- Volume 1, No. 3
Special Issue: Ductile Fiber Reinforced Cementitious Composites - DFRCC edited by Prof. H. Mihashi and Dr. S. Ohno
|On Engineered Cementitious Composites (ECC) A Review of the Material and Its Applications (Invited paper)
Victor C. Li
Journal of Advanced Concrete Technology, 1(3) 215-230, 2003
This article surveys the research and development of Engineered Cementitious Composites (ECC) over the last decade since its invention in the early 1990's. The importance of micromechanics in the materials design strategy is emphasized. Observations of unique characteristics of ECC based on a broad range of theoretical and experimental research are reviewed. The advantageous use of ECC in certain categories of structural, repair and retrofit applications is reviewed. While reflecting on past advances, future challenges for continued development and deployment of ECC are noted. This article is based on a keynote address given at the International Workshop on Ductile Fiber Reinforced Cementitious Composites (DFRCC)- Applications and Evaluations, sponsored by the Japan Concrete Institute, and held in October 2002 at Takayama, Japan.
|Concrete Prestressed with Textile Fabric (Invited paper)
Hans W. Reinhardt, Markus Kruger and Christian U. Grosse
Journal of Advanced Concrete Technology, 1(3) 231-239, 2003
Textile reinforcement is standard meanwhile since there is large experience with continuous and chopped fibers. However, the prestressing of continuous fibers opens more advantages since the initial strain is anticipated and larger tiffness is obtained. The paper shows that this theoretical prediction has been validated.
|Engineered Steel Fibers with Optimal Properties for Reinforcement of Cement Composites (Invited paper)
Antonie E. Naaman
Journal of Advanced Concrete Technology, 1(3) 241-252, 2003
Although steel fibers have been used in cement and concrete composites for more than four decades, most of the steel fibers on the market today have been introduced prior to 1980. This is in sharp contract to the continuous progress and development in the cement matrix itself. Following a brief summary of the main properties and limitations of steel fibers used in cement based composites, this paper describes the rationale and technical background behind the development and design of a new generation of steel fibers for use in cement, ceramic and polymeric matrices. These fibers are engineered to achieve optimal properties in terms of shape, size, and mechanical properties, as well as compatibility with a given matrix. They are identified as Torex fibers. Typical tests results are provided and illustrate without any doubt the superior performance (2 to 3 times) of Torex fibers in comparison to other steel fibers on the market. The new fibers will advance the broader use of high performance fiber reinforced cement composites in structural applications such as in blast and seismic resistant structures, as well as in stand-alone applications such as in thin cement sheet products.
|New Development in Analytical Modeling of Mechanical Behavior of ECC
Journal of Advanced Concrete Technology, 1(3) 253-264, 2003
Finite element method in conjunction with an appropriate material model may serve as a suitable tool to analyze structural performance of Engineered Cementitious Composites (ECCs). Several such models are reviewed and some new formulations are proposed. The new model represents a composite in multiple cracking state as an equivalent continuum with identical macromechanical properties. The constitutive law of the equivalent continuum is obtained as the relationship between overall stress and strain of a representative volume element (RVE). The RVE is modeled as a solid element intersected by fiber-bridged matrix cracks. In order to relate the relative displacements of crack faces to the bridging tractions, a generalized model of crack bridging is derived. A relationship between stress and crack density is also discussed. The resulting constitutive law is suitable for implementation in FEM, yet maintains transparent link to a composite microstructure. This paper has been also presented at the DFRCC-2002 workshop.
|Study on Evaluation Method for PVA Fiber Distribution in Engineered Cementitious Composite
Shin-ichi Torigoe, Tetsuo Horikoshi, Atsuhisa Ogawa and Tadashi Saito
Journal of Advanced Concrete Technology, 1(3) 265-268, 2003
The distribution of fibers in Engineered Cementitious Composite (ECC) is one of the most important factors in terms of the mechanical performance of the composite. However, it has not been estimated well because the distinction of each organic from other components in ECC has been a difficult problem. We demonstrated a new evaluation method for the distribution of discontinuous Polyvinylalcohol (PVA) fibers in ECC. By using fluorescence technique on the ECC, we found that the PVA fibers were observed as green to yellow dots in the cross section of the composite. After capturing the fluorescence image with a CCD camera through a microscope, the image was divided into small divisions having appropriate pixel size. Then, the degree of distribution was calculated with the deviation from the average number of fibers in one division. By adjusting a preferable division size, we found a relationship between the degree of distribution and ultimate tensile strain of composite.
|Tensile and Anti-Spalling Properties of Direct Sprayed ECC
Tetsushi Kanda, Tadashi Saito and Noboru Sakata
Journal of Advanced Concrete Technology, 1(3) 269-282, 2003
It has been highly expected to utilize Engineered cementitious composite (ECC), which has metal-like deformation and crack opening restriction ability, as retrofit materials for structures. For this application, direct spray method has been commonly accepted. This study focused on experimentally clarifying fundamental properties of direct sprayed ECC, which involved high performance Polyvinyl alcohol fiber. As a result of experiments, it was demonstrated that the direct sprayed ECC was successfully processed and showed pseudo-strain hardening performance comparable to ordinary placing ECC in literature. Furthermore, test results simulating concrete cover cracking due to re-bar corrosion demonstrated that direct sprayed ECC has significant potential to elongate service life of R/C member in heavy chloride environment.
