Day 2 :
Mackenzie Presbyterian University, Brazil
Keynote: Transient creep in plain and fiber reinforced concrete structures subjected to compressive load at high temperature
Time : 10:00-10:30
The prediction of transient creep involves a lot of uncertainties due to its complex mechanisms of activation. Transient creep is seated in the cement paste and occurs due to hygrothermal conditions: water evaporation and CSH dehydration. Above 400ºC, it is accelerated by the aggregates geomechanical properties decay. There is also a thermal mismatch between aggregate expansion and cement paste shrinkage after 150ºC, leading to concrete microcracking. As a result, due to concrete complex behavior and the coupling effects of the different strain components (viscous+elastic+plastic+thermal) at high temperature, it is a very difficult task to uncouple the viscous strain component (creep) from other thermomechanical strain sources. In practice, transient creep can be described accurately enough by the concept of LITS (Load Induced Thermal Strains), which is defined as the difference between the total strain, measured on a preloaded specimen, and the free thermal strain, measured on an unloaded specimen, subtracting the initial elastic deformation at 20°C. In order to investigate transiente creep phenomenon in plain and fiber reinforced concrete structures, a new LITS semi-empirical model is proposed, recognizing concrete as a heterogeneous biphasic material (aggregates + matrix) and assuming that LITS is the sum of thermomechanical and thermochemical strain contributions. The semi-empirical model is compared with experimental tests performed on steel fiber reinforced concrete samples with 11-years-old. Moreover, a mesoscopic analysis was carried out in Abaqus in order to uncouple LITS strain contributions and highlight the effects of the boundary conditions, aggregates decomposition and concrete dehydration.
The prediction of transient creep involves a lot of uncertainties due to its complex mechanisms of activation. Transient creep is seated in the cement paste and occurs due to hygrothermal conditions: water evaporation and CSH dehydration. Above 400ºC, it is accelerated by the aggregates geomechanical properties decay. There is also a thermal mismatch between aggregate expansion and cement paste shrinkage after 150ºC, leading to concrete microcracking. As a result, due to concrete complex behavior and the coupling effects of the different strain components (viscous+elastic+plastic+thermal) at high temperature, it is a very difficult task to uncouple the viscous strain component (creep) from other thermomechanical strain sources. In practice, transient creep can be described accurately enough by the concept of LITS (Load Induced Thermal Strains), which is defined as the difference between the total strain, measured on a preloaded specimen, and the free thermal strain, measured on an unloaded specimen, subtracting the initial elastic deformation at 20°C. In order to investigate transiente creep phenomenon in plain and fiber reinforced concrete structures, a new LITS semi-empirical model is proposed, recognizing concrete as a heterogeneous biphasic material (aggregates + matrix) and assuming that LITS is the sum of thermomechanical and thermochemical strain contributions. The semi-empirical model is compared with experimental tests performed on steel fiber reinforced concrete samples with 11-years-old. Moreover, a mesoscopic analysis was carried out in Abaqus in order to uncouple LITS strain contributions and highlight the effects of the boundary conditions, aggregates decomposition and concrete dehydration
Centre for Infrastructure Engineering and Safety
School of Civil and Environmental Engineering
The University of New South Wales, Australia
Time : 9:00-9:30
Dr Arnaud Castel is an Associate Professor in the School of Civil and Environmental Engineering at the University of New South Wales, Australia. Arnaud Castel graduated with his PhD in 2000 at the University of Toulouse in France where he has carried out his early career before his relocation to UNSW Australia in 2012. He has co-authored/authored 150 publications, including 70 journal papers with a current scopus H-index of 21 and more than 1500 citations. Since his relocation to UNSW, A/Professor Arnaud Castel has secured over AU$1,500,000 research funds including ARC Discovery projects, ARC Linkage projects and CRC projects
Geopolymer concrete (GC) is the result of the reaction of materials containing aluminosilicate such as fly ash and Ground Granulated Blast Furnace Slag with alkalis to produce an inorganic polymer binder. GC is Portland cement free low embodied carbon concrete. GC has been under intensive research around the world during the last 15 years. The major barriers to GC widespread adoption by the construction industry are concerns about durability and exclusion from current standards. Chemical reactions characterising alkali-activated binder systems differ drastically from conventional hydration process of Portland cement. Thus, the mechanisms by which concrete achieves potential durability are different between the two types of binders. As a result, testing methods and performance based requirements for geopolymer must be developed to be incorporated in a performance base standard. Testing methods presented will be looking at the risk of alkali leaching and efflorescence, passivity of reinforcement and chloride induced steel reinforcement corrosion in GC concrete.
