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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:
SP204-06
Date:
August 1, 2001
Author(s):
R. J. Frosch
Publication:
Symposium Papers
Volume:
204
Abstract:
The AC1 building code has adopted a new design method for the control of flexural cracking. This design method is intended for structures containing steel reinforcement and not requiring specialized crack control procedures. It is the objective of this paper to explore the background for this method, highlight the assumptions, and develop design tools that can be applied for special design cases. This paper presents a summary of a physical model for cracking that was the basis for the new design method, illustrates the development and limitations of the design method, and develops design tools that are applicable for the control of cracking in structures requiring increased levels of crack control and in structures incorporating alternative reinforcement materials. Examples illustrating the use of the new design method as well as tools extending its applicability are presented.
DOI:
10.14359/10817
SP204-07
A. Bentur, N. S. Berke, M. P. Dallaire, and T. A. Durning
Shrinkage reducing admixtures (SRA’s) are a new type of admixtures which is effective in reducing the drying shrinkage of concrete. SRA performance has typically been evaluated on the basis of unrestrained drying shrinkage tests. However, it is usually the cracking performance of concrete when shrinkage is restrained that is of primary interest to the marketplace. The current paper presents an evaluation of SRA’s based on several parameters: free shrinkage, tensile stresses which develop in a uniaxially restrained rig, and the sensitivity to cracking in such conditions. The positive influence of SRA’s on all of these three parameters is demonstrated. A comparison is made between the effect of SRA and of low-volume, polypropylene fiber reinforcement. The latter is known to be effective in controlling early age plastic shrinkage cracking. The present data show that in the case of hardened concrete, after one day of curing, low volumes of fibers do not give any advantage, and it is in this range where the SRA is effective. Thus, the two types of additives can complement each other: the fibers are efficient in controlling plastic shrinkage cracking while the SRA can take over the role of crack control in the hardened concrete, where low volume-low modulus fibers are not effective.
10.14359/10818
SP204-08
P. Balaguru
Use of discrete fibers to reduce plastic shrinkage cracking of concrete is discussed. The results presented cover a wide range of fibers in terms of their material properties such as modulus of elasticity, diameter, lengths, and surface characteristics. Fiber contents used ranges from 0.45 kg/m3 to 60 kg/m3 and the matrix composition evaluated vary from mortar to concrete with normal and low density aggregates. The influence of fiber properties, fiber geometries, volume fractions, and matrix compositions were evaluated for the crack reduction of concrete during the initial and final setting period. These cracks eventually influence the long-term durability of concrete. The results indicate that fibers provide a definite contribution to crack reduction and the major parameters that influence the crack reduction are: fiber count, geometry of the fiber, modulus of elasticity of the fiber, and fiber volume fraction. The fiber volume fraction needed for effective crack reduction ranges from 0.1 to 5 percent.
10.14359/10819
SP204-09
M. Saatcioglu
bridge columns; bridges; concrete columns; crack control; cracking; earthquake engineering; prestressed concrete; prestressing; retrofitting; seismic retrofit; shear design
10.14359/10820
SP204-10
J .K .Buffenbarger, C. K. Nmai, and M. A. Miltenberger
Drying shrinkage cracking can adversely affect the aesthetics, durability, and serviceability of reinforced concrete structures, thereby negating some of the benefits provided by high-performance concretes. Developed years ago but relatively new to the construction industry, shrinkage-reducing admixtures (SRAs) have been shown to provide significant reductions in concrete drying shrinkage and subsequent cracking. The potential benefits that SRAs provide have resulted in increased use of these products in the past few years. In this paper, data from laboratory testing and field investigations of SRA-treated concrete mixtures and their use in a few projects where watertightness was desired are presented and discussed. The findings of visual inspections of the projects performed shortly after construction and after a year in service will also be presented. The information to be presented verify the drying shrinkage reduction characteristics of SRAs and show that these innovative admixtures can provide substantial benefits with regards to improving watertightness and overall serviceability of reinforced concrete structures.
10.14359/10821
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