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"In the research project presented in this PhD-thesis, an innovative type of fibre concrete is developed, with improved both the tensile strength and the ductility: the Hybrid-Fibre Concrete (HFC). The expression "Hybrid" refers to the "hybridisation" of fibres: short and long steel fibres were combined together in one concrete mixture. This is opposite to conventional steel fibre concretes, which contain only one type of fibre. The basic goal of combining short and long fibres is from one side to improve the tensile strength by the action of short fibres, and from the other side to improve the ductility by the action of long fibres." "In this research project, all important aspects needed for the development and application of Hybrid-Fibre Concrete have been considered. In total 15 mixtures, with different types and amounts of steel fibres were developed and tested in the fresh state (workability) as well as in the hardened state (uniaxial tensile tests, flexural tests, pullout tests of single fibres and compressive tests). A new analytical model for bridging of cracks by fibres was developed and successfully implemented for tensile softening response of HFC. At the end, the utilisation of HFC in the engineering practice was discussed, including a case-study on light prestressed long-span beams made of HFC."--BOOK JACKET.
This state-of-the-art volume covers the latest and future trends in measuring, monitoring and modeling the properties of cement based materials. The book contains 94 papers and presents the latest research work of renowned experts. It acts as a survey of the most up-to-date research in the field.
High performance concrete is a key element in virtually all-large construction projects, from tall office and residential buildings to bridges, tunnels and roadways. The fully updated Second Edition helps professionals to understand the performance capabilities of these construction materials when selecting the type of concrete to use for particular projects. The author is one of the worlds acknowledged experts on high performance concrete.
This volume highlights the latest advances, innovations, and applications in the field of fibre-reinforced concrete (FRC), as presented by scientists and engineers at the RILEM-fib X International Symposium on Fibre Reinforced Concrete (BEFIB), held in Valencia, Spain, on September 20-22, 2021. It discusses a diverse range of topics concerning FRC: technological aspects, nanotechnologies related with FRC, mechanical properties, long-term properties, analytical and numerical models, structural design, codes and standards, quality control, case studies, Textile-Reinforced Concrete, Geopolymers and UHPFRC. After the symposium postponement in 2020, this new volume concludes the publication of the research works and knowledge of FRC in the frame of BEFIB from 2020 to 2021 with the successful celebration of the hybrid symposium BEFIB 2021. The contributions present traditional and new ideas that will open novel research directions and foster multidisciplinary collaboration between different specialists.
Fibre-reinforced Concretes for High-performance Structures presents key information about the development, performance and design of fibre-reinforced concrete, ultra-high-performance fibre-reinforced concrete and geopolymer concrete, and critically analyses their key mechanical properties and durability characteristics.
The leading international authorities bring together in this contributed volume the latest research and current thinking on advanced fiber reinforced cement composites. Under rigorous editorial control, 13 chapters map out the key properties and behaviour of these materials, which promise to extend their applications into many more areas in the coming years.
Concrete-related construction industry consumes considerable amount of energy, resulting in large CO2 release into the atmosphere. Cement which is used as the main binder in concrete is energy intensive to produce and contributes about 7% to total global anthropogenic carbon emission. Infrastructure across the globe suffers from durability problems and requires frequent repair and maintenance. This brings about high direct cost for rehabilitation and unaccounted indirect cost resulted from loss of productive time, traffic congestion and diversion, and in the process more CO2 emission. In the meantime, buildings which are part of the overall civil infrastructure system require extensive amount of energy to keep the internal environment comfortable to users. The sector accounts for about 40% of global primary energy consumption. With increasing population and demand, actions from various building disciplines are needed to build a more sustainable industry. This research addresses these issues through the development of a new high performance fiber-reinforced concrete, its durability studies and its application to reduce operational energy in buildings. Durability is critical for infrastructure systems whose frequent maintenance and rehabilitation pose adverse impacts to the environment and add considerable costs to the economy. By accounting for sustainability aspects from materials conception to usage and disposal, this study encompasses the concept of sustainability through life cycle consideration. This represents a deviation from conventional sustainable approach where a focus is usually spent on reducing embodied energy of concrete composites. The first area of focus was on the development of a new concrete composite called high performance green hybrid fiber-reinforced