Research Papers - Department of Civil Engineering
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Publication Open Access Sustainable Alternatives to Clay Bricks: A Review on PET-Based Masonry Units for Green Construction(Ontario International Development Agency, 2026) Wijesundara H; Perera S.V.T.JThe rapid escalation of global plastic consumption, particularly polyethylene terephthalate (PET), has created severe environmental challenges, while the conventional clay brick industry continues to generate significant greenhouse gas emissions and deplete nonrenewable resources. This paper reviews existing literature on two sustainable construction approaches aimed at addressing these dual issues: (i) the incorporation of melted PET in masonry blocks and (ii) the embedding of sand-filled PET bottles in masonry units. Findings indicate that melted PET-sand composite bricks, particularly at an optimal 1:3 plastic-to-sand ratio, exhibit superior performance compared to conventional clay bricks. These composites achieve compressive strength improvements of over 44% and reduce water absorption by up to 94.93%. They also demonstrate enhanced durability, with less than 2% strength loss under acid exposure, compared to over 15% in traditional bricks. Additionally, their production requires 79% less energy and reduces CO₂ emissions by a similar margin, underscoring their environmental advantages. The review also highlights the effectiveness of sand-filled PET bottles as structural masonry elements. Sand is a superior filler since it can hold up to 38.34 N/mm² of pressure, which is far more than bottles filled with dirt (8.99 N/mm²) or plastic bags (2.72 N/mm²). The review shows that both melted PET-sand bricks and sand-filled PET bottle masonry are good, eco-friendly substitutes for regular clay bricks. These methods have two benefits: they reduce plastic waste and encourage building techniques that are good for the environment. The results give an excellent justification to use PET-based masonry technologies as we shift toward building materials that are better for the environment.Publication 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, GThis 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 conditionsPublication Embargo Durability and mechanical performance of glass and natural fiber-reinforced concrete in acidic environments(Elsevier, 2025-02-28) Justin, S.; Thushanthan, K; Tharmarajah, GThis 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.Publication Embargo Ex situ characterization and modelling of fatigue crack propagation in catalyst coated membrane composites for fuel cell applications(Pergamon, 2019-05-03) Singh, Y; Khorasany, R. M. H; Kim, W. H. J; Alavijeh, A. S; Kjeang, E; Rajapakse, R. K. N. D; Wang, G. GInteractions between catalyst layers and membrane are known to influence the mechanical properties of catalyst coated membrane (CCM) composites used in fuel cells, and can further affect their fatigue-driven mechanical fracture — an important lifetime-limiting failure mode in automotive applications. Here, the fracture propagation phenomenon in CCMs is characterized through a series of ex situ experiments and microstructural investigations conducted across a range of stress, temperature (23-70 °C), and relative humidity (50–90%) conditions relevant to low-temperature polymer electrolyte fuel cells. In comparison to pure membranes, the crack propagation rates are slightly arrested in CCMs through mechanical reinforcement offered by the catalyst layers; however, the membrane layer still controls the overall crack growth trends through its temperature and humidity dependent ductile fracture characterized by confined yielding around the fracture surface. Local interfacial delamination and severe electrode cracking are found to accompany the CCM crack propagation, which aids membrane fracture by loss of local reinforcement. A Paris law based fracture modelling framework, incorporating the elastic-viscoplastic mechanical response of CCMs, is developed to semi-analytically evaluate one-dimensional crack growth rate during cyclic loading, and provides reasonably accurate predictions for the present ex situ problem.Publication Embargo Ex situ measurement and modelling of crack propagation in fuel cell membranes under mechanical fatigue loading(Pergamon, 2017-07-27) Singh, Y; Khorasany, R. M. H; Alavijeh, A. S; Kjeang, E; Wang, G. G; Rajapakse, R. K. N. DFatigue-induced membrane fracture due to dynamic stresses is an important lifetime-limiting failure mode in automotive fuel cell applications. Here, a series of ex situ experiments are first conducted to measure the rate of crack growth in Nafion NRE211 membranes for a range of stress, temperature (23–70 °C), and relative humidity (50–90%) conditions relevant to automotive fuel cell operation. The crack growth rate is found to be ∼1–10 nm per load cycle and strongly depends on the stress intensity: the rate increases by an order of magnitude for a mere 10–30% increase in stress, which suggests that improved stress uniformity and avoidance of high stress points is important for durability. Moreover, the sensitivity to applied stress doubles from room conditions to fuel cell conditions, where the temperature has 2–3x stronger impact on the fracture propagation than the relative humidity. Microstructural analysis indicates that plastic deformation (60% localized thinning) at the crack tip accompanies crack growth. A semi-analytical model based on Paris law is then developed to simulate crack growth as a function of cyclic loading. The model incorporates elastic-viscoplastic mechanical behaviour of ionomer membranes and provides crack growth predictions in agreement with ex situ data up to 100% strain.Publication Embargo Decay in Mechanical Properties of Catalyst Coated Membranes Subjected to Combined Chemical and Mechanical Membrane Degradation(Wily, 2014-11-28) Rajapakse, R. K. N. D; Wang, G. G; Lauritzen, M; Kjeang, E; Lim, C; Ghataurah, J; Khorasany, R. M. H; Goulet, M. A; Alavijeh, A. SThe mechanical stability of catalyst coated membranes (CCMs) is an important factor for the overall durability and lifetime of polymer electrolyte fuel cells. In this article, the evolution of the mechanical properties of degraded CCMs is comprehensively assessed. A combined chemical and mechanical accelerated stress test (AST) was applied to simulate field operation and rapidly generate partially degraded CCM samples for tensile and expansion experiments under both room and fuel cell conditions. The tensile results indicated significant reductions in ultimate tensile strength, toughness, and fracture strain as a function of AST cycles, accompanied by a mild increase in elastic modulus. The increased brittleness and reduced fracture toughness of the CCM, caused primarily by chemical membrane degradation, is expected to play an important role in the ultimate failure of the fuel cell. The expansion tests revealed a linear decay in hygrothermal expansion, similar in magnitude to the loss of mechanical strength. The decline in CCM sensitivity to environmental changes leads to non-uniform swelling and contraction that may exacerbate local degradation. Interestingly, the hygrothermal expansion in the late stages of degradation coincided with the fracture strain, which correlates to in situ development of fractures in chemically weakened membranes.Publication Embargo Mechanical degradation of fuel cell membranes under fatigue fracture tests(Elsevier, 2015-01-01) Khorasany, Ramin M.H; Alavijeh, A. S; Kjeang, E.; Wang, G.G.; Rajapakse, R. K. N. DThe effects of cyclic stresses on the fatigue and mechanical stability of perfluorosulfonic acid (PFSA) membranes are experimentally investigated under standard fuel cell conditions. The experiments are conducted ex-situ by subjecting membrane specimens to cyclic uniaxial tension at controlled temperature and relative humidity. The fatigue lifetime is measured in terms of the number of cycles until ultimate fracture. The results indicate that the membrane fatigue lifetime is a strong function of the applied stress, temperature, and relative humidity. The fatigue life increases exponentially with reduced stresses in all cases. The effect of temperature is found to be more significant than that of humidity, with reduced fatigue life at high temperatures. The maximum membrane strain at fracture is determined to decrease exponentially with increasing membrane lifetime. At a given fatigue life, a membrane exposed to fuel cell conditions is shown to accommodate more plastic strain before fracture than one exposed to room conditions. Overall, the proposed ex-situ membrane fatigue experiment can be utilized to benchmark the fatigue lifetime of new materials in a fraction of the time and cost associated with conventional in-situ accelerated stress testing methods.