US1911761A - Method of preparing bituminous road surfacing materials - Google Patents

Description

y 1933- F. o. w. Looms ET AL ,91 ,761

METHOD OF PREPARING BITUMINOUS ROAD SURFACING MATERIALS Filed June 5, 1931 WWWWp.

INVENTORS FREDERICK.0.W.LOOMIS DANIEL.M.LOOMI$ BY 3% ATTORNEY l atented May 30, 1933 units stares rREiiERIcK osoAR WARREN LOOMIS AND zoAmnnmacxaY LOOMIS, or mou'rmiug e QUEBEC, CANADA Emmi) F, PREPARING iar'ruminous moe i vi This'invention relates to the preparation of ro'ad surfacing materials and particularlyto the coating and mixing of the mineral partieles'of the aggregate.-

T preparing road surfacing materials in accordance with-prevailing methods wherein the bitumen is used in the form of a wateryemulsi'on; the-crushed stone or similar aggregateis initiallyplaced in a mixer anda gi tated to efi'ect the desired distribution of the particles of varying sizes. The bituminous emulsion is'then'added and the mixing op eration'continued to distribute the bitumen. The'mixing is usually carried out in a pug mill or similar mixer equipped with revolv ing blades or in a revolvin drum which may or'ma'y-not be equipped with mixing blades. Genemny speaking, these and similar methods ofmixing now in use arenot suitably adap'te'dto the use of bituminous emul-" si'o'nsiand do not produce satisfactory'resultsP When a pug mill or bladed mixer is used the pugging-jor blading action causes ail-immediate breaking down of the emulsion. whichint'erfe'res with proper distribution of thebit-umen and produces a dry appearing mix of unsatisfactory characteristics. In some instances the line particles of the aggregate may absorb and break down the emulsion by capillary action and this also produces a detective dry appearing mix containin balls of bitumen. In other instances wlgere the aggregate used is of a composite nature, including, for example, coarse particles of crushed stone and line particles of sand, there is a differential selection by the bitumen which generally leaves the sand uncoated. In an effort to avoid these difiiculties'it has been a practice to leave out the fines and to carry out the mixing operation in a rotary drum without the use of mixing blades. This produces a defective mix in thatthe coating of bitumen covering the mineral particles lacks stability and adhesiveness.

The improved method provided in accordance with this invention overcomes these difficulties and enable bituminous emulsions to be successfully used in the production of a 50 satisfactory mix in which the bitumen is unif IApphfcati on fi1ed .l'une 3, 1931,"Seria1 N 5. 54 11537? and iii magnet 54, ies'il formly distributed over the surfaces of the. coated particles and possesses" the' desired qualifications with respect to "stability" and In accordance {winters iire'ferred mthod of carrying ib t ithe' iiivenfion "the aggregate is' initially separated into Genet and t e particles; the besistastier-r teseparation iscanaied but being dependent upbntli n a' tu're ofthe aggi ate and the' ty'pe of mix to (so be produced EA tertheseparatioii theooarse particle's ai fed 1 at 1 a uniform rate into a revolving -'d'riim' preferably, equipped with suitable 'lilades arranged so that the tense? particles are given arolliii "and rota I shown diagrammatically in accompanying drawing fwherein Figure 1 is aview of the apparatus in side elevation, a part of themixing drum being broken away to disclose themeans provided for spraying the bituminous emulsion and the finer particles ofthe' aggregate onto the coarser particles/ v Y Figure 2 is a transverse sectional view through the mixing drum illustrating diagrammatically the manner in Whichthe bi- 9o tuminous emulsion is sprayed 'onto the coarse particles of the a gregate. In-this view the means provided %or spraying the" finer 'particles of the aggregate are omitted.

Figure 3 is a cross sectional View through the drum illustrating the manner in which the finer particles of the aggregate are sprayed onto the coated coarse particles;

The initial separation of the aggregate v may be regulated to give any desired ratio :to

of coarse to fine particles. Generally speaking, the separation should yield 70% to 90% of the aggregate as coarse particles and the remainder as fines. In one instance the aggregate used consisted of all sizes of parint." This aggregate was separated; .into

coarse particles of a size exceeding 4. tin? and fine particles of a size less than A in.

