US2760878A - Process for coating aggregate with bituminous binder - Google Patents

Description

XR 297609878 tX o l n Umted States l atent O PROCESS FOR COATING AGGREGATE WITH BITUMINOUS BINDER Marcel Louis Lhorty, Rouen, France, assignor to Shell Development Company, Emeryville, Calif., a corporation of Delaware No Drawing. Application July 15, 1953, Serial No. 368,212 Claims priority, application France July 22, 1952 19 Claims. (Cl.106-269) This invention relates to a process for the coating of aggregates. More particularly, it is concerned with the coating of mixed'a'ggregates with bituminous materials.

In the preparation of paving compositions it is normal practice to mix bituminous materials, such as asphalt, with aggregates of various sizes depending upon the end use. The efiiciency with which the bituminous material coats the aggregate is related to a number of properties such as the source and history of the binder material, the acidic or basic character of the aggregate, and the size of the aggregate particles. Various treatments and processes as well as additives have been employed for the purpose of increasing the adhesion of the binder to the aggregate. For the most part, the additives which are most successful may be described as those surface active agents bearing at least one lipophilic radical per molecule. It is believed that regardless of the method of application at least part of the additive migrates to the interface between the aggregate and the binder. The lipophilic radicals of the surface active agent provide the aggregate surface with an oleophilic coating, whereupon the binder is more strongly bound to the aggregate. This process for improving such compositions is only effective, of course, as long as each of the aggregate particles is substantially uniformly coated with an oleophilic surface active agent.

As long as the aggregate is relatively uniform in particle size the surfactant may be applied by several methods. It may, for example, be dispersed in the asphalt which is then mixed with the aggregate. Alternatively, the aggregate is primed with a dispersion of the surface active agent following which the binder is mixed with the primed aggregate. Combinations of these two processes also have been employed. However, these methods have not been successful for the adequate coating of the aggregates containing particles of widely differing surface areas. If, for example, the aggregate mixture contains a substantial proportion of fine particles such as fine sand, it has been found that both the primer and the bituminous binder are selectively attracted to the relatively finer aggregate particles, while the coarser particles remain unprimed and uncoated. Under these conditions a pavement such as a road commences to disintegrate within a short period of time, the uncoated coarse particles falling away as gravel. One possible means for overcoming this disadvantage would be to fractionate the aggregate into coarse and fine fractions, coating each fraction separately with the binder and then combining the several coated fractions. It is obvious that such an expedient is uneconomical.

It is an object of the present invention to improve the process for coating aggregates with bituminous binders. It is another object of this invention to improve the process for coating aggregates containing a substantial proportion of fine particles with asphaltic materials. It is a particular object of this invention to improve the process for coating mixed aggregates so as to provide both coarse and fine particles with a substantially uniform coating of a bituminous binder. Other objects will become apparent during the following discussion.

Now in accordance with the present invention, a means has been found for the uniform coating of mixed aggre- 2,760,878 Patented Aug. 28, 1956 gates wherein the aggregate contains both relatively fine aggregate particles and relatively coarse particles. The process comprises priming the aggregate with a surface active agent having at least one lipophilic radical as a portion of each molecule thereof, whereby the relatively fine aggregate particles are preferentially coated with the primer, mixing the partially primed aggregate with a bituminous binder whereby the binder is attracted to and coats the primed aggregate particles while the relatively coarse particles remain substantially unaltered; applying a second portion of the same or different surface active agent, which primes the relatively unaffected coarser aggregate particles and continuing the mixing whereby all of the aggregate, both fine and coarse particles, become substantially uniformly coated with the asphaltic binding.

The use of this invention enables the satisfactory preparation of asphaltic paving compositions wherein the aggregate employed contains a substantial proportion of fine particles, that is, particles having a maximum diameter of 5 millimeters or less. The process is particularly applicable to mixed mineral aggregates containing from about 5% to about 60% by weight of such fine particles (usually having minimum diameters of about 0.5 mm.) and especially where the aggregate contains at least 10% of the fine aggregate. Under such conditions it is preferred that the initial priming of the aggregate be accomplished with from about 25% to about by weight of the total surface active agent employed in the composition.

