CALCIUM/MAGNESIUM COMPOUND SLURRY FOR BITUMINOUS ROAD MATERIAL

Abstract

The invention concerns the use of an aqueous suspension of solid particles of a calcium/magnesium compound of formula (A): nCa(OH).sub.2.mCaCO.sub.3.aMgO.bMg(OH).sub.2.cMgCO.sub.3.I as an agent regulating the breaking of a bitumen emulsion. The invention also concerns a bituminous road material obtained by mixing a solid mineral fraction with a cationic bitumen emulsion of the type binder in water, characterised in that it involves adding, to the mineral fraction, an aqueous suspension of solid particles of a calcium/magnesium compound of formula (A). The invention also concerns a method for preparing a material according to the invention and the use of same for producing surface courses, tack coats or temporary surface courses. The invention finally concerns a method for obtaining a tack coat by spreading a cationic bitumen emulsion, comprising a step of applying an aqueous suspension of solid particles of a calcium/magnesium compound of formula (A).

Claims

1-14. (canceled)

15. A method for regulating the breaking of a cationic bitumen emulsion in which an aqueous suspension of solid particles of a calcium/magnesium compound of formula (A)
nCa(OH).sub.2.mCaCO.sub.3.aMgO.bMg(OH).sub.2.cMgCO.sub.3.I, wherein n, m, a, b and c represent molar coefficients for the calcium/magnesium compound in suspension in the aqueous phase such that n+m=x represents the proportion of calcium phase present in the calcium/magnesium compound and where 0<x1 a+b+c=y represents the proportion of magnesium phase present in the calcium/magnesium compound and where 0<y1 x/y represents the calcium phase/magnesium phase ratio I represents all of the various additional compounds is used as a regulating agent.

16. The method according to claim 15, wherein in formula (A) the ratio x/y is comprised between 0.7 and 1.3.

17. The method according to claim 15, wherein in formula (A) the ratio x/y is around 1.

18. The method according to claim 15, wherein in formula (A), a equals 0.

19. The method according to claim 15, wherein in formula (A), x, a and c are each close to 0.

20. The method according to claim 15, wherein in formula (A), the percentage by weight of I, compared to the total weight of the calcium/magnesium compound of formula (A), varies from 0.1 to 10%.

21. The method according to claim 15, wherein in formula (A), the percentage by weight of I, compared to the total weight of the calcium/magnesium compound of formula (A), varies from 0.2 to 5%.

22. The method according to claim 15, wherein in the aqueous suspension of solid particles, the dry matter content by weight is greater than 5% by weight compared to the total weight of the suspension.

23. The method according to claim 15, wherein in the aqueous suspension of solid particles, the dry matter content by weight is greater than 10% by weight compared to the total weight of the suspension.

24. A bituminous road material obtained by mixing a solid mineral fraction with a cationic bitumen emulsion, of the type binder in water, wherein an aqueous suspension of solid particles of a calcium/magnesium compound of formula (A) as defined in claim 15 is added to the mineral fraction.

25. The material according to claim 24, wherein said cationic bitumen emulsion is obtained by mixing, by weight compared to the total weight of the emulsion: 50% to 75% of a bituminous binder, 25 to 50% of an aqueous phase containing: i. 0.1% to 2%, by weight compared to the total weight of the emulsion, of an emulsifying composition ii. a sufficient quantity to adjust the pH of the aqueous phase to a value comprised between 1.5 and 8 of an acid and water to make up the formula to 100%.

26. The material according to claim 25, wherein the emulsifying composition comprises an amine that may be selected from alkyl propylene polyamines, fatty amines, alkyl diamines, amido polyamines, fatty chain quaternary ammoniums and mixtures thereof.

27. The material according to claim 24, wherein the calcium/magnesium compound content, expressed in dry solids, varies from 0.01 to 0.5 parts percent by weight compared to the weight of the dry solid mineral fraction.

28. The material according to claim 24 selected from cold mix bituminous materials, emulsified asphalt mixes, grave emulsion, emulsified bituminous concretes.