Department of Civil Engineering
University of Birmingham, United Kingdom
Time : 9:30-10:00
Samir Dirar is an internationally recognised expert in strengthening and repair of concrete structures. After receiving his PhD from the University of Cambridge, United Kingdom, he worked as Postdoctoral Researcher in Zienkiewicz Centre for Computational Engineering at Swansea University. He is currently a Senior Lecturer (Associate Professor) in Structural Engineering at the University of Birmingham with overall responsibility for the Structures Research Lab. He has published over 50 journal and conference publications and has been serving as Grant Reviewer for funding agencies as well as Member of ACI Committee 440-0F - FRP-Repair-Strengthening and ASTM International Committee D30 on Composite Materials
The strength enhancement of existing concrete infrastructure is an application of considerable economic importance. It has been estimated that the cost of replacing structurally deficient transport infrastructure in Europe, a significant amount of which are concrete structures, is about €400 billion. In the United States, thousands of concrete bridges have been rated as structurally deficient and $20.5 billion would need to be invested annually to eliminate the bridge deficient backlog by 2028. There is thus scope for safe, practical and economic strengthening techniques for existing concrete infrastructure. Extensive research has resulted in approved flexural strengthening methods for concrete structures. In contrast, shear strengthening of concrete members is a particular challenge due to the brittle nature of shear failure and the complex mechanics of the behaviour. The collapse of the de la Concorde Overpass in 2006 in Canada, which killed or injured eleven people, was a tragic reminder of the dire consequences of concrete shear failures. This Keynote Paper will critically review current concrete shear strengthening techniques, with a special focus on a promising method known as the deep embedment (DE), or embedded through-section (ETS), technique. The Keynote Paper will also highlight the experimental, numerical and analytical work on DE/ETS strengthening of concrete members carried out at the University of Birmingham. Topics will include development of bond models for reinforcement bars embedded into concrete, repair of corrosion-damaged beams, strengthening of large scale bridge girders, seismic strengthening of beam-column joints, nonlinear finite element modelling and development of design guidance
Associate Professor, North Dakota State University, USA
Dr. Ying Huang obtained her Ph.D. from Missouri Univeristy of Science and Technology in 2012. Right after her Ph. D., Dr. Huang joined the department of Civil and Environmental Engineering at North Dakota State Univeristy as a faculty till now. Her research backgrounds are in smart cities and autonomous systems, smart materials and structural health monitoring, intelligent transportation systems, pavement and traffic monitoring, pipeline corrosion protection and mitigation, railroad damage and defect assessment, big data for civil engineering application, and emergency evacuation for multi-hazards. She possess two US approved and pending patents, published over 70 high quality peer reviewed publications that include one book chapter, 30 journals, and 40 conference papers, which were cited 360 times with an i10-index of 9. She has more than 10 invited presentations and 20 international and national presentations. Dr. Huang is also an associate editor and editorial board member for five international journals, committee member for five distinguishing professional society such as ASCE Structural Condition Assessment and Rehabilitation of Buildings Committee, ASTM Fiber Optic Practices Committee, and SPIE Sensors and Smart Structures Technologies Committee. She also organizes and modulates four international conferences such as ASME IMECE, IWSHM, SPIE Smart Structures & NDE Conference, and the ASCE Pipelines Conference. She is a grant reviewer for NSF CMMI Program, U.S. DOT PHMSA R&D Program, National Research Foundation (NRF) of Singapore R & D, and Energy Market Authority of Singapore R & D. Dr. Huang is also a frequent peer reviewer for more than 40 international journals and conferences. Dr. Huang won the 2015 NDSU Ozbun Economic Development Award, 2016 NDSU Forward Leap Research Award, 2017 NDSU College of Engineering Researcher of the Year and 2017 NDSU Centennial Award.
