Browsing by Author "Tharmarajah, G"

Now showing 1 - 11 of 11

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Corrosion-resistant FRP reinforcement for bridge deck slabs
(Thomas Telford, 2014-11-26) Tharmarajah, G; Taylor, S. E; Cleland, D. J; Robinson, D
This paper discusses the beneficial influence of compressive membrane action in fibre reinforced polymer (FRP) reinforced in-plane restrained slabs in bridge deck slabs and the improved service performance when arching action occurs. Bridge deck slabs that are exposed to extreme environmental conditions can experience severe corrosion damage. Expansive corrosion in steel reinforcement significantly reduces the design life and durability of concrete structures; for example, on one short section of the M1 in Northern Ireland, nearly £1 million was spent last year on the maintenance and repair of bridges due to corrosion. Corrosion-resistant composite reinforcement such as basalt fibre reinforced polymer (BFRP) and glass fibre reinforced polymer (GFRP) provides a durable alternative to reinforcing steel. In this research, two BFRP reinforced slabs and two GFRP reinforced slabs were constructed using high-strength concrete with a target cube compressive strength of 65 N/mm2. The slabs represented typical full-scale dimensions of a real bridge deck slab 475 mm wide by 1425 mm long and 150 mm deep. The service and ultimate behaviour of the slabs are discussed and the results are compared with the relevant design guidelines.
Open Access
Development of Coir Fiber Reinforced Polymer Reinforcing Bars for Concrete Structures
(Sri Lanka Institute of Information Technology, 2023-03-25) Tharmarajah, G; Wimalasuriya, W.B.U
At present, global warming increment and petroleum reserve depletion have been a major threat to the environment. These occur due to various human activities. Construction industry contributes 40 % for the global carbon emission. From that 10% is contributed from the manufacture of cement and the rest is contributed by the other requirements in the construction industry. Therefore, scientists are now more focused to involve bio-based products to minimize the emission of carbon. This resulted in, paying more attention towards the natural composite materials that can be used instead of artificial materials. Scientists are eager to find natural materials which are locally available. The structures built today, does not survive the entire service life of the structure. This is due to corrosion of steel, especially in coastal areas. So, in order to overcome this, use of a natural material which can provide the same tensile strength can be used. Over the past few decades engineering materials like composites, plastics, ceramics has dominated the engineering industry. There are new polymer materials introduced such as glass fiber, carbon fiber and aramid but they are not eco-friendly. The main problem associated with these is the high production cost. Therefore, new composites which are environmentally friendly should be found in order to replace other materials. Even though there has been much research published on different natural fiber composite materials, here an attempt has been made to use coir to produce reinforcement bars in order to combat corrosion
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Durability and mechanical performance of glass and natural fiber-reinforced concrete in acidic environments
(Elsevier, 2025-02-28) Justin, S.; Thushanthan, K; Tharmarajah, G
This study investigates the mechanical and durability characteristics of fiber-reinforced concrete when exposed to acidic environments. The research focuses on the effects of adding 1 % of treated coir fibers (TCF), treated rice husk fibers (TRH), and glass fibers (GF), along with 5 % silica fume (SF), to concrete. Experimental results show that the inclusion of these fibers and SF enhances both compressive and tensile strengths, with the most significant improvements observed in GF-reinforced concrete. The durability of the concrete was tested by immersing samples in acidic solutions with pH values of 3 and 5 for 28 days. Ultrasonic Pulse Velocity (UPV) tests indicated that the concrete's quality remained stable, while compressive strength tests revealed an increase in strength, particularly in samples exposed to pH 5. Sorptivity tests, which measure water absorption, indicated higher initial absorption rates due to the porous nature of fiber-reinforced concrete. However, as hydration progressed, the rate decreased. SEM images show that incorporating silica fume improves the microstructure of the specimens benefitting the strength of the structure. The study concludes that concrete reinforced with GF and SF exhibits superior mechanical properties and durability in acidic environments, making it a promising material for use in harsh conditions.
