Note: Descriptions are shown in the official language in which they were submitted.
CA 02551288 2006-06-22
WO 2005/065906 - 1 - PCT/EP2005/050045
Method For Processing Gunned Concrete 8y Means Of A
Spraying Machine, And Spraying Machine
Technical Field
The invention starts out from a method of processing
gunned concrete by means of a spraying machine
according to the preamble of the first claim. The
invention likewise starts out from a spraying machine
according to the preamble of the independent apparatus
claim.
Prior Art
Concrete-gunned concrete processes and the spraying
machines used for this purpose, e.g. Sika~ Aliva~
spraying machines, are generally known. A distinction
is made essentially between dry spraying processes and
wet spraying processes.
In the wet spraying process, the hydraulic binder, for
example cement, lime or gypsum plaster, appropriate
aggregates such as gravel and sand, if necessary,
concrete additives are mixed with water before
spraying. The wet concrete to be sprayed is then
conveyed hydraulically in the dense stream process or
pneumatically in the thin stream process to the spray
nozzle. In the dense stream process, the dense stream
is broken up shortly before the spray nozzle by means
of a high air pressure and, if necessary, accelerators
are introduced by means of the air stream. In the thin
stream process, the accelerator is likewise introduced
by means of air into the concrete to be sprayed shortly
before the spray nozzle.
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In the dry spraying process, the dry concrete to be
sprayed comprising hydraulic binder, aggregates and, if
necessary, concrete additives is introduced into the
concrete spraying machine . It is in this case conveyed
pneumatically in the thin stream process. Water admixed
with accelerator is introduced shortly before the spray
nozzle.
The concrete additives, in particular accelerators,
which are added in the region of the spray nozzle are
always introduced in liquid form. These liquid
additives, in particular setting accelerators, are
usually brought in containers to the spraying apparatus
or to the spraying machine. However, a problem with
these liquid additives is the storage stability which
is frequently unsatisfactory, as a result of which the
additives can become unusable on prolonged storage. In
addition, these liquid concrete additives have a
relatively large volume, which is why the feeding to
the spraying machine can present transport and feeding
problems.
To overcome the stability problems, additives, in
particular setting accelerators, have for this reason
been transported in powder form to the building site
and there dissolved in water on site. The liquid
setting accelerators obtained in this way have then
been transported from the building site to the spraying
apparatus and used in a manner analogous to the already
liquid setting accelerators for spraying of the gunned
concrete. However, this requires an additional step and
the processing of the pulverulent accelerator places
severe demands on personnel and leads to severe dust
pollution. After dissolution of the pulverulent
additive, the liquid accelerator obtained likewise has
to be processed relatively quickly since stability
problems can also occur here.
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Descriptioa,of the Iavention
It is an object of the invention, in a method of
processing gunned concrete by means of a spraying
machine and a spraying machine of the type mentioned at
the outset, to be able to process additives simply and
without stability problems in the spraying of the
concrete.
According to the invention, this is achieved by the
features of the first claim.
The key aspect of the invention is thus that at least
one additive which has a proportion of solids is mixed
with water in a mixing apparatus and is fed from the
mixing apparatus into the concrete to be sprayed before
it leaves the spray nozzle.
The advantages of the invention are, inter alia, that
in the concrete spraying process according to the
invention, the concrete additive or additives which
have a particular solids content and are, in
particular, pulverulent are brought directly to the
spraying machine, and in each case only the required
2S amounts of additive are directly mixed with the
appropriate amount of water there. This method incurs
lower transport costs because of the lower mass to be
transported and the storage stability of the dissolved
additives is no longer important. Due to this reduction
in the stability requirements, the additives to be used
can be improved chemically since the stability of the
components in the liquid state now plays only a very
minor role.
Furthermore, the amount of additive in the liquid
additive mixture fed to the concrete to be sprayed can
be adjusted very simply and thus allows the properties
of the sprayed gunned concrete to be matched to
specific requirements. In addition, the liquid additive
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mixture produced can have a. higher concentration of
active ingredients than conventional liquid additives,
as a result of which the properties of the concrete
produced can be improved.
It is likewise advantageous that additives which have
hitherto not been able to be used because of their
stability-reducing action can be introduced into the
concrete to be sprayed by means of the present method.
The adjustability of the viscosity of the liquid
additive mixture in the mixing apparatus enables the
viscosity to be set so that the additive is distributed
as well as possible in the gunned concrete.