Concrete has become more and more popular in road constructions due to the facts that concrete lasts longer and its environmental friendness. The United States has 160,955 miles of roads, including the interstate highway system. Lots of roads within the US are suffering various distress problems. To assess the road conditions and track the traffic, multiple facilities are required simultaneously. For instance, vehicle-based image techniques are available for pavements’ mechanical behavior detection such as cracks, high-speed vehicle-based profilers are used upon request for the road ride quality evaluation, and inductive loops or strain sensors are deployed inside pavements for traffic data collection. Having multiple facilities and systems for the road conditions and traffic information monitoring raises the cost for the assessment and complicates the process. In this presentation, a concept of smart concrete pavement system will be discussed for integrated road condition and traffic monitoring to have the concrete pavement performing multiple functions using in-pavement strain-based sensors, which will phenomenally simplify the road condition and traffic monitoring. This system is expected to simultaneously assess and measure the pavement’s structural health condition, the road’s ride quality, the weighing and classification of vehicles passing with a high speed on the road. Such a superior system requires an innovative sensor system, which has been installed and validated in Minnesota's Cold Weather Road Research Facility (MnROAD) operated by MnDOT. The system was approved to be effective for monitoring the health conditions of the pavements, the traffic counts, ride quality evaluation, and weigh-in-motion measurements, and vehicle identification. The smart concrete pavement system is promising to use the existing concrete pavement system for multiple purposes, which gains a considerable efficiency increase as well as a potential significant cost reduction for intelligent transportation system
Université of Cergy-Pontoise, France
Keynote: Comparative study of repairing concrete using Carbon Fiber Reinforced Epoxy Composites and Bioressourced composites
Time : 10:30-11:00
Elhem GHORBEL has completed his PhD at the age of 27 years in materials science and engineering from the National High Engineering School of Mines - Paris. She is Professor at the university of Cergy-Pontoise in the department of Civil Engineering (IUT) since 2003. She has several institutional activities and scientific responsibilities at the national and international levels.
Her research interests cover the mix design, the mechanical and fracture behavior of materials ( self-compacting and resin concretes,composites , polymers), the valorization of inert and industrial wastes in concrete,the repairing of concrete by composites, the durability of heterogeneous materials (aging, Chemical attacks, biodegradationand freezing-thawing resistance), …
She has published more than 50 papers in reputed journals and 100 conference papers. She is editorial board member of Advances in Civil Engineering and Modern Civil and Structural Engineering. She was member of organizing and scientific committees of more than 30 conferences.
The main objective of this investigation is to evaluate the effectiveness of repairing damaged concrete using bioressourced composite by comparison to traditional ones.
To hit this target, the developed approaches are both experimental and analytical.
The first part of this study is dedicated to the characterization of the both resins (determination of the gel point and reticulation duration, glass transition temperature and mechanical behavior), the unidirectional composites used in the repairing process (mechanical characteristics) and the concrete (compressive and damage behaviors).
The second part is devoted to the experimental study of repaired damaged concrete loaded under compressive tests. Three different damage rates are applied on the concrete before the reparation. For damage rates less than 30%, mechanical performances (Compressive resistance, Stiffness and ductility) are completely restored or even enhanced for repaired concretes using UCFREP composites. A comparative effectiveness of repairing with UFFRBP requires applying two layers on composites instead one for UCFRE .
The third part of this work is dedicated to analytical modeling of mechanical behavior of confined concrete with composite under compression in one hand, and the tensile behavior of the composite in other hand.
Using Bioressourced composite for concrete reparation seems to have excellent performances comparable to Carbone one which encourages its application for concrete structures in civil engineering.