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International Concrete Abstracts Portal

Showing 1-5 of 12 Abstracts search results

Document: 

SP185-06

Date: 

February 1, 2000

Author(s):

J. J. Beaudoin, P. Gu, N. M. P. Low, and N. P. Mailvaganam

Publication:

Symposium Papers

Volume:

185

Abstract:

The performance of wollastonite-reinforced portland cement-based binders hydrated in saturated Ca(OH)2 solution, 1N NaOH solution, 1N KOH solution, distilled water and saturated moist air was evaluated as a precursor to the development of a test for assessing the durability of these composites. The cementitious binders are made of cement and silica fume. The effect of the different solutions on the mechanical behavior and microstructural characteristics of the systems investigated at 24 degrees Celsius and 80 degrees calicoes was determined. Porosity and pore structure determinations were made using mercury intrusion porosimetry, helium pycnometry, and isopropyl alcohol saturation techniques. Flexural strength and fracture toughness behavior was also determined. Pore structure modifications, leaching effects and mechanical test results were stability of wollastonite micro-fibers in cement binders. Wollastonite microfiber appears to merit serious consideration as a candidate reinforcement for the development of new composite systems.

DOI:

10.14359/5712


Document: 

SP185-03

Date: 

February 1, 2000

Author(s):

S. C. Goel and M. Khuntia

Publication:

Symposium Papers

Volume:

185

Abstract:

This paper reports the results of an investigation on the performance of FRC-encased open web steel joists under cyclic loading. The system completely eliminates the need for any shear connectors between steel joists and surrounding FRC as well as that for conventional longitudinal and transverse reinforcing bars, all of which are quite labor intensive. Cyclic load test on some half-scale specimens consisting of composite beams with end connections were carried out. The parameters included the configuration of web steel elements, and the amount of steel in longitudinal and web elements of the joists. The results are most encouraging. interact in a y so as to provide stable hysteretic behavior with excellent energy dissipation and ductuility. The study indicates that shear strength of the composite beam can be remarkably enhanced by addition of structures. The flexural capacity is also considerably increased. It can be quite accurately calculated by analytical models based on full composite action.

DOI:

10.14359/5709


Document: 

SP185-02

Date: 

February 1, 2000

Author(s):

Y. Shao, R. Srinivasan, and S. P. Shah

Publication:

Symposium Papers

Volume:

185

Abstract:

High performance fiber reinforced cement composites (HPFRC) are defined as the materials which exhibit a postpeak strain hardening type of response with a multiple crack pattern. Such a ductile behavior makes the HPFRC an ideal material to be used in structural repair and retrofit for dimensional stability, tensile-load carrying capacity, impact resistance, flexibility and long term impermeability. The critical parameter for continuous fiber reinforced cementitious materials to obtain the high performance response is the minimum fiber volume ratio with well dispersed fibers. As long as continuous fiber composites have a sufficient number of fibers to bridge the cracks, strain hardening and multiple cracking can always happen. However, there is no single dominant parameter which can control the multiple cracking process in discontinuous fiber composites. Various parameters can affect the postpeak response of discontinuous fiber reinforced cementitious materials. They are related to fibers, matrix and the processing methods. Parameters relating to the reinforcement include the type of fiber, fiber length, fiber volume ratio, fiber orientation, state of fiber dispersion and the degree of adhesion to the matrix. These primary variables are in turn influenced by selection of the matrix type, presence of additives, and the processing conditions. The latter acts through controlling the state of dispersion, establishing a fiber design a high performance fiber reinforced cementitious repair material, the approach in which the repair will be carried out should be considered simultaneously.

DOI:

10.14359/5708


Document: 

SP185-07

Date: 

February 1, 2000

Author(s):

D. R. Morgan, A. Lobo, and L. Rich

Publication:

Symposium Papers

Volume:

185

Abstract:

Concrete berth faces in the St. Lawrence river at the Port of Montreal constructed in the early 1900's are undergoing continuing deterioration from the combined effects of frost damage, alkali aggregate reactivity and in some areas attack from deicing chemicals stored on the adjacent wharves. In some places the concrete is turning to rubble, and a major retrofit program is required to restore the berth faces to a serviceable condition. Both cast-in-place reinforced concrete and anchored and tied-back fiber reinforced shotcrete remedial potions are being evaluated to establish the most technically sound and cost-effective remedial alternatives for this work. This paper describes a prototype construction project in which about two thirds of a berth face, 122m long and 7.1m. High, was repaired with a synthetic fiber reinforced shotcrete and the remaining third with a steel fiber reinforced 25mm long by .38mm diameter added at an addition rate of 1.25 percent by volume of the shotcrete. The deformed steel fiber 38mm long was added at an addition rate of .75 percent by volume of the shortcrete. The shotcrete used was air entrained, silica fume modified, supplied by transit mixers from a central-mix plant and applied by the wet-mix plant and applied by the wet-mix shotcrete process. This paper describes the remedial design, shotcrete mixture designs, preconstruction mock-up production and quality control testing and provides a summary of construction quality control test results. Test results reported include plastic shotcrete properties such as as-batched and as-shot slump and air-content, compressive strength, boiled absorption and volume of permeable voids and toughness. The behavior of the shotcrete repairs is being monitored service is described. Comparative data is provided regarding the relative costs of the cast-in-place reinforced concrete and fiber reinforced shotcrete alternatives.

DOI:

10.14359/5713


Document: 

SP185-09

Date: 

February 1, 2000

Author(s):

N. Krstulovic-Opara, J. M. LaFave, E. Dogan, and C.-M. Uang

Publication:

Symposium Papers

Volume:

185

Abstract:

Older reinforced concrete structures constructed in seismically active areas of the United States are usually non-ductile and are thus identified as hazardous. Extensive efforts have been devoted to the development of adequate retrofitting techniques for these buildings. While laboratory studies have shown that the use of "conventional" Fiber Reinforced Concretes (FRCs) and High Performance FRCs (HPFRCs) in new construction leads to substantially improved seismic response, seismic retrofit techniques have not yet taken advantage of these advanced composites. The advantages of conventional FRCs is a significant increase in ductility over that of reinforced concrete. The advantage of HPFRCs is that, when loaded beyond the elastic limit, they exhibit significant increases in structure to dissipate energy--a feature particularly desirable for earthquake resistant design. The goal of the presented research was to develop a novel seismic retrofit technique, using recently developed HPFRCs, to solve the following common problems of non-seismically designed reinforced concrete frames: 1) inadequate anchorage of the discontinuous bottom beam reinforcement, 2) inadequate confinement of the column lap splices, and 3) inadequate confinement of the joint. HPFRCs used in the presented research include Slurry Infiltrated Fiber Concrete (SIFCON) and Slurry Infiltrated Mat Concrete (SIMCON). The presented research was conducted in collaboration with a project Advisory Panel consisting of consulting structural engineer from Wiss, Janney, Elstner Associates, Inc.

DOI:

10.14359/5715


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