|Properties of Hybrid Fiber Reinforced Cement-based Composites
Atsushi Kawamata, Hirozo Mihashi and Hiroshi Fukuyama
Journal of Advanced Concrete Technology, 1(3) 283-290, 2003
Three-point bending tests and uniaxial tension tests on Hybrid Fiber Reinforced cement-based Composites (HFRCC) were carried out. HFRCC contains both specially-processed steel fiber (steel cord) and synthetic fiber. As the result of the bending tests, it was confirmed that coarse and wide cracks were observed near the notch of the specimens reinforced with only steel cord. On the other hand, HFRCC showed high strength and ductility. Furthermore HFRCC developed in this study showed multiple cracks and pseudostrain hardening under uniaxial tension. Therefore it could be confirmed that HFRCC has a sufficiently high performance as High Performance Fiber Reinforced Cement-based Composites (HPFRCC) defined in previous studies.
|Observation of Multiple Cracking in Hybrid FRCC at Micro and Meso Levels
Koji Otsuka, Hirozo Mihashi, Satoshi Mori and Atsushi Kawamata
Journal of Advanced Concrete Technology, 1(3) 291-298, 2003
Development of high-performance construction materials is one of the key issues for the sustainability of structures, while some ductile fiber reinforced cementitious composites (FRCC) have been developed. The purpose of this study is to observe microcracking in the high-performance FRCC on micro and meso levels for making clear the detailed mechanisms causing the ductile behavior. In the experiments, a compound machine system was used to observe the surface of specimens under tensile loading by means of electron microscope. X-ray technique with a contrast medium was also applied to observe internal cracking around a deformed bar. As a result, it was shown that a number of micro cracks were formed on the surface of FRCC even before the loading. Then those micro cracks grew and/or othecracks occurred to generate multiple cracking as the load increases. It was also shown that the extended nonlinearity of FRCC was produced only by the accumulation of multiple cracks. In the vicinity of the deformed bar in FRCC, multiple cracks were formed from the lug of the bar and the crack width was much thinner than that in plain mortar. Thus FRCC surely contributes to disperse bond cracks and to resist the expansion of the cracks.
|Mechanisms of Multiple Cracking and Fracture of DFRCC under Fatigue Flexure
Takashi Matsumoto, Peerapong Suthiwarapirak and Tetsushi Kanda
Journal of Advanced Concrete Technology, 1(3) 299-306, 2003
This paper presents an experimental study on the flexural fatigue characteristics of PVA-ECC and PE-ECC. The ECCs showed a unique S-N relation and exhibited the development of multiple cracks even under fatigue loading. The development of multiple cracks was found to be dependent on fatigue stress levels, and the mechanism is discussed in reference to the static multiple cracking mechanism. The difference of two ECCs appeared especially in the deformation capacity under fatigue loading. The deformation is shown to be affected by the number of cracks as well as the crack width, where the fracture mechanism of a bridged crack is related to either fiber rupture or fiber pullout.
|Corrosion Durability and Structural Response of Functionally-Graded Concrete Beams
Mohamed Maalej, Shaikh F.U.Ahmed and P. Paramasivam
Journal of Advanced Concrete Technology, 1(3) 307-316, 2003
This paper reports the results of an experimental program on the effectiveness of Ductile Fiber Reinforced Cementitious Composites (DFRCC) in retarding the corrosion of steel in Reinforced Concrete (RC) beams. The experimental results showed that a Functionally-Graded Concrete (FGC) beam, where a layer of DFRCC material was used around the main longitudinal reinforcement, had a noticeably higher resistance against reinforcement corrosion compared to a conventional RC beam. At the end of about 83 days of accelerated corrosion, an FGC beam lost only 6.6% of its steel reinforcement compared to 10.1% observed on a conventional RC beam. The better performance of the FGC beam was also evident from the absence of any corrosion-induced cracking and the very low tendency of the concrete cover to delaminate as measured by a concrete embeddable fiber optic strain sensor.
|Experimental Response of HPFRCC Damper for Structural Control
Hiroshi Fukuyama and Haruhiko Suwada
Journal of Advanced Concrete Technology, 1(3) 317-326, 2003
Structural performance of the cementitious damper made by steel bar and HPFRCC was experimentally observed. These dampers will be applied for reducing seismic damage as well as seismic response of RC structures under the performance based design system. Since stiffness of RC structures is relatively higher than that of steel structures, stiffer damper compared to the conventional one mainly applied for steel structures are required for reducing the seismic response of RC structures drastically. The advantage of the HPFRCC damper is selective structural performance, strength, stiffness, and ductility, by changing configuration, bar arrangements and type of materials used. The experimental results indicate that elemental ductility is much increased with decreasing damage when the HPFRCC are applied to the damper. It means cementitious damper for structural control is available which has much merit in performance and cost. Compressive resistance of the damper is also a unique advantage for structural control.
|Experimental Response of Precast Infill Panel Connections and Panels Made with DFRCC
Keith E. Kesner and Sarah Billington
Journal of Advanced Concrete Technology, 1(3) 327-333, 2003
Engineered Cementitious Composites (ECC), which exhibit pseudo-strain hardening behavior and steady-state cracking are being explored for use in retrofitting critical facilities in seismic regions. ECC materials offer several advantages for seismic retrofitting such as energy absorption capacity, excellent tensile and compressive strength, and the ability to be cast into various shapes. Structural components made from precast ECC materials have the ability to be connected by welds, bolts or with grout.
Preliminary results from a material development study wherein a new type of polymeric fiber, the effect of curing and drying conditions and cyclic load response are explored. New types of fibers are being investigated to evaluate their suitability for use in ECC materials. The nature of the structural applications being developed necessitates the evaluation of the effects of curing and drying conditions. Evaluation of the cyclic load response of the ECC materials will be used in modeling the energy dissipation of the materials.