FR2675521A1 - Microstudding of road concrete - Google Patents

Abstract

Method for surface treatment of road covering concretes with a high calcium (limestone) proportion in order to give them a sufficient surface roughness lifetime. This treatment consists in a surface microstudding by stone gravel (grit) with a very high polishing resistance and high density or artificial gravel with the same qualities. The maximum size of the gravel is defined in order to avert the risk of vehicle windscreen breakage in the event of accidental detachment (debonding) of a piece of gravel. Bonding may be promoted by the use of doping solutions for a pretreatment of the gravel. The spreading of the gravel may be preceded by a sweeping/rippling process and should normally be followed by a protective concrete curing treatment which does not run the risk of disturbing the bonding of the gravel.

Description

MICRO CL OUTAGE OF ROAD CONCRETE
Hydraulic concrete road surfaces must accommodate an unavoidable handicap of the concrete material: cracking.

This handicap is the result:
- hydraulic shrinkage and thermal shrinkage linked to the setting of the
cement therefore inevitably linked to the very nature of the material
concrete
- thermal shrinkage in cold weather, which essentially depends on
the nature of the aggregates and the temperature at which the concrete has
makes his catch
- the very high elasticity coefficient of concrete which makes it a material:
very effective in protecting the support it covers and
thus protects from traffic attacks
but also very little deformable so unable to absorb without
break the 2 previous withdrawals.

One way to reduce this handicap is to favor materials with a low coefficient of thermal expansion such as limestone aggregates.

This family of aggregates also often has the advantage of being relatively economically attractive. Unfortunately, aggregates of this family also generally have poor resistance to polishing and even often to attrition.

They are therefore, therefore, partly excluded from the formulations of very demanding road concretes in this area and can only be accepted there in a limited proportion and combined with aggregates having very good characteristics on these 2 criteria of polishing and attrition .

It is then these latter aggregates which guarantee the durability of the roughness of the coating essential to the safety of users.

In certain techniques such as chemical stripping, this roughness is ensured as soon as it is put into service by a surface pickling ensuring the immediate emergence of aggregates with high characteristics.

Several techniques for using road concrete have been developed to allow the use, in a large proportion, of limestone aggregates without harming the durability of the roughness. We can cite in particular:
- bilayer tiles: technique in which, with the same train of
concreting therefore almost simultaneously, two different concretes are
implemented successively:
one based on calcareous aggregate in a thick lower layer
the other based on materials with high resistance characteristics
polish as thin an upper layer as possible.

- superficial nailing by superficial spreading and sinking
checked on and in fresh concrete, from stones or large gravel to
high characteristics with an optimized dosage per square meter.

These techniques provide a solution to the problem but are not free from economic, technological or technical defects such as:
high cost of implementation
risk of separation of the 2 layers
high noise floor
risk of loosening large gravel or stones which may cons
create a serious danger for the user (broken windshield).

The object of the present invention is to retain the advantage of an almost unique use of limestone aggregates by avoiding such defects.

The invention consists of:
- to spread on fresh concrete, mainly limestone,
small enough chippings to practically not entail
no risk of vehicle windshield breakage. Tests have
shown that below a dimension of 8 mm in square mesh the
risk became very low and practically canceled out for a
dimension less than 6 mm. 4 mm16 mm gravel will be
therefore perfectly suitable.

- of course choose gravel with excellent
resistance to polishing but also a specific gravity
high possible accelerating their indentation in the fresh concrete under
the action of their own weight.

- to favor the effective sealing of the gravel in the fresh mortar
of the concrete surface by preparing their surface by washing
effective followed by incorporation of doping solution reinforcing
the affinity of the gravel surface with the hydraulic binder of the
mortar. Such surface preparation does not disturb the
gravel flow conditions in a conventional system
of spreading at regular dosage.

- to retain a gravel dosage ensuring a loose cover
without risk of excess, about 4 liters per square meter.

- possibly and advantageously to precede the spreading
chippings of an oscillating transverse or longitidunal sweep,
ensuring a slight, superficial streaking of the concrete without harming the
Long profile. The presence of these streaks will promote indentation and
the sealing of the gravel which will be positioned there in the final.

- finally, to retain a concrete curing protection technique which does not
no risk of disturbing the gravel sealing process
by setting the surface mortar. The technique of covering by a
continuous thin plastic veil will be perfectly adapted and ensures
moreover effective protection against possible falls of
rain.

In the context of this invention, the initial roughness will be ensured by the streaks of the sweeping and then immediately relayed by the gradual emergence of hard gravel. The small particle size of the latter will then provide a surface with low noise pollution.

The permanence of their presence in a sufficient number to ensure a roughness conforming to safety will remain for a period of at least 5 years beyond which the regeneration of roughness can be obtained by installing a thin and advantageously draining coating. .

Claims (5)

1 Surface treatment of concrete for road surfaces (or  equivalent) using mostly limestone and polishable aggregates.  of the coating.  accidental loosening and simultaneously reduce noise pollution  is determined to avoid the risk of vehicle windshield breakage by  sealing by setting the penetrated mortar. The maximum size of gravel  the action of their own weight. This partial depression is followed by a  on fresh concrete in which their partial penetration is obtained under  surface essential for user safety. These chippings are widespread  qualities aims to ensure sufficient longevity, has a roughness of  resistance to polishing and high density or similar gravel  This micro-nailing treatment based on very high stone gravels 2 Claim according to (1) and in which the sealing efficiency is  improved by effective washing of the gravel, followed by coating with a  doping solution vis-à-vis the hydraulic binder but not disturbing  the operation of regular spreading of gravel. 3 Claim according to (1) and (2) in which the gravel dosage is  optimized to obtain loose coverage of the surface. 4 Claim according to (1) (2) and possibly (3) in which the  spreading of gravel is preceded by a transverse streak scan or  longitudinal oscillating. 5 Claim according to (1) (2) and possibly (3) and or (4) in which  the spreading of gravel is followed by the application of a cure treatment  concrete surface presenting no risk of disturbance of the  sealing of gravel.