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International Concrete Abstracts Portal

Showing 1-5 of 14 Abstracts search results

Document: 

SP182-07

Date: 

May 1, 1999

Author(s):

K. Noghabai

Publication:

Symposium Papers

Volume:

182

Abstract:

This paper is based on two different experiments: !) Splitting tests on thick-walled concrete rings subjected to an inner pressure. 2) Pull-tension tests on deformed rebars embedded in concrete prisms. The experiments consider different aspects of bond between deformed rebars and fiber reinforced high-strength concrete (FRHSC). Tests according to 1) study mechanisms for spalling of the concrete cover, due to the radial pressure exerted to the concrete by the ribs of a rebar in tension. There are analytical models (based on nonlinear fracture mechanics) for capacity assessment of the ring. In the experiments according to 2), the bond forces decide the development of transverse cracks in the concrete. By these tests, the so-called tension-stiffening effect on rebars may be studied. In composing the FRHSC, five different types of fibers were used: 2 steel fibers (crimped and straight), 2 polyolefin fibers and one carbon fiber. The fibers were added to a HSC with an expected 28-days compressive strength of 120MPa. Volume fraction of fibers was 1% in all cases. FRHSC is here characterized by its response under uniaxial tension. By using the tensile load-deformation curve in available analytical and/or numerical tools (such as FEM), the effect of a fiber inclusion on the structural response may be explained. Both the analytical and FE-models used herein, seem capable to describe the physical events that take place in the experiments. Thus, it is promising that in order to achieve a desired performance in the test pieces ( and consequently with respect to a desired bond capacity), a fibrous concrete may be tailor-made for a purpose.

DOI:

10.14359/5524


Document: 

SP182-05

Date: 

May 1, 1999

Author(s):

G. Bernier, M. Behoul, and N. Roux

Publication:

Symposium Papers

Volume:

182

Abstract:

Considerable progress has recently been achieved in strength and ductility of concretes. The use of superplasticizers and large amounts of silica fume led to densified cementitious matrices and improved adherence to the fiber reinforcement. These two properties are obtained with Compact Reinforced Composite (CRC) developed at Aalborg Portland and closely studied during a 3-year EC. The investigations reported in this paper cover the application of ultrahigh strength-fiber reinforced concrete to enhance performance of beams, columns and beam to column connections. Mechanical tests were performed on full scale structural elements. Beams of 13 m in length, columns of 2.9 m in compression with and without eccentricity of the load, and beam to column connections were tested. In all cases, concrete strengths of more than 150 Mpa were achieved. Due to CRC's high compacity and its extreme resistance to the penetration of aggressive elements, the CRC cover to the reinforcement was typically reduced from 30 mm to at least 12 mm. It has been shown that a reduction in concrete cover to the reinforcement is compatible with the requirements of structural applications. The tests carried out have shown the possibility of using ultra-high strength concrete for large-scale structural concrete elements and opens new fields of applications. This contributes to saving raw materials, weight and volume and to improving ductility and durability.

DOI:

10.14359/5522


Document: 

SP182-02

Date: 

May 1, 1999

Author(s):

B. Oh, D. Lim, K. Hong, S. Yoo, and S. Chae

Publication:

Symposium Papers

Volume:

182

Abstract:

The structural behavior of steel fiber reinforce concrete beams in shear is studied. A comprehensive experimental program has been set up and several series of reinforced concrete beams with steel fibers have been tested. The test variables include the volume contents of steel fibers and stirrups. The fiber contents varies from 0% to 2% by volume. It is seen form these tests that the cracking and ultimate shear strengths increase as fiber content increase. The present study indicates that fiber reinforcement can reduce the amount of shear stirrups may accomplish strength requirements s well as ductility requirements. A theoretical approach is proposed to predict the shear strength of reinforced concrete beams containing steel fibers and good correlations obtained with test data. The present study allows more efficient structural application of steel fibers for shear reinforcement in reinforced concrete structures.

DOI:

10.14359/5519


Document: 

SP182-12

Date: 

May 1, 1999

Author(s):

V. Kodur

Publication:

Symposium Papers

Volume:

182

Abstract:

This paper deals with the application of fibre-reinforced concrete to enhance structural fire resistance. Materials, such as fibre-reinforced concrete, have good fire resistance properties and by properly designing the building elements, fire resistance, in the practical range, can be obtained. The properties of steel fibre-reinforce concrete are discussed. Examples of some fire resistance applications of steel fibre-reinforced concrete in buildings are illustrated. Results from studies on the fire resistance of concrete-filled steel columns show that the addition of steel fibres in concrete filling improves the fire resistance of steel columns and eliminates the need for external fire protection. The application of fibre-reinforced concrete in enhancing the fire resistance of high strength concrete columns is also discussed.

DOI:

10.14359/5529


Document: 

SP182-01

Date: 

May 1, 1999

Author(s):

B. Aarup

Publication:

Symposium Papers

Volume:

182

Abstract:

CRC ( Compact Reinforced Composite) is the designation for a special type of fiber reinforced concrete with high strength (150-400 Mpa) and closely spaced reinforcing bars. The dense matrix-with water/powder ratios of typically 0.16-provide a good bond to fibers and reinforcing bars, and the large content of steel fibers provide the ductility necessary for utilizing reinforcement effectively. The steel fiber content is typically 2-6% by volume and the content of reinforcing steel is 2-10% by volume. The improved durability of the matrix- due to a high micro silica content-makes it possible to use a concrete cover to the reinforcement of only 10mm in aggressive environments, improving the effectiveness of the reinforcement. The CRC concept was developed in 1986 and aimed specifically for use in structures such as beams, columns and joints, but most of the applications so far have been in the security industry, for corrosion protection and in heavily loaded floors. However, in the last few years CRC has also been applied in structures. One of these applications, production of 40,000 drain covers for a tunnel as a replacement for cast-iron covers, is described as an example of a project where the properties o high performance fiber reinforced concrete were utilized.

DOI:

10.14359/5518


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