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Item Potential of Scoria, Pumice, and RHA as Supplementary Cementitious Materials for Reducing Setting Time and Improving Early Strength of Pozzolan Blended Composite Cement(NMAIST, 2019) Mboya, Hieronimi AlphonceTanzania has huge deposits of scoria (S-N) and pumice (P-N) minerals that can be used as supplementary cementing materials (SCMs) in cement factories to cut down the cost of cement and its pollution effect to the environment. Besides this, agricultural wastes such as rice husk produce rice husk ash (RHA) having high silica content that can be used with cement to reduce the cost of cement and its impact to environment. Performance indicators of mortar and concrete such as slump, flow, permeability, shrinkage, modulus of rupture, compressive and tensile splitting strength were tested with different proportions of SCMs. It was found out that in addition to cutting the CO2 emissions, SCMs reduce energy bills and that they confer extra strength and resistance to mortar and concrete. This work only examined the properties of scoria (S-N) and pumice (P-N) and rice husk ash (RHA) as supplementary cementing materials (SCMs) for Portland cement. The investigation considered these materials in binary and ternary module. X-ray fluorescence, X-ray diffraction, and pozzolanic activity index (PAI) tests confirmed the suitability of these materials as potential SCMs. Initial and final mean setting times observed for a binary composite cement were 166 and 285 min respectively. The setting times were longer than those of Ordinary Portland cement (OPC) but shorter when compared to Portland pozzolana cement. Characteristic and target mean strengths of 30 and 38.2 MPa were considered. The ultimate mean compressive strengths achieved at 28 days of curing were 42.5, 44.8, and 43.0 MPa for S-N, P-N, and RHA respectively indicating the potentials of these materials as SCMs. Further observation show that, the 28-days maximum compressive strength achieved by the blended cement concrete (with 10% replacement of SCMs) were 44.2 and 43.1 MPa for S-N 10 and P-N 10, respectively. The modulus of rupture decreased with an increase in the amount of S-N. On the other hand with P-N, a maximum of 8.0 MPa at 20% replacement was observed iii but then dropped to a minimum value of 6.4 MPa at 40% replacement level. This indicated potentially a superior ability of the P-N concrete to endure more sustained stress such as those caused by tremors and earthquakes and impact-related stresses. The residual compressive strength of P-N blended cement concrete samples, after subjection to a high temperatures of 600 ºC, was higher compared to S-N blended cement indicating the superior resistance of P-N to higher temperatures. S-N 10, S-N 20 and S-N 30 gave coefficients of permeability, (K), of 5.2526E-08, 5.20833E-08, and 4.9741E-08 m/s, in that order. This low permeability was attested by their dense microstructure, with implied reduced chemical attack, less carbonation, improved steel protection against corrosion, and enhanced durability of the reinforced concrete. The maximum compressive strength of ternary materials of 53.8 MPa was attained at 10/20% P-N/RHA replacement level. The 28 days Strength Activity Index (SAI) of S-N/RHA blended cement at 30/0, 10/20, 5/25 and 0/30% S-N/RHA were above 75% recommended by ASTM. On the other hand the SAI of P-N/RHA blended cement were higher than the ASTM recommended value at all replacement levels. Therefore, 10% of S-N, P-N or RHA is recommended as the optimum replacement for Portland cement in binary materials and 10/20% P-N/RHA for ternary materials to enhance performance of cement.Item Evaluation of Pumice Lightweight Concrete as Material for Thin-Shell Structures(Mbeya University of Science and Technology Journal of Research and Development (MJRD), 2022-06-07) Shiganza, O,J; Msambichaka, J, J & Mboya, H, A,The properties of concrete depend on cement content, water-cement ratio, and the types and mechanical properties of aggregates used. The strength of pumice lightweight concrete is governed by the strength of mortar and pumice aggregates in the mixture. The properties of fresh and hardened pumice lightweight concrete, such as workability, density, compressive and flexural strengths, are among the parameters required in the design of thin shell structures. These parameters, which involved two batches, were dealt with in this research, and the results are in line with American Concrete Institute 318 requirements. Absolute volume methods as stipulated by American Concrete Institute Committee 211.2-98 were used for selecting and adjusting proportions for lightweight concrete. The two hand mixed batches were used to evaluate the concrete. As a result, the excessive pumice lightweight aggregates