FR2684397A1 - Method for producing continuous roadways or industrial areas made of fibre-reinforced compacted concrete - Google Patents

Abstract

The invention relates to a method for producing continuous roadways or industrial areas without joints, in which the cracking is evenly distributed and has limited aperture, this method is characterised by the operations consisting in: - preparing a concrete with a cement content lying between 240 and 400 kg of cement per cubic metre, with a water content lying between 95 litres and 155 litres per cubic metre; - adding ductile steel fibres with undeformable anchoring device to the concrete during mixing, at a ratio of a concentration by mass lying between 1.25% and 3%, which lower and upper limits take into account control of the cracking and placing of the concrete, the concrete consisting of between 4 and 10% of fine elements smaller than 250 microns; between 25 and 35% of elements smaller than 2 mm; between 40 and 55% of elements smaller than 4 mm; between 60 and 75% of elements smaller than 8 mm; 90% of elements smaller than 16 mm; - laying the fibre-reinforced concrete with the traditional methods for compacted rolled concrete by using a finishing rig; - compacting by rolling with a vibrating roller and by using a pneumatic compactor; - immediately after compacting, protecting the roadway from loss of water by evaporation. Application to producing roadways and runways and industrial areas.

Description

 The invention relates to a process for producing pavements or continuous industrial areas in compacted concrete reinforced with fibers.

 Most concrete pavements with heavy traffic are victims of accelerated aging by fatigue phenomenon: the effects of aging are marked mainly in the vicinity and in the joints. Pavement joints were designed to locate the shrinkage of the concrete and allow dimensional variations due to temperature variations.

 Despite the invention of numerous joint systems which should allow the concrete to be bonded on either side of it without preventing dimensional variations to the right of it, the phenomenon of accelerated aging could not be stopped.

 Great progress has been made in the development of continuous reinforced concrete pavements.

 Indeed, according to this technique, all of the dimensional variations due to temperature variations and the shrinkage of the concrete results in micro-cracking regularly spaced in the pavement by the tensioning of the main continuous reinforcement.

 This technique is widely used today in many countries and accommodates many different types of concrete compositions.

In general, the coating of these pavements is as follows - thickness from 16 cm to 25 cm - concrete: cement content: from 300 to 375 kg per cubic meter;
water-cement ratio: from 0.38 to 0.55 depending on the materials
constituting the concrete and the workability desired for laying;
workability measured with the Abrams cone varying between 3 cm and
10 cm - the concrete is laid in a slipform machine on a sheet
of continuous reinforcement laid in advance by a corresponding quantity
with a geometric percentage of 0.7%; the frames are
in general main bars of 16 mm in diameter laid
on spacers and transverse distribution reinforcement.

The cracking observed in the long term is sufficiently controlled so that: - there is no degradation of the lips of the cracks due to the
traffic - there is no chemical attack on the reinforcement by penetration
in the cracks of agents causing corrosion: carbona
station, water, de-icing salts,
The cracks have openings from 0.3 mm to 0.7 mm with a spacing of 1 m to 4 m depending on the case. The behavior to dimensional variations is moreover very well predictable by theoretical models such as that of Mr. Vetter.

 Continuous reinforced concrete, if it is well developed and widely used is however reserved for high traffic pavements, given the difficulties of preparation and installation of the reinforcement.

 A much more convenient method would be to make a continuous pavement of concrete reinforced with steel fibers ready for use.

 The possibility offered by such a material is however limited by the nature of the steel fibers determining their ability to reinforce the concrete, the workability of the concrete to be used in a sliding formwork machine and the condition of the pavement surface. which cannot have an excess of visible steel fibers.

 Experiments have been attempted and have revealed an insufficient distribution and an unacceptable opening of the cracks due to the dimensional variations of the pavement.

 For example, for a concrete with 350 kg of cement per cubic meter, with a water-cement ratio of 0.52, a sag in the Abrams cone of about 50 mm, 0.77% by volume content of fiber steel, of the drawn type with a diameter of 1 mm, wavy length 60 mm described in European patent No. 0 130 191, an average crack opening of 1.3 mm and a maximum of 2.8 mm have been observed for an average crack spacing of 19 meters.

 Similarly, according to European patent No. 0 137 024, the embodiment of industrial floors in continuous concrete reinforced with fibers is indicated.

 This prior invention relates to interior structures, not subject to temperature variations and subject to traffic whose frequency of passage and loads are much lower.

 The industrial floors according to this prior invention are of a limited surface, of a rather square plan shape, subject to limited loads of use also.

 Patent No. 0 137 024, describing a prior state of the art, shows that continuous concrete reinforced with steel fibers, even applied for interior use, is subject to strict limits which cannot be observed in road engineering.

 French Patent No. 2,197,088 provides an embodiment of continuous slabs made of fiber-reinforced concrete by attaching the concrete to the covering by means of studs in the foundation layer. According to this process, the covering is regularly attached to the lower layer, asphalt concrete or old concrete pavement, so as to limit the development of tensile stresses in the covering concrete.

This process is therefore not a continuous concreting process since it does not allow the concrete to resist by itself all the tensile forces of which it is the seat.

 In addition, the operation of making the tenon attachment is difficult, slow and expensive.

 To our knowledge, this process has not been used to date.

 Furthermore, European patent application No. 0 350 365 discloses a composition of compacted concrete as well as its use for the production of industrial pavements, embankments, road or aeronautical pavements.

