Browsing by Author "Kareem MA"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Investigation on thermal properties of rice husk ash-blended palm kernel shell concrete
    (2021) Raheem AA; Oriola KO; Kareem MA; Abdulwahab R
    The contribution of buildings to climate change as a result of energy consumption and greenhouse gas emissions necessitates the use of agro-industrial by-products as alternative construction materials. The present study examines the thermal properties of Rice husk ash-blended Palm Kernel Shell Concrete (RHA-blended PKSC). Three control concrete mixes with mix ratios of 1:1½:3, 1:2:4 and 1:3:6 using water-to-cement (w/c) ratios of 0.5, 0.6 and 0.7, respectively were made with cement, river sand and granite. For each mix ratio with the respective w/c ratio, five concrete mixes containing RHA fixed at 15% as replacement for cement and PKS at 20, 40, 60, 80 and 100% as replacement for crushed granite were produced. The oven-dry density, compressive strength and thermal properties (thermal conductivity, thermal diffusivity, volumetric heat capacity and thermal resistivity) were determined. The results showed that the oven-dry density and compressive strength of concrete declined with increasing PKS content. Nevertheless, the compressive strength increased with curing age and the gain in strength of RHA-blended PKSC were higher than the control at the later age. The thermal conductivity and diffusivity decreased with increasing PKS contents but increase with curing age while volumetric heat capacity and thermal resistivity increased as PKS content increases but decreased with curing age. In addition, concrete with 1:3:6 mix ratio exhibited the lowest thermal conductivity and diffusivity but higher volumetric heat capacity and thermal resistivity than those with 1:1½:3, 1:2:4 mix ratios. RHA-blended PKSC with 40% PKS and 15% RHA for 1:1½:3 mix ratio attained the compressive strength and thermal conductivity values recommended for lightweight aggregate concrete which is suitable for structural and insulation purposes. It was concluded that the combined use of PKS and RHA as raw materials in concrete is effective in improving concrete's thermal and insulation properties.
  • Thumbnail Image
    Item
    Synthesis, characterization, and photocatalytic application of silver doped zinc oxide nanoparticles
    (2022) Kareem MA; Bello IT; Shittu HA; Sivaprakash P; Adedokun O; Arumugam S
    The advancement in nanotechnology has influenced the improvement in the photocatalytic performance of zinc oxide nanoparticles (ZnO NPs). The photocatalytic activities of ZnO are within irradiation wavelengths in the ultraviolet region and this hinders its efficiency in photocatalytic applications. Undoped and silver doped ZnO nanoparticles (Ag-doped ZnO NPs) were successfully prepared by co-precipitation technique at Ag doping concentrations of 0, 0.25, 0.5, 0.75, and 1 % to enhance the photocatalytic ability of ZnO NPs. The XRD results indicate a hexagonal wurtzite structure of the undoped and Ag-doped ZnO NPs with the estimated crystalline size ranges from 30.79, 23.72, 36.97, 21.49, and 25.66 nm, respectively, for ZnO at Ag doping concentrations. The SEM micrograph revealed the uniform distribution of Ag on the surface of ZnO NPs and a decrease in the size of the particle as concentration increases. The displacement in the absorption edge of ZnO to a higher wavelength led to narrowing the optical bandgap of ZnO due to Ag doping, as observed in the DRS spectra. Photocatalytic performance and photodegradation experiments were conducted using a model methylene blue (MB) dye contaminated in water. The dye concentration decreases as irradiation time increases in the presence of the photocatalyst with the improved performance of less exposure time and the highest dye degradation of about 98 %. It was revealed that the photocatalytic activity of ZnO toward MB degradation was effectively improved by Ag doping. Therefore, Ag doping of ZnO NPs had the synergetic effect of enhancing the photocatalytic activity of ZnO NPs.