29. A method for preparing a material according to claim 24, comprising the following steps a. adding, to a solid mineral fraction, an aqueous suspension of solid particles of a calcium/magnesium compound of formula (A) as defined in claim 15 b. If need be, adding to the solid mineral fraction added water and/or a setting retarder additive c. Adding the solid mineral fraction from step a) or b) to a cationic bitumen emulsion

30. A method for obtaining a tack coat on a support by spreading a cationic bitumen emulsion, characterised in that it comprises the following steps: i. application of the cationic bitumen emulsion, as defined in claim 25, on the support, ii. application of a breaking agent, wherein the breaking agent comprises an aqueous suspension of solid particles of a calcium/magnesium compound of formula (A) as defined in claim 15.

31. The method according to claim 30, wherein the calcium/magnesium compound content varies from 0.1 to 6% dry matter by weight of calcium/magnesium compound compared to the total weight of the emulsion.

32. The method according to claim 30, wherein the calcium/magnesium compound content varies from 0.2 to 3% dry matter by weight of calcium/magnesium compound compared to the total weight of the emulsion.

Description

CAPTION FOR THE FIGURES

[0191] For all the figures: abscissa: time in min, ordinate: pH

[0192] FIG. 1:

Solid line, diamonds: . . . HCl/lime
Dotted line, squares: . . . H.sub.3PO.sub.4/lime
Dotted line, triangles: . . . HCl/cement
Dotted line, crosses: . . . H.sub.3PO.sub.4/cement
Solid line, stars: . . . HCl/slurry of SLS 33 lime
Dashes, circles: . . . H.sub.3PO.sub.4/slurry of SLS 33 lime

[0193] FIGS. 2 and 3:

Solid line, triangles: HCl/slurry of lime n 1
Dashes, triangles: H.sub.3PO.sub.4/slurry of lime n 1
Solid line, circles: HCl/slurry n 2
Dashes, circles: H.sub.3PO.sub.4/slurry n 2
Solid line, squares: HCl/slurry n 3
Dashes, squares: H.sub.3PO.sub.4/slurry n 3
Dotted lines, crosses: H.sub.3PO.sub.4/cement

EXAMPLE 1: PH RISE TESTS

[0194] The rise in pH of a cold mix bituminous mixture is simulated by measuring the evolution of the pH of a solution comprising: [0195] 20 g of filler <63 m [0196] 18 g of demineralised water [0197] 11 g of water acidified to pH=2 (with HCl or H.sub.3PO.sub.4 acid) [0198] 0.1 g of mineral additive (0.5 ppc/dry filler)this value is expressed by weight of the suspension.

With Reference Additives:

[0199] The pH rise in a cold mix bituminous material (CMBM) was simulated in the presence of hydrated lime (Asphacal H from the Lhoist de Boran factory), hydrated lime slurry (Asphacal SLS33 from the firm Lhoist) or cement (CEM II 32.5) with hydrochloric acid or phosphoric acid.
These tests were carried out with 63 m passing from the Moreau quarry.
The results are shown in FIG. 1.
The pH rise curves of FIG. 1 clearly show that cement in the presence of phosphoric acid makes it possible to buffer the pH of the medium to a plateau close to 8 after stabilisation.
For more important pH rises, the CMBM have either too short workability times or a too long kinetic of rise in cohesion, or even adhesiveness defects.

With the Compounds According to the Invention:

[0200] Four calcium/magnesium slurries were tested: [0201] Slurry n 1: industrial product supplied by Lhoist, containing 30% by weight of semi-hydrated dolomitic lime of composition, after being placed in suspension, n=0.460, m=0.065 i.e. x=0.525, and a=0.440, b=0.035, c=0.000 i.e. y=0.475 and x/y=1.11) and I=2.3%. This slurry has a d50 of 35 m and a d90 of 152 m. [0202] Slurry n 2: dilution to 10% by weight of dry matter of slurry n 1, thus having the same composition and the same particle size. [0203] Slurry n 3: Industrial solution of magnesia (Mg(OH).sub.2) obtained by precipitation from marine MgCl.sub.2 and lime, diluted to 10% by weight, of composition after being placed in suspension n=0.010, m=0.000 i.e. x=0.010, a=0.000, b=0.959, c=0.031 (i.e. y=0.990 and x/y=0.010) and I=1.09%. This slurry has a d50 of 7 m and a d90 of 27 m. [0204] Slurry n 4: Mixture of 60% by weight of calcium carbonate slurry (CaCO.sub.3) obtained by placing in suspension 75% by weight of ground CaCO.sub.3 with a d50 of 1.6 m and a d90 of 12 m, and 40% by weight of slurry n 3. This gives for slurry n 4 a composition after being placed in suspension n=0.004, m=0.557 i.e. x=0.561, a=0.000, b=0.422, c=0.017 (i.e. y=0.435 and x/y=1.28) and I=1.27%.

