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International Concrete Abstracts Portal

Showing 1-5 of 7 Abstracts search results

Document: 

SP276-04

Date: 

March 1, 2011

Author(s):

L.A.P Lourenco, J.A.O Barros, and J.G.A Alves

Publication:

Symposium Papers

Volume:

276

Abstract:

In the last decades, technical and scientific efforts have been done to increase the concrete strength, based on the assumption that more economic, lightweight, durable and good looking structures can be built. This strength enhancement, however, has been obtained by increasing the compactness of the concrete internal structure, resulting concretes with voids of smaller size, and lower connectivity than in concretes of current strength classes. Research and fire accidents have shown that the concrete failure of structures exposed to fire is as explosive as high is the concrete strength class, since the restrictions for the escape of water vapor from the interior of concrete increase with the concrete compressive strength. In the present work a fiber reinforced concrete of enhanced fire resistance is developed and its properties are characterized by experimental research. This concrete is intended to have enough strength for concrete precast tunnel segments, while the performance of the fibrous reinforcement system is evaluated in terms of verifying its possibilities for replacing, partially or totally, conventional reinforcement used in these structural elements.

DOI:

10.14359/51682362


Document: 

SP276-06

Date: 

March 1, 2011

Author(s):

Kamal S. Tawfiq, Brenda Robinson, and Nur Yazdani

Publication:

Symposium Papers

Volume:

276

Abstract:

The objective of this study was to investigate the possibility of using steel fiber reinforced concrete (SFRC) to enhance the performance of in the anchorage zone and to minimize the amount of mild steel reinforcement required by the code. For that purpose, different ratios per volume of different steel fibers were used in the study. The basic SFRC properties were obtained and then used in a thorough finite element analysis on 3D models of SFRC blocks representing the anchorage zone. The purpose of the numerical analysis was to define the proper dimensions of the need block specimens for laboratory testing, and to determine the locations of the internal and external strain gages in the block. Test results showed that the addition of steel fibers improved the loading capacity of the anchorage blocks. Further finite element analysis on 3D models proved that addition of 0.5 percent by volume of fiber was enough to reduce the mild steel reinforcement at the anchorage zone by about 40 percent. However, such an option needs to be dealt with caution. The addition of steel fiber to substitute mild steel could result in an abrupt failure in the anchorage zone.

DOI:

10.14359/51682364


Document: 

SP276

Date: 

March 1, 2011

Author(s):

Editors: Corina-Maria Aldea and Nur Yazdani / Sponsored by: ACI Committee 544

Publication:

Symposium Papers

Volume:

276

Abstract:

This CD-ROM contains six papers that were presented at sessions sponsored by ACI Committee 544 at the Spring 2008 ACI Convention in Los Angeles, CA, and the Spring 2009 ACI Convention in San Antonio, TX. The papers provide insight into the state of the art of the topic in academia, the industry, and real-life applications and cover some of the benefits of using fibers to enhance long-term performance of concrete with and without conventional reinforcement. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-276

DOI:

10.14359/51682325


Document: 

SP276-05

Date: 

March 1, 2011

Author(s):

Shih-Ho Chao, Jae-Sung Cho, Netra B. Karki, Dipti R. Sahoo, and Nur Yazdani

Publication:

Symposium Papers

Volume:

276

Abstract:

The evaluation of the properties of FRC mixtures is of prime importance for these mixtures to be used effectively and economically in practice. Although currently there are various standards or testing methods for evaluation of the properties of FRC, there is no agreement on which standard is the best for a specific structural application. This can be a major reason that has inhibited the introduction of FRC into structural design code. This study investigated three major different material evaluation methods, i.e. uniaxial direct tensile test, third-point bending test, and round panel test, as well as behavior of specimens tested by the three methods. The advantages and limitations of those methods are discussed.

DOI:

10.14359/51682363


Document: 

SP276-03

Date: 

March 1, 2011

Author(s):

Corina-Maria Aldea and Surendra P. Shah

Publication:

Symposium Papers

Volume:

276

Abstract:

Permeability and cracking affect the durability and integrity of a structure. The addition of reinforcing fibers changes the cracking process in cement based composites. The goal of this paper was to review the research work related to the effect of fiber reinforcement on tensile cracks and water permeability of cementitious composites. Factors affecting this relationship included matrix type, fiber type, geometry and volume fraction, and crack width. Water flow was studied through individual fiber and hybrid fiber reinforced composites. Widthcontrolled tensile cracks were induced for the polyvinyl alcohol (PVA) and steel fiber reinforced composite samples by feedback-controlled split tension or by feedback controlled wedge splitting. Then water flow was measured with a low pressure test set up. For the hybrid fiber reinforced composites containing blends of macro- steel and microsteel and PVA fibers tensile cracks were induced by uniaxial tension, while water was forced through the samples under a relatively low pressure. The addition of fibers had beneficial effects on water flow for cracks in the micron range. This was mainly due to changes in crack morphology compared to unreinforced composites and multiple crack development. Permeability thresholds were identified for the crack widths, which varied with the matrix type and the fiber type. Synergistic effects of micro- and macrofibers were obtained through engineered composites mix designs, and hybrid fiber reinforcement showed improved results in terms of mechanical performance and permeability of cracked cementitious composites compared to single fiber reinforcement.

DOI:

10.14359/51682361


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