Civil Engineering

Permanent URI for this collectionhttps://etd.hu.edu.et/handle/123456789/675

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    INVESTIGATION ON THE PRODUCTION PROCESS AND QUALITY OF AGGREGATES AND HOLLOW CONCRETE BLOCK: A CASE STUDY OF GEDEO ZONE
    (Hawassa University, 2019-12-16) TINSAE MENGISTU YIMER
    In order to produce Aggregates and hollow concrete blocks with good quality which satisfy strength and durability requirements, great care have to be taken for their production starting from ingredient selection to finished product. In addition to this, every production process should follow proper scientific procedures. Considering this, investigation focusing on production process and quality of Aggregates and HCB has been conducted in various Aggregate and HCB production sites located in Gedeo Zone. The research is carried out by observing the production process, collecting information on method of production through interviews and performing different tests in the laboratory to evaluate the quality of the products. Based on the findings, conclusions are drawn and recommendations are forwarded. The findings of the investigation have shown that in most of Aggregate production site process of production is not modern and scientific. From the investigated crushing sites the Wenago and Golla crushing sites follows the best production process and also the quality of aggregates produced also better than the Waleme and the Mechisho crushing sites, especially the grading requirement was not satisfactory and the aggregates are coarser in Waleme and Mechisho Aggreagtes. All fine aggregate sources investigated in this research were natural sand excavated from river bed and the Gidabo and the Gollelicha sands were unsatisfied in grading requirement, Kilkile sand was better grading and also it passes the organic impurity test and the other two did not. Based on their quality C-30 concrete mix was prepared and the compressive strength test was performed. The mix prepared using Wenago aggregate and Kilkile sand achieved 34.85MPa 28th days compressive strength and the other mix prepared using the Waleme aggregate and Gollelicha sand achieved 28.40MPa. In HCB production sites laboratory tests were not conducted for all ingredients used for production of hollow concrete blocks and they use nominal mixing proportion, no mix design is drown based on materials property. The main products in all production sites is class C and it does not fulfill the standard provided in its compressive strength and block density. In addition to this, handling of those ingredients was very poor, and production process also not conducted properly as specified in the recommended standards.
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    EFFECT OF LOCAL SAND SOURCE AND COARSE AGGREGATE PRODUCTION ON CONCRETE PROPERTIES: A CASE OF HAWASSA CITY
    (Hawassa University, 2021-10-17) MINTESINOT KASSAHUN ZAFU
    Concrete structures are integral parts of modern civil infrastructures constituting a large portion of the national wealth of any country. Concrete consists of 60–75% volume with aggregates. Therefore be expected to have most suitable aggregate properties utilization in concrete are reducing volume change, improving the concrete properties against applied load and environment on concrete. Currently, it is normal practice to see the traditional method of fine aggregate production and both traditional and modern means of coarse aggregate production in Hawassa city to produce concrete. In this study, an investigation has been performed on properties of sand sources from Bilate, Dimtu, and Halaba while coarse aggregate production from Waye Bonge Quarry, Daete Quarry, and Derago Quarry and their effect on fresh and hardened concrete properties. This experimental investigation has been performed on nine concrete batches for each C-30 and C-50 concrete grades with different selected quarries that supply aggregate to Hawassa city. The fresh concrete property was done through concrete workability in terms of slump cone and compaction factor tests. Hardened concrete properties were done through concrete hardened density, compressive strength, splitting tensile strength, water absorption, sulfate attack resistance, and chloride attack resistance tests. For hardened density, compressive strength, and durability tests 150mm concrete cube specimens and for splitting tensile strength test cylinder specimens (150mm diameter and 300mm length) were used. Detailed experimental test results of different aggregates and concrete properties were presented, analyzed and discussion was done based on standards and previous related literature to investigate aggregates properties and their effect on concrete properties. The results show that all sand sources classified under poorly graded sand with high silt content; coarse aggregate production with poorly graded and high percentage of flaky and elongated aggregate in concrete negatively affects the workability, strength, and durability of concrete. It is recommended that aggregate producers should give proper attention to producing consistent and quality products in terms of relevant parameters, which are compatible with the standard requirements