134 research outputs found
Hybrid intelligence framework for optimizing shear capacity of lightweight FRP-reinforced concrete beams
No full textThis study rigorously assesses the shear capacity of fiber-reinforced polymer (FRP) reinforced concrete (RC) beams as a lightweight material alternative, scrutinizing the efficacy of the Eurocode and ACI design codes. Leveraging a dataset of 260 experimental FRP-RC beam cases, two distinct Artificial Neural Network (ANN) models were developed using the Levenberg-Marquardt algorithm. Beams with and without stirrups were considered, with parameters including beam width (b), depth (d), length (L), concrete compressive strength (fc′), FRP modulus of elasticity (Efr, Efs) and FRP reinforcement ratios (ρf, ρfs). Multi-objective optimization was deployed to integrate Genetic Algorithms (GA) and fmincon to optimize beam parameters for maximizing the shear capacity, Vc. Sensitivity analysis allowed to quantify the influence of each parameter, revealing that b and d significantly affect Vc, with sensitivity scores of 0.39 and 0.35, respectively. The optimization process, highlighted by a 3D scatter plot, dynamically illustrated trade-offs among key design parameters (ρf, ρfs, d), giving insights into the complex interplay in FRP beam design. The hybrid intelligence models reached superior predictive accuracy over traditional codes, achieving R2 values of 0.89. Notably, for beams without stirrups, model predictions closely matched experimental data, with a lower average ratio (1.02) compared to Eurocode (1.65) and ACI (1.58). Principal Component Analysis (PCA) has elucidated the intricate interactions among variables, thereby deepening insights into the structural dynamics of FRP-RC beams. Incorporating artificial intelligence, sophisticated optimization methodologies, and thorough statistical evaluations establishes a holistic approach for the structural examination of FRP-RC beams, providing improved precision and valuable viewpoints for the refinement of future designs
EFFECT OF ILMENITE AND FERROBORON ON RADIATION SHIELDING ULTRA-HIGH-PERFORMANCE CONCRETE
No full textThis research was undertaken to develop an innovative concrete formulation capable of mitigating the environmental impact of ionizing radiation produced by nuclear applications.The rapid expansion of Canada’s nuclear energy sector requires new facility construction while ensuring compliance with the highest safety and security standards. Concrete serves as the primary physical barrier in nuclear infrastructure, shielding against radiation and preventing leakage into the environment and public spaces during normal operational conditions as well in the event of accidents. Consequently, nuclear facility safety depends on the quality of concrete used. This research focuses on developing radiation shielding ultra-high-performance concrete (RS-UHPC) with enhanced mechanical and radiation shielding properties. First, a state-of-the-art review identified Ilmenite and Ferroboron—both rarely studied in the literature—as promising aggregates due to their high densities, heavy atomic element content, and Ferroboron's elevated boron levels necessary for neutron shielding. Subsequently, an extensive experimental program was designed to assess the individual and combined effects of partially replacing Quartz Sand with Ilmenite and Ferroboron (up to 50% each) on RS-UHPC’s physical, mechanical, and radiation shielding properties. We coupled particle packing optimization with statistical modeling to capture the optimal compositional domain space that balances mechanical performance with radiation shielding characteristics. A relatively high water-to-binder ratio of 0.25 was intentionally implemented to serve dual functions: providing sufficient hydrogen content for fast neutron moderation while maintaining optimal mixture flowability. The Modified Andreasen & Andreasen model was applied to maximize particle packing density, enhancing mixture compactness. The Simplex Centroid Design enabled capturing the separate and joint interaction effects of Ilmenite and Ferroboron on RS-UHPC performance. Results indicated that while these aggregates slightly reduced compressive strength, they significantly improved radiation shielding, yielding 33%, 1,200%, and 25% enhancements for
