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International Concrete Abstracts Portal

Showing 1-5 of 9 Abstracts search results

Document: 

SP274-05

Date: 

October 1, 2010

Author(s):

M. C. Brown, H. C. Ozyildirim, and W. L. Duke

Publication:

Symposium Papers

Volume:

274

Abstract:

Self-consolidating concrete (SCC) promises to shorten construction time while reducing the need for skilled labor. However, experience has shown that SCC may be prone to shrinkage cracking, which may compromise durability. In conventional concrete, fiber reinforcement has been used to control cracking and increase post-cracking tensile strength and flexural toughness. These benefits could be achieved in SCC without compromising the workability or stability, provided that the amount of fiber reinforcement is optimized. This project sought to evaluate the feasibility of fiber reinforced self-consolidating concrete (FR-SCC) for structural applications. Tests were conducted in the laboratory to assess the fresh and hardened properties of FR-SCC containing various types and concentrations of fiber. The results indicate that SCC with high flowability and some residual strength beneficial for crack control can be prepared for use in transportation facilities. The results of the experiments further show that, at optimal fiber additions, FR-SCC mixtures can have the same fresh concrete properties as traditional SCC mixtures. FR-SCC also demonstrates a considerable improvement in the residual strength and toughness of a cracked section. Though not specifically measured, increase in residual strength and toughness is expected to lead to control of crack width and length (ACI 544.1R, 1996). The increase in the FR-SCCs’ cracked section performance indicates that it can be expected to have better durability in service conditions than an identical SCC without fibers. In transportation structures FR-SCC can be used in link slabs, closure pours, formed concrete substructure repairs; or prestressed beams where end zone cracking has been an issue.

DOI:

10.14359/51664079


Document: 

SP274-02

Date: 

October 1, 2010

Author(s):

S. Grunewald and J. C. Walraven

Publication:

Symposium Papers

Volume:

274

Abstract:

Self-consolidating fiber-reinforced concrete (SCFRC) combines the benefits of self-consolidating concrete (SCC) in the fresh state and an enhanced performance of fiber reinforced concrete (FRC) in the hardened state. The application of SCC improves the efficiency at building sites, allows rationally producing prefabricated concrete elements and improves the working conditions, the quality and the aesthetical appearance of concrete structures. By adding fibers to SCC bar reinforcement can be replaced, crack widths reduced, the durability improved and the load bearing capacity of a structure increased. An extensive research study1 was carried out on the characteristics and the mix design of SCFRC that consisted of three parts: the fresh as well as the hardened state of SCFRC and the influence of the production process determined in three full-scale studies. This paper discusses two aspects of the mix design of SCFRC: the maximum fiber content and the required spacing of reinforcement at which blocking does not occur. Based on the analysis of experimental results mix design tools are proposed that allow predicting the maximum fiber content and the passing ability of SCFRC, which is essential information to obtain a homogeneous distribution of the fibers in a structure.

DOI:

10.14359/51664075


Document: 

SP274-08

Date: 

October 1, 2010

Author(s):

L. Ferrara, M. di Prisco, and N. Ozyurt

Publication:

Symposium Papers

Volume:

274

Abstract:

The addition of fibers into a self-consolidating concrete (SCC) matrix can take advantage of the superior fresh state performance to achieve homogeneous dispersion of the discontinuous wirelike reinforcement. Such a positive synergy between SCC and FRC technologies is of paramount importance to promote reliable structural applications. It has been furthermore shown that, through a well balanced set of fresh state properties of the mix, fibers can be effectively oriented along the direction of the fresh concrete flow. Superior mechanical performance of the material hence is obtained in the same direction. A “tailored” orientation of the fibers may be pursued to obtain a deflection-, or even a strain-hardening, behavior, which may be required by the specific application to be designed. With reference to a project on going in Italy, this paper details the steps of a “holistic” approach to the design of Self Consolidating High Performance Fiber Reinforced Concrete (SCHPFRC) elements. In this framework both the mix composition and the casting process are designed to the anticipated performance of the structural element, in the sight of an optimized material and structural efficiency. This would allow to pursue, in the design process, a desirable closer correspondence between the shape of an element and the function it performs in a structure assembly. A suitably balanced fresh-state performance of the fiber reinforced cementitious composite would allow to “mold” the shape of an element and, thanks to a tailored casting process, to orient the fibers along the direction of the principal tensile stresses resulting from its structural function.

DOI:

10.14359/51664083


Document: 

SP274-07

Date: 

October 1, 2010

Author(s):

B. Mobasher and X. Destree

Publication:

Symposium Papers

Volume:

274

Abstract:

Applications of slabs supported on piles are quite common for areas where soil- structure interaction may create differential settlement or long term tolerance issues. An application for the use of steel fiber reinforced slabs that are continuous and supported on piles is discussed in this paper. The experience and design methodology for slabs on piles is further extended to floor slabs of multi-story buildings, where a high dosage of steel fibers (50-100 kg/m³, 84-168 lbs/ft3) is used as the sole method of reinforcement. Suspended ground slabs are generally subjected to high concentrated point loading (150 kN, or 33.7 kips) intensities as well as high uniformly distributed loadings (50 kN/m² or 1000 lb/ft2) and wheel loads. The span to depth ratios of the SFRSS is between 8 and 20 and depends on the loading intensity and the pile/column capacity. Standard procedures for obtaining material properties and finite element models for structural analysis of the slabs are discussed. Methods of construction, curing, and full scale testing of slabs are also presented.

DOI:

10.14359/51664082


Document: 

SP274-03

Date: 

October 1, 2010

Author(s):

J. Carlsward and M. Emborg

Publication:

Symposium Papers

Volume:

274

Abstract:

Shrinkage cracking of self-compacting concrete (SCC) overlays with and without steel fibres has been assessed through laboratory testing and theoretical analysis. Test results verified that steel fibre reinforcement has a crack width limiting effect. However, the contribution in case of fibre contents up to 0.75 vol% was not found to be sufficient to distribute cracks in situations where bond to the substrate was nonexistent. Thus, even higher steel fibre contents (or other types of fibres) are required in order to control cracks. A distributed pattern of fine cracks was however obtained even for unreinforced SCC within bonded areas of the overlays. This implies that steel fibres, or other crack reinforcement, are not required if high bond strength is obtained. An analytical model, proposed to assess the risk of cracking and to predict crack widths in overlays, was found to give reasonable correlation with experimental results.

DOI:

10.14359/51664077


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