Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
Background of the Invention
The present invention relates to lightweight aggregates and in
particular to a lightweight expanded polymer used as an aggregate when
coated with a mixture formed with dehydrated lime and hydrated alumina
and to a method of coating an expanded polymer with the specific mix-
ture preparatory to mixing with cement,sand and water for producing
a lightweight construction material.
In the past, concrete blocks and other materials have been manu-
factured by mixing predetermined mixes of Portland cement, sand and
water and adding various types of aggregates made from a great variety
o-f materials, such as rock granite and slag from smelting operations.
Lightwcight aggregates may be produced from slags from the production
of phosphoric acid, and the like. Lightweight aggregates have the
advantage of producing a lighter building block or material having
great strength in compression and with reduced problems of shipping
and handling due to the lighter weight and while advantageously pro-
viding additional insulation value. The prior art also suggests using
a variety of products, as aggregates~ as well as various compositions
for mixing with aggregates which include the use of polystyrene with
a homogenizing agent as set forth in U.S. Patent 3,257,338 for a con-
crete composition comprising cement, a primary aggregate, expanded
polystyrene and a homogenizing agent, the homogenizing agent being
an alkali metal salt. The use of a foamed thermoplastic polymer for
plastering masonry surfaces is taught in U.S. Patent 3,291,762 and
uses flakes of a foamed thermoplastic polymer with up to 97% by weight
of a dry filler and minor proportions of drying oil in a solvent. U.S.
Patent 3,066,031 teaches a cementous material and method of preparing
such material using calcium oxide mixed with a reactant of silicon di-
oxide and aluminum dioxides while U.S. Patent 3,699,701 teaches a
lightweight cement for oil wells which utilizes small cenospheres con-
sisting primarily of silica-alumina. Other compositions may be seen
in U.S. Patent 3,076,717 for building load supporting surfaces; IJ.S.
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Patent 2,060,295 for an acoustical or insulating plaster; and in U.S.
Patent 3,021,291 for preparation of concrete containing expanding
polymeric particles in which a concrete mixture of Portland cement
is mixed with polymeric material in the form o-f small particles, in-
cluding the polymers of styrene and ethylene. IJ.S. Patent 3,272,765
teaches a lightweight concrete having a lightweight aggregate of
closed celled multicellular expanded polymeric particles and a binder
containing entrained air. U.S. Patent 3,214,393 teaches a concrete
mixture containing expanded polystyrene and homogenizing agent in
which cement, a primary aggregate, expanded styrene polymer and homo-
genizing agent consisting of polyvinyl alchol and a bituminous com-
pound and the alkali metal salt of the aliphatic insoluble portion of
the aromatic extract of pinewood are combined. U.S. Patent 2,517,993
teaches a hydraulic cement composition of Portland cement, burned
slag, and other ~aterials while U.S. Patent 3,679,445 teaches a ~ow
density concrete having Portland cement and high alumina cement with
a fine aggregate and a course aggregate and short fibers and air en-
trained therein. U.S. Patent 3,498,809 teaches a finishing mortar
composed of a fillerbinder in water and utilizing an inorganic gel
which is a reaction product of an inorganic base and a metal salt a-
long with a water soluble cellulose derivative. United Kingdom Patent
spedification No. 836,499 teaches improvements to lightweight concrete
and aggregates in which a nonbrittle cellular springy particle of por-
ous material are dispersed substantially uniform through a construction
material.
In contrast to the prior patents, the present invention teaches
a mixture used to coat expanded polystyrene beads, or the like, which
have obtained high thermal resistant qualities and compressive strengths.
The present coating of expanded polystyrene beads improves the quality
and physical characteristics of a concrete product using expanded
polystyrene beads as an aggregate.
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Summary of the Invention
The present invention relates to lightweight aggregates and inparticular to a coated, expanded polymer bead such as expanded poly-
styrene beads which are used as a lightweight aggregate in concrete
products and are coated with a mixture formed o-f dehydrated lime and
hydrated alumina with water in an amount to impart a suitable consis-
tency and a wetting agent. Cement can also be added to the bead coat-
ing during the mixing of the mixture with the beads, as well as
fiberglass to impart additional strength to the final product. The
coated beads are mixed with cement, sand and water and cured for
producing a lightweight construction material. A method is also des-
cribed in which a lightweight coated aggregate is prepared by forming
a mixture of dehydrated lime and hydrated alumina with water having
a wetting agent therein to form a suitable consistency with the de-
hydrated lime and hydrated alumina and then coating lightweight,
expanded polymer beads with said mixture while mixing a predetermined
amount of cement with the coated, expanded beads and adding -fiber-
glass to the mixture if desired. The coated beads may then be com-
bined with additional cement, sand and water which upon curing will
form a lightweight, concrete material which may also be formed with
a coating on one side which may be colored and textured as desired.