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gamma, thermal neutron, and fast neutron shielding, respectively. Based on pre-defined desirability criteria considering nuclear-grade UHPC, the optimal compositional domain space lies at 26% Quartz Sand, 24% Ilmenite, and 50% Ferroboron. These findings constitute a significant leap forward in engineering novel concrete formulations with enhanced mechanical performance and radiation shielding, thereby contributing to the deployment of safer and more secure nuclear facilities.ThesisMaster of Applied Science (MASc)Concrete serves as the ultimate physical barrier in nuclear infrastructure, providing a secure shield against radiation and preventing its leakage into the environment and public spaces in the event of accidents. This research focuses on developing radiation-shielding ultra-high-performance concrete (RS-UHPC) with enhanced shielding capabilities. It explores the use of two underutilized materials—Ilmenite and Ferroboron—as replacements for Quartz Sand. While these heavyweight aggregates slightly reduce the compressive strength, they significantly enhance the radiation shielding properties of RS-UHPC. The study aims to achieve an optimal balance between the mechanical properties of RS-UHPC and its radiation shielding performance through mixture refinement, including optimizing the particle packing structure and employing statistical modeling to minimize the need for extensive testing. The research outcomes contribute to the development of safer and more secure nuclear facilities, reinforcing defense-in-depth strategies in nuclear infrastructure
RADIATION SHIELDING ULTRA-HIGH-PERFORMANCE CONCRETE
No full textThis thesis investigates the development and optimization of a novel radiation shielding ultra-high-performance concrete (RS-UHPC) incorporating magnetite and colemanite as sustainable fine aggregate replacements. Using Response Surface Methodology (RSM), this study evaluates the influence of varying magnetite and colemanite contents on the concrete’s density, mechanical performance, and radiation attenuation properties. The findings aim to contribute to the advancement of durable, high-performance shielding materials for nuclear infrastructure.Concrete containment structures play a critical safety role in nuclear infrastructure. However, conventional radiation shielding concrete (RSC) exhibits limited design strength, reinforcement congestion, and durability issues. This study develops a novel radiation shielding ultra-high-performance concrete (RS-UHPC) incorporating magnetite and colemanite aggregates. A control UHPC mixture was tailored using particle packing optimization, and magnetite and colemanite contents were systematically varied using a statistical experimental design. A spectrum of RS-UHPC designs were formulated and evaluated for density, compressive strength, and radiation attenuation (i.e., gamma, fast neutron, and thermal neutron). Results demonstrated that full replacement of silica sand with magnetite significantly enhanced mechanical and gamma shielding properties, while achieving the highest density (3420 kg/m³, a 41% improvement), linear attenuation coefficient (0.260 cm⁻¹, a 38% improvement), and fast neutron removal cross-section (0.119 cm⁻¹, a 23% improvement). Colemanite, while slightly reducing compressive strength, improved thermal neutron shielding by 130%. The combination of magnetite and colemanite (at 100% magnetite replacement of silica sand and 7% colemanite replacement of cement) exhibited the highest shielding properties, achieving 21 and 161% increases in fast and thermal neutron attenuations, respectively. To balance strength and shielding performance, an optimal mix was developed with 100% magnetite and 5.25% colemanite, achieving 120 MPa compressive strength while maintaining significant radiation attenuation. The use of such optimized mixture as shielding material enables the construction of thinner, safer nuclear containment structures. Moreover, recommendations are made to further enhance the developed RS-UHPC mixture. The findings of this study contribute to the advancement of RS-UHPC as a high-performance shielding material for nuclear applications.ThesisMaster of Applied Science (MASc)As nuclear energy plays a vital role in building and maintaining sustainable cities and communities, addressing its inherent safety concerns remains critical for wider spread adoption of this technology, particularly regarding radiation shielding. Traditional shielding concrete often lacks the strength and durability needed for long-term use in nuclear infrastructure. This study introduces a novel radiation shielding ultra-high-performance concrete (RS-UHPC) incorporating magnetite and colemanite. Magnetite, a dense iron-rich mineral, improves density and shields against gamma rays and fast neutrons, while colemanite, rich in boron, enhances thermal neutron absorption. Although colemanite slightly reduces compressive strength in this study, an optimized mix containing 100% magnetite and 5.25% colemanite achieved high compressive strength (120 MPa) and superior radiation shielding. The RS-UHPC developed in this study can lead to safer, thinner, and more durable shielding in nuclear facilities
Mécanismes de transfert de masse dans le béton comme critère de durabilité : application in situ aux bétons de barrage
