Master of Science in Materials Science
http://dl.lib.uom.lk/handle/123/15929
2024-03-29T12:07:15ZModification of mix design to utilize fly ash and gliricidia ash in concrete paving block
http://dl.lib.uom.lk/handle/123/20906
Modification of mix design to utilize fly ash and gliricidia ash in concrete paving block
Amunugama HMTM
Last few decades demand for renewable energy has increased. Among those resources, biomass is widely used to produce energy as it renewable and low-cost material. Therefore, it has led to the accumulation of industrial byproducts such as wood ash. Wood ash is the byproduct produced from the biomass power plant as used for the generation of electricity. The production of cement leads to emitting a large number of greenhouse gases caused environmental disasters all around the world. Also, cement is the expensive cost factor in manufacturing cement-based products. Concrete paving block (CPB) is a successful alternative for asphalt or concrete pavement. It is different from other paving methods from manufacturing, structural design, installation and replacing techniques, etc. It can be easily placed and removed when it is damaged. The present study was conducted to produce low-cost and performance-effective (complying with the standard requirements) paving blocks by using industrial by-products produced from the Tokyo Cement Ⓡ biomass power plant. Laboratory trials were carried out at the Tokyo cement construction research center laboratory which has been accredited as per ISO 17025. The 15MPa mix designs were used as per SLS 1425 standard. 5%, 10%, 15%, 20% of wood (Gliricidia) ash was replaced from cement content for mix design. workability, dimensions, verification of visual aspects, compressive strength, flexural strength, total water absorption were determined. Workability was reduced when increasing the percentage of wood ash. Dimensions were measured of all of the paving blocks. The length, width, and height of the B05 block have deviated from standard specifications. Visual aspects have shown that when increasing the wood ash percentage texture of those blocks was roughened. Smoothness has gradually decreased when increasing the wood ash percentage. Flexural strength and compressive strength have also been reduced when increasing the wood ash percentage. Total water absorption value has increased when increasing the wood ash percentage. Due to the increase of porosity of the paving block. Therefore, from all the results observed it can be concluded that 20% replacement of wood ash (B05) results were exceeded the standard requirements in SLS 1425. Also, we observed the scanning electron microscope (SEM) images of cross-sections of all 05 block types. It shows a gradual increment in porosity by increasing the wood ash percentage. Materials cost per cubic meter of every block type were calculated. The lowest materials cost is shown by the B05 type. 15% wood ash replacement (B04) results were complying with the standard requirements and show 2nd lowest materials cost from all block types.
2022-01-01T00:00:00ZComparison of corrosion behavior of steel reinforcement bars in ordinary Portland cement and Portland Pozzolana cement environments
http://dl.lib.uom.lk/handle/123/20128
Comparison of corrosion behavior of steel reinforcement bars in ordinary Portland cement and Portland Pozzolana cement environments
De Costa KBMVS
In the Sri Lankan cement market present time blended hydraulic cement which is composited with fly ash or blast furnace slag are given a noticeable marketing share as supplementary cement. It has obtained more popularity for incorporating higher workability and achieving a higher lateral strength in the construction industry. But due to the pozzolanic reactivity of blended cement, there is a possibility of reduction of pH of concrete or cement mortar which may be detrimental to the passivity of reinforced steel.
In this study, the comparison of corrosion effect was researched with 15% fly ash blended cement as the pozzolanic cement (Bag-cement of Blended hydraulic cement) and Ordinary Portland cement. Coarse aggregates were excluded to get a clearer picture of the corrosion effect with the change of cement type. The cement mortar mixtures with 1.0: 3.0: 0.5 of cement: sand: water respectively, from both cement types were prepared. Specimens were cast in moulds with reinforcement bars to prepare the specimens for the pull-out test, Half cell potential test, compression test & loss of mass (due to corrosion). After casting test specimens were salt-conditioned by dipping in 5% NaCl solution for 30 minutes per day for 180 days.
Pull-out and compression test results acknowledge that pozzolanic cement contributes higher lateral strength than ordinary Portland cement. After the compression test, reinforced steel bars were removed from the cubes and it was observed that no corrosion has happened in bars that were fully enclosed with (both types of: PPC and OPC) cement covers. Therefore, it reveals that 15% of fly ash blended hydraulic cement does not disturb the passivity layer of steel reinforcements as a result of consumption of Ca(OH)2. This study can be extended for further research with 25% or higher ratios of fly ash blended hydraulic cement.
