Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1985-10-16
1986-12-09
Bell, James J.
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
264105, 264135, 264234, 264333, 264 82, 428284, 428256, 428408, 428418, 428457, 428703, B32B 1500
Patent
active
046279989
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement of a carbon fiber reinforced concrete. More particularly, it relates to an improvement in curing of a carbon fiber reinforced concrete in which the concrete is cured while being in contact with a surface of ferrous metal. In one aspect the invention provides a precast composite structure comprising a matrix of cured carbon fiber reinforced concrete and at least one ferrous metallic member at least partly buried in the matrix. In another aspect the invention provides a process for manufacturing such a precast composite structure.
BACKGROUND OF THE INVENTION
The inherent brittleness of a cement matrix can be substantially overcome by dispersing therein a suitable amount of a suitable fibrous material, such as carbon fiber. Since the development of inexpensive pitch-based carbon fibers, extensive studies on a practical use of carbon fiber reinforced concrete have been made, and great expectations are entertained of this new construction material having strngth, distortion and elastic properties which have not been realized by the heretofore available cement concretes.
We have been engaged for a long year in a research and development work on the carbon fiber reinforced concrete. During our work we have encountered a problem which is not the case with ordinary concrete. The problem is a phenomenon that if metal is in contact with carbon fiber reinforced concrete, corrosion (oxidation) of the metal extensively proceeds during the curing of the concrete. More specifically, when carbon fiber reinforced concrete is cured while being in contact with ferrous metallic members, such as reinforcing steel bars and meshes, steel molds, bond wires, anchor fasteners, spacers and the like, corrosion of the metal rapidly proceeds during the curing of the concrete on those areas of the ferrous metallic members where they are in contact with the concrete to an extent unexpected with ordinary concrete.
DESCRIPTION OF THE INVENTION
An object of the invention is to solve the above-mentioned problem. We have ascertained that when carbon fiber, which is very conductive and has a noble potential well comparative to that of a noble metal, is in contact with a basic metal (ferrous metal), there is formed a local cell, which is a primary cause of the metal corrosion, and found that upon curing of concete containing from 0.2 to 10% by volume of carbon fiber dispersed therein while being in contact with a surface of ferrous metal, the problem of the metal corrosion peculiar to the carbon fiber reinforced concrete can be substantially completely ovecome, if an insulating layer having an electric resistance of at least 100 ohms is preformed on the surface of the ferrous metal in advance of the curing.
Thus, the invention provides a process for manufacturing a precast composite structure of carbon fiber reinforced concrete comprising a matrix of cured carbon fiber reinforced concrete and at least one ferrous metallic member at least partly buried in said matrix, said process comprising the steps of: 100 ohms at least on that surface of said ferrous metallic member, which will otherwise be brought in contact with a concrete mix, thereon in position in a mold, aggregate and 0.2 to 10% by volume of carbon fiber so that said ferrous metallic member may be at least partly buried in said concrete mix, becomes self-supporting, temperature between 100.degree. C. and 215.degree. C.
The invention further provides a precast composite structure of carbon fiber reinforced concrete comprising a matrix of cured carbon fiber reinforced concrete containing 0.2 to 10% by volume of carbon fiber, at least one ferrous metallic member at least partly buried in said matrix and an insulating layer on the surface of said ferrous metallic member for preventing contact of said ferrous metallic member with the carbon fiber, said insulating layer having an electric resistance of at least about 100 ohms.
The composite structures in accordance with the invention have excellent strengh
REFERENCES:
patent: 3922413 (1975-11-01), Reineman
patent: 4314003 (1982-02-01), Curnow et al.
patent: 4349398 (1982-09-01), Hearns et al.
patent: 4392335 (1983-07-01), Heiman
patent: 4419853 (1983-12-01), Failmezger et al.
Akihama Shigeyuki
Aya Masanori
Ikeda Hideki
Kamakura Masashi
Koyama Seiichi
Bell James J.
Kajima Corporation
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