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International Concrete Abstracts Portal

Showing 1-5 of 12 Abstracts search results

Document: 

SP190-11

Date: 

April 1, 2000

Author(s):

P. Soroushian

Publication:

Symposium Papers

Volume:

190

Abstract:

This paper reviews the key effects of processed cellulous fibers at practi-cal dosage rates in cement-based mixtures of different cement contents and aggregate particle sizes, produced by normal casting or using different thin sheet processing systems. Mechanical characteristics, restrained plastic and drying shrinkage cracking attributes, and durability characteristics under dif-ferent accelerated aging conditions are investigated. Performance character-istics of processed cellulose fibers in thin sheet cement products subjected to . different processing systems are compared.

DOI:

10.14359/5729


Document: 

SP190-05

Date: 

April 1, 2000

Author(s):

Hans W. Reinhardt

Publication:

Symposium Papers

Volume:

190

Abstract:

Panels were made of concrete and glass rovings for use as integral (or permanent) formwork for reinforced concrete. Extensive testing has been carried out in order to check bending strength, durability, composite action, and fire resistance of the panels either in the stage of the construction process or after completion of the structure. The test results are described and discussed. The final design of the formwork panel is presented.

DOI:

10.14359/5722


Document: 

SP190-09

Date: 

April 1, 2000

Author(s):

P. Soukatchoff

Publication:

Symposium Papers

Volume:

190

Abstract:

It is well known that glass fiber cement composites may suffer a loss of strength and toughness when exposed to natural environments. Even though buildings in Europe clad with GFRC panels have performed well for nearly 30 years now, this has restricted its use in certain circumstances because of a lack of confidence on behalf of the designer and specifiers. The loss of long term properties of GFRC is explained by two main phenomena: 0 The chemical attack of the glass fibers. 0 The morphological modification of the interfaces due to the growth of hydrates (Ca(OH)2 + CSH) which leads to em brittlement of the fibers in the matrix. The most widely used solution against the first type of attack is to use Alkali Resistance, AR, glass fibers with Cem-FIL being the original and Cem-FIL 2 giving the best long-term results. However, the way to obtain both constant flexural strength and ultimate strain (toughness) is to use both AR fibers and to modify the cementitious matrix in order to optimize the nature of the hydrate in the interface between the fiber and the matrix. Until recently, no totally satis-factory solution has been found even with the use of low alkali cements such as calcium sulpho-aluminate cement or portland cement with silica fume or flv ash. The CEM-FIL Star mix, developed by the Saint-Gobain group some 1 0 years ago, now has worldwide experience. It is based on using AR fiber with a specific type of the manmade, and therefore controllable, pozzolanic mate-rial, metakaolin, with a portland cement matrix. This reacts in a controllable way with the liberated lime, (calcium hydroxide), thus eliminating the main reason for the embrittlement of GFRC with time. By reacting with and re-moving this lime, long-term properties are improved.

DOI:

10.14359/5727


Document: 

SP190-06

Date: 

April 1, 2000

Author(s):

A. E. Naaman and K. Chandrangsu

Publication:

Symposium Papers

Volume:

190

Abstract:

This paper describes the bending behavior of advanced laminated cementitious composites reinforced with FRP meshes embedded in a cement mortar matrix with or without discontinuous fibers. When fibers are added the term hybrid laminated composite is used. Three different types of meshes (Kevlar, Spectra and carbon) were used in combination with three different discontinuous fibers, two PVA fibers and one carbon fiber. Since previous investigations by Naaman and Guerrero (1996) have indicated that the com-bined use of two layers of mesh reinforcement and discontinuous fibers gives a cost optimum combination for bending response, only two layers of mesh reinforcement, placed near each extreme surface of the specimen, were used in this study. The specimens were tested in four point bending. The loads and midspan deflections were measured. Equivalent elastic bending stress versus deflection curves are generated and representative curves are used to com-pare the first cracking strength, the post-cracking behavior, the maximum post-cracking strength or modulus of rupture, the unidirectional cyclic behavior and the toughness indexes.

DOI:

10.14359/5723


Document: 

SP190-04

Date: 

April 1, 2000

Author(s):

A. Pivacek, G. J. Haupt, R. Vodela, and B. Mobasher

Publication:

Symposium Papers

Volume:

190

Abstract:

A class of new structural materials with a significant degree of ductility and strength are introduced that are durable, strong, and cost effective. High fiber content cementitious materials (FRC materials) are manufactured using a computer controlled closed loop system for pultrusion and filament winding. Composites consisting of unidirectional lamina, and [0/90/0] are manufactured. In addition, sandwich composites with a lightweight aggregate core and 0/90 lamina as the skin elements are studied. Mechanical response of laminates is measured using closed loop uniaxial tensile and flexural tests. Results indicate that tensile strength of composites containing 5% alkali-resistant (AR) glass fibers can exceed 40 MPa. The ultimate strain capacity can also be increased to more than 2% using cross plies at various orientations. Significant cost savings and weight reduction may be achieved by replacing the inner layers of the boards with a lightweight aggregate mixture at a marginal loss of strength. The ultimate strain capacity of the composites is a function of ply orientation, thickness, and stacking sequence. Various mechanisms of delamination, debonding, and crack deflection are identified, resulting in an ultimate strain capacity of 2%, and a fracture toughness as much as two orders of magnitude higher than the conventional FRC materials. The extent of matrix cracking, ply delamination, and crack deflection mechanisms are studied by means of fluorescent microscopy.

DOI:

10.14359/5721


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