The priming may be accomplished with any of the known varieties of surface active agents which contain at least one lipophilic radical per molecule. In general, these comprise anionic substances such as organic acids (oleic acid, stearic acid, and other fatty acids having 12-24 carbon atoms per molecule), soaps, preferably those of polyvalent metals with fatty acids (aluminum stearate, zinc oleate, etc.), and cationic materials. The latter class are the most widely used and are preferred.

For the most part, the cationic materials comprise organic nitrogenous bases, although other onium compounds may be employed such as phosphonium, iodonium, stibonium, arsonium and the like.

Suitable substances to be used as the amino compound are the organic compounds containing an amino group and a. lipophilic radical in the molecule, as well as derivatives of such compounds. A preferred group of amino compounds consists of products containing a radical derived from the fatty glycerides such as vegetable oils. Such amino compounds can, for instance, be obtained by condensation of ammonia with a fatty substance of vegetable origin to form nitriles which are then hydrolyzed to amines.

The amino compounds containing a radical derived from a fatty substance may be the soaps of a monoamine or a polyamine of a higher fatty acid having at least 12 carbon atoms, and probably 16-20 carbon atoms per molecule. Suitable acids are variously derived from vegetable and animal oils such as oleic acid, linoleic acid, and stearic acid, as well as their homologs and analogs.

The acyl amides derived from a higher fatty acid as well as the acyl amido amines derived from a higher fatty acids are also suitable. The acyl amido amines can be obtained by reacting a polyamine with an acid while converting at least one of the amino groups of the polyamine into the acyl amide structure and leaving at least one other of the amino groups in a free state. The soaps of the acyl amido amines obtained by reacting at least one of the free amino groups of the acyl amido amine with an organic or inorganic acid may also be used.

The soaps of an amine, the acyl amides, and the acyl amido amines referred to above can also be derived from organic acids of high molecular weight other than the higher fatty acids. Preferred varieties of alternative materials comprise those obtained from the naphthenie acid fractions derived from petroleum oil as well as such other natural occurring materials as tall oil and the like- Examples of polyamines which may be used as initial material for obtaining the above mentioned derivatives of the organic acids are preferably alkylene polyamines and polyalkylene polyamines including ethylene diamine, propylene diamine, diethylene triamine, triethylene tetram-ine, tetraethylene pentamine, and hexamethylene diamine. A preferred group of polyamines comprises the materials obtained by hydrogenation of the condensation products of acr-olein or of epoxides such as epichlorohydrin with ammonia or with lower molecular weight primary or secondary amines. Preferably the lipophilic character of 'such materials is enhanced by reaction of the condensation product with less than an equivalent amount of an oleophilic organic acid such as the higher fatty acids including those referred to hereinbefore.

\Another class of amino compounds suitable for the purpose of the present invention consists of higher alkyl amines and alkenylamines having at least 12 carbon atoms and preferably 16-20 carbon atoms per molecule. These include species such as hexadecyl amine, heptadecyl amine, octadecyl amine, and octadecenylamine as well as the polyalkylene polyamines containing more than 8 carbon atoms. Other suitable amines are those bearing cyclic hydrocarbon radicals such as abietylamine and naphthenylamine.

In order to enhance the adhesion characteristics promoted by these materials it is preferred, but not essential, that they be combined in the present process with an inorganic salt of a polyvalent metal. The polyvalent metal is preferably an amphoteric metal, such substances as zinc, tin, iron, lead, and chromium being preferred. Especially when the aggregate is primed with an aqueous dispersion of these materials it is preferred that the latter also include an inorganic acid, especially the mineral acids such as sulfuric, nitric, hydrochloric, hydrobromic, or phosphoric acids. The inorganic salts are preferably those of the same type of acids, although mixtures of either acids or salts or both may be employed.

