Faculty of Engineering, Materials Engineering
http://dl.lib.uom.lk/handle/123/15925
Theses / Dissertations submitted to Department of Materials Engineering2024-03-28T07:10:34ZModification 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.
2022-01-01T00:00:00ZDevelopment of coir fiber based insulative composite material to reduce thermal heat in buildings
http://dl.lib.uom.lk/handle/123/21397
Development of coir fiber based insulative composite material to reduce thermal heat in buildings
Chamath LG
Energy consumption is a critical factor in building design. Maintaining a comfortable
indoor temperature consumes high energy than other necessities such as lighting and
cooking. The building envelope is the main component of the building that transfers
heat between indoor and outdoor environments. During the daytime, a proper
ventilation system or an air conditioning system can control the heat in a building.
Insulation layers are also used under the roofing sheets to control the heat transfer
through the roof because a building’s roof contributes to a significant heat gain in
tropical countries.
Sustainable insulation materials have been more attractive in the last two decades due
to biodegradability, low embodied energy, availability, and non-toxicity. Sustainable
insulation materials are primarily fabricated using lignocellulose fiber (natural plant
fibers). Then it is mandatory to add binder material to adhere to fibers and the material
formulated as a composite material, and an air void should be introduced to the
combination of fiber and binder to increase insulation properties. Now the whole
material can be identified as a three-phase composite material. Thus, the volume
fraction of each phase (fiber, binder, and air void) is the most critical factor which
controls these composites’ insulation properties.
The insulation properties of the material can be analysed using experimental,
analytical, and numerical methods. Analytical and numerical methods are more
attractive than experimental methods. However, there are limited number of studies on
the effect of volume fraction with insulation properties in a three-phase composite. In
this study, the effective thermal conductivity (K
eff
) of the composite was analysed
through the analytical and numerical models and validated through the experimental
results. The results concluded that the experimental results agreed with the numerical
and analytical results. Furthermore, a novel mathematical model has been proposed to
find the K
eff
of the three-phase composite using the analytical and numerical methods.
The proposed model shows better agreement with the experimental result. Therefore,
it can be used to develop this research area further.
2022-01-01T00:00:00ZSynthesis of porous graphene from Sri Lankan graphite for supercapacitor applications
http://dl.lib.uom.lk/handle/123/21395
Synthesis of porous graphene from Sri Lankan graphite for supercapacitor applications
Sandaruwani MKA
A feasible process to synthesize porous graphene with ultra-high surface area is
presented in this thesis. Graphene oxide (GO) was synthesized from Sri Lankan
graphite via the modified hummers method. Then, GO was subjected to a chemical
activation process to produce graphene with a mesoporous structure, where KOH was
used as the activation agent. The influence of the critical activation process parameters
on the specific surface area of graphene was studied. In this study, activation time at
60 min, activation temperature at 800 ℃ and KOH/GO mass ratio at 4 were identified
as the optimum activation parameters for high surface area. As an alternative route to
find the specific surface area (SSA), a dye adsorption based SSA calculation method
was followed, and the methylene blue adsorption kinetics were studied for that. Second
order kinetic model and Langmuir isotherms were the most suitable kinetic models for
the methylene blue adsorption onto porous graphene which were produced from Sri
Lankan vein graphite. A combined mathematical model of methylene blue number
(MBN) and iodine number (IN) was used to calculate the SSA for high accuracy. The
obtained optimum activated graphene sample showed a high specific surface area of
768.15 m
2
/g as measured from the dye adsorption method and it was verified by BET
analysis. Furthermore, methylene blue and Iodine adsorption methods are studied as a
low-cost and feasible method for surface area determination of porous graphene. The
high surface area of the obtained graphene would make it a promising material for
supercapacitor applications. The present study mainly focuses on the value addition to
Sri Lankan vein graphite trough the utilization of vein graphite as an electrode material
in electrochemical double layer capacitor (EDLC).
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.
2022-01-01T00:00:00Z