ABOUT THE INTERNATIONAL CONCRETE ABSTRACTS PORTAL

  • 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 13 Abstracts search results

Document: 

SP155-02

Date: 

August 1, 1995

Author(s):

D. Jamet

Publication:

Symposium Papers

Volume:

155

Abstract:

The toughness of fiber reinforced concretes (FRC) was characterized from notched beam tests. The tests were performed under CMOD control in a servo-hydraulic machine to obtain the stable response of both the unreinforced concrete and the FRC. Several toughness measures were defined in terms of the experimentally obtained load versus crack opening (CMOD) curves. They give a better indication of the fundamental behavior of the concrete, avoid the problems associated with the approach based on the deflection of unnotched beams, and are amenable to the incorporation of serviceability considerations (for example, crack widths). The effect of specimen size on toughness was found to be significant in both the matrix- and fiber-dominated regimes of the FRC behavior. In general, toughness increases with specimen size and needs to be accounted for in the characterization. The study was conducted on beams of a 70 MPa compressive strength silica fume concrete, with and without high-strength hooked steel fibers. It was found that the incorporation of a low volume fraction (one percent) of steel fibers is sufficient to significantly decrease the brittleness of high-strength concretes.

DOI:

10.14359/927


Document: 

SP155-09

Date: 

August 1, 1995

Author(s):

N. Banthia, K. Chokri, and J. F. Trottier

Publication:

Symposium Papers

Volume:

155

Abstract:

Describes the construction of two simple impact machines, one small with a capacity of 100 Joules and the other large with a capacity of 1000 Joules, designed to conduct impact tests on fiber reinforced mortars and concretes in the uniaxial tensile mode. During a test, the applied load, accelerations, and velocities are measured such that with a proper analysis scheme, the raw data can be analyzed to obtain fundamental material properties under impact loading. Carbon, steel, and polypropylene micro-fiber reinforced mortars and steel fiber reinforced concrete were tested; it was demonstrated that the proposed technique is a simple and rational method of obtaining meaningful material properties. In general, fiber reinforced composites were found to be more impact resistant than their unreinforced counterparts, with the improvements found to be proportional to the fiber volume fraction. In addition, both the unreinforced matrix as well as fiber reinforced composites were found to be stress-rate sensitive, but the extent of sensitivity observed was smaller than usually reported in the literature for cement-based materials under uniaxial tensile loading.

DOI:

10.14359/934


Document: 

SP155-01

Date: 

August 1, 1995

Author(s):

C. D. Johnston

Publication:

Symposium Papers

Volume:

155

Abstract:

The issue of how the method of determining midspan deflection in ASTM C 1018 toughness tests influences first-crack strength, first-crack deflection, toughness indices, and residual strength factors is addressed in this paper by comparing results obtained using the method now required in the current standard, which is based on net midspan deflection determined as the nominal midspan deflection minus the average of the deflections measured at the beam supports, with corresponding same specimen results based on nominal midspan deflection only which was not explicitly excluded in earlier versions of the standard. The problem of dealing with the portion of load-deflection relationship immediately after first crack when it is unstable is discussed. The range of test specimens for which comparative data are reported includes a series of third-point-loaded 500 x 150 x 150 mm beams with three different steel fibers ranging in length from 18 mm to 63 mm; a second, smaller series of 350 x 100 x 100 mm beams allowed for assessment of the effects of beam size and fiber alignment. Fiber contents varied from 20 to 75 kg/m 3 (0.25 to 0.94 percent by volume). Also included was a series of 350 x 100 x 100 mm beams with a single type of fibrillated polypropylene fiber of length 38 to 64 mm in amounts of 0.5 to 0.75 percent by volume. The results illustrate the extent to which the ASTM C 1018 parameters I 5, I 10, I 20, R 5,10, and R 10,20 are effective in distinguishing the performance of the various fiber reinforced concretes (FRC) mixtures in terms of fiber type, geometry, and amount. The index I 5 was found to be least effective. A case is made for greater emphasis on use of residual strength factors, especially R 10,20, when employing the test to specify and control the quality of FRC.

DOI:

10.14359/926


Document: 

SP155-11

Date: 

August 1, 1995

Author(s):

C. D. Hays and R. F. Zollo

Publication:

Symposium Papers

Volume:

155

Abstract:

Recent natural disasters involving high wind events have demonstrated the fact that building envelopes, including structural walls and roofs, can lose structural integrity as a result of penetration by missile objects. Because of this, there is heightened interest in the testing of components and cladding that are used as a part of building envelopes of habitable structures. A large missile impact test has been designed and is being evaluated in laboratories around the country. The test, discussed in this paper, is suitable for laboratory or field applications and is currently undergoing scrutiny by the ASTM Task Force of Committee E6, Performance of Buildings. Adoption of the test by the South Florida Building Code came in the wake of Hurricane Andrew in 1992. The test has been applied to numerous types of wall systems and building products, including a fiber reinforced cellular concrete panel which is designed to be used as an alternate to masonry infill construction, architectural precast, demising walls, and security fencing. Additional tests of the missile impact resistance of fiber reinforced cellular concrete involving the use of large caliber ballistics are also discussed. The high energy impact resistance of fiber reinforced systems is demonstrated and discussed.

DOI:

10.14359/936


Document: 

SP155-10

Date: 

August 1, 1995

Author(s):

A. Pacios and S. P. Shah

Publication:

Symposium Papers

Volume:

155

Abstract:

With the objective of understanding the reinforcing mechanisms of fibers in steel fiber reinforced concrete, the adherence between the fiber and the matrix was studied by conducting pullout tests of fibers from a cementitious matrix. In this paper, the effect of factors such as loading rate, inclination of fibers, and number of fibers have been investigated. An innovative measurement system was developed for high rates. It was experimentally obtained that by increasing the rate of loading, both pullout resistance and slip at peak were increased. Peak pullout force presents a higher rate sensitivity for a higher number of fibers. The lower the number of fibers, the higher the slip at peak rate sensitivity. Regardless of the number of fibers, a higher rate sensitivity for inclined fibers was observed.

DOI:

10.14359/935


123

Results Per Page