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.

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.

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

Self-consolidating concrete has become an important material in the concrete construction industry, however the modifications required to produce self-consolidating concrete (SCC) can significantly increase its susceptibility to cracking. This is an important durability issue when SCC is considered for use in reinforced concrete marine and highway structures. A common method of increasing the resistance of concrete to cracking is the addition of discrete monofilament macro-synthetic fiber reinforcement. However, the addition of fibers to SCC has the negative effect of reducing its self-consolidating characteristics. An experimental program was conducted to investigate the mixture modifications required to maintain the self-compactability of SCC with the addition of various rates between 0.2% and 0.4% by volume (1.8kg/m3 (3.0 lbs/yd3) - 3.6kg/m3 (6.0 lbs/yd3)) of a commercially available monofilament self-fibrillating macro-synthetic fiber. The effect of fiber addition rate on the plastic shrinkage resistance of SCC was also evaluated. The addition of fiber volume fractions ranging from 0.2% to 0.4% by volume were easily incorporated into several SCC mixtures (w/c =0.4, 0.42, 0.45) with adjustments made to the coarse/fine aggregate ratio and high range water reducer dosage rates. Interestingly, the addition of as little as 0.2% by volume of the monofilament self-fibrillating macro-synthetic fiber resulted in a 44.6% decrease in plastic shrinkage cracking area, when compared to its unreinforced counterpart, while also reducing the maximum observed crack widths by 43%. The addition of a higher fiber dosage (0.4% by volume) resulted in as much as a 70.4% reduction in cracking area and a 62% reduction in maximum crack widths for SCC mixtures with w/c ratios ranging from 0.4 to 0.45. From this study, it can be concluded that monofilament self-fibrillating macro-synthetic fiber reinforcement can be successfully incorporated into an SCC mixture to significantly increase its resistance to plastic shrinkage cracking while maintaining the workability expected from this type of concrete.

In 1994, the bridge over Interstate 90 at mile marker 212 in South Dakota, USA, used synthetic fiber reinforced concrete in the approach, deck topping, and Jersey barriers. Crack widths were measured and counted on the three applications with a histogram developed for the Jersey barrier. The synthetic fiber dosages were 1.3% and 1.6%. This location and applications have been monitored almost yearly and more thoroughly in 2007. Comments, including crack history, on other applications placed 1994 to 1995 and 2002 to 2006 are included for comparison. Further comparisons include synthetic fiber reinforced concrete with and without conventional steel reinforcing, and with plain concrete. There is a significant measurable difference in crack frequency and width with a decided benefit from synthetic fiber reinforcement. The historical and philosophical review is accomplished with selected examples of synthetic fiber reinforced concrete projects to allow for a generalized beneficial conclusion.