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  • The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

International Concrete Abstracts Portal

Showing 1-5 of 1339 Abstracts search results

Document: 

SP343

Date: 

November 3, 2020

Author(s):

fib and ACI

Publication:

Symposium Papers

Volume:

343

Abstract:

The first international FRC workshop supported by RILEM and ACI was held in Bergamo (Italy) in 2004. At that time, a lack of specific building codes and standards was identified as the main inhibitor to the application of this technology in engineering practice. The workshop aim was placed on the identification of applications, guidelines, and research needs in order for this advanced technology to be transferred to professional practice. The second international FRC workshop, held in Montreal (Canada) in 2014, was the first ACI-fib joint technical event. Many of the objectives identified in 2004 had been achieved by various groups of researchers who shared a common interest in extending the application of FRC materials into the realm of structural engineering and design. The aim of the workshop was to provide the State-of-the-Art on the recent progress that had been made in term of specifications and actual applications for buildings, underground structures, and bridge projects worldwide. The rapid development of codes, the introduction of new materials and the growing interest of the construction industry suggested presenting this forum at closer intervals. In this context, the third international FRC workshop was held in Desenzano (Italy), four years after Montreal. In this first ACI-fib-RILEM joint technical event, the maturity gained through the recent technological developments and large-scale applications were used to show the acceptability of the concrete design using various fibre compositions. The growing interests of civil infrastructure owners in ultra-high-performance fibre-reinforced concrete (UHPFRC) and synthetic fibres in structural applications bring new challenges in terms of concrete technology and design recommendations. In such a short period of time, we have witnessed the proliferation of the use of fibres as structural reinforcement in various applications such as industrial floors, elevated slabs, precast tunnel lining sections, foundations, as well as bridge decks. We are now moving towards addressing many durability-based design requirements by the use of fibres, as well as the general serviceability-based design. However, the possibility of having a residual tensile strength after cracking of the concrete matrix requires a new conceptual approach for a proper design of FRC structural elements. With such a perspective in mind, the aim of FRC2018 workshop was to provide the State-of-the-Art on the recent progress in terms of specifications development, actual applications, and to expose users and researchers to the challenges in the design and construction of a wide variety of structural applications. Considering that at the time of the first workshop, in 2004, no structural codes were available on FRC, we have to recognize the enormous work done by researchers all over the world, who have presented at many FRC events, and convinced code bodies to include FRC among the reliable alternatives for structural applications. This will allow engineers to increasingly utilize FRC with confidence for designing safe and durable structures. Many presentations also clearly showed that FRC is a promising material for efficient rehabilitation of existing infrastructure in a broad spectrum of repair applications. These cases range from sustained gravity loads to harsh environmental conditions and seismic applications, which are some of the broadest ranges of applications in Civil Engineering. The workshop was attended by researchers, designers, owner and government representatives as well as participants from the construction and fibre industries. The presence of people with different expertise provided a unique opportunity to share knowledge and promote collaborative efforts. These interactions are essential for the common goal of making better and sustainable constructions in the near future. The workshop was attended by about 150 participants coming from 30 countries. Researchers from all the continents participated in the workshop, including 24 Ph.D. students, who brought their enthusiasm in FRC structural applications. For this reason, the workshop Co-chairs sincerely thank all the enterprises that sponsored this event. They also extend their appreciation for the support provided by the industry over the last 30 years which allowed research centers to study FRC materials and their properties, and develop applications to making its use more routine and accepted throughout the world. Their important contribution has been essential for moving the knowledge base forward. Finally, we appreciate the enormous support received from all three sponsoring organizations of ACI, fib and Rilem and look forward to paving the path for future collaborations in various areas of common interest so that the developmental work and implementation of new specifications and design procedures can be expedited internationally. June 2018 Bruno Massicotte, Fausto Minelli, Barzin Mobasher, Giovanni Plizzari


Document: 

SP-343_37

Date: 

October 1, 2020

Author(s):

Berrocal, C.G.; Lundgren, K.; Löfgren, I.

Publication:

Symposium Papers

Volume:

343

Abstract:

In the present paper, long-term experiments involving natural corrosion of RC beams subjected to chloride solution cyclic exposure were carried out to investigate the effect of fibres on different aspects of the corrosion process as well as their contribution to the structural behaviour of RC elements damaged by corrosion. The long-term experiments were complemented with short-term accelerated corrosion experiments and mechanical tests to investigate the influence that low fibre contents may have on individual mechanisms that play an important role in the corrosion process of steel in concrete. These showed that fibres promote crack branching which results in a change of the internal crack pattern towards multiple thinner cracks, particularly near the reinforcement. This agrees with the long-term experiment results, which exhibited longer times to corrosion initiation for FRC beams with bending cracks and revealed a more distributed corrosion with more pits but less crosssectional loss compared to bars in plain concrete. Fibres also proved beneficial in delaying corrosion-induced cracks and preventing cover spalling, which greatly enhanced the bondbehaviour of corroded bars. Furthermore, a positive effect of the fibres was also observed on the residual flexural capacity of corroded beams, which generally increased the load-carrying capacity and rotation capacity.


