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Home > Publications > 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.
Showing 1-5 of 14 Abstracts search results
Document:
108-M38
Date:
July 1, 2011
Author(s):
Alexandre R. Pacheco, Andrea J. Schokker, Jeffery S. Volz, and H. R. (Trey) Hamilton III
Publication:
Materials Journal
Volume:
108
Issue:
4
Abstract:
The current industry practice for acceptance testing of post-tensioning grouts includes an accelerated corrosion test (ACT), as recommended in Post-Tensioning Institute (PTI) M55.1-03, “Specification for Grouting of Post-Tensioned Structures.” The most significant downside of the current ACT method is the length of time required to run the test, which typically ranges from 1 to 2 months to complete. The linear polarization resistance (LPR) technique, on the other hand, requires only a few hours to complete; and the research presented in this paper indicates a strong correlation between the time to corrosion, as measured by the ACT method, and the system polarization resistance, as measured by the LPR technique. Based on the test results to date, the authors recommend the use of the LPR method as a prescreen for very high-quality grouts so that lengthy ACT testing is not necessary.
DOI:
10.14359/51683107
103-M47
November 1, 2006
Peter Laursen, Gavin Wight, and Jason Ingham
103
6
Prestress losses due to creep, shrinkage, and steel relaxation lead to a reduction in structural efficiency in post-tensioned concrete masonry walls. This paper investigates the magnitude of losses that can be expected from medium-weight concrete masonry units. The findings from two series of creep and shrinkage experiments are presented and compared with test data from other researchers and with values stipulated in international standards. A creep coefficient of 3.0 is found, a value that is in agreement with the Australian, British, and Canadian standards. Shrinkage strains of 1000 and 600 microstrain for grouted and ungrouted walls, respectively, were obtained under laboratory conditions. Prestress force losses due to creep and shrinkage are shown to be significant and consistent with the recommendations made in the U.S. code.
10.14359/18220
103-M48
Ehab Shaheen and Nigel Shrive
A nonmetallic anchorage for carbon fiber-reinforced polymer (CFRP) tendons, made from a specially developed ultra high-performance concrete (UHPC), was described. The UHPC anchorage system, however, was too large for use on site (120 mm [7.9 in.] diameter x 180 mm [7.1 in.] long). A smaller anchor of tougher material, requiring less wrapping of the barrel, was needed for use on site. A new reactive powder concrete (RPC) anchorage consisting of a CFRP-wrapped barrel and four wedges has therefore been developed. The system is similar in size to standard steel anchorage. Specimens were cast and tested with CFRP tendons to determine if the new system could meet the Post Tensioning Institute (PTI) test requirements.
10.14359/18221
98-M19
March 1, 2001
Mahmoud M. Reda Taha and Nigel G. Shrive
98
2
The development of a nonmetallic anchorage for post-tensioned fiber-reinforced polymer (FRP) tendons required the production of high toughness cement composites. Therefore, the fracture toughness of high-performance carbon fiber cement composites was examined with the intention of maximizing this property within practical limits. The experimental program described herein included trials to enhance the fracture toughness of two different high-performance concrete mixtures by incorporating chopped carbon fibers. In these experiments, different fracture toughness parameters were determined for these mixtures. Statistical analysis of the test results revealed that changing the fiber length has a significant effect on the fracture toughness of fiber-reinforced high-performance cement composites. GIC and JIC were found to be the most sensitive measures of fracture toughness for these materials.
10.14359/10200
96-M37
May 1, 1999
Hamid Saadatmanesh and Fares E. Tannous
96
3
The recent advancements in the fields of materials science and composites have resulted in the development of high-strength corrosion resistant fiber reinforced plastic (FRP) tendons that could potentially replace steel tendons in prestressed or post-tensioned concrete structures, particularly in areas where corrosion is a problem. The more common types of FRPs used in construction are made from high-strength filaments of glass, carbon, or aramid placed in a resin matrix. Each combination of fiber and resin presents a unique advantage for particular application. In this paper, the behavior of armada fiber reinforced plastic (AFRP) tendons will be examined. Test results of relaxation, creep, and fatigue behavior of 10 mm (3/8 in.) diameter AFRP tendons under simulated field conditions are presented. Twelve specimens were tested in air at temperatures of -30, 25, and 60 C, and 24 specimens were tested in alkaline, acidic, and salt solutions at temperatures of 25 and 60 C to evaluate the relaxation behavior. In addition, 45 specimens were tested in tension-tension fatigue to investigate the effect of repeated loading on the mechanical properties of the tendon, such as the elastic modulus E, Poisson’s ratio n, and the residual tensile strength Pr. A preliminary investigation of the creep behavior was also conducted at room temperature in air, in alkaline solution, and in acidic solution. The fatigue and creep performance of the ARFP tendons tested in this study was very good. The relaxation losses were higher in solutions as compared to those specimens tested in air. In particular, the losses in acidic solutions were the highest.
10.14359/626
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