BETON NECESSITANT UN FAIBLE COMPACTAGE

LIGHTLY COMPACTED CONCRETE

Abrégé français

L'invention concerne un béton utilisé pour former une couche de support d'une voie ferrée de chemin de fer ou de tramway réalisée sans ballast, ainsi que son utilisation pour la réalisation d'une telle couche de support. Avec ce béton, on doit obtenir une réduction nette de l'ampleur des travaux manuels nécessaires depuis longtemps pour la réalisation de la mise en place et du compactage, en particulier pour des surélévations de voie dans des courbes. Cet objectif est atteint par le fait que ledit béton présente une teneur de 240-280 kg /m?3¿ de poudre de pierre à chaux, et une teneur en agrégats de 1500-1700 kg/m?3¿, ces agrégats étant constitués de 35 à 45 % d'agrégats dont la taille de particule est comprise dans la plage 0-2 mm, de 25-35 % d'agrégats dont la taille de particule est comprise dans la plage 2-8 mm, et de 25-35 % d'agrégats dont la taille de particule est comprise dans la plage 8-16 mm, le numéro de classe de consistance de ce béton diminuant, par réduction de sa teneur en solvants, au fur et à mesure que la surélévation géométrique de la couche de support de la superstructure augmente.

Abrégé anglais

The invention pertains to a concrete material for a support
layer of a permanent way for railroads or streetcars that is
realized in a ballastless fashion, as well as the utilization
of this material for producing such a support layer.
This material should make it possible to effectively reduce
the thus far required expenditure of manual labor for
installation and compacting work--particularly for banked
tracks in curves.
This is achieved in that the concrete material has a limestone
powder content of 240-280 kg/m3 and an aggregate content of
1500-1700 kg/m3, wherein 35-45% of the aggregate consist of an
aggregate with grain sizes on the order of 0 to 2 mm, 25-35%
consist of an aggregate with grain sizes on the order of 2 to
8 mm and 25-35% consist of an aggregate with grain sizes on
the order of 8 to 16 mm, and wherein a flow agent content is
inversely proportional to the geometric cant of the support
layer of the permanent way.

Revendications

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CLAIMS
1. A concrete material for a support layer of a permanent
way for railroads or streetcars that is realized in a
ballastless design, wherein the concrete material has
a limestone powder content of 240-280 kg/m3,
an aggregate content of 1500-1700 kg/m3, wherein 35-45%-
of the weight of these aggregates consist of aggregates
with grain sizes in the range of up to 2 mm, 25-35%
consist of aggregates with grain sizes in the range of 2
to 8 mm and 25-35% consist of aggregates with grain sizes
in the range of 8 to 16 mm,
a mass ratio of water to cement of 0.4,
a retarder, present in the amount of 0.8% by mass of
cement, and
a flow agent content which is inversely proportional to a
geometric cant of the support layer of the permanent way.
2. The concrete material for a support layer of a permanent
way for railroads or streetcars that is realized in a
ballastless design according to claim 1, wherein the
concrete material has
a flow agent content of 1.7-1.8 kg/m3 for achieving a
consistency class F6,
a flow agent content of 1.65-1.75 kg/m3 for achieving a
consistency class F5,
a flow agent content of 1.6-1.7 kg/m3 for achieving a
consistency class F4,
a flow agent content of 1.4-1.5 kg/m3 for achieving a
consistency class F3,
a flow agent content of 1.1-1.25 kg/m3 for achieving a
consistency class F2 or
a flow agent content of 0.5-0.75 kg/m3 for achieving a
consistency class F1.

-7-
3. The concrete material for a support layer of a permanent
way for railroads or streetcars that is realized in a
ballastless design according to claim 1 or 2, wherein the
concrete material contains a flow agent on the basis of a
polycarboxylateether.
4. Use of the concrete material according to any one of
claims 1 to 3 for constructing a support layer of a
permanent way for railroads or streetcars that is
realized in a ballastless design.

Description

CA 02548269 2009-11-13
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LIGHTLY COMPACTED CONCRETE
The invention pertains to a concrete material for a support
layer of a permanent way for railroads or streetcars that is
realized in a ballastless design, as well as the use of this
concrete material for producing such a support layer.
In the construction of the permanent way for track-bound
railroad traffic systems, ballastless systems have been
advantageously utilized for certain applications and operating
conditions over the past decades. During the course of various
development activities, a broad variety of different technical
approaches were proposed and evaluated with respect to their
suitability for use in practical applications. In addition to
systems in which the supporting points for receiving the rails
are already integrated into precast concrete parts at the
factory (e.g., rigid rail of the type "Bogl"), systems in
which a track system consisting of rails, rail-fixing material
and crossties is fixed by means of in-situ-grouting - usually
cast-in-place concrete or asphalt - proved particularly
advantageous (e.g., ballastless systems of the type "Rheda").
In addition to the adjustment of the track system on the
supporting substructure, the main problem of such cast-in-
place concrete systems proved to be the grouting of the
crossties within the concrete material of the track slab. In
the regions of curved tracks, in particular, the outer rail is
arranged higher than the inner rail referred to the vertical
direction. This difference in height between the two rails is
professionally referred to as geometric cant.
Until now, the construction of a concrete support layer in the
region of such geometrically canted track sections required a
very stiff concrete recipe in order to prevent the cast-in-
place concrete of the track-slab from flowing over the
formwork sections on the inner side of the curve. In this