While the priming materials may be added directly to the aggregate without substantial modification, it is preferred for economic and technical reasons to disperse them either in solution or more preferably, in an aqueous emulsion. In the latter case, an oil-in-water emulsion is preferred. When employing a priming composition comprising an aqueous emulsion, a polyvalent metal salt and an inorganic acid are dispersed in the aqueous phase, the oleophilic surface active agent being substantially dispersed in the oil phase of the emulsion. Under some circumstances, when salts are formed between the inorganic acid and a surface active amino compound, the salt may be dispersed in both phases.

The oil phase of such emulsions is preferably a mineral oil of heavy character such as road oil, or fuel oil. The mineral oil may also be a mixture of a heavy oil and a lighter oil, such as the mixture of road oil and kerosene. In the latter instance, a mixture of 50-80% road oil with 20-50% kerosene is satisfactory. It is also possible to use an aromatic extract obtained by the extraction of a mineral oil by means of a selective solvent. The mineral oil phase may constitute from about 1% to about 50% by weight of the total priming emulsion. It is preferred that the amine be present in an amount between about 3% and about 30% by weight of the priming emulsion. Any water soluble polyvalent metal salt which is present should be employed in amounts less than about by weight of the emulsion. If an inorganic acid is employed, it should be utilized in amounts between about 0.5% and about 10%, based on the total weight of the emulsion. It will 'be understood that this proportion of acid may be distributed between free inorganic acid and any that is combined in salt form with the amino compound. In order to be effective for the present purpose suficient priming composition is employed in the comhined priming operations so that from about 0.001% to about 0.1% of the surface active agent based on the aggregate is deposited on the surface thereof.

After the initial priming operation, when the relatively fine aggregate particles are primed, the asphaltic binder is mixed therewith usually in amounts between about 0.5% and about 10% by weight of the aggregate and based upon the relatively non-volatile portions of the binder composition. For the purpose of application and convenience in handling, the binder may be dispersed as an aqueous emulsion or may be used in the form of a cut back or solution.

Under the preferred conditions, and when the mineral aggregate contains from about 10% to about 60% of particles having maximum diameters less than 5 millimeters, the first priming operation is effected with the use of between about 40% and about 65% by weigh-t of the total surface active agents. Under such circumstances, when employing an emulsion for the purpose of priming the emulsion should contain between about 0.1% and about 1% by weight of the emulsion of amphoteric metal inorganic salt and between about 1% and about 6% by weight of the emulsion of the mineral acid. The emulsion should also contain from about 10% to about 20% based on the weight of the emulsion of the hydrophobic surface active agent and depositing on the aggregate between about 0.005% and about 0.03% based on the weight of the aggregate of the surface active agent. Under such circumstances it is preferred that the binder be employed in amounts between about 3% and about 7% based on the weight of the aggregate.

The aqueous suspension can be prepared by intimately mixing the oil and the amino compound with an aqueous solution of the water-soluble inorganic salt of a polyvalent metal at a temperature of 70-80 C. An emulsion of water in the oil phase is formed. The acid used, such as strong inorganic acid, is slowly added to this emulsion. By adding the acid, the emulsion is reversed whereby the desired emulsion of oil in the aqueous phase is obtained. When it is desired to prepare and use an aqueous suspension containing no inorganic salt the preparation of the suspension can be carried out in a similar way.

Preferably, all the operations for preparing the aqueous emulsions are carried out at temperatures not exceeding about C. The aggregate may be pre-coated with the emulsion or other composition containing the oleophilic surface active agent by spraying or by wetting the aggregate in any manner. It is advantageous to atomize the aqueous suspension on the surface of the aggregates. The priming may be carried out in a mixing or crushing plant, especially when the crushed aggregate is transported on a conveyor belt, in such a way as to permit the installation of a spraying device about the belt. In particular, this technique may be employed in the case of pre-treatment or priming of fine gravel intended for surface spreading. Wetting the aggregate with the emulsion of the primer can be done during loading of the gravel trucks at the moment when the aggregate is being transported on the conveyor belt leading from the shovelling device to the trucks.