concrete (HP-G-HyFRC) reinforced with polyvinyl alcohol (PVA) micro- and hooked-end steel macrofibers. For easy construction and durability, the design criteria were defined to cover high workability, high strength and deflection hardening which is defined as an ability of the composite to carry increasing load after the first crack is formed. It was demonstrated that theoretical analysis could be used to limit the number of trials in determining the critical fiber volume fractions for the deflection hardening behavior in the composite. As compared to conventional self-consolidating concrete (SCC), fine aggregate over coarse aggregate ratio had to be increased in FRC for enhanced workability. Addition of supplementary cementitious materials (SCMs) in concrete especially fly ash helped to improve the composite's workability. This is attributed to fly ash's favorable fineness, size distribution and spherical shape which resulted in ball-bearing action provided to other concrete constituents. PVA microfibers controlled propagation of micro cracks inherent in concrete or formed during loading. They also provided toughening around steel fibers and ensured a gradual pullout of steel fibers. The synergy of PVA micro- and steel macrofibers led to a smooth deflection hardening behavior of the composite under flexure at a relatively low fiber volume fractions of 1.5% steel fibers and 0.15% PVA fibers. A study on corrosion performance of HP-G-HyFRC with accelerated corrosion test with an impressed current was then conducted. It was found that wide cracks ranging from 1.1 to 2 mm were observed in high performance concrete (HPC) without fibers. The presence of hybrid fibers in HP-G-HyFRC, on the other hand, reduced corrosion rates by half, attributable to crack bridging of fibers and the resulting formation of distributed cracks of small sizes. Also, under no applied current, all embedded steel rebars in HP-G-HyFRC were in the inactive corrosion zone even with the presence of 4% NaCl in the mixing water. Microscopic observation at steel-concrete interface showed a densification of corrosion products, which is postulated to limit iron dissolution and subsequently to reduce corrosion rates of the embedded bars. HP-G-HyFRC corrosion samples were also able to retain most of its strength after the accelerated corrosion tests. As corrosion resistance of HP-G-HyFRC was considered at a composite level, the effects of individual mix component such as slag and fibers on corrosion were yet unknown. The next area of focus was on the influence of high-volume slag as cement replacement, hybrid fibers and steel-concrete interface on corrosion of steel in concrete. The studies elaborated various phenomena observed in the corrosion study of HP-G-HyFRC and also provided a fundamental understanding of different concrete parameters on corrosion. It was found that due to shrinkage-induced cracking and possibly poor quality passive film due to the presence of reducing agents in concrete pore solutions, samples with 60% slag replacement and with no fiber reinforcement showed an early corrosion initiation and higher mass loss induced by the impressed current. Microstructural imaging showed that the samples with slag, despite having a higher gas permeability, showed a denser matrix but more continuous distributed microcracking in the matrix. This led to its poor ability to accommodate corrosion products at the interface and as a result the concrete experienced an early onset of cracking. Under the same regime of applied current, samples made of slag concrete also experienced higher gravimetric mass losses. This is attributed to a less stable passive film and more intense acidification at the interface due to a reduction in calcium hydroxide (CH) in the matrix. Also, an inclusion of hybrid fibers in concrete slightly increased concrete permeability although this did not adversely affect corrosion initiation performance of concrete. However, under propagation stage achieved by an induced current, hybrid fibers in concrete significantly reduced corrosion rates through confinement and densification of corrosion products at steel-concrete interface. The influence of interface qualities on corrosion of steel in concrete showed conflicting performance in corrosion initiation and propagation stages. It was found that higher porosity at the steel-concrete interface initiated an early corrosion. However, the porous interface could accommodate more corrosion products. This led to a smaller pressure buildup from the corrosion products and less damage to the surrounding concrete. As a result, smaller corrosion rates were observed in the samples with more porous interfaces after impressed current regimes. The finding helps to explain the more extensive damage in high performance concrete (HPC) as compared to normal strength concrete. This warrants the inclusion of fibers in HPC to extend the service life of structures constructed with the composite. The study ended with a proposed application of HP-G-HyFRC in an innovative double skin façade (DSF) system in place of a conventional solid façade system to enhance operational energy performance of buildings. It was found that although the DSF is more energy intensive and more costly to construct, it allowed for a full recovery of the additional embodied energy within the first year of operation and cost recovery within the first 6 years of operation. The overall study exemplifies a life-cycle consideration adopted for materials design, durability investigation and application to ensure more sustainable infrastructure and buildings for our society.