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United States Patent |
6,010,566
|
Nemegeer, ;, , , -->
Nemegeer
,   et al.
|
January 4, 2000
|
Preparation of bituminous concrete comprising wire pieces
Abstract
The invention relates to the manufacturing of a castable hot mixture of
bituminous concrete, in which a multiplicity of steel wire pieces are
equally distributed in the mixture. According to the invention, an
ingredient is used in the form of a multiplicity of bundles in which the
wire pieces are held together by a binding substance that is able to
disintegrate in cementitious concrete, as already known, but that in
addition is disintegrated by melting, in such a way that such bundles are
usable for both cementitious and bituminous concretes.
Inventors:
|
Nemegeer; Dirk (B- 8730, Harelbeke, BE);
Vancraeynest; Yves (B- 8550, Zwevegem, BE)
|
Appl. No.:
|
860523 |
Filed:
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April 1, 1992 |
Foreign Application Priority Data
Intern'l Class: |
C09D 195/00 |
Field of Search: |
106/277,282
|
References Cited
U.S. Patent Documents
4284667 | Aug., 1981 | Moens | 427/331.
|
4314853 | Feb., 1982 | Moens | 106/99.
|
4360473 | Nov., 1982 | Marzocchi et al. | 260/429.
|
4382988 | May., 1983 | Gallman | 428/222.
|
5028266 | Jul., 1991 | Rettenmaier et al. | 106/282.
|
Other References
Joseph, CHE 477, Process Technology Lecture Notes, Washington Univ., School
of Engineering and Applied Science, Aug. 1986, p. 3.5.
|
Primary Examiner: Brunsman; David
Parent Case Text
This application is a continuation-in-part, continuation, division, of
application Ser. No. 07/523,524, filed May 15, 1990.
Claims
We claim:
1. A process for preparing a castable hot mixture of bituminous concrete,
comprising the steps of:
introducing into a mixture of hot bituminous concrete a multiplicity of
steel wire pieces adapted for strengthening said mixture of hot bituminous
concrete after its solidification; and
mixing said steel wire pieces in said mixture of hot bituminous concrete
until said steel wire pieces are equally distributed in said mixture of
hot bituminous concrete, wherein
said steel wire pieces are introduced in the form of bundles of such steel
wire pieces that are held together into said bundles by a binding
substance which is adapted to disintegrate by water when mixed into a wet
cementitious concrete and which disintegrates by melting when mixed in a
hot bituminous concrete mixture, and wherein said steel bundles
disintegrate during mixing of said mixture of hot bituminous concrete.
2. A process as recited in claim 1, wherein the steel wire pieces which are
introduced into said mixture of hot bituminous concrete are stiff.
3. A process as recited in claim 2, wherein the steel wire pieces which are
introduced into said mixture of hot bituminous concrete have a thickness
between 0.3 to 1.5mm and a length to thickness ratio of between 40 and
120.
4. A process according to claim 1, wherein a mixing temperature of said
mixture of hot bituminous concrete lies in the range between 80.degree. C
and 200.degree. C., and in a range between 30 and 50 centigrade degrees
above a softening point temperature of said binding substance.
5. A process according to claim 1 wherein said bundles are dumped in bulk
into said mixture.
6. A process for preparing a castable hot mixture of bituminous concrete,
comprising the steps of:
introducing into a mixture of hot bituminous concrete a multiplicity of
steel wire pieces adapted for strengthening said mixture of hot bituminous
concrete after its solidification; and
mixing said steel wire pieces in said mixture of hot bituminous concrete at
a temperature of between 80.degree. C and 200.degree. C. until said steel
wire pieces are equally distributed in said mixture of hot bituminous
concrete, wherein
said steel wire pieces are introduced in the form of bundles of such steel
wire pieces that are held together into said bundles by a binding
substance which is adapted to disintegrate by water when mixed into a wet
cementitious concrete and which disintegrates by melting when mixed in a
hot bituminous concrete mixture, and wherein said steel bundles
disintegrate during mixing of said mixture of hot bituminous concrete.
