalloysite) at different proportions (10-30 wt%) were used for the formulation of mortars. The kinetic parameters of the reactivity of the pegmatite mixed with different calcined clays in an alkaline medium were evaluated via the heat of reaction data measured at an isothermal conduction calorimeter (ICC) at 27 degrees C for the first 24 h. As feedstock precursors, the different products obtained were characterized by means of mechanical flexural and compressive resistances (dry and wet), physical properties, Fourier Transform infrared spectroscopy and Scanning Electron Microscope. The results showed that the compressive strength values vary with the type and percentage of calcined clays. The highest values were achieved with mortars containing 30 wt% of the different calcined clays, ranging from approximately 25-35 MPa in dry conditions. The flexural strength values of the mortars increase also with the incorporation of calcined clay and vary from 1.0 to 4.5 MPa. After 72 h of immersion of these samples in water, they lost less than 60% of their mechanical performance. The water absorption rate of the mortars decreases with the incorporation of calcined clays and ranges from 7.5 to 13.8%. FT-IR indicated the reactivity of pegmatite during the geopolymerisation process while SEM micrographs exhibited a better cohesion between the aggregates (river sand, 200 & mu;m & LE; ɸ & LE; 2000 & mu;m) and the binder. The above-mentioned pegmatite-calcined clay mortars appear to be a suitable candidate for engineering applications (civil engineering)

Particles size and distribution on the improvement of the mechanical performance of high strength solid solution based inorganic polymer composites: A microstructural approach

This research reports on the influence of particle size and distribution on the physical, mechanical and microstructural features of solid solutions (feldspathic materials) based inorganic polymer composites (IPCs). Both granite and pegmatite were ground to different degree of finess making four different granulometry with particles of 63, 80, 125 and 200 μm. The respective mixes receive 15 wt% of metakaolin and were activated with a well designed alkaline solution. Matrices obtained showed high compressive and flexural strengths in the range 101.2–131.3 MPa, and 29–35.5 MPa, respectively. It was observed that the optimum mechanical performance of these matrices can be achieved through a mix-design of different grades of granulometry. This was suggested by mechanism combining reactivity and particles packing. In fact, although it can be expected that the finess of the combination of the particles size under 63 μm might present the better reactivity, it is showing that the combination of fine, medium and coarse particles is efficient in achieving denser and tougher microstructure. Lower cumulative pore volume (17 mL g−1) of the composites based on pegmatite, value not far from that of natural stones, resulted in a higher impact resistance of 3.03 J. It was concluded that designing the feldspathic rock-based composites with high strengths appear as sustainable, low energy consumption and environmentally-friendly materials for the structural construction

Structural and Physico-mechanical Investigations of Mine Tailing-Calcined Kaolinite Based Phosphate Geopolymer Binder

This work explores the possibility of using Mine tailing (MT) as a feedstock in the synthesis of phosphate geopolymer binder. MT was activated at different concentrations of phosphoric acid (4, 6, 8, 10 and 12 M). The modification of the Si/Al weight ratio was done by the incorporation of 5, 10, 15, 20 and 25 wt% of calcined kaolinite (CK). After 28 days of curing, the products obtained were analyzed using XRD, FTIR, compressive strength and water absorption. The results of the XRD and FTIR analyses reveal a partial dissolution of the crystalline phase of iron oxide in this medium and the formation of aluminium phosphate hydrate as new crystalline phase. The optimum values of compressive strength (45.5 MPa) and water absorption (3.0 %) show that the binder obtained by activation with 6 M phosphoric acid and 10 wt% CK incorporation can be used in the manufacture of structural materials. Acid activation of MT thus appears as an innovative way to recycle these fine wastes in the synthesis of geopolymer

Comparison of feldspar and meta-halloysite geopolymers by alkaline and acidic activation

Geopolymerisation, a sustainable route to advanced binders, has traditionally been explored using common activators and single precursors such as metakaolin. Although previous investigations have explored the potential of feldspathic minerals, particularly with metakaolin as a partial replacement, there remains a gap in understanding the nuances of feldspar-phosphate-based geopolymers. This study seeks to fill this gap by providing an in-depth investigation of the properties and reactivity behavior of three different feldspar quarry wastes, each modified with meta-halloysite at a 15% inclusion rate. This research not only evaluates the effects of both acidic and alkaline activators on the resulting geopolymer properties but also explores the broader implications of such modifications in different environments at ambient conditions. Using a series of experimental assessments, we have explored how the mineralogical and crystalline identities of these feldspars influence key aspects such as reaction kinetics, physico-mechanical performance, structural and microstructural properties, and even thermal behavior. The results of the physicomechanical properties showed that lower water absorption (i.e. less than 9.2%) as well as higher flexural (i.e. about 30 MPa) and compressive strength (i.e. about 40 MPa) can be achieved with the feldspar-based geopolymer in alkaline medium. In acidic medium, the highest flexural and compressive strengths were less than 10 and 19 MPa, respectively, with about 13.5% of water absorption. In acidic to basic medium, the highest cumulative pore volume of the geopolymers increases from 26.5 to 75.2 mm3/g, respectively. The outcomes of this study hold promise for tailoring geopolymer properties for various applications and provide a basis for further work in this area

Biodiesel Production From High-free Fatty Acids Podocarpus falcatus Oil and Identification of Fatty Acid Methyl Esters by FT-IR, NMR (1H and 13C) and GC/MS Studies

Biodiesel occupies a prominent place as the alternative fuel to fossil diesel owing to socio-economic and environmental factors. In this present study, Podocarpus falcatus oil (PFO), having undergone a storage effect, was converted into biodiesel. PFO had a high fatty acid content (FFA = 8.19%). For this reason, a two-step transesterification procedure was developed to convert this high-free fatty acid (FFA) oils into their corresponding monoesters. In the initial step, an acid-catalyzed esterification was employed to lower the FFA content of the oil to below 2%. Subsequently, a second step involving an alkaline catalysis transesterification process was used to convert the product obtained in the first step into monoesters and glycerol. The methyl esters obtained were analyzed using nuclear magnetic resonance (H-1, C-13 NMR), Fourier transform infrared spectroscopy (FT-IR), Thermal gravimetric analysis (TGA), carbon, hydrogen, nitrogen, and sulfur (CHNS), and Gas chromatography-mass spectrometry (GC-MS) analysis. The identity FAME were Hexadecanoic acid, methyl ester (C16:0), 9,11-Octadecadienoic acid, methyl ester, (E, E)- (C18:0), 6-Octadecenoic acid, methyl ester, (Z)- (C18:2), Methyl stearate (C18:1), Methyl (Z)-5,11,14,17-eicosatetraenoate (C20:5), 11,14-Eicosadienoic acid, methyl ester (C20:3), 11-Eicosenoic acid, methyl ester (C20:2). The study examined the thermal stability of synthesized biodiesel, revealing it remained stable up to 189 degrees C. Furthermore, the physicochemical properties of biodiesel were validated using ASTM6751 standards