Embargo
Durability and mechanical performance of glass and natural fiber-reinforced concrete in acidic environments
(Elsevier Ltd, 2025-02-28) Justin, S; Thushanthan, K; Tharmarajah, G
This study investigates the mechanical and durability characteristics of fiber-reinforced concrete when exposed to acidic environments. The research focuses on the effects of adding 1 % of treated coir fibers (TCF), treated rice husk fibers (TRH), and glass fibers (GF), along with 5 % silica fume (SF), to concrete. Experimental results show that the inclusion of these fibers and SF enhances both compressive and tensile strengths, with the most significant improvements observed in GF-reinforced concrete. The durability of the concrete was tested by immersing samples in acidic solutions with pH values of 3 and 5 for 28 days. Ultrasonic Pulse Velocity (UPV) tests indicated that the concrete’s quality remained stable, while compressive strength tests revealed an increase in strength, particularly in samples exposed to pH 5. Sorptivity tests, which measure water absorption, indicated higher initial absorption rates due to the porous nature of fiber-reinforced concrete. However, as hydration progressed, the rate decreased. SEM images show that incorporating silica fume improves the microstructure of the specimens benefitting the strength of the structure. The study concludes that concrete reinforced with GF and SF exhibits superior mechanical properties and durability in acidic environments, making it a promising material for use in harsh conditions
Open Access
Durability of Cold Formed Steel Structures used in residential and industrial construction
(Sri Lanka Institute of Information Technology, 2023-03-25) Cooray, K.P.; Tharmarajah, G
Cold formed steel is an attractive alternative to traditional construction materials such as masonry and concrete owing to the advantages such as easy fabrication, light weight, reusability of the material and higher level of recyclability. Cold formed steel buildings are also appreciated for better insulation and lower energy consumption during operation. However, durability of the steel was the main concern for stakeholders as corrosive conditions can damage the material and deteriorate the condition of the building. Therefore, it is important to understand the durability of cold formed steel coated with zinc and zinc alloys. In this study, experimental data related to durability studies available in literature was collected and presented through an analysis. The data obtained from literature indicate that if the building envelop was designed appropriately to protect the steel from exposure conditions, the steel can fulfil the expected service life of residential buildings independent of environmental and climatic conditions. Therefore, this study helps to alleviate concerns regarding durability of cold formed steel in residential construction.
Embargo
Effect of Surface Modification and Fibre Content on the Mechanical Properties of Coconut Fibre Reinforced Concrete
(https://www.scientific.net/, 2020-09) Hettiarachchi, C; Tharmarajah, G
. In the past few decades, concrete has been the most widely used material for structural applications in the world and uses steel reinforcement as aide to meet the flexural, tensile and ductility demands required of concrete structures. Manufacturing of concrete and steel reinforced concrete structures is associated with millions of tons of carbon dioxide emissions and mineral waste. This activity is also responsible for the depletion of a large number of non-renewable resources. Reinforcing steel is also a high cost material, consumes a lot of energy in its production. Consequently, the use of natural fibres as an alternative for steel reinforcement is widely investigated, to promote the use of sustainable concrete structures. This study aims to investigate the effect on durability, flexural, compressive, tensile properties, and workability of concrete by incorporating coir fibre at varying fibre content to find the fibre content which gives optimum results. The fibre contents used were 0%, 0.5%, 1.0%, 1.5% and 2.0% by weight of cement. Furthermore, the effect of modifying the surface of the coir fibres by alkali treatment (i.e. 5 wt.% NaOH solution) and coating the fibres with epoxy paint and polyurethane varnish on coir fibre reinforced concrete (CFRC) were also investigated. Tests conducted on the CFRC specimens included slump test and flexural, compressive and tensile strength tests. Water absorption and sorptivity tests were also conducted to investigate the durability. Slump (workability) and unit weight reduced with an increase in fibre content. The surface modification methods used, had resulted in an increased workability and a reduced unit-weight. A coconut fibre content of 1% produced the best combination of flexural, tensile and compressive properties. Water absorption and sorption rate per unit time, increased with an increase of coir fibre content. It is also found that epoxy paint and alkali treatment of the fibres has a positive effect on the mechanical strength properties and also the durability and workability of the CFRC specimens. However, polyurethane varnish coating had a detrimental effect on the mechanical strength properties of the CFRC specimens.
Open Access
Evaluation of Mechanical Characteristics of Rice-Husk-Bricks
(SLIIT, Faculty of Engineering, 2023-10) Tilakasena, R.S; Tharmarajah, G
Construction activities and materials extraction are major contributors to environmental pollution. To address this issue, the utilization of bio-based materials presents a promising sustainable alternative for the construction industry. Bio-based materials encompass a broad category of organic matter that can be either synthesized or naturally derived. One such noteworthy bio-based material is rice husk, which exhibits pozzolanic properties. Abundantly available as an agricultural waste product, rice husk holds potential as a viable substitute in construction processes. This study is dedicated to investigating the feasibility of replacing fine aggregates, traditionally comprised of sand, in cement blocks with untreated rice husk on a volumetric basis. In contrast to being used merely as an additive, this research delves into the possibility of substantially replacing sand with a higher proportion of rice husk, ranging from 20% to 80%, in the composition of cement blocks. The findings of this study reveal that up to 40% of the sand content in cement blocks can be effectively replaced with untreated rice husk while still meeting the requisite strength standards for non-load bearing blocks. Moreover, this study demonstrates an additional advantage in terms of weight reduction. Substituting sand with rice husk leads to a remarkable 30% reduction in the overall weight of the blocks. These results underscore the potential benefits of integrating rice husk into construction materials as an environmentally friendly and weight-efficient alternative.
