Concrete and process to make same

Details Concrete and process to make same Concrete and process to make same

2001-03-12

2003-11-18

Mulcahy, Peter D. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S004000, C524S007000, C524S008000

Reexamination Certificate

active

06649671

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to improved concrete and methods of forming the improved concrete. In particular, the invention relates to concrete containing plastic fibers.
BACKGROUND OF THE INVENTION
Generally, concrete is a brittle material with high compressive strength but low tensile strength. In the concrete industry, all concrete work is typically specified on the basis of the compressive strength. Any attempt to improve the crack strength (tensile strength) and toughness of the concrete almost always requires the introduction of reinforcing addition. For example, rebar (steel rods) is added which provides structural integrity but does not eliminate cracking. Metal mesh has also been added to reduce cracking but it cannot be used effectively, for example, to reinforce concrete of complex geometry.
Plastic fibers have also been used to improve the tensile strength and toughness (resistance to cracking). For example, polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), aramids (e.g., KEVLAR, a trademark of E.I. du Pont de Nemours & Co.) and polyvinyl alcohol fibers have been used. However, all of these fibers suffer from one or more problems, such as high cost, low alkaline resistance, low tenacity or low interfacial bonding between the concrete and the fiber. Polypropylene and polyethylene have been the most preferred fiber to date due to their high tenacity and low cost. Unfortunately, these fibers suffer from very low interfacial bonding.
To remedy this problem, coatings have been formed on the surface of the fibers by applying a liquid, such as glycerol ether or glycol ether on the fiber surface, as described by WO 980766. Coatings have also been applied by vapor deposition, such as described in JP 60054950. Similarly, chemically modifying the surface has been done, such as described by JP 10236855 (treatment of the surface with a polyoxyalkylenephenyl ether phosphate and polyoxyalkyl fatty acid ester). Unfortunately, these methods naturally lead to increased cost, complexity and potentially insufficient bonding of the coating to the fiber.
Another remedy has been the incorporation of inorganic particles in and on the fiber, such as described by JP 07002554. Unfortunately, the fiber process becomes much more difficult (e.g., fiber breakage) and increases the cost and generally decreases the tenacity of the fiber.
Accordingly, it would be desirable to provide a concrete formulation that, for example, improves one or more of the problems of the prior art, such as improving the toughness without substantially increasing the cost of the concrete.
SUMMARY OF THE INVENTION
We have now discovered a new type of concrete containing a polyolefin reinforcing polymer that has improved bonding to the concrete in the absence of any treatment of the surface of the reinforcing polymer. This in turn has resulted in concrete with improved properties, lower cost, or both, compared to other reinforced concrete.
A first aspect of the invention is a concrete article comprised of concrete having therein a reinforcing polymer that has a surface in contact with the concrete, said surface being comprised of a substantially random interpolymer of at least one &agr;-olefin with at least one vinyl or vinylidene aromatic monomer.
A second aspect of the invention is a method of preparing concrete comprised of mixing concrete, water and a reinforcing polymer comprised of a substantially random interpolymer of at least one &agr;-olefin, with at least one vinyl or vinylidene aromatic monomer, and curing said concrete mixture to form the concrete article having the reinforcing polymer therein, such that the reinforcing polymer has a surface comprised of the substantially random interpolymer in contact with the concrete.
A third aspect of the invention is a concrete article formed by the process of the second aspect.
The concrete of this invention may be used in any application suitable for concrete, but it is especially well-suited for parking garages, bridge decks, white toppings, tunnels, mining, slope stabilization, architectural purposes, such as landscaping stones, skate boarding rinks, modern architecture, art sculptures, fast setting
on-slumping ceilings, swimming pools, and for repairing and retrofitting existing structures.
DETAILED DESCRIPTION OF THE INVENTION
The concrete used to form the concrete article of this invention may be any suitable concrete, such as those known in the art. Generally, the concrete is a mixture comprised of Portland cement. Portland cement is used as is commonly understood in the art and defined by
Hawley's Condensed Chemical Dictionary,
12
th
Ed., R. Lewis, Van Nostrand Co., NY, p 239, 1993.
It is understood that the reinforcing polymer in the concrete is a solid at ambient conditions. That is to say, the polymer is added as a solid object and is a solid after the concrete is cured. The polymer may be any shape useful in making the concrete article. Preferably the polymer is a fiber, bundles of fibers, sheets, tapes, laminates or combinations thereof. Preferably the reinforcing polymer is a fiber as described herein. Desirably, the reinforcing polymer is uniformly distributed within the concrete.
The amount of reinforcing polymer in the concrete generally ranges from about 0.05 volume percent to about 10 volume percent of the concrete article. Preferably the amount of the reinforcing polymer is at least about 0.1 percent, more preferably at least about 0.3 percent and most preferably at least about 0.5 percent, to preferably at most about 7 percent, more preferably at most about 5 percent and most preferably at most about 3 percent by volume of the article.
The reinforcing polymer may be any polymer so long as it has a surface comprised of a substantially random interpolymer (interpolymer) of at least one &agr;-olefin with at least one vinyl or vinylidene aromatic monomer. Needless to say, the reinforcing polymer may be entirely comprised of an interpolymer, but it is preferred that the polymer is comprised of a core that is a polymer (core polymer) other than the interpolymer.
The interpolymer may cover any portion of the core polymer sufficient to impart one or more desirable properties, such as one of those previously described. Generally, at least about 1 percent of the surface area of the core polymer is comprised of the interpolymer polymer (also referred to as the surface polymer).
The interpolymer is prepared by polymerizing one or more &agr;-olefins with one or more vinyl or vinylidene aromatic monomers and, optionally, other polymerizable monomers, as described by U.S. Pat. Nos. 6,156,842 and 6,190,768. Herein, the substantially random interpolymers also include pseudo-random interpolymers, as described in EP-A-0,416,815 by James C. Stevens, et al. and U.S. Pat. No. 5,703,187 by Francis J. Timmers, both of which are incorporated herein by reference in their entirety.
Suitable &agr;-olefins include, for example, &agr;-olefins containing from 2 to about 20, preferably from 2 to about 12, more preferably from 2 to about 8 carbon atoms. Particularly suitable are ethylene, propylene, butene-1,4-methyl-1-pentene, hexene-1 or octene-1 or ethylene in combination with one or more of propylene, butene-1,4-methyl-1-pentene, hexene-1 or octene-1. Preferably the &agr;-olefin is propylene or ethylene. Most preferably the &agr;-olefin is propylene. The &agr;-olefins, as used herein, do not contain an aromatic moiety.
Other optional polymerizable ethylenically unsaturated monomer(s) include strained ring olefins, such as norbornene and C
1-10
alkyl or C
6-10
aryl substituted norbornenes, with an exemplary interpolymer being ethylene/styrene
orbornene.
Suitable vinyl or vinylidene aromatic monomers, which can be employed to prepare the interpolymers include, for example, those represented by the following formula:
wherein R
1
is selected from the group of radicals consisting of hydrogen and alkyl radicals containing from 1 to about 4 carbon atoms, preferably hydrogen or methyl; each R
2
is independently selected from the

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