After the initial application of the desired portion of the priming solution the bituminous binder may be applied to the aggregate in any known manner. The priming of the aggregate with the suspension makes it possible to coat the relatively fine particles thereof with the bituminous binder in an effective manner, but leaves the relatively coarser particles in substantially their original condition.

Bituminous binders which may be employed include residual asphalts, pyrogenous asphalts, blown asphalts, and natural asphalts or asphaltites.

Having effectively coated the relatively finer aggregate particles, the remaining portion of the oleophilic surface active agent is applied with agitation whereupon the relatively coarser aggregate particles are primed therewith. Upon continued agitation of the entire mixture the asphaltic binder is relatively uniformly distributed on all of the aggregate particles regardless of their relative size or surface area.

One of the advantages gained by the use of the present process, in addition to the relatively uniform coating of all of the aggregate particles, Comprises the substantial reduction in the minimum requirement for surface active agent in order to promote satisfactory adhesion of the asphalt or other bituminous substance to the aggregate.

The example which follows describes a typical embodiment of the present invention: 1430 kilograms of water were introduced into a mixer and heated to 60 C. Aluminum sulfate, crushed to nut size, was added and dissolved in the water. The temperature was raised to about 70 C. after which 240 kilograms of hydrocarbon oil comprising 25% by weight of fuel oil and 75% by weight of aromatic extract obtained from lubricating oil fractionation were dispersed in the water. Following this, a mixture of fatty amines predominating in octadecyl amine were introduced so as to provide the emulsion with an amine concentration of approximately 5%. Hydrochloric acid was finally added in an amount of about 2% based on the weight of the total emulsion.

When this emulsion is added in a single step to aggregate comprising approximately 35% by weight of particles having diameters less than 5 millimeters, the priming is not satisfactory since it adheres largely to the finer particles while the relatively coarser material is not primed. Consequently, when asphalt is added thereto an incomplete coating of the aggregate occurs and the resulting composition exhibits poor weathering properties. In overcoming these difiiculties the present invention is employed by using two substantially equal applications of the abovedescribed priming emulsion and applying the asphalt binder between the primer applications. The resulting composition is found to have substantially uniform coating of the binder throughout the aggregate particles regardless of their relative size and the composition exhibits greatly improved weathering properties.

A preferred process for preparing priming emulsions having superior properties with respect to increasing the adhesion of later applied bituminous coatings comprises dispersing the adhesion agent i. e., an amine, an an aqueous medium, comprising either water or a water solution of an inorganic polyvalent metal salt, following which an inorganic acid, such as hydrochloric acid, and mineral oil are added. For some reason as yet undetermined, it has been found that emulsions so formed exhibit at least about 20% additional adhesion improvement as compared with emulsions prepared by other means. For example, if the emulsions are prepared by mixing oil and the amino compound with an aqueous solution of the polyvalent metal salt, a water-in-oil emulsion is formed following which acid is added in order to cause inversion of the emulsion. However, it has been determined that such emulsions,

while satisfactory for most purposes, are only about as effective as primers as compared with emulsions prepared by the above preferred process.

The examples which follow illustrate the advantages gained by the use of the present invention:

EXAMPLE 1 An emulsion having the following composition was used for priming a quartzite having aggregate particles whose maximum diameters vary from about 1 mm. to 20 mm.

Parts by weight Water 71.5 Aluminum sulfate (calc. anhyd.) 1 Fuel oil 12 CisCis fatty amines 12 Hydrochloric acid (density 1.19) 3.5

6% by weight based on the aggregate of an asphalt cut back was used to coat the quartzite.

Table l, which follows, shows comparative data proving that (1) less primer is required when using multiple addition and (2) adhesion values are increased by multiple addition, even if the total quantity of primer is less than that used in a single addition. Test 3 shows that further benefits result from atomizing the primer instead of employing ordinary spray.

Table I.Laborat0ry tests carried out with quartzite 0/20 EXAMPLE II A second set of comparative tests were made, utilizing a porphyry aggregate having a wide particle size distribution and a priming emulsion as follows:

Parts by weight Water 62.5 Aluminum sulfate 2.5 Road oil l0 Kerosene 5 C1s1s fatty amines 15 Hydrocholric acid 5 Table II below shows that the advantage of multiple addition for the treatment of this type of aggregate is especially beneficial.

