METHODE DE FABRICATION D'UN BETON THERMO-ISOLANT A BASE DE CIMENT HYDRALIQUE AUX AGREGATS DE DENSITE SUBSTANTIELLEMENT MOINDRE

METHOD FOR MAKING A HEAT INSULATING CONCRETE OF MORTAR MIX CONTAINING AGGREGATES HAVING SUBSTANTIALLY LOWER SPECIFIC GRAVITY

Abrégé anglais

81.410
METHOD FOR MAKING A HEAT INSULATING CONCRETE
OR MORTAR MIX CONTAINING AGGREGATES HAVING
SUBSTANTIALLY LOWER SPECIFIC GRAVITY
ABSTRACT
The invention relates to a method for making a heat
insulating concrete or mortar mix containing aggregates
having substantially lower specific gravity than that of
concrete or mortar. The additive used according to the
invention from the group air pore formers, liquefiers and
plasticizers inhibits the upward movement or the accumulation
and/or demixing of the light aggregates especially during
the preparation, the transport, the pumping operation by
means of conventional concrete conveying pumps, the placing
and the hardening of the concrete or mortar so that a heat
insulating product is provided which has an extremely
homogeneous structure.
- 1 -

Revendications

WHAT IS CLAIMED IS:
1. Method for making a heat insulating concrete
or mortar mix containing aggregates having a lower specific
gravity than said concrete or mortar mix; said method being
characterized in that during preparation of the heat insu-
lating concrete or mortar mix, at least one agent from the
group consisting of air pore formers, liquefiers and plasti-
cizers is added, whereby air bubbles of differing shape are
formed within said concrete or mortar mix.
2. Method according to Claim 1 characterized in
that foam particles are used as aggregates having a lower
specific gravity.
3. Method according to Claim 2 characterized in
that particles of foamed polystyrene are used as foam parti-
cles.
4. Method according to Claim 3 characterized in
that particles obtained by grinding polystyrene foam are
used as foam particles.
5. Method according to Claim 3 characterized in
that particles obtained by grinding polystyrene foam waste
material are used.
6. Method according to Claim 1 characterized in
that expanded clay particles are used as aggregates having
a lower specific gravity than said concrete or mortar mix.
7. Method according to Claim 1 characterized in
that particles pretreated at their surfaces are used as
aggregates having a lower specific gravity than said con-
crete or mortar mix.

8. Method according to Claim 1 characterized in
that a total of 0.05 to 0.5% by weight of at least one agent
from the group consisting of air pore formers, liquefiers
and plasticizers, based on the total weight of the mineral
binders, is used.
9. Method according to Claim 8 characterized in
that 0.1 to 0.2% by weight of at least one agent from the
group consisting of air pore formers, liquefiers and plasti-
cizers, based on the total weight of the mineral binders, is
used.
10. Method according to Claim 9 characterized in
that 0.15% by weight of at least one agent from the group
consisting of air pore formers, liquefiers and plasticizers,
based on the total weight of the mineral binders, is used.

Description

1~51'Z~ I
819410
Use is known in the building sector of concrete and mortar
mixes containing particles having much lower specific gravity
than that of the concrete or mortar mixes in order to reduce
the specific gravity of the material and to impart thereto
specific, e.g., thermal or acoustic properties. Mixing in
these lighter particles, however, provides the desired proper-
ties only when the same are distributed uniformly throughout
the mix.
Light aggregates are known in this respect whose surfaces
are processed such that upon addition of specific additives,
a marked cohesion is achieved between the binders and the light
aggregates which inhibits an upward movement of the light
aggregates during processing.
That known method, however, has the disadvantage that it
requires a preceding processing of the light aggregates and
therewith excludes the use of conventional light aggregates
such as ground material, e.g. recovered polystyrene foam
particles.
The object of the invention is to provide a method for
making a concrete or mortar mix or the like which contains
aggregates having substantially lower specific gravity, a
homogeneous structure of the concrete or mortar being achieved
without pretreatment of the light aggregates.
In order to achieve this, plasticizers, air pore formers
anc1 liquefiers knowr1 per se are added in accordance with the
invention to the concrete or mortar mix or the like.

~2S~;~Z~7
81.410
Those materials generally known in the building trade
and which liquefy the mixes bring about in accordance with the
invention a dlstribution of microscopically small air bubbles
in the mix which fill the interspaces between the solid
aggregates of the mix by these air bubbles being able to
assume a multiplicity of shapes and sizes. These microscop-
ically small bubbles are each enveloped in a very thîn binder
film. The surface of each small bubble is relatively large
because spherical bubbles are seldom concerned. The bubbles
bring about a marked cohesion between the particles of the
light aggregates and/or between those particles and the other
particles of the mix. This extremely high cohesion is to be
attributed to the adaptability of the bubbles in respect of
their shape to the adjacent surfaces of the solid or liquid
components and the binder film surrounding the bubbles.
Apart rom the effect on the cohesion, the liquefying and
the flowability resulting therefrom, the distribution of the
bubbles has an effect in accordance with the invention on
the specific gravity of the mix in such a manner that upward
movement of the light aggregates is reduced.
In accordance with the invention, any additive is suitable
which brings about a distribution in the mix of microscopically
small bubbles enveloped in a film of binder.
The a~ount of additive to be added, based on the total
ar~ount of the mineral binders (cement and/or lime), is 0.05
to 0.5~ by wei~ht, especially o.l to 0.2% by weight. The best

lZ5~
81.410
results are obtained with an amount of 0.15% by weight of
additive.
There can be used as light aqgregates with the method
according to the invention all known such aggregates, e.g.
foam particles; especially of polystyrene foam, also particles
of used foam which have been obtained by grinding; expanded
clay particles or light aggregate particles pretreated at
their surfaces.
By virtue of the method according to the invention, a
demixing and/or agglomeration of the light aggregates during
or after making the mix, the transport, the pumping operation,
the placing and the hardeninn operation, t~hereby a finished
product having a very homogeneous structure is achieved at
any density of the mix.