https://www.um.edu.mt/library/oar/handle/123456789/17858 2026-04-14T20:26:58Z https://www.um.edu.mt/library/oar/handle/123456789/145481 Title: The feasibility of precast concrete structural systems in the local construction industry Abstract: Malta has experienced a significant increase in construction activity in recent years, driven by its economic development. This growth has placed increasing pressure on the local construction industry to enhance project efficiency, control costs, improve quality, and adopt more sustainable practices. At the same time, the industry faces challenges such as a limited skilled labour force, high levels of on-site activity, and strict project timelines. In response to these issues, precast concrete has emerged as a promising alternative to conventional construction methods. This research investigates the feasibility of precast concrete structural systems within the Maltese context by examining the key factors influencing their adoption, highlighting both the potential benefits and the challenges associated with their implementation. A mixed-methods research approach was adopted, involving semi-structured interviews with architects/structural engineers, and suppliers, as well as structured questionnaires distributed to a wider group of industry professionals, including architects/structural engineers, project managers, cost consultants, and quantity surveyors. In addition, selected case studies were reviewed to support the analysis of time and cost implications across projects of varying scale and structural systems. Quantitative data were assessed using percentage distributions, while qualitative data were thematically analysed using NVIVO Software to identify key themes, subthemes, and relationships. Findings suggest that precast concrete is most suitable for medium to large scale commercial and industrial developments, where repetitive design allows for mould reuse, increased efficiency, and faster construction. Smaller or residential projects face limitations due to lower standardisation and logistical constraints. Architectural typology, particularly in terms of scale, project type and aesthetics, strongly influences system selection. The success of precast depends on early design finalisation and planning, as it offers limited flexibility for late changes. Structural design remains a challenge, especially in connection detailing, due to limited local expertise. While initial costs are relatively high, long-term advantages include reduced on-site labour, shorter timelines, and consistent quality through factory-controlled production. However, certification and quality assurance vary across suppliers. Logistics and supply chain coordination are critical, requiring early planning and alignment between design, manufacturing, and site operations. Sustainability is generally perceived positively, with benefits in material efficiency and reduced site impact, although there are concerns about similar embodied carbon when compared to traditional methods. Its broader feasibility, when considered alongside cast in situ and steel systems, depends on factors such as project scale, site constraints, construction timeframes, cost considerations, and the local industry's capacity to adopt more industrialised construction methods. Description: M.Eng.(Melit.) 2025-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/145266 Title: Carbon dioxide sequestration in cement-based materials : carbonation treatment of recycled concrete powder Abstract: Urbanisation growth has brought about (i) an increased use of concrete and consequently an increase in Cem I production which is a major contributor to carbon dioxide (CO2) emissions and (ii) an increase of construction and demolition waste (C&DW). The objective of this study is to explore ways of how to provide a partial Cem I replacement whilst mitigating the problems mentioned above, namely by (i) reducing CO2 emissions by using CO2 captured during cement production in a process to produce supplementary cementitious material and (ii) using recycled concrete from construction and demolition waste in the afore-mentioned process to produce supplementary cementitious material (SCM). This dissertation focuses on the production of recycled concrete powder (RCP) and its activation via different treatment methods, to identify the process which yields the best supplementary cementitious material. Treatment processes researched in this dissertation included calcination, dry carbonation, aqueous carbonation, calcination followed by dry carbonation, calcination followed by aqueous carbonation and limewater soaking followed by dry carbonation. Initially, characteristic testing was done on the various treated powders to determine their physical and chemical properties. This was followed by the assessment of these treated powders when introduced as a 20% cement replacement within the mix design of paste and mortar samples, to determine their fresh, mechanical and durability properties. Calcination treatment achieved a material with the highest pozzolanic activity, as XRD results showed it to have the highest percentages of portlandite, tobermorite, gismondine, and belite at 17.4%, 12%, 2.1% and 17.2% respectively, when compared to the other treated samples. Through XRD, compressive strength and durability testing, it was determined that both dry and aqueous carbonation treatments also yielded materials with potential to be suitable supplementary cementitious material. The combined calcination and carbonation treatments yielded the best chemical and mechanical results due to the formation of both calcite and hydrated phases, creating materials of increased reactivity and strength. The dry carbonation in the calcination and dry carbonation process contributed to produce a material with better properties than that produced in the calcination and aqueous carbonation treatment. In fact, calcination followed by dry carbonation achieved the highest compressive strength of 114.90 MPa at 21 days, surpassing that of the cement control. Description: M.Eng.(Melit.) 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/145265 Title: Exploring the use of recycled rubber aggregate in seismically resilient concrete structures Abstract: This dissertation investigates the structural performance of rubberised concrete with a focus on its behaviour under static and cyclic loading. Building upon previous research conducted at the Faculty for the Built Environment at the University of Malta, an experimental programme was undertaken to compare a conventional control concrete mix with a rubberised concrete mix incorporating 25% crumb rubber replacement of fine aggregate (CR25). The experimental investigation comprised concrete cube compressive strength tests, static and cyclic reinforced concrete short column compressive strength tests, and static and cyclic reinforced concrete beam flexural tests. The experimental results confirmed that the inclusion of crumb rubber as partial fine aggregate replacement in reinforced concrete structural members leads to 56.39% and 16.16% reductions in compressive and flexural strength respectively when compared to conventional reinforced concrete structural members. However, under cyclic loading, rubberised reinforced concrete specimens exhibited enhanced deformation capacity, improved crack closure during unloading, and more ductile modes of failure. In contrast, conventional reinforced concrete specimens exhibited stiffer responses at the cost of brittle failure with reduced energy dissipation. Cyclic testing highlighted that rubberised concrete experiences accelerated stiffness degradation at higher stress levels relative to lower and moderate stress levels, where they retain superior shape recovery and damage tolerance. Overall, the experimental results obtained indicate that rubberised concrete may not be suitable for strength-critical structural elements, rather excelling in applications where characteristics such as ductility, energy dissipation, and seismic resilience are preferred. This research study demonstrates that rubberised concrete has potential as a specialised structural material in tailored cyclic and seismic environments, provided its use is appropriately supported by further research work. Description: M.Eng.(Melit.) 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/145263 Title: Tensile behaviour of glue-laminated timber : a comparative analysis between solid and finger-jointed specimens Abstract: This dissertation investigates the structural performance of finger-jointed glue-laminated timber elements, focusing on their behaviour under tensile, creep and cyclic loading scenarios, while also providing comparative analysis of the results with their solid counterparts. The main aim of this study is to evaluate the impact of finger-joints on the ultimate tensile strength and long-term behaviour of glue-laminated timber, as used in structural applications. To accomplish this, dogbone specimens were prepared from a local, commercially purchased glue-laminated beam, in order to have a consistency in the material properties like grade and moisture content. The results demonstrated that the finger-jointed timber specimens, generally exhibited reduced tensile strength when compared to the solid counterparts. Having said this, the finger-jointed specimens showcased satisfactory results under uniaxialtensile conditions, making them suitable for structural applications. Overall, the results of this study show that as long as the structural constraints are appropriately accounted for, the use of finger-jointing technique in timber is still a feasible methodology for sustainable and economical structural applications, since it enables efficient use of material and minimises wastage. Description: M.Eng.(Melit.) 2026-01-01T00:00:00Z