FR2751956A1 - Concrete composition with self levelling and self sliding structure - Google Patents

Abstract

A concrete composition with self levelling and self sliding structure consists of cement, sand, loose chippings, some granular components, some additive and water and has the following composition: Cement and other granular fine components of particle size less than 100 mu m is 100-400 Kg/m<3> of composition ready to use Sand's wt. is 46 wt.% of composition ready to use superplasticiser and a chloro plasticiser at content determined by the superplasticiser to give the self levelling and the self sliding properties to the concrete.

Description

The invention relates to a self-leveling and self-leveling structural concrete composition.

The self-leveling concrete compositions are very fluid compositions which are set up and tighten under the sole effect of gravity without any input of energy by external or internal vibration.

Examples of such compositions are described in the publication FR-A-2704853 and in the review article by Thierry Sedran published in the liaison bulletin of the Laboratoire des Ponts et Chaussées No. 196, March-April 1995, pages 53 to 60 .

These compositions have two technical and economic interests
- a reduction in time and personnel during the installation of the composition on site. This is all the more important as it becomes more and more expensive and generates delays, given the ever increasing complexity of formwork (form) and reinforcement,
- obtaining a better quality of the concrete, in situ, practically independent of the know-how of the workers during the realization. This goes in the direction of increased durability of the structures.

It has hitherto been considered that in order to obtain a self-leveling concrete composition, it was necessary to incorporate into the concrete composition an adequate percentage viscosity agent.

These viscosity agents are generally
- cellulose derivatives: hydroxyethylcellulose (HEC), carboxymethyl cellulose (CMC), hydroxypropylmethyl cellulose (HPMC),
polymers resulting from biotechnology: xanthan gum, welan gum.

These products are generally very expensive. The dosages used vary between 200 g and 800 g of dry extracts / m3. Associated with superplasticizers used in high dosage (8 to 11 kg of dry extracts / m3), these products generate significant additional costs for concrete. Thus, for average performance (35 to 45 Mpa at 28 days), the cost of such a self-leveling concrete is approximately double that of a traditional current concrete.

An aim of the present invention is to provide a concrete composition with a self-leveling and self-leveling structure that is substantially less expensive than the known compositions, in particular due to the fact that the self-leveling and self-leveling character is not due to the presence of a viscosity agent.

Another aim of the invention is to provide a composition which can be used with a site concrete batching plant, whereas the known compositions generally need to be mixed in more sophisticated fixed installations.

Another aim of the invention is to provide a composition which can replace common building concretes with low cement content.

Another aim of the invention is also to provide a composition which makes it possible to obtain a thin facing.

According to the invention, the concrete composition of the invention is a structural concrete composition, self-leveling and self-leveling, which comprises cement, sand, gravel and other granular components, admixtures and water in sufficient quantity. for the implementation of the composition, characterized in that the dosage of cement and other fine granular components (other than sand) with a particle size less than 100 micrometers is included in a range of 100-400 kg per cubic meter of ready-to-use composition use, in that the weight of sand represents at least 46% of the weight of the ready-to-use composition and in that the composition comprises a superplasticizer and a chlorinated plasticizer, the amount of chlorinated plasticizer being determined for a superplasticizer given in such a way as to give the concrete the desired self-leveling and self-leveling character.

The term “ready-to-use composition” means that the composition comprises the water necessary for the use of the composition.

Preferably, the fine components other than cement are fly ash and / or fine limestones.

Preferably, the dosage of fine components (other than sand) with a particle size of less than 100 micrometers (or even better less than 80 micrometers) is included in the range 300 -400 kg / m3, even better in the range 320 - 350 kg per m3 of ready-to-use composition.

Preferably, chippings are used which essentially have a grain size of at most 20 millimeters.

Preferably, the adjuvants consist only of the chlorinated plasticizer and the superplasticizer.

It is easy for those skilled in the art, after having chosen a superplasticizer and after having chosen the amount of superplasticizer normally required, to determine by a few tests the amount of chlorinated plasticizer effective to obtain the desired self-leveling and self-leveling character.

This amount can be optimized in each case depending on the superplasticizer used, but it is also possible to be satisfied with a less fine assessment of the amount of chlorinated plasticizer, even if it means using an excess amount.

Thus, it was determined that satisfactory results were obtained using quantities (dry extracts) of superplasticizer (SP) and chlorinated plasticizer (PC) such that the ratio K = PC / (SP + PC) is included in the range 0.2-0.8 depending on the nature of the superplasticizer used.

The total amount (dry extracts) of superplasticizer and chlorinated plasticizer in the composition is generally between 5 and 15 kgs, preferably between 8 and 12 kgs per m 3 of ready-to-use composition.

The superplasticizer may be a commercial superplasticizer preferably chosen from the group consisting of melamine condensates, sulphurized naphthalene and vinyl polymers.

The chlorinated plasticizer is preferably a nitrogenous plasticizer, in particular a product containing epoxy glycol and quaternary amine groups.