Z5 Further advantageous embodiments of the invention are
indicated in the subordinate claims.
Brief Description of the Drawings
Examples of the invention are described below with the
aid of the drawings. Identical elements are denoted by
the same reference numerals in the various figures. The
flow direction of the media is indicated by arrows.
In the figures:
Fig. 1 schematically shows a spraying machine;
Fig. 2 schematically shows a mixing apparatus
according to the invention;
Fig. 3 schematically shows a further mixing apparatus
according to the invention.
Only the elements essential for a direct understanding
of the invention axe shown.
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Hlay of Performing the Iavention
Fig. 1 shows, schematically and in greatly simplified
form, a spraying machine 1. Such a machine comprises a
water and compressed air feed line 2, wheels 3 with a
wagon, a feed hopper 4 for introduction of the concrete
to be sprayed, a hose 5 and a spray nozzle 6 connected
to the hose. The hose 5 can also consist of tubes but
has to be flexible at least in the region of the spray
nozzle 6 so that the gunned concrete can be applied. In
addition, the spraying machine 1 is provided with a
further line 7 which opens into the hose in the region
of the spray nozzle 6. In the wet spraying process, air
admixed with additives is introduced via the line 7,
and in the dry spraying process water admixed with
additives is introduced via the line 7.
The spraying machine 1 is additionally provided with a
mixing apparatus 8 for additives, which can be
integrated directly into the machine 1 or else can be
connected to the machine by means of lines which are
not shown.
Fig. 2 schematically shows the mixing apparatus 8 and
the associated parts of the spraying machine 1. The
mixing apparatus comprises essentially a reservoir 10,
a water feed line 9 and a mixer 11. Concrete additive
12, advantageously an accelerator, is introduced in
powder or granule form into the reservoir 10. Such
additives, e.g. setting accelerators, corrosion
inhibitors, fluidizers, etc., are generally known.
Accelerators are particularly important for the
spraying of concrete; these are marketed by Sika~, e.g.
under the name Sigunit~.
The container 10 is advantageously provided with a
tightly closing lid so that no atmospheric moisture can
get to the additive 12. A metering device 13, for
example a slider, or a metering screw, star feeder,
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etc., performs the function of metering the pulverulent
additive 12 into the mixer 11. If the container 1 with
the pulverulent additive 12 is located on a weighing
device 14, the use of a slider is sufficient for
metering. If a metering screw is used as metering
device, a weighing device 14 is not necessary.
Water is metered via the water feed line 9 by means of
a metering valve 15 into the mixer 11. The water can
also be temporarily stored in a container which is not
shown and there brought to a particular processing
temperature. Impeller mixers, dispersers or rotor-
stator mixers, for example, are used for the mixing of
water and pulverulent additive in the mixer 11. The
resulting liquid additive mixture can be a solution, a
dispersion or a combination of a solution and a
dispersion. This is in each case dependent on the
solubility of the additive used. Dispersions comprising
relatively insoluble additives should advantageously
have a certain stability so that they do not sediment
in the case of any interruption to the spraying
process. Complete solutions are not absolutely
necessary since additives which are sparingly soluble
in water can also lead to good results in the gunned
concrete.
Any amounts of additive can in principle be added to
the water in the mixer. The proportion of pulverulent
additive 12 in the water is usually from 5 to 95% by
weight, preferably from 40 to 80% by weight,
particularly preferably from 40 to 60% by weight.
The liquid additive mixture obtained in this way can be
pumped by means of the mixing tools located in the
mixer 11 out of the mixer 11 through a circulation line
16 and back into the mixer 11, which improves mixing.
It is also possible for a pump to be located in the
circulation line, as a result of which it may no longer
be necessary to use mixing tools in the mixer. One or
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more heating devices which are not shown can optionally
be located either in the water feed line 9, in the
temporary water storage which is not shown, in the
mixer 11 and/or in the line 16, by means of which the
liquid additive mixture or the water fed in is heated
to relatively high temperatures, in particular to a
temperature above 40°C, in order to improve the
solubility of the powder and to influence the viscosity
of the liquid additive mixture.
The liquid additive mixture is then fed by means of a
feed line 17, which branches off directly from the
mixer 11 or the circulation line 16, to the line 7
which conveys, depending on the spraying process, water
or air to the spray nozzle. The feed line 17 can for
this purpose be provided with a metering valve or a
metering pump 18 by means of which the amount of liquid
additive mixture to be introduced into the concrete to
be sprayed can be set. From about 2 to 15% by weight of
the liquid additive mixture is introduced into the
concrete to be sprayed, based on 100% by weight of the
hydraulic binder in the concrete. The addition of the
liquid additive mixture is thus controlled by the
throughput of the concrete being sprayed and the
proportion of hydraulic binder present therein.