Table II.Tests carried out in a concrete mixer with corbigny porphyry Test 1 Test 2 Test 3 Test 4 Temperature 14 C 14 C 12 C 12 0. Weight of gravel per mix kg 90 kg 90 kg 90 kg. Water content of gravel 5% 5%.-- 5% 5%. Percent of asphalt cutback calc. on 6%. 6% 6% 6%.

aggregate. Term. of binder 90100 C 90-100 C 90-100 C 90-100 C. Priming emulsion:

Total quantity used calc. on 2 kg./ton 3 kg./ton 1.5 kg./ton.

aggregate. Concentrated emulsion diluted 15% 20% 15%.

0. Time of use before coating before coating, 50% before coating, 50% before coating, is after coating. 50% after coating. 50% after coating. Percent of surface of gravel coated. 20% "A 90%. Destruction of coating upon negligible negligible negligible negligible.

immediate immersion.

I claim as my invention:

1. The method of coating mineral aggregate containing both fine and coarse aggregate particles which comprises priming said aggregate with a first portion of an oil-inwater emulsion, said emulsion comprising an aqueous phase having dissolved therein from about 0.1% and about 1% by weight of the emulsion of a water soluble amphoteric metal inorganic salt and from about 1% to about 6% by weight based on the emulsion of a mineral acid, and a hydrocarbon phase having dissolved therein from about 10% to about 20% based on the weight of the emulsion of an aliphatic amino compound bearing at least one lipophilic radical per molecule, whereby the fine aggregate particles having maximum diameters less than about mm. are coated with the primer and the coarser particles are substantially unaffected; mixing with the primed aggregate between about 3% to about 7% by weigh-t, based on the aggregate, of a bituminous binder, whereby the fine aggregate particles are coated therewith while the coarser aggregate particles are substantially uncoated; admixing a second portion of said priming emulsion, whereby the coarse aggregate particles are primed therewith; and mixing the entire composition, whereby both fine and coarse aggregate particles are coated with the binder; the total proportion of amino compound being between about 0.005% to about 0.03% based on the weight of the aggregate.

2. A process according to claim 1 wherein the acid is 4 hydrochloric acid.

3. A process according to claim 1 wherein the salt is aluminum sulfate.

4. A process according to claim 1 wherein the amino compound is a higher aliphatic amine.

5. A process according to claim 1 wherein the amino compound is an alkyl amine having an alkyl radical of 12-20 carbon atoms.

6. A process according to claim 1 wherein the amino compound is a partial amide of a higher fatty acid and an aliphatic polyamine.

7. A process according to claim 1 wherein the bituminous binder is asphalt.

' a first portion of an aqueous emulsion of an amino compound bearing at least one lipophilic radical and a watersoluble inorganic salt of a polyvalent metal, whereby the fine aggregate particles are preferentially primed, but the coarse particles are substantially unaffected, applying a bituminous binder, whereby the fine particles are coated therewith, applying a second portion of said priming emulsion, whereby the coarse particles are primed, and mixing the entire composition whereby both the coarse and fine particles are coated with the binder, the first portion of the priming solution containing from about 40% to about 65% by weight of the total amino compound, the total amount of amino compound utilized being between about 0.001% and about 0.1% by weight based on the aggregate.

12. The method of coating mineral aggregate containing both fine and coarse aggregate particles which comprises priming said aggregate with a first portion of an oil-in-water emulsion, said emulsion comprising an aqueous phase having dissolved therein from 0.0% to about by weight of the emulsion of a water-soluble polyvalent metal salt and between about 0.5% and about 10% based on the emulsion of an inorganic acid, and

a hydrocarbon phase having dissolved therein, from about 3% to about 30% by weight of the emulsion of an amino compound bearing at least one lipophilic radical per molecule, whereby the fine aggregate particles having maximum diameters less than about 5 mm. are coated with the primer and the coarser particles are substantially unaffected; mixing with the primed aggregate between about 0.5% and about 10% by weight, based on the aggregate, of a bituminous binder, whereby the fine aggregate particles are coated therewith; admixing a second portion-of said priming emulsion, whereby the coarse aggregate particles are coated therewith; and mixing the entire composition, whereby both fine and coarse aggregate particles are coated with the binder; the total proportion of amino compound being between about 0.001% to about 0.1% by weight based on the aggregate.