Description
BACKGROUND OF THE INVENTION
The invention relates to a process for the preparation of a castable hot
mixture of bituminous concrete. Such concrete is often used for
strengthening the banks of waterways and for roadway surfaces. As is well
known, it comprises a mixture of filling material (such as sand, lime,
and/or stone pieces e.g. of dimension from 2 mm up to 20 mm) and a fusible
bitumen that, in a hardened state, binds the filling material together.
"Bitumen" is to be understood as a mixture of mainly hydrocarbons with
residual impurities, as obtained as residues from refining coal or
petroleum, such as pitch or tar or asphalt. The chosen bitumen is adapted
to be sufficiently hard for the temperatures at which it is exposed for
use, which in general is a temperature below 40 C., and further adapted to
be sufficient liquid at the mixing temperature, so as to be mixable with
the filling material during mixing, and to keep sufficiently soft during a
subsequent time after dumping, so that it can be deformed and compacted
into its final form in which it has to harden. A suitable mixing
temperature ranges between 80.degree. C. and 200.degree. C. Mixing below
80.degree. C. leaves insufficient free time between dumping and
compacting, and above 200.degree. C. the process is less economical and
less practical for handling the hot mixture. A mixture of such bituminous
concrete at such mixing temperature is meant when referring hereinafter to
a "castable hot mixture of bituminous concrete".
In order to strengthen the bituminous concrete, it is known, e.g. from U.S.
Pat. No. 4,382,988, to introduce into the mixture a multiplicity of steel
wire pieces, adapted for strengthening the bituminous concrete after its
solidification, and mixing the steel wire pieces into the mixture. There
are already steel wire elements on the market, adapted for reinforcement
of cementitious concrete, in the form of bundles of such steel wire pieces
that are held together in the bundles by a binding substance adapted to
disintegrate by water when mixed into a wet cementitious concrete. Such
wire bundles are introduced into the wet mixture of cementitious concrete,
they disintegrate into individual wire pieces by the water of the mixture
and by the mixing movement, and, by further mixing, the individual wire
pieces come to be equally distributed in the mixture. Owing to the
introduction in the form of bundles, it is avoided that the individual
wires come to conglomerate into balls instead of being equally
distributed. Such a mixing method and a bundle adapted has for this method
been described in U.S. Pat. No. 4.314.853. Such bundles are now produced
in mass by a method in which a number of wires are bundled and then glued
together by applying a water emulsion of the glue (that, after drying,
will re-emulgate or dissolve later again in the cementitious concrete) and
then the bundles are caused to dry in a drying furnace. Then bundle is
then finally transversally cut into pieces of short bundles, as described
in U.S. Pat. No. 4.284.667. A known glue for that use is a glue of about
75% polyvinyl-acetate dispersion with a softening agent and with about 25%
of a glue that is soluble in water, such as polyvinylalcohol or
ethylene-vinyl acetate.
OBJECTS AND SUMMARY OF THE INVENTION
In adapting this mixing method with bundles of wire pieces to bituminous
concrete, it has been found that the same wire bundles on the market for
use in cementitious concrete can be directly usable for bituminous
concrete, notwithstanding the fact that a mixture of the latter does not
comprise any water, because the binding substance, that keeps the wire
pieces together, is, or can be made adapted also to melt at the mixing
temperature of the bituminous concrete and to cause the bundles to
disintegrate. When such fiber bundles are chosen for bituminous concrete,
it is not necessary to keep a separate stock for cementitious and for
bituminous concrete.
The invention is consequently characterized by the fact that the steel wire
pieces are introduced into a mixture for such bituminous concrete in the
form of bundles of such steel wire pieces that are held together into the
bundles by a binding substance adapted to disintegrate by water when mixed
into a cementitious concrete, the bundles being also adapted to
disintegrate by melting when mixed in the hot bituminous concrete mixture,
and that the bundles are caused to disintegrate during mixing of said
bituminous concrete. By "adapted to disintegrate by melting" is meant here
that the binding substance, when mixed into the castable hot mixture of
bituminous concrete, loses sufficient solidity to allow the bundles of
wire pieces to disintegrate into individual wire pieces under the mixing
movement, where this loss of solidity is due to the substance passing
wholly or partially from the solid to the molten state. The loss of
solidity does not necessarily occur at a sharply defined melting point.