content of batch No.1 proved to have poor strength. The reduced pumice lightweight aggregates content of batch No. 2 established satisfactory strength results. The average specific gravity and water absorption of pumice lightweight aggregates were 1.1 and 98.3%, respectively. Pumice lightweight concrete achieved a compressive strength of 23.6 N/mm2 measured at 28 days as compared with American Concrete Institute 318, which requires at least 17 N/mm2. Pumice lightweight concrete satisfies the requirements of the code for the design of thin shell structures. Therefore, pumice lightweight aggregates can be used as a partial replacement of normal weight aggregates for the design and construction of thin shell structures up to 18.75%.Item Contamination and Human Health Risk due to Toxic Metals in Dust from Transport Stations and Markets in the Kumasi Metropolis, Ghana(Kwame Nkrumah University of Science and Technology, 2019) Rweyemamu, Almachiusi. RwegasiraHeavy metals are very harmful to human health and their increasing contamination of dust in the urban areas calls for serious attention to them. The aim of this study was to determine the concentrations and assess the potential human health risk associated with exposure to selected heavy metals in dust from transport stations and markets within the Kumasi metropolis, Ghana. A total of 50 dust samples from transport stations and markets were collected by sweeping ground surface dust and analyzed for Arsenic (As), Cadmium (Cd), Chromium (Cr), Copper (Cu), Nickel (Ni), Lead (Pb), Zinc (Zn), Iron (Fe), Mercury (Hg) and Antimony (Sb). The concentrations of Hg were determined by Atomic Absorption Spectrophotomery using a Lumex RA-915M Zeeman Automatic Mercury Analyzer while the levels of other metals were determined by using X-ray Fluorescence analyzer (Niton XL3t GOLDD+). The concentrations of As, Cd, Cr, Hg, Cu, Ni, Pb, Zn, Fe and Sb in transport stations ranged from below detection to 9.66, below detection to 37.13, below detection to 260.11, 0.01 to 0.62, below detection to 143.77, below detection to 47.62, below detection to 61.73, 48.89 to 218.61, 3768.97 to 40936.07 and below detection to26.01 mg/kg respectively.The concentrations of As, Cd, Cr, Hg, Cu, Ni, Pb, Zn, Fe and Sb in markets ranged from below detection to 6.20, below detection to 14.61, below detection to 232.90, 0.01 to 1.38, below detection to 181.85, below detection to 44.79, below detection to 72.10, 59.29 to 293.68, 8283.66 to 34953.63 and below detection to 21.72 mg/kg respectively. The study revealed no significant difference between the mean concentrations of heavy metals in dust from transport stations and markets at 95% confidence limit of T-test analysis (p>0.05). The mean geo-accumulation, contamination factor and modified degree of contaminations indicated that dust from both transport stations and markets were moderately to extremely polluted by metals compared to their abundance in the dust of the control site vi (KNUST Botanic Gardens). Mean enrichment factors indicated that metals were highly enriched in the dust and originated from anthropogenic sources. Pollution load index which ranged from 1.39 to 12.55 for transport stations and from 1.48 to 15.62 for markets revealed high pollution load. The hazard index (HI) and carcinogenic risk index (CRI) were used to assess human health risk. Hazard indices for all the metals were less than the safe limit of 1, signifying no potential non-carcinogenic risk for both children and adults. Exposure to multiple metals was observed as a major concern of non-carcinogenic risk to children. Among the metals assessed for carcinogenic risk, the CRI of Cd in both transport stations and markets exceeded the safe limit of 1x10-4 for children. Health risk assessment indicated children to be highly exposed to heavy metals in dust via ingestion compared to adults. This study observed high pollution load of heavy metals in the studied areas and therefore appropriate measures need to be taken in order to manage the pollutionItem Effect of Ipomoea Hildebrandtii and I. Kituiensis on Loss of Native Herbages of Maasai Steppe Rangelands in Simanjiro District(The University Of Dodoma, 2018) Ndaki, ManyanzaSustainability of many rangelands including Simanjiro Maasai steppe rangelands is limited in part by invasive plant species. A study was conducted among two selected village rangelands (Terrat and Sukuro) of the Simanjiro district aimed to (1) determine the effect of Ipomoea hildebrandtii and I. kituiensis on herbage species composition, richness, and basal cover; and (2) determine the effect of Ipomoea hildebrandtii and I. kituiensis on herbage biomass productivity. Other objectives were to (3) assess the distribution of Ipomoea hildebrandtii and I. kituiensis across grassland and woodland