13. The method of coating mineral aggregate containing both fine and coarse particles which comprises priming the aggregate with a first portion of a surface active agent having at least one lipophilic radical per molecule, whereby the relatively fine aggregate particles are preferentially primed, applying a bituminous binder, whereby the primed particles are coated with binder, applying a second portion of a surface active agent to the partially coated aggregate, whereby the uncoated relatively coarse aggregated particles are primed, and mixing the entire composition, whereby both the coarse and fine aggregate particles become coated with the bituminous binder, said surface active agent being an anionic material the total amount of said surface-active agent being between about 0.001% and about 0.1% by weight based on the aggregate.

14. The method of coating mineral aggregate containing both fine and coarse particles which comprises priming the aggregate with a first portion of a surface active agent having at least one lipophilic radical per molecule, whereby the relatively fine aggregate particles are preferentially primed, applying a bituminous binder, whereby the primed particles are coated with binder, applying a second portion of a surface active agent to the partially coated aggregate, whereby the uncoated relatively coarse aggregated particles are primed, and mixing the entire composition, whereby the coarse and fine aggregate particles become coated with the bituminous binder, said surface active agent being a cationic material the total amount of said surface-active agent being between about 0.001% and about 0.1% by weight based on the aggregate.

15. The method of coating mineral aggregate containing both fine and coarse aggregate particles which comprises priming the aggregate with a first portion of a surface active agent having at least one lipophilic radical per molecule, whereby the relatively fine aggregate particles are preferentially primed, applying a bituminous binder, whereby the primed particles are coated with binder, applying a second portion of a surface active agent to the partially coated aggregate, whereby the uncoated relatively coarse aggregated particles are primed, and mixing the entire composition, whereby the coarse and fine aggregate particles become coated with the bitumi nous binder, said surface active agent being applied in the form of a solution the total amount of said surfaceactive agent being between about 0.001% and about 0.1% by weight based on the aggregate.

16. The method of coating mineral aggregate containing both fine and coarse aggregate particles which comprises priming the aggregate with a first portion of a. surface active agent having at least one lipophilic radical per molecule, whereby the relatively fine aggregate particles are preferentially primed, applying a bituminous hinder, whereby the primed particles are coated with binder, applying a second portion of a surface active agent to the partially coated aggregate, whereby the uncoated relatively coarse aggregated particles are primed, and

mixing the entire composition, whereby the coarse and fine aggregate particles become coated with the bituminous binder, said surface active agent being applied in the form of an aqueous emulsion the total amount of said surface-active agent being between about 0.001% and about 0.1% by weight based on the aggregate.

17. The method of coating mineral aggregate containing both fine and coarse aggregate particles which comprises priming the aggregate with a first portion of a surface active agent having at least one lipophilic radical per molecule, whereby the relatively fine aggregate particles are preferentially primed, applying a bituminous binder, whereby the primed particles are coated with binder, applying a second portion of a surface active agent to the partially coated aggregate, whereby the uncoated relatively coarse aggregated particles are primed, and mixing the entire composition, whereby the coarse and fine aggregate particles become coated with the bituminous binder, said surface active agent being applied to the aggregate in the form of a dispersion the total amount of said surface-active agent being between about 0.001% and about 0.1% by weight based on the aggregate.