For substances that are composed of different molecules with different
melting points, as e.g. for synthetic resins, the loss of solidity occurs
by gradually softening through a softening temperature range. For these
substances, the temperature level of softening is determined here by the
softening point according to the Ring & Ball test. And for the substances
with sharply defined melting point, the "softening" occurs at the melting
temperature. This is what is meant here by "softening point".
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
It is advisable to use a mixing temperature that lies in a range between 30
and 50 degrees centigrade above the softening point of the binding
substance of the bundles. If the mixing temperature lies too high above
that softening point, then it will be observed that the binding substance
melts too rapidly before the undisintegrated bundles are firstly equally
distributed into the mixture, and when the mixing temperature lies too
near above the softening point, then there is a risk that the bundles are
not completely disintegrated. As the suitable mixing temperature ranges
between 80.degree. C. and 200.degree. C., and as a softening point below
50.degree. C. is undesirable in order to avoid that the bundles begin to
stick to each other when exposed to the sun or to warm climate
circumstances,this means that the softening point for the binder will lie
in the range between 50.degree. C. and 170.degree. C.
In order to come into consideration for the strengthening of the hardened
bituminous concrete, the steel wire pieces shall have an essentially
oblong form, with a thickness of 0.3 to 1.5 mm, a length-to-thickness
ratio between 40 and 120 and a maximal length of 120 mm. By "oblong" is
meant, that the wire piece is not so bent or curled, that it would no
longer be possible to distinguish a general length direction in which the
wire piece has to exert its strengthening effect. In this respect, the
apparent length of the wire piece, i.e. the distance between both ends of
the wire piece, has not to be smaller than 0.7 times the length, as
measured along the wire piece. The thickness of the wire piece, for
non-circular cross sections, is calculated as the diameter of the circle
having the same area.
A bundle then comprises a number of such wire pieces, preferably between 5
and 40. These wire pieces are then held together by the binding substance,
not necessarily by the fact that the wire pieces are glued to each other,
where the binding substance is located between the wire pieces, but e.g.
also by the fact that the binding substance is located around the bundle,
in the form of a tight sleeve around the bundle, or one or more tight
rings, or one or more wrapping filaments. The bundle need not necessarily
be a bundle with round cross-section, but shall preferably be a flat
bundle of wires that are glued together side by side. Such bundles are
easier for disintegration during mixing.
For the intended double possibility of use, the binding substance,
disintegratable by melting, has also to be disintegratable in the water of
cementitious concrete. This can be obtained by using a substance that is
completely dissoluble in water, as well as by using a composition that is
only partially dissoluble, in such a way that the non-dissoluble part
sufficiently softens and/or emulgates for allowing the steel wire pieces
to be separated by the mixing movement. Preferably, an adhesive on the
basis of polyacetate, as mentioned above is used. If an
ethylene-vinylacetate is added as the water soluble component, the
softening point can be adapted by changing the ethylene/vinylacetate
ratio.
The binding substance can be a polymer or copolymer that is soluble in
water, preferably in the form of a conventional hot melt adhesive, which
comprises additional resins, waxes, softeners, stabilizers and possible
filler substance. Suitable hot melt adhesives are those that are used for
applying in molten state on paper or cardboard, and intended to be tacky
again by moistening with water, such as those that are obtainable on the
market, and, for instance described in the book of D.L. Bateman, "Hot Melt
Adhesives", Third Edition, Noyes Data Corporation.
In use, the bundles of steel wire pieces are dumped in bulk into the
mixture. They can be added first and mixed into a dry mixture, before
adding the bitumen, and the latter can then be added thereafter. The
bundles can also be added to the hot mixture that already contains the
molten bitumen. In each of these cases, the bundles themselves will
firstly be equally distributed in the mixture under influence of the
mixing movement. And afterwards, still during further mixing, the binding
substance will soften and/or melt, whereby the bundles break open into
separate wire pieces that are further mixed and come to be equally
distributed as separate wire pieces.
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