[0205] The tests were carried out with 63 m passing from the Moreau quarry. The results are shown in FIG. 2 (the H.sub.3PO.sub.4/cement curve is also shown for comparison).

[0206] Slurries n 3 and n 2 have a pH rise in the presence of phosphoric acid equivalent to that measured with the cement/H.sub.3PO.sub.4 pairing.

[0207] Slurry n 3 in the presence of hydrochloric acid has a pH rise close to the cement/H.sub.3PO.sub.4 pairing.

[0208] Slurry n 4 (not represented) has the same pH rise as slurry n 3.

[0209] To ensure the buffer power of these new calcium/magnesium slurries, these pH rise tests were also carried out with an acid aggregate (Duro): FIG. 3. Compared to the pH rise curves obtained with Moreau materials, no significant difference was observed after stabilisation.

EXAMPLE 2: CMBM WITH A CALCIUM/MAGNESIUM SLURRY ACCORDING TO THE INVENTION AND COMPARATIVE

[0210] Tests of formulations of CMBM with calcium/magnesium slurries according to the invention, of hydrated lime and of cement were carried out. The aggregates used for these tests came from the Moreau quarries. Slurry n 2 as defined in example 1 was used.
Three emulsion formulas were used:

TABLE-US-00001 TABLE 1 Formulas F1 F2 F3 Bitumen Nature 70/100 70/100 70/100 Paraffinic + Paraffinic + Naphthenic 0.8% 0.8% Radiacid 121 Radiacid 121 Content (kg/t) 600 600 600 Aqueous Emulsifier Nature Duomeen Duomeen Stabiram phase * TTM/ TTM/ MS 301 Redicote 404 Redicote 404 Content (kg/t) 3/2 4,5/3 9 Acid Nature H.sub.3PO.sub.4 H.sub.3PO.sub.4 HCl Content (kg/t) 4 8 1.2 Water (kg/t) 400 400 400 *The brand names are defined in the description
The solid mineral fraction is constituted of aggregates from the Moreau quarry with the following particle sizes: 40% 0/2+30% 2/4+30% 4/6. The solid mineral fraction further comprises 0.07 ppc (parts per 100 by weight) of fibres.
The emulsion content is 11.2 ppc.
The values are expressed by weight compared to the total weight of the mineral fraction.
The CMBM formulas are the following:

TABLE-US-00002 TABLE 2 CMBM formula 1 2 3 4 5 6 Aggregate Moreau Moreau Moreau Moreau Moreau Moreau Emulsion formula F3 F1 F1 F2 20% F1 + 80% F1 + 80% F2 20% F2 Mineral Nature Lime Lime Cement Slurry Slurry Slurry additive no2 no3 no4 Content 0.5 0.5 0.5 0.5 0.5 0.5 (ppc/aggregates) Damping water (ppc/dry aggregates) 10 10 11 10 10 10 Workability time (s) 90 <5 90 130 140 120 Break time (min) 5 5 5 4 5 Fracture time (s) 12 25 24 40 12 WTAT (%) 18 C. 55% RH 3 4 4 3 4
The percentages of the emulsions F1 and F2 are expressed by weight, compared to the total weight of the emulsion F1+F2.
It may be noted that the use of a calcium/magnesium slurry according to the invention makes it possible to obtain a CMBM with satisfactory properties. The CMBM formulas n 1, 3 and 4 make it possible to obtain a material meeting all of the requirements of CMBM. For a paraffinic bitumen with these emulsifiers, the use of lime does not enable the production of a CMBM with the expected requirements definition (not sufficient workability). The calcium/magnesium slurry according to the invention, just like cement, enables the production of a compliant CMBM. Compared to cement, the calcium/magnesium slurry according to the invention has the non-negligible advantage of not being powdery.