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respect, it proved particularly disadvantageous that the
processing of such a stiff or firm concrete requires a high
expenditure of manual labor because extensive leveling and
compacting work needs to be performed.
In the 1980's, a self-compacting concrete from Japan was
introduced on the market, wherein this type of concrete is in
the meantime also used in isolated instances for civil
engineering structures being constructed in Europe. In the
context of the present problem definition, a simple adaptation
of such a self-compacting concrete to the construction of a
continuous concrete support layer of a track can only be
considered in areas without longitudinal or lateral
inclination due to the self-leveling properties of the self-
compacting concrete. However, such a track routing without any
inclination essentially cannot be found or realized on any
railroad tracks. In comparison with railroads tracks that have
a classic gravel ballast, ballastless track systems provide
the decisive advantage that the track routing can have much
more extreme inclination values due to the inherently superior
load application and distribution characteristics of the
ballastless track such that the civil engineering and soil
shifting expenditures can be significantly reduced (shorter
tunnels, shorter bridges, less steep through-cuts, etc.). In
light of the desired track routing, the utilization of a
conventional self-compacting concrete would be a contradiction
in itself.
The invention is based on the objective of making available a
concrete material for a support layer of a permanent way for
railroads or streetcars that is realized in a ballastless
design, wherein this concrete material makes it possible to
effectively reduce the expenditure of manual labor for the
leveling and compacting work to be performed--particularly
with respect to geometrically canted tracks in curves.

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According to an embodiment of the present disclosure there is
provided a concrete material for a support layer of a
permanent way for railroads or streetcars that is realized in
a ballastless design, which has a limestone powder content of
240-280 kg/m3, an aggregate content of 1500-1700 kg/m3,
wherein 35-45% of the weight of these aggregates consist of
aggregates with grain sizes in the range of up to 2 mm, 25-35%
consist of aggregates with grain sizes in the range of 2 to 8
mm and 25-35% consist of aggregates with grain sizes in the
range of 8 to 16 mm, a mass ratio of water to cement of 0.4, a
retarder, present in the amount of 0.8% by mass of cement, and
a flow agent content which is reduced with increasing
geometric cant of the support layer of the permanent way.
In addition to this mixing ratio, the usual applicable
requirements (particularly ZTV concrete - StB 01) naturally
also apply, namely with respect to a minimum cement content of
350 kg/m3 of the quality CEM I 32,5 R, as well as a
water/cement ratio (= mass ratio of water to cement) of 0.45.
According to the invention, the water/cement ratio is 0.4. The
inventive concrete material also contains a retarder, the mass
fraction of which referred to the total mass amounts to 0.8%
of the cement mass fraction.
The main advantage of the present invention can be seen in
that the properties of the hardened concrete (e.g.,
compressive strength, modulus of elasticity, bending tensile
strength, resistance to splitting tension and frost
resistance) remain almost unchanged in a thusly mixed material
despite the required variation of the flow agent in order to
realize different consistencies while the processing
parameters, (e.g., plasticity, compacting efforts and
processing speed) can be optimally adapted to the respective
track geometry.

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The aforementioned deviation ranges are based on the required
adaptations to the regionally varying properties of the
locally used aggregate deposits and the locally available
cements. For example, a limestone powder with a coarser grain
requires a larger mass than limestone powder with a finer
grain because the specific water absorption capacity of
limestone powder drops as the grain size increases. The best
results were achieved with an aggregate comprising 40% of the
weight of the aggregate with grain sizes in the range of up to
2 mm, 30% aggregate with grain sizes in the range of 2 to 8 mm
and 30% aggregate with grain sizes in the range of 8 to 16 mm.
According to an additional development of the inventive
concept, it proved particularly effective that the concrete
material has a flow agent content of 1.7-1.8 kg/m3 in order to
achieve a consistency class F6. This refers to the consistency
classes F1 ("stiff") to F6 ("free-flowing") standardized in
DIN-EN 12350-5. The variations described below proved
practical for achieving different consistency classes, wherein
a flow agent content of 1.65-1.75 kg/m3 is used for achieving
a consistency class F5, a flow agent content of 1.6-1.7 kg/m3
is used for achieving a consistency class F4, a flow agent
content of 1.4-1.5 kg/m3 is used for achieving a consistency
class F3, a flow agent content of 1.1-1.25 kg/m3 is used for
achieving a consistency class F2 and a flow agent content of
0.5-0.75 kg/m3 is used for achieving a consistency class Fl.
In this respect, the cited deviation ranges are also caused by
the required adaptations to the regionally varying properties
of the locally used aggregate deposits and the locally
available cements.
Extensive investigations showed that inventive concrete
materials of the consistency classes F5 and F4 are most
suitable for instances in which the ballastless slab track to
be constructed has a ratio of inclination between 7 and 10%.
Inventive concrete materials of the consistency classes F3 to

CA 02548269 2009-11-13
F1 are suitable for more significant inclinations up to
approximately 12%.
It is particularly practical if the flow agent used is based
5 on a polycarboxylateether. This promotes the adjustment of a
low frictional resistance within the concrete suspension such
that any air inclusions created during the concreting are able
to rise within the concrete suspension and to be finally
ventilated.