title: Improving the performance and durability of offshore concrete structures using FRHSC and UHPFRC
Creators: name: Zurgani, Mohamed Abdulhakim
Publisher: name: Memorial University of Newfoundland
Year: 2027

description: An experimental program was conducted to investigate the possibility of producing reinforced concrete elements that could be effectively and feasibly used in the harsh and abrasive marine environment. Mechanical, structural, and technical requirements such as high strength, lower weight, high abrasion resistance, high energy absorption capacity, high ductility, less construction time, and lower production cost are intended to be achieved. Four experimental studies were carried out with small and large specimens’ sizes to achieve the main goals. The first study aimed to produce fiber reinforced high concrete (FRHSC) that could be used as an ice-shield for offshore structures. Different supplementary cementitious materials (metakaolin and silica fume), types of fibers (basalt and steel fibers), types of basalt fibers (bundle and filament), types of steel fibers (single and double-hooked ends), length of steel fibers (35 mm and 60 mm), and volume ratio of the fibers in the mixture (0%, 0.25%, 0.5%, and 0.75%) were used to produce FRHSC mixtures with a compressive strength exceeding 100 MPa. The mechanical properties and the abrasion resistance of all mixtures produced were evaluated using small scale specimens. The second study was developed to generate structural reinforced elements with a satisfactory ability to carry loads, deform, withstand impact loads, and absorb energy. It also aimed to minimize the overall weight of the elements by using steel fiber lightweight aggregate concrete. Fibers are considered to eliminate the conventional shear reinforcements fully or partially, contributing to reducing the overall weight, manufacturing time and cost of the structures, particularly in the marine environment, where the fabrication and casting of reinforced concrete elements are more troublesome. The experimental program was carried out on seventeen reinforced concrete beams. Two different steel fiber ends’ shapes were used (single and double hooked ends) with a length of 60 mm. The employed variables included the longitudinal reinforcement ratio, the beams’ sizes, coarse aggregate to fine aggregate ratio (C/F), the concrete type, and presence of web reinforcements. The structural behaviour of the test beams was determined in terms of load-deflection behaviour, crack behaviour, mode of failure, flexural capacity, ductility, and toughness. In addition, the accuracy of some design codes and models was evaluated. In the first phase of the third study, ultra-high performance fiber reinforced concrete (UHPFRC) was developed with compressive strength exceeding 120 MPa. Cement, fine sand, silica fume, metakaolin, steel fibers, and superplasticizer were utilized to produce the concrete mixtures. The optimized FRHSC (from study 1) and UHPFRC mixtures were then used for the second phase, in which layered beams with a protective and strengthening layer of UHPFRC and/or FRHSC were structurally investigated. Ten composite beams were fabricated with high strength concrete HSC for the tension side and the optimized UHPFRC and/or FRHSC for the top compression side of the beams. The effects of different parameters on the overall structural response of the composite beams were determined in this phase. These parameters included varying the tensile reinforcement ratio, varying the thickness of the protective layer, using different interface configurations, and varying the web reinforcements’ ratio. The fourth study aimed to improve the abrasion resistance, durability, and structural performance of steel fiber high strength lightweight aggregate concrete (SFLWAC) beams, produced in the second study by providing the beams with a protective ice-shield layer made with an optimized concrete mixture developed in third study. Five composite beams were cast and tested. The composite beams were fabricated based on the previous two studies. The bottom and the top layers were constructed with SFLWAC and UHPFRC, respectively. The effect of the presence of a UHPFRC layer at the top of composite beams on the overall structural performance was determined based on the load-deflection response, crack development, mode of failure, flexural capacity, ductility, and energy absorption capacity.