2022-01-01T00:00:00ZCost effective method to analyze lubrication oil
http://dl.lib.uom.lk/handle/123/16772
Cost effective method to analyze lubrication oil
Rathnayake TNA
The lubricating oil analysis is the most common method to identify the condition of any machinery. There are various ways to analyze lubricating oil, and those methods are based on an individual examination of lubricant properties such as Viscosity, Total Base Number (TBN), Total Acidic Number (TAN), Water Content, Impurities (element analysis), etc. However, to carry out these analyses, sophisticated pieces of equipment are required. They are costly and need specific environmental conditions. Furthermore, as the tests are done in a laboratory, away from the machine, carefully collected lubricating oil samples must be transported to them. The whole process, from collecting samples to obtained results, takes a considerable amount of time. Therefore, this process will hamper the maintenance program's efficiency since the machine has to be kept in idle until receiving the results. Hence, it is of utmost importance to have a cost-effective and faster results-giving method to analyze lubricating oil at the place where the machines are installed. Then the operator himself can check the condition of lubricating oil to ensure the safe and smooth operation of the machine.
A comprehensive literature survey was carried out to understand the current trends in lubricating oil analysis. Most of the tests described in the literature are based upon Physical, Chemical, Electro-magnetic and Optical methods. The proposed design is based on an optical technique that deals with the Refractive Index (RI) since it is an indicator of the physical as well as the chemical property characteristic of a substance. The critical angle of a material is directly related to RI. Therefore, monitoring the critical angle changes leads to an understanding of the quality of the lube-oil. During the design stage, special attention was paid to the cost of the fabrication and user-friendliness of the device.
The performance of a proposed lube-oil analyzer was assessed using Shell Gardenia 40 (lubricating oil used in high-speed marine engines of Fast Attack Craft) lubricant. The lubricant used for different operating hours were analyzed. This analysis unveiled that, though Original Equipment Manufacturer (OEM) emphasize changing the lubricating oil after 500 hours, lube-oil quality has not deteriorated below the specified levels at this stage. This shows that the lifetime of lube-oil can be further extended, and frequent quality testing of lube-oil can save large sums of money without putting the machine life into any danger.
The results obtained from the proposed device was compared with the tests carried out according to the American Society for Testing and Materials (ASTM) standards. Moreover, forced diluted lube-oil samples were analyzed using the proposed device. Both tests confirm the effectiveness of the proposed device.
2020-01-01T00:00:00Z2D - 3D Hybrid perovskites for perovskite solar cells
http://dl.lib.uom.lk/handle/123/16773
2D - 3D Hybrid perovskites for perovskite solar cells
Gunasekara HKYPG
Hybrid Organic-Inorganic Perovskites (HOIP) have been studied extensively and grown popular. Especially in Three-dimensional (3D) Perovskites, achieving power conversion efficiency (PCE) exceeds 23%. Nevertheless, some of the morphological imperfections will limit their structural capabilities. Pinholes in discontinuous perovskite films induces the huge leakage current which can cut down the device efficiency and creates a short circuit. Therefore, it is essential to deposit a compact film with passivated defects. Two-dimensional (2D) halide perovskites, conversely attracted significant attention and become a positive alternative with their uncomplicated synthesis, stability, and excellent photoelectric properties. This study, investigates the formation and properties of 2D Tetrabutylammonium lead halide (TBAPbBrxI3-x) HOIP. Tetrabutylammonium ion is a large cation, and more likely forms a 2D perovskite structure which was confirmed by the XRD spectrum. Substantiate by SEM images, TBAPbBrxI3-x establishing and favors crystals with enhance orientation and few grain boundaries and. However, the absorption spectra of the film shows an excitonic peak at 411 nm and a clear band edge at 450 nm. Resulting in poor absorbance in the visible range, with optical band gap of 2.76 eV, narrowing the ability to use TBAPbBrxI3-x alone in solar cells. Conversely, TBAPbBrxI3-x can use as separate capping layer on the top of 3D perovskite layer, enhancing the properties of the 3D perovskite layer. Incorporating TBAPbBrxI3-x into CH3NH3PbI3 shows a better film formation with few holes. The application of mixed perovskite layers incorporated solar cells will result in better structural and optoelectronic properties.
2020-01-01T00:00:00Z