Open Access
Experimental and Numerical Investigation of Compressive Membrane Action in GFRP-Reinforced Concrete Slabs
(MDPI, 2023-02-28) Tharmarajah, G; Taylor, S; Robinson, D
Experimental and numerical analyses of eight in-plane restrained slabs (1425 mm (length) × 475 mm (width) × 150 mm (thickness)) reinforced with glass fiber-reinforced polymer (GFRP) bars are reported in this paper. The test slabs were installed into a rig, that provided 855 kN/mm in-plane stiffness and rotational stiffness. The effective depths of the reinforcement in the slabs varied from 75 mm to 150 mm, and the amount of reinforcement changed from 0 to 1.2% with 8, 12, and 16 mm bar diameters. A comparison of the service and ultimate limit state behavior of the tested one-way spanning slabs shows that a different design approach is necessary for GFRP-reinforced in-plane restrained slabs that demonstrate compressive membrane action behavior. Design codes based on yield line theory, which considers simply supported and rotationally restrained slabs, are not sufficient to predict the ultimate limit state behavior of restrained GFRP-reinforced slabs. Tests reported a higher failure load for GFRP-reinforced slabs by a factor of 2, which was further validated by numerical models. The experimental investigation was validated by a numerical analysis, and the acceptability of the model was further confirmed by consistent results obtained by analyzing in-plane restrained slab data from the literature.
Open Access
Experimental study On Addition of Pine Fibres to High Strength Concrete
(researchgate.net, 2017-03) Seneviratne, R; Tharmarajah, G
This study focuses on influence of pine fibres on unit weight, compressive strength and flexural strength of high strength concrete. Concrete mixes with 2%, 4% and 6% fibre content were produced while length of the fibres were varied from 10 mm to 40 mm. From the pine fibre reinforced mixes, 36 test cubes and 36 beam specimens were casted to identify the desired variations. Unit weight of the concrete showed significant variations in the test cubes. However, the variations of the unit weight observed in the beam specimens were low compared to the variations observed in test cubes. Compressive strength of the high strength concrete also reduced significantly with the addition of pine fibres. Also a reduction in flexural strength was observed. Variation of both compressive and flexural strength showed a relationship with the fibre content and fibre length as well.
Embargo
Mechanical and durability analysis of eco-friendly light weight cement blocks using raw rice husk as a partial replacement for manufactured sand
(Elsevier Ltd, 2025-03-08) Thavarajah, L; Sundaralingam, K; Tharmarajah, G
The study investigates the mechanical and durability properties of cement blocks made by partially replacing manufactured sand (M-sand) with raw rice husk (RRH). The rising demand for sand in construction, coupled with the environmental impact of its extraction, has prompted the exploration of alternative materials. RRH, a byproduct of rice milling, offers an eco-friendly substitute for sand. The research examines blocks containing varying proportions of RRH (20 %, 40 %, and 60 %) and compares treated and untreated husks. Key parameters, including compressive strength, tensile strength, density, performance when exposed to heat, and water absorption, were analyzed. The results show that up to 40 % of RRH can be used to replace sand without compromising the blocks' structural integrity. Treated RRH blocks demonstrated better bonding with cement, leading to higher compressive and tensile strengths compared to untreated ones. A 40 % RRH replacement achieved an average compressive strength of 3.57 MPa, surpassing the minimum requirements for non-load-bearing masonry units as per Sri Lankan and Australian standards. However, increasing RRH content to 60 % significantly reduced strength and durability. Additionally, RRH blocks exhibited a decrease in density, offering advantages in terms of transportation and handling. Water absorption increased with higher RRH content due to its porous nature yet remained within acceptable limits for treated blocks. These findings suggest that RRH can be a sustainable alternative to sand in masonry applications, especially in rural and eco-conscious construction.
Open Access
Use of Natural Fibres to enhance tensile strength of concrete
(ACADEMIC JOURNAL OF CIVIL ENGINEERING, 2017-07-21) Seneviratne, R.A.C.J; Tharmarajah, G; Archbold, p
This paper discusses the influence of natural fibres on density, compressive strength and flexural strength of fibre reinforced concrete specimens. Coir fibre extracted from coconut husk was added to high strength concrete to produced 36 test cubes and 36 beam samples. Tests carried out on cube and beam samples show that compressive strength of high strength concrete reduces with addition of coir fibres. The reduction is noticed varying with the change of fibre content and fibre length. Further, comparison between cubes and beams indicate variation in density of the concrete as well. The test results show that a reduction in flexural strength in most cases except for 2% coir fibre reinforced concrete, where a slight enhancement was noticed in flexural strength.