 The content of this previous application does not take into account the very different application conditions when it comes to industrial pavements and medians and pavements exposed to the weather and their consequences with regard to the different types of joints in provide.

 We have now discovered that it is possible to obtain a continuous pavement or industrial area of compacted concrete reinforced with steel fibers where the cracking is regularly distributed and of limited opening by suitably adapting the composition of the concrete and by selecting the fibers. of steel.

Consequently, the invention relates to a process characterized by the operations consisting in - preparing a concrete with a cement content of between 240 kg
and 400 kg of cement per cubic meter, type CPJ 45 or CPA 55,
normal quality, R or HP, with a water content between
95 liters and 155 liters per cubic meter; - add steel fibers to the concrete during kneading
ductile with preferably non-deformable anchoring device
as described in European patents No 0 130 191 and
No. 0 098 825 and in particular those described in the patent
European No 0 098 825 due to mass concentration
between 1.25% and 3%, lower limit proportion
and higher taking into account cracking control and
concrete placement, the concrete being made up of
between 4 and 10% of fine elements less than 250 microns;
between 25 and 35% of elements less than 2 mm;
between 40 and 55% of elements less than 4 mm;
between 60 and 75% of elements smaller than 8 mm;
90% of elements smaller than 16 mm ;; - lay concrete reinforced with fibers which does not present any workability
lity using traditional rolled concrete methods
compacted using a finishing train; Roller compactor with vibrating roller or vibrating ball
and using a tire compactor; - as soon as the final compaction is finished, protect the roadway from the
loss of water by evaporation.

The running surface can then be produced successively - spreading 3 to 15 kg per square meter of premixed mortar
wet compound of CPA or CPJ cement and quartz sand 0 to
5 mm in mass proportion of 1/3 and 2/3 respectively; - and incorporation by passage of vibrating tire rollers
until an intimate connection is obtained between the two layers.

The running surface can also be produced - by adding a layer of bituminous coated with a
bituminous collaboration layer with fiber reinforced concrete
compacted roll; - by a surface coating with emulsion of gravel bitumen and - by a cold-cast coating.

 This way of proceeding, unlike previous experiments and Vetter's theory, makes it possible to produce a continuous reinforced concrete pavement without the installation of traditional reinforcements, while observing the control of dimensional variations.

 As an example, we can describe a typical embodiment according to the invention.

 Construction of a continuous concrete pavement 15 cm thick, 800 m long and 7 m wide.

The concrete used was such that
Cement content CPJ 45 12% (288 kg / m3)
Sand content 0/4 mm 43.8%
Sand content 4/8 mm 16%
Sand content 8/16 mm 22.6%
Water content 5.6% (Corresponding to an W / C ratio = 0.47)
Steel fiber with non-deformable anchoring according to the European patent
No 0 098 825 at a rate of 1.6 by weight (38 kg / m3 or 0.49% by volume).

Use of a water reducing plasticizer improving the compaction conditions at the rate of 0.4% by weight of cement.

 The use of compacted fiber concrete for carrying out the process can be carried out with one or more finishers in parallel to increase the width of the strip, of the same type as those used for bituminous mixes so as to eliminate the joints along the longitudinal axis of the road.

 Compaction is ensured by successive passages of the vibrating ball compactors and by tire compactors.

The compacted fiber concrete can be used according to the present invention in new pavements or in reinforcements. In new pavements, the foundation can be made of different materials, depending on the traffic and the bearing capacity of the supporting soil, either - gravel or untreated sand; in this case, the lift at
the foundation material plate must be greater than
30 MPa / m3 (i.e. a Westergaard coefficient k greater than
30 daN / cm3); - a fine material treated in place with lime and cement (or
only lime); - a gravel or sand treated centrally with cement or slag; - lean concrete.

Claims (4)

 1. Method for producing road and aeronautical pavements or continuous industrial areas without joints where the cracking is regularly distributed and of limited opening, characterized by the operations consisting in - preparing a concrete with a cement content of between 240 and  400 kg of cement per cubic meter, with a water content included  between 95 liters and 155 liters per cubic meter - add ductile steel fibers to the concrete being kneaded  with non-deformable anchoring device due to a concentra  mass ration between 1.25% and 3%, limit proportion  lower and upper taking into account the crack control  tion and placement of concrete, the concrete being made up of  between 4 and 10% of fine elements less than 250 microns;  between 25 and 35% of elements less than 2 mm ;;  between 40 and 55% of elements less than 4 mm;  between 60 and 75% of elements smaller than 8 mm  90% of elements smaller than 16 mm; - lay concrete reinforced with fibers according to traditional methods  of rolled concrete compacted using a finishing train; - compact by rolling with a vibrating roller and using a  tire compactor - at the end of compaction, protect the roadway from loss  of water by evaporation.  2. Method according to claim 1, characterized in that the steel fibers are chosen from those with non-deformable inking.  3. Method according to any one of claims 1 and 2, characterized in that the rolling surface is then carried out using one of the following methods as desired - spreading of 3 to 15 kg per square meter of premixed mortar  wet compound of CPA or CPJ cement and quartz sand 0 to  5 mm in mass proportion of 1/3 and 2/3 respectively; - and incorporation by passage of vibrating tire rollers  until an intimate connection is obtained between the two  layers.  4. Method according to any one of claims 1 and 2, characterized in that the running surface is produced by one of the following methods - by adding a layer of bituminous mix attached by a  bituminous collaboration layer with fiber reinforced concrete  compacted roll; - by a surface coating with the emulsion of gravel bitumen; and - by a cold poured mix.