WO1993014042A1

WO1993014042A1 - Material containing powdered rubber for protecting concrete from the effects of freezing and thawing

Info

Publication number: WO1993014042A1
Application number: PCT/FR1993/000042
Authority: WO
Inventors: Gilles Moriconi; Philippe Antoine; Dany Vincent
Original assignee: Pieri (S.A.)
Priority date: 1992-01-17
Filing date: 1993-01-15
Publication date: 1993-07-22
Also published as: FR2686334A1; FR2686334B1

Abstract

A material containing powdered rubber for protecting concrete from the effects of freezing and thawing. The material further includes a compound selected from the group consisting of an alkali, alkaline earth and ammonium polynaphthalene sulphate, a sulphite melamine formaldehyde resin, an alkali, alkaline earth and ammonium lignosulphonate, and combinations thereof in a proportion of 10-40 wt % of the final material. The powdered rubber preferably includes 10-60 % of natural rubber.

Description

PROTECTIVE PRODUCT FOR CONCRETE AGAINST THE EFFECTS OF GEL AND DEFROST COMPRISING RUBBER POWDER

The present invention relates to a product for protecting concrete against the effects of freezing and thawing. It relates more particularly to a product comprising rubber crumb.

Cement and mortar compositions are known which are intended for very specific applications. Thus, document EP-A-0 091 377 relates to cement compositions for cementing wells which make it possible to effectively combat the path of gas under pressure up to more than 250 ° C. These compositions have four essential constituents: a cement, a latex, a latex stabilizer and water. The essential role of the stabilizer is to inhibit the film-forming properties of the latex, but nevertheless allows this property to appear in the presence of the phenomenon of gas flow. Documents GB-A-2,083,015 and GB-A-2,069,477 relate to mortar compositions and their uses; more particularly, they relate to mortar compositions which, after mixing with water, form a mortar which produces elastic layers on substrates of various types and / or under coatings of various types. These documents relate to mortar compositions which are therefore intended to be used for low volume and thickness.

Document US-A-4,088,804 relates to a hydraulic cement composition which comprises, in addition to a mineral cement and various mineral aggregates, a synthetic polymer latex chosen from the group of polymers which form a film at room temperature. With regard to concrete, we know that it is a hardened material very resistant to external aggressions. Only repeated freeze-thaw cycles can alter its durability, especially in the presence of water and de-icing salt, which results in surface chipping and the development of cracks. This leads to an alteration of the aspects and above all can jeopardize the durability of the structures, especially when they are located by the roadsides or the sea. To solve this problem it is usual to incorporate in the concrete of 5 at 7% air by volume by adding a surfactant called air entraining agent. While this process provides some satisfaction, it nevertheless has serious drawbacks. The more concrete includes the air ^Λ, less mechanical strength is good. In addition, it is very difficult to control the precise dispersion of the air entrainer, and therefore micro air bubbles inside the concrete. Finally, the effectiveness of these air entrainers depends very much on the concrete itself and its preparation. Document FR-A-2 310 983 describes such a solution in which the air is trapped in spheres of an inert synthetic polymer of very small size making it possible to control the general content of concrete obtained in air. Another known method for solving the same problem, described in documents EP-A-0 413 072 and US-A-4 546 132, consists in incorporating into the concrete during its manufacture a rubber crumb of very small particle size. According to this process, the water absorbed in the pores of the concrete can expand during freezing in the spaces occupied by the rubber crumb. This solution makes it possible not to use an air entrainer and, therefore, to obtain a much better mechanical strength of the final concrete. These two methods do not, however, provide a satisfactory solution to the problem of flaking concrete for engineering structures undergoing repeated and aggressive weathering. The object of the present invention is to provide a product for protecting concrete against the effects of freezing and thawing, providing a more than satisfactory solution to the problem of surface flaking in response to significant thermal cycles and in no way altering the mechanical resistance of the concrete, this having the effect of avoiding oversizing concrete structures subjected to significant and repeated thermal cycles.

According to the invention, the product for protecting concrete against the effects of freezing and thawing comprises, in addition to the rubber crumb, a compound chosen from the group comprising an alkaline, alkaline-earth, ammonium polynaphthalene sulfonate , a sulphited melamine formaldehyde resin, an alkali, alkaline-earth, ammonium lignosulfonate, and combinations thereof, in a proportion of between 10 and 40% by weight of the final product and, preferably, between 20 and 35%.

Preferably also, the rubber crumb comprises between 10 and 60% of rubber of natural origin. Finally, the product can advantageously contain less than 5% by weight of a gluconate, for example of alkali or alkali metals.

The invention also relates to the concrete obtained after incorporating the above-mentioned protective product, in particular in the proportions of between 3 and 15 kg of the product per m ³ of concrete.

The invention will be better understood and other objects, advantages and characteristics thereof will appear more clearly on reading the following description of modes. of realization given without limitation and to which no drawing board is attached.