Description of the Preferred Embodiments
; A mixture is prepared in a dry form using equal parts by volume
of dehydrated lime and hydrated alumina such as approximately 50 parts
of dehydrated lime together with approximately 50 parts of hydrated
alumina, which mixture is thoroughly mixed prior to the adding of
water having a wetting agent of approximately one quarter of 1% to
bring the consistency of the material to where it is suitable for
coating polystyrene beads. Expanded polystyrene beads are introduced
into a paddle type mixer to which glass fibers may be added on the
order of 1 pound per six cubic feet of expanded beads which are mixed
dry until thoroughly distributed The mixture formed from the dehy-
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dra-ted lime, hydrated alumina, water and wetting agent which has been
mixed in a blender to form a mixture is added at the rate of approx-
imately 2 quarts to six cubic feet o-f expanded polystyrene beads. The
mixture in the beads having the fiberglass therein, of desired, may
have approximately 2 quarts of dry cement sprinkled into the mixer
for mixing therewith until the expanded polystyrene beads are comple-
tecL coatecl with the mixture and cement and any fiberglass therein. The
mixer is turned to a higher speed to complete the coating. Once the
beads are coated, they are taken from the mixer and placed into storage
containers for introduction into a cement mixture of Portland cement,
or the like, and sand and water as desired. This concrete mixture is
then available -for use with many applications from small, precast con-
crete items to large precast concrete panels for roofing and wall
panels and can be used for precasting sanitary wares and furniture~ as
well as insulation in solar heaters, therapeutic whirl pool baths and
in the manufacture of hydroponic systems. The invention will be further
illustrated by the following examples wherein, unless otherwise desig-
nated, parts are by volume.
Example One
The mixture is prepared by adding 50 parts dehydrated lime and
50 parts hydrated alumina with sufficient water having a wetting agent
therein to form a suitable consistency. This forms a mixture when
thoroughly mixed in a high speed blender and 2 quarts of this mixture
are added to 6 cubic feet of expanded polystyrene beads and 2 quarts
of dry cement are sprinkled over each 6 cubic feet of polystyrene
beads and 2 quarts of mixture to coat the polystyrene beads. The coated
beads are then ready for the addition as a lightweight aggregate to
a Portland cement mixture.
Example Two
A method of making a lightweight, coated aggregate has the steps
of forming a mixture of 50 parts dehydrated lime and 50 parts of hy-
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drated alumina with water having one quarter of 1% wetting agenttherein to form a suitable consistency and mixing in a high speed
blender to form a mixture. Two quarts of the mixture are added :in a
mixer to 6 cubic Eeet of expanded polystyrene beads and mixed until
the expanded polystyrene beads are fully coated with the mixture.
Two quarts of Portland cement are added during the mixing which con-
tinues until all beads are fully coated. The coated, expanded poly-
styrene beads are then added to a mixture of Portland cement, sand
and water and cured to form a lightweight concrete material.
Example Three
The ratio of the required mixture to -the amount of beads can
be reduced when the beads have been recently expanded and have mois-
ture from steam coating the beads. The following table indicates pro-
portions by volume and weight for the coating and cement mix.
COATING
Volume Weight
Beads 6 cubic feet 6 pounds
Mixture 1 quart 1-1/4 pounds
Water 1 quart 2-1/4 pounds
Cement 2 quarts 5 pounds
Glass 1 quart 1 pound
Wetting Agent 1/2 ounce 1/2 ounce
CEMENT MIX
Volume Weight
Beads 77 quarts 19-1/2 pounds
Sand 6 quarts 17-3/4 pounds
Cement 22 quarts 60-1/2 pounds
Wetting Agent 1/2 pint 3/4 pound
The foregoing has presented a novel coating and method of
coating expanded, polystyrene beads but it should, of course, be clear
that other expanded polymers can be utilized with the coating in the
present invention and that the term "beads" is meant to include a
variety of small particles, such as flakes or spheres, or the like. It
should also be clear that the resulting curing of a concrete product
with the coating provides a lightweight, concrete composition whose
characteristics provide an improved thermal characteristic as well
as lightweight in class A and class B blocks and other materials, but
whose characteristics may be widely varied depending upon the amount
of coating on the expanded polymer and on the type of concrete and
expanded polymer used in the composition. The coated beads allow a
better bond with the cement mixtures and prevent the beads from float-
ing to the top of the cement mixture and prevents the build up of
static electricity. It should also be clear that various other propeT-
ties can be changed, such as the color of the product by the addition
of pigments to the cement and providing a coated gel surface or the
like to the product being produced. Accordingly, the present invention
is not limited to the particular forms disclosed herein which are to
be considered illustrative rather than restrictive.