habitats, and (4) evaluate the available mitigation measures among the Maasai pastoralists on the effects of Ipomoea hildebrandtii and I. kituiensis on their rangelands. A total of 10 plots of 70 m2 each with 9 quadrats of 1 m2 each in the invaded and non-invaded grazing-lands coupled with point sampling technique. Purposeful sampling involved 10 key informants’ interviewees; 24 participants for focus group discussions. Simple random sampling involved 30 hamlets representatives for questionnaire surveys. Data on herbage species composition, richness, basal cover, biomass productivity; distribution of invasive Ipomoea spp; and mitigation measures for effects of invasive Ipomoea spp. were analysed using STATA, Microsoft Excel and SPSS, respectively. Non-invaded grazing-lands had a higher basal cover (54.71%±1.95% for grasses, 45.29%±1.95% for forb) than invaded grazing-lands (29.38%±1.34% for grasses, 24.70%±1.20% for forb), (P0.05). Non-invaded grazing-lands had higher biomass productivity (0.289±0.03 t DM/ha) than invaded grazing-lands (0.202±0.02 t DM/ha), (PItem Mapping the Distribution of Digitate and Tabulate Acropora Corals in Selected Reefs of Zanzibar(Mbeya University of Science and Technology, 2013) Mwakalapa, Eliezer. BrownMapping the boundaries and distribution of reef corals, especially at growth form level, is an important coastal zone management step. Digitate and tabulate Acropora are growth forms of stone corals associated with abundance of reef fishes and are important in building reef framework. In this study boundaries of coral reefs and the distribution of digitate and tabulate Acropora around Bawe and Mnemba Islets, Zanzibar Island were mapped and results compared with environmental parameters. Data were collected by manta tow technique, line intercept transect, belt intersect transect, GPS unit and an underwater camera. Geo-referenced data was processed using ArcMap 9.3 software. The border line was set where live coral cover was above 5%. At the boundaries reef corals are intermixed with seagrasses, sand, rock and algal mats. The estimated area of coral reef was 1.9 km2 at Bawe Island and 20 km2 at Mnemba Island. Tabulate Acropora were aggregated on Bawe and Mnemba coral reefs, while digitate Acropora were aggregated on the reef flats, randomly distributed on Bawe and dispersed on Mnemba reef slopes. Small sized colonies of 11 to 40 cm and 21 to 60 cm diameters dominated the distributions of digitate and tabulate Acropora respectively. Higher contribution of digitate Acropora (2.07 cm) were observed in terms of coral cover as compared to tabulate Acropora (0.03 cm). The study also revealed that the distribution of tabulate and digitate Acropora is influenced by depth, turbidity and habitat type. This study provides useful information on the location and distribution of digitate and tabulate Acropora and provides recommendations for management and future studies on ecosystem changes and vulnerability.Item Evaluation of Local Ceramic Materials for High Voltage Insulation Application(Nelson Mandela African Institution of Science and Technology, 2014) Moyo, Moses GeorgeThis study investigated the Tanzanian local ceramic material for their potential as raw materials for production of high voltage insulators based on the mix proportion of raw materials and firing temperatures. The raw materials used were: Pugu kaolin, quartz supplied by the Kilimanjaro Industrial Development Trust (KIDT), and Kilimanjaro feldspar. The study characterised both individual raw materials and the blends produced from these raw materials. A total of six batches were prepared by varying the proportion of raw materials. Cylindrical samples of 10 and 60 mm diameter were produced by slip casting method and fired at the maximum temperature of 1100, 1200 and 1300 ºC. Fired samples were tested for insulation resistance, bending strength, and bulk properties. The X-ray diffraction (XRD) analysis showed that on heating Pugu kaolin produces mullite phase which is very important for mechanical and dielectric properties. Furthermore, the highest trend in insulation resistance and bending strength is revealed to samples fired at 1200 ºC with lower values for those fired at 1100 and 1300 ºC. The optimum mix proportion and firing temperature, which compromise both insulation resistance and bending strength is with 33 wt% Pugu kaolin, 11 wt% Kilimanjaro quartz, and 56 wt% Kilimanjaro feldspar at the firing temperature of 1200 ºC. With this mix proportion and firing temperature at maximum insulation resistance of 205800 MΩ at the injection of 1000 V is achieved. The bending strength and water absorption for this mix proportion and firing temperature is 65.358 MPa and 0.01 %, respectively. These results correspond to the standard specifications for ceramic insulators.