The incorporation into concrete during its manufacture of a rubber crumb with a particle size less than 1 mm and even, preferably, less than or equal to 500 microns is therefore well known in itself. This crumb can be favorably obtained by grinding used tires from vehicles. However, there have been significant differences between two types of rubber crumbs depending on the origin of the tires. Indeed, we see that some rubber crumbs sometimes play the role of air entrainer. They are essentially crumbs originating from used tires for light vehicles. On the other hand, the rubber crumb from the grinding of used tires of heavy goods vehicles has only a very low air-entraining effect. The essential difference between these two types of crumbs is that the rubber crumb originating from used tires for heavy vehicles comprises between 10 and 60% of rubber of natural origin and more precisely around 30% of rubber of natural origin. This last crumb is therefore preferred when it is desired to preserve the qualities of mechanical strength of the final concrete.

This rubber crumb is therefore mixed with a compound chosen from the aforementioned group, for example a sodium polynaphthalene sulfonate, in the form of a finely ground resin. The proportion of polynaphthalene sulfonate in the final product obtained is between 10 and 40% by weight and, preferably, between 20 and 35% by weight.

In an exemplary embodiment intended to produce 1 m ³ of concrete, 1.4 kg of sodium polynaphthalene sulfonate and 7.5 kg of rubber crumb were used, the product having a particle size less than 500 microns.

Tests have been carried out to demonstrate the resistance to chipping of hardened concrete surfaces exposed to de-icing salt and to intensive freeze-thaw cycles according to the method known under the reference RA 88-01. The procedure used consists in taking parallelepiped hardened concrete slabs, the contour of the face to be tested has been previously fitted with a rubber band and then sealed with silicone sealant so as to expose a determined surface. This surface is immersed in at least 5 mm of a saline solution prepared by dissolving 150 g of sodium chloride in 5 liters of demineralized water, ie a saline solution containing 3% NaCl. Samples thus prepared are then exposed to the gel for 16 hours at a temperature of -20 ° C and then to a thaw for 8 hours at a temperature of 20 ° C with a hygrometry greater than 65%. This cycle is repeated at least 50 times. The cumulative weight loss, for example in kg per m, gives a measure of the resistance to flaking. By way of example, it can be said that a concrete normally resists chipping when its weight loss is less than 1 kg per m ² after the above-mentioned 50 cycles. The lower the weight loss, the better the chipping resistance, of course. It is thus desirable to obtain a concrete whose weight loss is less than 100 g per m ² after the aforementioned 50 cycles. Four concrete samples were thus produced, the concrete being composed of Doubs aggregates of 0-20 particle size dosed at 350 kg / m ³ in CPA 55, the fall to the Abrams cone ("slump") being between 10 and 12 cm. The first sample was a control sample without additives. The second sample was made by incorporating, during the manufacture of concrete, the only rubber crumb in a proportion of 10 kg per m of concrete. The third sample was carried out with the addition of an air entrainer, specifically a resin distributed commercially under the brand VINSOL, incorporated during mixing at the rate of 33 g per m ³ of concrete so as to obtain a percentage of air incorporated around 6%. The fourth sample was carried out with the product which has just been described, this product comprising 20% of sodium polynaphthalene sulfonate and the crumb of used tires comprising 30% of rubber of natural origin and 2% of gluconate, rightly 9 kg per m of concrete.

The results were as follows. By the fifteenth cycle, the control sample had shown a weight loss greater than 1 kg per m. The second sample incorporating the rubber crumb had lost after 50 cycles 400 g per m ² and the sample incorporating the air entrainer had lost 150 g by τa ^~ - after 50 cycles. As for the fourth sample incorporating the product which is the subject of the present invention, its weight loss was 80 g per m ² after 50 cycles. It should also be noted that for the second, third and fourth samples, the weight loss was substantially stabilized after the thirtieth cycle.

Compressive strength tests were also carried out on these samples. It should be noted that if the third sample comprising the air entrainer had a compressive strength significantly lower than that of the control sample, the fourth sample incorporating the product object of the invention had on the contrary a slightly improved compressive strength compared to that of the control sample. All the above tests were of course carried out after curing the concrete for 28 days at 20 ° C and 100% relative humidity. The surprising effect of the concrete protection product according to the invention has therefore been clearly demonstrated. In addition, this product has the advantage of being able to be incorporated with the aggregates forming the concrete and, therefore, allows complete control of the content of the product in the concrete. In addition, this product, whose action does not depend on the random development of air bubbles, has the advantage of complete control of the incorporated content of rubber particles, their particle size distribution, as well as their dispersion. homogeneous in concrete.

Although only certain preferred embodiments of the invention have been described, it is obvious that any modification made in the same spirit would not depart from the scope of the present invention.

Claims

1. Product for protecting concrete against the effects of freezing and thawing comprising rubber crumb, characterized in that it also comprises a compound chosen from the group comprising an alkaline, alkaline-earth polynaphthalene sulfonate , ammonium, a sulfited melamine formaldehyde resin, an alkali, alkaline earth, ammonium lignosulfonate, and combinations thereof in a proportion of between 10 and 40% by weight of the final product.

2. Product according to claim 1 characterized in that it comprises between 20 and 35% by weight of said compound.

3. Product according to claim 1 or 2 characterized in that it further comprises less than 5% by weight of a gluconate.

4. Product according to any one of claims 1 to 3 characterized in that the rubber crumb comprises between 10 and 60% of rubber of natural origin.

5. Product according to claim 4 characterized in that said crumb is obtained by grinding used tires from heavy vehicles.

6. Concrete characterized in that it was obtained after incorporation of 3 to 15 kg of the product according to any one of the preceding claims, per m ³ of concrete.