18. The method of coating mineral aggregate containing -60% by weight of fine particles having maximum diameters between about 0.5 mm. and about 5 mm. and coarse particles of greater diameter, which comprises priming the aggregate with a first portion of a surface active agent agent having at least one lipophilic radical per molecule, whereby the relatively fine aggregate particles are preferentially primed, applying a bituminous binder, whereby the primed particles are coated with binder, applying a second portion of a surface active agent to the partially coated aggregate, whereby the uncoated relatively coarse aggregated particles are primed, and mixing the entire composition, whereby the coarse and fine aggregate particles become coated with the bituminous binder, said first portion being from about 25% to about by weight of the total surface active agent the total amount of said surface-active agent being between about 0.001% and about 0.1% by weight based on the aggregate.

19. The method of coating mineral aggregate containing both fine and coarse aggregate particles which comprises priming the aggregate with a first portion of a surface active agent having at least one lipophilic radical per molecule, whereby the relatively fine aggregate particles are preferentially primed, applying a bituminous binder, whereby the primed particles are coated with binder, applying a second portion of a surface active agent to the partially coated aggregate, whereby the uncoated relatively coarse aggregated particles are primed, and mixing the entire composition, whereby the coarse and fine aggregate particles become coated with the bituminous hinder the total amount of said surface-active agent being between about 0.001% and about 0.1% by weight based on the aggregate.

References Cited in the file of this patent UNITED STATES PATENTS 1,975,902 McConnaughay Oct. 9, 1934 2,003,861 McConnaughay June 4, 1935 2,025,945 Forrest Dec. 31, 1935 2,313,759 McCoy Mar. 16, 1943 2,339,853 Hemmer Jan. 25, 1944 2,416,134 Allen Feb. 18, 1947 2,430,546 Agnew Nov. 11, 1947 2,438,318 Johnson Mar. 23, 1948 2,461,971 Fischer Feb. 15, 1949 2,498,862 Petitjean Feb. 28, 1950

Claims (1)

1. THE METHOD OF COATING MINERAL AGGREGATE CONTAINING BOTH FINE AND COARSE AGGREGATE PARTICLES WHICH COMPRISES PRIMING SAID AGGREGATE WITH A FIRST PORTION OF AN OIL-INWATER EMULSION, SAID EMULSION COMPRISING AN AQUEOUS PHASE HAVING DISSOLVED THEREIN FROM ABOUT 0.1% AND ABOUT 1% BY WEIGHT OF THE EMULSION OF A WATER SOLUBLE AMPHOTERIC METAL INORGANIC SALT AND FROM ABOUT 1% TO ABOUT 6% BY WEIGHT BASED ON THE EMULSION OF A MINERAL ACID, AND A HYDROCARBON PHASE HAVING DISSOLVED THEREIN FROM ABOUT 10% TO ABOUT 20% BASED ON THE WEIGHT OF THE EMULSION OF AN ALIPHATIC AMINO COMPOUND BEARING AT LEAST ONE LIPOPHILIC RADICAL PER MOLECULE, WHEREBY THE FINE AGGREGATE PARTICLES HAVING MAXIMUM DIAMETERS LESS THAN ABOUT 5 MM. ARE COATED WITH THE PRIMER AND THE COARSER PARTICLES ARE SUBSTANTIALLY UNAFFECTED; MIXING WITH THE PRIMED AGGREGATE BETWEEN ABOUT 3% TO ABOUT 7% BY WEIGHT, BASED ON THE AGGREGATE, OF A BITUMINOUS BINDER, WHEREBY THE FINE AGGREGATE PARTICLES ARE COATED THEREWITH WHILE THE COARSER AGGREGATE PARTICLES ARE SUBSTANTIALLY UNCOATED; ADMIXING A SECOND PORTION OF SAID PRIMING EMULSION, WHEREBY THE COARSE AGGREGATE PARTICLES ARE PRIMED THEREWITH; AND MIXING THE ENTIRE COMPOSITION, WHEREBY BOTH FINE AND COARSE AGGREGATE PARTICLES ARE COATED WITH THE BINDER; THE TOTAL PROPORTION OF AMINO COMPOUND BEING BETWEEN ABOUT 0.005% TO ABOUT 0.03% BASED ON THE WEIGHT OF THE AGGREGATE.