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International Concrete Abstracts Portal

Showing 1-5 of 15 Abstracts search results

Document: 

SP268-07

Date: 

March 1, 2010

Author(s):

T. Atkinson and P. C. Tatnall

Publication:

Symposium Papers

Volume:

268

Abstract:

This paper discusses the recent tragedies of a number of tunnel fires occurring in transport tunnels, and the effects of these fires on concrete tunnel support linings. The mechanisms of explosive spalling of concrete in fires is described, and the research conducted to assess the ability of fine, polypropylene fibers to mitigate the effects of explosive spalling in severe fires is described. The test program to assess the fire resistance of the 25 miles (40 km) of concrete-lined tunnels in the Channel Tunnel Rail Link project in the United Kingdom is described in detail. A program to ascertain the effects of using these fibers in shotcrete tunnel linings is also considered. These programs demonstrate that small quantities – as little as 1.7 lb/yd3 (1 kg/m3) – of mono-filament polypropylene fibers provide resistance to explosive spalling in fires. Examples of the application of this new technology are listed.

DOI:

10.14359/51663710


Document: 

SP268-06

Date: 

March 1, 2010

Author(s):

R. I. Bell and J. H. Morton

Publication:

Symposium Papers

Volume:

268

Abstract:

This paper discusses the use of alkali resistant cellulose fibers for decorative applications. The penetration of fibrous reinforcement for decorative concrete applications has been somewhat limited. The main barrier has been interference of the fiber during many of the intricate and complicated finishing steps employed in these high-end concrete applications. Some of the complications encountered are fibers sticking to the stamps and dragging out of the surface, fiber clumps found at the surface creating blemishes, lack of stain receptivity by the fibers, etc. These aesthetic complications can often result in customer dissatisfaction with the final product. The commercial entry of alkali resistant cellulose fibers for fibrous reinforcement in concrete has provided a new option for fiber reinforced concrete in decorative concrete applications. The potential benefits of cellulose fibers in concrete are expected to help further enlarge the use of fiber reinforced concrete in the market place.

DOI:

10.14359/51663709


Document: 

SP268-01

Date: 

March 1, 2010

Author(s):

D. M. Brodowski, M. G. Katona, and J. A. Pope

Publication:

Symposium Papers

Volume:

268

Abstract:

The current research shows that the addition of steel fibers to plain concrete is effective in enhancing the tensile ductility and loading capacity of buried concrete structures such as bridges, culverts, and vaults. This paper details the development of a steel fiber reinforced concrete (SFRC) analytical model used in the finite element program, CANDE, and describes the experimental and analytical approach used to test the accuracy of the model. The results of full-scale, in-place load tests on many precast buried SFRC arch structures (composed of less than or equal to 1% steel fibers by volume) correlated well with the CANDE model predictions. The CANDE program exhibits the ability to model the material behavior of SFRC as well as the effects of soil-structure interaction. The analytical and experimental research summarized in this paper leads to the ability to design SFRC for structural applications such as buried bridges, culverts, and vaults.

DOI:

10.14359/51663704


Document: 

SP268-11

Date: 

March 1, 2010

Author(s):

J. Wong and P. D. Carter

Publication:

Symposium Papers

Volume:

268

Abstract:

The use of steel fiber-reinforced, silica-fume-modified concrete overlays and shotcrete for bridge repairs has long been the standard for Alberta Transportation (AT). Approximately 200 provincial bridges have been repaired with steel fiber reinforced, silica-fume-modified materials since 1984, mostly to decks, which had been exposed to aggressive conditions including freezing and thawing, de-icing salts, and moisture. The purpose of using steel fiber in bridge concrete repair materials was primarily to prevent or reduce repair cracks and to improve durability. Standard fiber lengths were 25 mm (1 in.) for shotcrete and 50 mm (2 in.) for overlays with standard fiber dosages of 60 km/m3 (100 pounds/yd3). Most of the repairs were done with superplasticized, silica-fume-modified, low water-cement ratio concrete mixes. This paper reports on the early historical development of the repair method basics and the lessons learned from monitoring bridge repairs. Conclusions are presented from AT’s Level 1 and Level 2 inspection data. Level 2 data quantifies several repair performance indicators, such as wide cracks, stains, delamination, spalls, patches, and debonds, as well as a breakdown of numerical condition ratings on important bridge elements. Crack data from Level 2 inspections was available from 154 silica fume modified bridge deck overlays, 124 of which contained steel fiber. The crack data was analyzed to assess the performance of fibers in reducing the amount of easily visible cracks: those wider than 0.3 mm (0.012 in.). The results showed that the steel fibers resulted in significant crack reduction and improved overlay durability and service life.

DOI:

10.14359/51663714


Document: 

SP268-13

Date: 

March 1, 2010

Author(s):

C. N. MacDonald

Publication:

Symposium Papers

Volume:

268

Abstract:

The case history presented in this paper describes a small sized project for design and construction of a macro synthetic fiber reinforced concrete (SnFRC) residential driveway with an average grade of 17%. The study highlights risks and benefits of choosing this material for this project. Five almost-equal lengths of SnFRC sections were placed in two groups 11 months apart. The delay between placements allowed for some experience to better analyze and determine if this was the best solution given the customer’s performance criteria and the difficult construction conditions. The design included a high cementitious content mixture with small aggregate, synthetic macro fibers, and air-entraining admixture. The resulting driveway was constructed down hill and has performed well in spite of minimal surface preparations and no jointing or saw cuts in the overlay. Some small cracking has occurred but has been of no consequence because the concrete has been held together by the synthetic fibers. For the construction of this residential driveway utilizing synthetic fiber reinforced concrete, the performance criteria was met, the construction schedule was on time, and the construction costs were significantly lower.

DOI:

10.14359/51663716


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