No full textUne étude visant à évaluer l'état de vieillissement des bétons d'ouvrages hydroélectriques à l'aide d'essais de perméabilité et d'absorption réalisés in-situ a été entreprise. Six bétons de barrage ayant différents rapports eau/ciment et différentes teneurs en air entraîné ont été confectionnés. Ils ont été utilisés comme bétons sains de référence pour nos études de simulation en laboratoire. Leurs propriétés mécaniques et leurs perméabilités ont été caractérisées. En parallèle, nous avons développé un essai de perméabilité à l'air et d'absorption d'eau in situ qui peuvent être utilisés de façon très simple en chantier sur les bétons de barrage. Ces techniques d'essais de chantier ont été mises à l'épreuve, d'une part en examinant la réponse des différents bétons confectionnés au laboratoire et d'autre part en comparant les résultats obtenus à ceux d'essais de laboratoire beaucoup plus classiques tels que la perméabilité à l'eau, la perméabilité à l'air, la perméabilité aux ions chlores, l'absorption d'eau par immersion et la porosimétrie par intrusion de mercure. Pour terminer, nous avons fait une série d'essais de chantier sur le barrage de Beauharnois et le barrage Heming. Nous avons pu mettre en évidence la sensibilité de ces essais à la variation de la qualité du béton mais aussi l'effet de l'humidité du béton sur la variabilité des résultats
Why some carbonate fillers cause rapid increases of viscosity in dispersed cement-based materials
No full textCrisis of Civil Engineering Education in Information Technology Age: Analysis and Prospects
No full textMicrofiller effect on rheology, microstructure, and mechanical properties of high-performance concrete
No full textThe objective of this study was to develop a fundamental understanding of the microfiller effect
in high-performance concrete. Ultimately, this would help in the development of blended highperformance
cements containing recycled materials and industrial byproducts, offering both
significant economic advantages and environmental relief.
The mechanisms underlying the microfiller effect on the rheology were investigated in cement
paste using a coaxial-cylinders viscometer, a mini slump test, the Marsh cone flow time, and a
pressure bleed test. They were also studied in mortars using the ASTM flow-table test, and in
concrete using a computer-controlled rheometer, a slump-flow test, the conventional slump test,
and an induced bleeding test. It was found that microfillers enhance the superplasticizer
efficiency because they increase the surface layer water and reduce the bulk water through a
reduced void space in the particulate mixture. In the presence of a superplasticizer, microfillers
also decrease the viscosity of concrete mixtures; the finer the particle size of the microfiller the
greater the decrease. This seems to be due to a reduction of the mechanical interlocking between
coarser particles. Ultrafine particles also decrease the bleed water, which reduces the occurrence
of bleed channels and low density microstructural features at interfaces. As a result of the above,
microfillers make the production of fluid and self-leveling concrete much easier. It was also
demonstrated that triple-blended cements containing pozzolanic and non-pozzolanic fillers can
achieve superior rheological properties.
The microfiller effect on mechanical properties was investigated in mortars and in concrete both
at early and later ages. It was discovered that this effect depends on the initial porosity of the
system. At very low w/b ratios, partial replacement of cement with non-cementitious fillers
would not result in lower density hydration products because the initial porosity is already very
low. The hydration reactions in fact yielded denser hydration products. Thus, up to 15%
replacement of cement by a non-cementitious filler caused significant increases in strength. This
was even more significant in triple-blended cements containing combinations of pozzolanic and
non-pozzolanic fillers for which up to 30% partial replacement of cement resulted in significant
strength increases. Ultrafine carbonate fillers increased the very early age strength by about one order of magnitude,
because certain microfillers appear to present energetically preferential substrates for the
germination and growth of calcium hydroxide. Removal of calcium ions from the solution
catalyzes the dissolution of C₃S in an attempt to regain equilibrium. This signals an earlier end of
the induction period and a faster rate of the hydration reactions at early ages.
Quantitative image analysis of backscattered electron micrographs was used to quantify the
microfiller effect on the microstructure of high-performance concrete. Analysis was carried out
on cement paste and concrete both at Id and at 28d. The acceleration of the hydration reactions
at early ages due to carbonate microfillers was confirmed by this technique. Microfillers
generally decreased the porosity and refined the microstructural features. This was accompanied
by increased strength only when the ratio of inner hydration products to outer hydration products
was increased. Densification of the paste-aggregate interface did not seem to necessarily increase
the compressive strength.
