Mechanical and physical properties of stabilised compressed coal bottom ash blocks with inclusion of lateritic soils in Niger

This is the final version. Available on open access from Elsevier via the DOI in this recordThis paper describes the results from an investigation on the production of compressed block made with coal combustion by-products and local clayey soil in Niger. Stabilisation with Portland cement and a mixture of Portland cement and lime was adopted. Mechanical, physical, hydric, and thermal characterisation of the produced bricks was carried out. Blocks with satisfactory compressive strength were produced, with samples consistently exceeding the compressive strength of 4 MPa. Stabilisation with Portland cement proved to be the most effective in terms of strength development. However, satisfactory results were obtained with partial substitution of cement with lime (up to 30%). Porosity was found to be in the range 33% to 40% for all samples. The low thermal conductivity (in the range 0.31 to 0.48 W/m•K) was presumably influenced by the high porosity. Water absorption of the bricks was found to be very fast, although total water absorption (in the range 20.6 to 28.7%) was lower than the calculated porosity, suggesting that some of the pores were not accessible by water. Samples subjected to heating showed very promising results in terms of strength and mass loss. An increase in compressive strength was recorded up to temperatures of 400°C. This might be due to the triggering of other reactions in the binding matrix due to the chemistry of the bottom ash. A change in colour of samples (from grey to red) was observed, due to the dehydroxilation of iron hydroxide turning into ferric oxide

Development of Cement Stabilised Compressed Blocks Using Coal Bottom Ash: Influence of the Grain Size on Mechanical and Physical Properties of Blocks

This is the final version. Available on open access from Tecno Scientifica Publishing via the DOI in this recordThis study investigated the physical and mechanical properties of cement-stabilized compressed blocks manufactured with coal bottom ash sourced from a power plant in Niger. Three different grain sizes were used for the production of compressed blocks with a hand-operated press. Thermal, hydric, mechanical, and fire resistance properties were assessed on the samples. It was found that the use of finer bottom ash resulted in lighter blocks with a density of about 1.02 mg/m3 and thermal conductivity in the range of 0.27 – 0.41 W/m·K. The size of the bottom ash used for the production of blocks did not significantly affect the value of mechanical strength. The exposure of blocks to temperatures of 200°C and 400°C did not reduce the strength of the samples. Neat bottom ash blocks can offer better thermal properties than typical building materials and provide acceptable mechanical strength.Sonicha

Hygrothermal Features of Laterite Dimension Stones for Sub-Saharan Residential Building Construction

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Production de biomasse de Brachiaria ruziziensis (Germain et Evrard) en vue de la mise en place de systèmes de culture sous couvertures végétales dans la zone cotonnière du Cameroun

Résumé Les systèmes de culture sous couvertures végétales vulgarisés dans la zone cotonnière du Nord Cameroun reposent sur la production en première année de fortes biomasses sur lesquelles sont installées les cultures subséquentes. La présente étude avait pour objectif d’évaluer la production de biomasse de l’espèce Brachiaria ruziziensis en tête de rotation dans les systèmes de culture de la zone cotonnière du Cameroun, en présence des fumures organique et minérale recommandées. La production moyenne de biomasse de l’espèce B. ruziziensis a été significativement différente entre les sites de Guiring, Djalingo et Touboro au Nord, au Centre et au Sud de la zone cotonnière, respectivement. Le site de Touboro a été le plus productif (20,2 t MS ha-1), suivi de Guiring (11,7  t MS ha-1) et Djalingo (8,6  t MS ha-1). Les quantités de biomasse ainsi obtenues sont suffisantes pour l’installation des systèmes de culture sous couverture végétale l’année subséquente. Les différences observées entre les sites recommandent une évaluation de leur potentiel de production de biomasse avant la mise en place des systèmes de culture vulgarisés. La fertilisation recommandée devrait être maintenue, bien qu’elle soit générale pour l’ensemble des graminées, en attendant que des essais pour la détermination des doses optimales utilisant une gamme plus étendue de nutriments soient effectués. Mots clés: Agriculture de conservation, Plante de couverture, Brachiaria ruziziensis,  biomasse.   Abstract Direct seeding mulch-based cropping systems that have been recently introduced in Northern Cameroon recommend sowing cover crops in the first year of rotations which are followed by subsequent crops of interest. The objective of this study was to evaluate the seeding year biomass production of Brachiaria ruziziensis in the cotton producing zone of Cameroon, under recommended organic and mineral fertilizer rates. Biomass production of B. ruziziensis was significantly different among the experimental sites. The highest dry matter yield was recorded in Touboro (20.2 t DM ha-1), followed by Guiring (11.7 t DM ha-1) and Djalingo (8.6 t DM ha-1), stations located to the South, North and Centre of the cotton production zone, respectively. These biomasses are enough for the implementation of direct seeding mulch-based cropping systems. The differences observed among sites suggest their evaluation for biomass production before the use of such systems. Though common to all grasses, the present fertilizer recommendations should be maintained but further work is needed for the determination of optimal fertilizer recommendations using a more extended nutrient scale. Key words: Conservation agriculture, Cover crop, Brachiaria ruziziensis, biomass