The mixing apparatus is operated by means of a computer
control system which is not shown. The determination of
the respective amounts of water, pulverulent
additive 12 and hydraulic binder introduced can be
effected by means of separate measuring instruments/
meters or directly by means of the metering device 13,
the weighing device 14, the metering valve 15, the
metering valve 18 or via the amount of concrete or
hydraulic binder fed in.
For example, the desired mixing ratio can be set via
the amount of additive 12 and water fed to the
mixer 11. If a particular amount of liquid additive
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mixture is taken from . the ' mixer by means of the
metering valve 18, the amount taken off can be
determined by the regulation by means of the opening
time of the metering valve 18 or by a measuring
instrument which is not shown. To replace the amount
taken off in the mixer, the required amounts of
additive 12 and water are fed via the metering
device 13 and the metering valve 15 into the mixer 11.
The storage volume of the mixer 11 also leaves the
operating personnel some time to refill the
container 10 if the additive has been used up or in the
case of disruptions to the water flow through the water
feed line, to rectify these.
The present method also enables the content of the
pulverulent additive 12 in the water to be set to any
desired value within the abovementioned limits. Thus,
it is possible to react quickly to a changing content
of hydraulic binder or the concrete to be sprayed.
In the present method according to the invention, no
large amounts of the liquid additive mixture are
prepared beforehand, with the volume of the mixer 11
usually being in the range from 1 to 80 liters. Due to
the small amounts and due to the fact that in each case
only the necessary amounts of additive are liquefied,
no problems with the stability of the liquid additive
occur in the present method. Furthermore, the volume of
the pulverulent additive is at least a factor of two
smaller than when liquid additives are used, as a
result of which lower transport costs are incurred and
environmental pollution is reduced and the spraying
machine can have smaller dimensions.
3 5 In fig . 3 , the mixer 11 and the circulation line 16 of
fig. 2 are replaced by a permanent mixer 19, e.g. an
extruder . Such an extruder has at least one mixing and
transport screw. As permanent mixer, it is also
possible to use, for example, only a mixing rod with
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mixing elements which is arranged in an essentially
horizontal hollow cylinder. In the permanent mixer, the
additive introduced via the metering device 13 and the
water introduced via the water feed line 9 are mixed
and a solution and/or a dispersion are/is formed in a
manner analogous to that described above.
Here, the use of the metering pump 18 is not necessary
since the extruder 19 takes over the transport and the
metering of the liquid additive mixture. Since very
good mixing is achieved by means of the extruder 19, a
circulation line is not necessary. The extruder 19 can
be heatable in order to improve the solubility of the
powder and to influence the viscosity of the liquid
additive mixture.
Of course, the invention is not restricted to the
example shown and described. The mixer or the extruder
can also be replaced by components having an identical
or similar action.
It is also possible to use a thickened additive or
moist powder instead of the pulverulent additive; this
is brought to the appropriate mixed contents with water
in the mixing apparatus. However, attention may have to
be paid to stability problems here. The additive to be
used for the purposes of the invention should have a
certain solids content of at least 1%, preferably above
10%, particularly preferably above 50%, in particular
above 80%.
The use of a plurality of mixing apparatuses also
enables additives which are inherently incompatible or
slightly moist or liquid additives as mentioned above,
in particular ones which do not suffer from stability
problems, and pulverulent additives to be processed
separately in the various mixing apparatuses and
introduced into the concrete to be sprayed. When a
plurality of mixing apparatuses is used, these can be
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arranged in parallel and the liquid additive mixtures
can be introduced separately or via a joint line into
the concrete to be sprayed. To obtained better mixing,
the mixer 11 and permanent mixer 19 can also be
combined in one mixing apparatus and connected in
parallel or in series.
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List of Reference Numerals
1 Spraying machine
2 Compressed air feed line
3 Wheel
4 Feed hopper
5 Hose
6 Spray nozzle
7 Line for water or air
8 Mixing apparatus
9 Water feed line
10 Reservoir
11 Mixer
12 Concrete additive
13 Metering device
14 Weighing device
15 Metering valve
16 Circulation line
17 Feed line
18 Metering valve or metering pump
19 Permanent mixer
