OLUWAFEMI, JOHN OLUWATOBI and Covenant University, Theses (2023) RELIABILITY-BASED OPTIMAL ASSESSMENT OF GROUND GRANULATED BLAST-FURNACE SLAG AND COW BONE ASH-BASED GEOPOLYMER CONCRETE. ["eprint_fieldopt_thesis_type_phd" not defined] thesis, COVENANT UNIVERSITY.
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Abstract
Consequent to the knowledge gap in the area of reliability of geopolymer concrete, this research focuses on the reliability-based optimal assessment of ground granulated blast furnace slag and cow bone ash-based (GGBS-CBA) geopolymer concrete (GePoCc). The geopolymer concrete mix was designed using the British DOE (1988) method and the batching was done by weight method. The mixture of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) of twelve molarity (12M) was used as alkaline activators. The materials used were tested for specific gravity, fineness, and water absorption capacity, and X-ray fluorescence was carried out to understand the chemical composition of cement, GGBS, and CBA. Workability tests were also carried out to understand the fresh properties of the fresh GePoCc. Following this, the effect of varied alkaline activators ratio (AAR) (2.0:1, 2.5:1, and 3.0:1) and varied curing conditions were investigated on the mechanical properties of the GePoCc. The curing of the hardened GePoCc was observed for 7, 14, 28, 56, and 90 days. Compressive, flexural, and split tensile tests were carried out on the hardened GePoCc. The strength of the hardened GePoCc was considered as parameter for prediction, optimization and reliability assessment of the GePoCc. To achieve these, the strength optimization was carried out using the Central Composite Design Response Surface Method and the reliability analysis was carried out using constant failure rate model, a time-dependent reliability method with consideration of the design life of 50 years. The reliability index of the GePoCc was checked against the control experiment for 150 years. Laboratory analyses such as X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Energy Dispersive X-Ray (EDX) were carried out to further understudy the GePoCc while cost-benefit analysis used to establish the economic performance of the GePoCc. The AAR of 2.5:1 yielded the highest mechanical strength across the compressive, flexural, and split tensile strength for all GePoCc mixes. The GePoCc mixes with 40 % to 100 % GGBS composition showed a satisfactory reliability level for AAR 2.0:1, 2.5:1 and 3.0:1 while the mixes with 0 % to 20 % GGBS were not reliable. The mix with 40 % GGBS, 60 % CBA and AAR of 2.5:1 is reliable and suitable for developing GePoCc with 30 N/mm2 strength, 60 % GGBS and 40 % CBA mix of 2.5:1 AAR is reliable and suitable for developing GePoCc with 35 N/mm2 strength, and 80 % GGBS and 20 % CBA of 2.5:1 AAR is reliable and suitable for developing GePoCc with 40 N/mm2 strength. The cost-benefit analyses revealed that the cost-to-strength ratio of GePoCc mixes with 100% to 60% GGBS produced with AAR of 2.0:1, 2.5:1, and 3.0:1 are lower than the Cost to Strength Ratio of the conventional concrete. The results of the mechanical tests, reliability analyses and economic performance analyses establish the mix with 60% GGBS and 40% CBA of AAR of 2.5:1 as the optimum mix in this research.
| Item Type: | Thesis (["eprint_fieldopt_thesis_type_phd" not defined]) |
|---|---|
| Uncontrolled Keywords: | Geopolymer Concrete, Reliability, Optimization, Strength, Regression Models, Cost-Benefit Analysis |
| Subjects: | UNSPECIFIED |
| Divisions: | Faculty of Engineering, Science and Mathematics > School of Civil Engineering and the Environment |
| Depositing User: | AKINWUMI |
| Date Deposited: | 02 Jun 2023 10:26 |
| Last Modified: | 02 Jun 2023 10:26 |
| URI: | http://eprints.covenantuniversity.edu.ng/id/eprint/16972 |
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