Browsing by Author "Holmer Savastano"

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    Development of unfired earthen building materials using muscovite rich soils and alkali activators
    (Case Studies in Construction Materials, 2019) Emeso Beckley Ojo; Kabiru Mustapha; Ronaldo S. Teixeira; Holmer Savastano
    Most studies have focused on the alkali activation of thermally activated kaolinitic clays for the production of innovative building materials. Whilst the widespread use of these minerals may be hindered due to geographical availability; a combination of thermal activation and alkali activator solutions yields a material with high embodied energy with implications on eco-friendliness. This study presents an eco-friendly approach for the development of a low environmental impact building material using a low molarity alkali activator solution for the stabilisation of uncalcined muscovite rich soil. Influence of curing conditions on the physical, mechanical, microstructural and mineralogical properties were evaluated. Results show that alkali activation of uncalcined muscovite in the soil significantly improved the physical and mechanical properties of extruded earthen materials. Samples tested yielded compressive strength values between 9–11 MPa for varying curing regimes. The binding was mainly attributed to the formation of amorphous sodium aluminosilicate gels as a result of the partial dissolution of muscovite. These results show that low environmental impact building materials may be developed with uncalcined muscovite rich soils in developing regions around the world where these minerals are predominant for the provision of sustainable low-cost housing solutions.
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    Effects of fibre reinforcements on properties of extruded alkali activated earthen building materials
    (2019-12-10) Emeso B. Ojo; Kabirat O. Bello; Kabiru Mustapha; Ronaldo S. Teixeira; Sérgio F. Santos; Holmer Savastano
    The reaction between clay minerals present in soil and an alkaline solution has the potential to develop in situ binders, which can be harnessed in the development of earth based construction materials. To ascertain the efficacy of this stabilisation mechanism in conjunction with fibres which are commonly used in earthen construction, this study presents a comparative analysis of the reinforcing effect of different fibre types (sisal, Eucalyptus pulp microfibers and polypropylene) in an alkali activated stabilised soil produced using extrusion technique. An evaluation of flexural properties in oven-dry and saturated conditions was conducted to simulate mechanical response in ideal and extreme conditions to evaluate effect of fibre type and content (0–2 vol%). Physical properties were also studied and optimum fibre contents evaluated. Results show that with respect to lignocellulosic fibres, sisal fibre reinforcements yielded the most remarkable result with the highest statistically significant improvement in flexural strength (79% relative to the unreinforced matrix) compared to composites reinforced with Eucalyptus pulp micro-fibres. Improved packing density and attendant reduction in water absorption associated with sisal fibre reinforced composites was attributed to synergistic interactions between sisal fibres and alkali activated matrix. On the other hand, synthetic fibre reinforcement (polypropylene), which had no statistically significant effect on composite flexural strength, transformed brittle unreinforced matrices to deflection hardening composites due to weak fibre-matrix interactions. Sisal fibres have thereby demonstrated a significant reinforcing potential in extruded alkali activated earth-based materials and presents a satisfactory balance of strength, density and ductility for the development of eco-friendly building materials for low cost housing solutions.
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    Mechanical performance of fiber-reinforced alkali activated un-calcined earth-based composites
    (2020) Emeso B. Ojo; Kabirat O. Bello; Odette F. Ngasoh; Tido T. Stanislas; Kabiru Mustapha; Holmer Savastano; Wole Soboyejo
    This paper presents the results of a multi-scale study of the mechanical properties of model earth-based composites. The composites are produced by the alkali activation of in-situ clay minerals within an earthbased matrix that is reinforced with two different fibers (sisal and polypropylene). The local mechanical properties of the fibers, binder and matrix materials are characterized at the nano- and micro-scales using nano-indentation and statistical deconvolution techniques. The macro-mechanical properties are also elucidated using a combination of flexural strength testing, and resistance-curve experiments. The underlying strengthening and toughening mechanisms are explored using a combination of in-situ/exsitu observations and micro-mechanical models. The implications of the results are then discussed for the design of strengthened and toughened earth-based composites that are reinforced with natural fibers (such as sisal) and synthetic fibers (such as polypropylene fibers).