It was determined that, surprisingly, the additive described in the publication FR-A-2 693 719 as an agent increasing the rate of hardening of cements, mortars and concretes, could be suitable as a chlorinated plasticizer for the purposes. of the present invention. This additive as defined in the publication corresponds to the formula:

in which
- R1, R2, and R3 which may be identical or different,
represent a hydrogen atom or an alkyl, substituted alkyl, alkene,
aryl or aryl, preferably a C1 to C4 alkyl radical,
- B represents a hydrocarbon chain comprising at least one -CH2- unit and of which the number of carbon atoms located on the chain is lower
or equal to 10, preferably (CH2) n where 1 sns 6 - A represents one of the groups:

wherein
X represents a halogen
R5, R6 and R7, which may be the same or different, represent alkyl, substituted alkyl, alkene, aryl or araikyl radicals.

In a preferred embodiment, as defined in the aforementioned publication, this agent corresponds to the formula:

in which:
R5, R6 and R7, which may be the same or different, are C1 to C4 alkyl radicals, isn s
Examples of the composition (in kg) of a self-leveling and self-leveling concrete in accordance with the present invention will be described below, the weights indicated correspond to the preparation of 1 m 3 of the composition ready for re-use.

In these examples, the paver is a mixture of sand and gravel which comprises 58% by weight of sand in the grain size range 0 - 5 mm and 42% by weight of gravel in the grain size range 5 - 20 mm and the adjuvants are a superplasticizer and a chlorinated plasticizer.

PAVER (KG) 1750 1750 1750 1750 1750 1750 CEMENT (KG) 240 250 240 240 260 260
C. WHEELS (KG) 160 120 110 100 110 80
ADDITIVES (KG)
DRIED EXTRACTS 9 10 10 8.5 9 8
WATERICIMENT 1 0.87 / 0.8 0.85 0.8
R24h (MPa) 1 I 1 4.9 4.1 1
R7j (MPa) 18.2 23.4 21.6 / 29.9 30.5
R28j (MPa) 24.4 37 25.5 / 35.5 34.7
It will be noted that these compositions do not contain a viscosity agent.

In these examples, the product "LAB" from the company ROQUETTE was used as chlorinated plasticizer and BB40 from CIA was used as melamine superplasticizer.

It was determined by a few simple tests that preferably the effective amount of LAB for this superplasticizer (SP) should be such that the ratio K = LAB / (SP + LAB) is between 0.37 and 0.61.

For comparison, it was determined that if SIKA superplasticizer FF86 was used, the K ratio should be between 0.54 and 0.76.

Claims (12)

1. Self-leveling and self-leveling structural concrete composition, which comprises cement, sand, gravel and other granular components, additives and water in sufficient quantity for the implementation of the composition, characterized in that the dosage of cement and other fine granular components (other than sand) with a particle size of less than 100 micrometers is within a range of 100-400 kg per cubic meter of ready-to-use composition, in that the weight of sand represents at at least 46% of the weight of the ready-to-use composition and in that the composition comprises a superplasticizer and a chlorinated plasticizer, the amount of chlorinated plasticizer being determined for a given superplasticizer so as to give the concrete the desired self-leveling and self-leveling character . 2. Composition according to claim 1, in which said other fine granular components comprise components selected from the group consisting of fly ash and fine limestone. 3. Composition according to claim 1 or 2, in which the dosage of cement and other fine granular components is within the range 300-400 kg / m3 of ready-to-use composition. 4. Composition according to claim 3, in which the dosage of cement and other fine granular components is within the range 320-350 kg / m3 of ready-to-use composition. 5. Composition according to one of claims 1 to 4, the adjuvants of which consist only of the chlorinated plasticizer and of the superplasticizer. 6. Composition according to one of claims 1 to 5, in which the superplasticizer is chosen from the group consisting of melamine condensates, sulfonated naphthalene and vinyl polymers. 7. Composition according to claim 6, and in which the amounts (dry extracts) of superplasticizer (SP) and of chlorinated plasticizer (PC) are such that the ratio K = PC / (SP + PC) is within the range 0, 2-0.8. 8. Composition according to one of the preceding claims and in which the total amount (dry extracts) of superplasticizer and chlorinated plasticizer is in the range 5-15 kgs, preferably 8-12 kgs, per m3 of ready-to-use composition. 'employment. 9. Composition according to one of claims 1 to 8, in which the plasticizer is a nitrogenous product, preferably containing epoxy glycol and quaternary amine groups. 10. Composition according to claim 9, in which the chlorinated plasticizer corresponds to the formula:

- A represents one of the groups: - B represents a hydrocarbon chain comprising at least one -C 112- unit and whose number of carbon atoms located on the chain is less than or equal to 10, preferably (CH2) n where 1 <n <6 - R1, R2 and R3 which may be identical or different, represent the hydrogen atom or an alkyl, substituted alkyl, alkene, aryl or aryl group, preferably a C1 to C4 alkyl radical, in which R5, R6 and R7, which may be the same or different, represent allyl, substituted alkyl, alkene, aryl or aralkyl radicals. X represents a halogen atom wherein: 11. Composition according to claim 10, the plasticizer of which corresponds to the formula:

R5, R6 and R7, which may be the same or different, are C1-C4 alkyl radicals, 1 # n s5 12. Self-leveling and self-leveling concretes obtained by the use of a composition according to one of claims 1 to 11. in which