Investigation of structural and radiological shielding properties of pozzolana-portland cement

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The physical properties of the ordinary Portland cement (OPC) are enhanced when the matrix of the OPC is partially replaced by admixtures such as Pozzolana. This research investigated the radiological shielding properties and the structural strength of Pozzolana-Portland Concrete (PPC) at different ratios of 0% (S0), 10% (S1), 20% (S2), 30% (S3), 40% (S4), 50% (S5), 60% (S6), 70% (S7) and 80% (S8) of Pozzolana. Radiological shielding property of a material is its ability to shield or absorb ionizing particles/rays; thus preventing it from being released into the environment when a source thereof is housed in containment. Ionizing radiations are found in nuclear reactors, γ-rays and x-rays equipment used in energy and health sectors. They are also found in sources used in quality assurance industries. Compression test was performed using CONTROL electronic type compressiontesting machine. Test samples were made of concrete (mixture of Portland and Pozzolana cement) cubes and cylinders. The experiments were conducted at a temperature of 27 ± 2 o C at the following days of aging; 2, 7, 14 and 28. The compression test results showed that concrete of Portland-Pozzolana cement (PPC) at 20% Pozzolana has more compressive strength than that of the ordinary Portland cement at 28 days of curing. Flexural and ultrasonic tests were conducted to confirm the results. Neutron activation analysis (NAA) was also carried out to determine the elemental compositions of Pozzolana and ordinary Portland cement. The neutron activation analysis results showed that Europium, Hafnium, Copper, Calcium, Iron, Cobalt and Aluminum, all of which have significant macroscopiccross sections (shielding properties) dominating more in Pozzolana cement than in the ordinary Portland cement. X-ray shielding analysis was carried out toascertain the veracity of the NAA results. Linear attenuation coefficient (µ l ) of each sample at photon energy of 0.15 iv MeV was determined with the 50% PPC showing highestvalue. Further, X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) analyses were performed to identify the phases contributing to the highest strength at 20% PPC (33 MPa) and highest shielding, µ lat 50% PPC (1.533 cm -1 ). The results in all showed that Pozzolana positively affects structural and radiological shielding properties of the ordinary Portland cement (OPC), since the OPC (Control) concrete had a compressive strength of 28.44 MPa at day 28 and a linear attenuation coefficient (µ l ) of 0.140 cm -1 . The XRD results showed that Calcite (CaCO3), which is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3) accounts for the very high strength in the 20% PPC while Iron (Fe), Copper (Cu), Manganese (Mn) and Aluminum Hydroxide (AlHO2) account for the very high shielding ability of the 50% PPC.
A Thesis submitted to the Department of Materials Engineering, College of Engineering, in partial fulfilment of the requirements for the degree of DOCTOR OF PHILOSOPHY in Materials Science and Engineering,