The microfiller effect in high-performance concrete was studied from the standpoint of the
theory of particle packing. An insight into particle packing models, the effects of particle
packing on rheology, and the effects of particle size distribution on hydration reactions was
obtained. A new parameter, the microfiller efficiency factor was developed, based on an
estimation of packing density and microfiller effect on hydration rate. A close correlation was
found between the microfiller efficiency factor and compressive strength. In addition, a new
model relating microstructure to strength was proposed. Most available models relate porosity to
strength without accounting for the nature of the solid phase. The model proposed herein
considers for the first time a quantitative value representing the nature of the hydration products
to help estimate strength. This value is the ratio of the dense inner hydration products to the bulk
of the rest of the hydration products. The proposed model achieved good estimations of strength.
Overall, this study proposes a new approach to achieving high-strength materials. Traditionally,
high strength is obtained through increased cement content, reduced w/b ratios, and high rates of
hydration. This work suggests that high strength can be achieved through high initial particle
packing combined with a low rate of hydration, which causes less chemical contraction, less
drying shrinkage and self dessication stresses, and a higher content of inner hydration products.Applied Science, Faculty ofCivil Engineering, Department ofGraduat
Coupled effects of limestone powder and high-volume fly ash on mechanical properties of ECC
No full textOwing to its exceptional strain capacity, which can reach hundreds of times that of normal concrete, and its reduced crack width, engineered cementitious composites (ECC) are a very promising solution for mitigating many of the problems that generate colossal backlogs of deteriorated concrete structures worldwide. However, research is needed to develop more sustainable ECC with flexible formulation that uses local materials. This paper investigates the coupled effects of using limestone powder in ECC as partial or total replacement for silica sand aggregate, coupled with using high-volume fly ash as a binder. The compressive and flexural strengths and fracture toughness for the formulated ECCs were examined at 3, 28 and 90 days. The results of this study demonstrate that sustainable ECC for resilient structural applications can be produced. It is aimed that more flexible formulations of ECC using local materials with lower environmental footprint could emerge and contribute to more durable and sustainable civil infrastructure. (C) 2017 Elsevier Ltd. All rights reserved
Condition Assessment of Reinforced Concrete Bridges: Current Practice and Research Challenges
No full textOne quarter of bridges in Canada and the United States need repair. The present study provides a critical overview of the state-of-the-art existing condition assessment techniques for reinforced concrete bridges, with an emphasis on current practice in North America. The techniques were classified into five categories, including visual inspection, load testing, non-destructive evaluation, structural health monitoring, and finite element modelling. The potential applications of these technologies are discussed and compared, highlighting their primary advantages and limitations. The review revealed that quantitative assessment could be effectively achieved using several complementary technologies. It is shown that there is need for concerted research efforts to achieve automated data collection and interpretation analyses. Also, the configuration of monitoring systems was found to be paramount in effectively assessing bridge performance parameters of interest. The study suggests appropriate investigation methods for some bridge deterioration mechanisms. Knowledge gaps and challenges in this field are outlined in order to motivate further research and development of these technologies
Behaviour of reinforced self-consolidating concrete frames
No full textMulti-storey reinforced concrete (RC) structural frames represent some of the most congested structural elements. Placing and consolidating concrete in such structural frames imposes substantial challenges. This offers a unique area of application for self-consolidating concrete (SCC) because of its inherent ability to flow under its own weight and fill congested sections, complicated formwork and hard-to-reach areas. Research is, however, needed to demonstrate the ability of SCC structural frames adequately to resist vertical and lateral loads. In the present study, full-scale 3 m high beam-column joints reinforced as per the Canadian Standards CSA A23·3-94 and ACI-352R-02 were made with normal concrete (NC) and SCC. They were tested under reversed cyclic loading applied at the beam tip and at a constant axial load applied on the column. The beam–column joint specimens were instrumented with linear variable displacement transducers and strain gauges to determine load–displacement traces, cumulative dissipated energy and secant stiffness. The current paper compares the performance of reinforced NC and SCC structural frames and discusses the potential use of SCC in such structural elements. Results indicate that reducing the coarse aggregate content in SCC mixtures can reduce the contribution of the aggregate interlock mechanism to total shear resistance, which leads to more rapid deterioration under cyclic loading. Further research is needed to ensure the safety of using low coarse aggregate content in SCC in highly seismic areas and assess the safety of already existing buildings cast using SCC
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