Document: 

SP-343_26

Date: 

October 1, 2020

Author(s):

Fantilli, A.P.; Tondolo, F.

Publication:

Symposium Papers

Volume:

343

Abstract:

Durability of reinforced concrete (RC) structure is mostly related to the ability of concrete cover to protect the embedded rebar from corrosion initiation and propagation. As cracks due to loads or rheological phenomena are almost inevitable, the geometry of crack pattern in service is a key parameter that needs to be evaluated in plain and fiber-reinforced R/FRC members. In fact, not only the direct ingress of aggressive agents, such as oxygen and water, is a function of crack width, but also concrete carbonation and the chloride ion ingress are accelerated by the presence of wide cracks. Furthermore, the use of fiber reinforced concrete requires detailed investigations, in order to define the relationship between durability and crack width even in presence of cyclic loads. Accordingly, in this research project, crack width is measured by using traditional mechanical strain gauges and a new device based on the optical conoscopic holography. The latter allows the non-contact measure of crack profile, at the end of each loading cycle, both in plain and fiber-reinforced ties subjected to sets of repeated loads. As a result, contrarily to crack width at the peak of load, the width of residual cracks is not always reduced by the presence of fiber, and this could affect the durability of RC and R/FRC structures.


Document: 

SP-343_09

Date: 

October 1, 2020

Author(s):

Ferrara, L.; Asensio, E.C.; Lo Monte, F.; Snoeck, D.; De Belie, N.

Publication:

Symposium Papers

Volume:

343

Abstract:

The design of building structures and infrastructures is mainly based on four concepts: safety, serviceability, durability and sustainability. The latter is becoming increasingly relevant in the field of civil engineering. Reinforced concrete structures are subjected to conditions that produce cracks which, if not repaired, can lead to a rapid deterioration and would result in increasing maintenance costs to guarantee the anticipated level of performance. Therefore, self-healing concrete can be very useful in any type of structure, as it allows to control and repair cracks as soon as they to occur. As a matter of fact, the synergy between fibre-reinforced cementitious composites and selfhealing techniques may result in promising solutions. Fibres improve the self-healing process due to their capacity to restrict crack widths and enable multiple crack formation. In particular, cracks smaller than 30-50 μm are able to heal completely. Moreover, in the case of High Performance Fibre Reinforced Cementitious Composites (HPFRCC), high content of cementitious/pozzolanic materials and low water-binder ratios are likely to make the composites naturally conducive to self-healing. In this framework the main goal of this paper is twofold. On the one hand, a state-of-the-art survey on self-healing of fibre-reinforced cementitious composites will be provided. This will be analysed with the goal of providing a “healable crack opening based” design concept which could pave the way for the incorporation of healing concepts into design approaches for FRC and also conventional R/C structures. On the other hand, the same state-of-the-art will be instrumental in identifying research needs, which still have to be addressed for the proper use of self-healing fibre-reinforced cementitious composites in the construction field.


Document: 

SP-343_27

Date: 

October 1, 2020

Author(s):

Frazão, C.; Barros, J.; Bogas, A.; Pilakoutas, K.; de Sousa, C.M.

Publication:

Symposium Papers

Volume:

343

Abstract:

Steel fibres resulting from the industry of tyre recycling can be efficiently employed for the reinforcement of concrete structures. Recycled Steel Fibre Reinforced Concrete (RSFRC) is a promising candidate with technical, environmental and economic benefits for the development of ductile, high strength and durable structural elements. The heterogeneity of the geometry of each Recycled Steel Fibre (RSF) due to the recycling process of the tires, can provide a plurality of strengthening mechanisms to concrete that promote efficiency and durability, as long as the RSFRC composition is carefully adjusted to the presence of RSF. For assessing the potentialities of recycled steel fibres (RSF) as concrete reinforcement, an experimental program was performed in the present study by comparing the following properties of concrete reinforced with industrial steel fibres (ISF) and with RSF: compressive strength, modulus of elasticity, flexural strength, flexural toughness and indirect tensile strength. The obtained results suggest that RSF reinforcement can significantly reduce the brittle behaviour of concrete by improving its toughness and post-cracking resistance. For the adopted industrial and recycled fibres, the last ones have not presented inferior post-cracking strengthening performance than the first ones.


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