This basis'bfs'epalation usually affords 75% to 80% coarse particles and 157 .,When,nsing anuapparatus such as shown inQthe present drawing the coarse particles resulting from. the initial separation are placed in a storage bin 5 equipped with a 29-. discharge controlling gate 6. whilethe fine particles are placed in -a similar. discharge bin-.7; equipped witha controlling gate 8; The coarse particles are delivered from thebin; 5 ,tothe hopper 10 of a mechanical ;,feieder }whieh is herein .shown as .including anendless conveyor 11 driven by a belt connection 12 fromamain drive shaft 13. The conveyor 11 functions. to v deliver the coarse particles, at a uniform rate, to the feed hop- 0 per:14;of a revolving drum 15 ,whichis preferably equippedwithmixing blades .16. As herein .shown .the drum is provided with annular track members 17 mounted on supporting rollers 18 so that the drum has a ,-.slight downward inclination towards 1 the discharge opening which is located at the end remote from the feed hopper 14. The drum supporting rollers ;18 are carried by suitableshafts l9 and oneor both of these 4o shaftsfmay 'be driven from a motor 20 through any suitable form of gearing such as that indicatedat 21. During rotation of the drum the coarse particles progress towards the discharge end by a spiral motion in the, course of which the various surfaces of the particles are exposed to the action of the spraying devices 22 which are supplied with bituminous emulsion through a supplyfpipe 23 connected to the discharge side of a suitable pump 24 which is also driven by a belt 25 from the main drive shaft 13. The pump is equipped with an intake pipe 24a and a funnel 246. The bitumen is delivered to the funnel through 5 a supply pipe 240 equipped with a valve 24d the, apparatus.

from the bin 7 into a feed hopper 26 and from thence onto the receiving end of a belt conveyor 27 having its discharge end located within the drum 15. The conveyor 27 delivers the fine particles through a chute 28 into t e. path. of .a blast of air coming from an. air nozzle 29 ,connected to the discharge side of a blower 30 which is driven by a belt "connection 31 from the main drive shaft 13. From-i'the disclosures; of Figures ll and' 3' *it' will be noted that the fine particles are sprayed onto the coarse articlesafter the lattr have 'beenpassed" 'eneaththe spray devices 22,and coated ,with the bituminous emulsion." After" the spraying' ofthe finer particles the resulting; mix issubjected to a fewrevolutions of the drum. before passing outwardly thro ugh the discharge opening; at the lower endof-the drum, Tl1 e..conveyor 27. is driven from the shaft l3 through the be t se n e e i 3. a e -sea e 1131 4.

and .35..

. Wh aia ngiaea i 11 ftens i afa l 19f Zips-in length is 'i'evolved at. a speed :of approximately.

revolutions per minute the c oarse. particles will traverse the lengthofthedrum in about. 1 mins. Such a drum 1 will handle from 8 to 12tons.of;coarse particles per hour; When using a drum of this character the bituminous emulsion is, usually pum'ped or otherwise supplied; to the; spray nozzles 22 ata uniform rate of about- 8Q to 1 2O1g allons per. hour.

such asemployed in connection with paint sprays or may be simply fprced through the nozzlev openings by'pressure gas in the case of water spray nozzles. Generally speaking,

it is advisable to provide a number of: re

atively small sprays 22 in preferencegto a single large spray since this enables the sprays to be distributed over a greater area and insures that each coarse particle is com-- ening the coarse or line particles-with water before feeding the same into the drum may be resorted to in order to eliminate differential selection by the bituminous emulsion and to ensure uniform coating of all particles.

The method of operation described in the foregoing may be readily altered or controlled to adapt the same to the use of p The emulsion may-be, sprayedthr ough the nozzles: by the use ofiair or steam The finer particles of the aggre gate are preferably delivered into the mix sermondifi'erent aggregates and bituminous emulsions and to produce various types of finished mixes. For example, bituminous emulsions which are very sensitive to vibrations may be used by reducing the speed of the drum Whereas the breaking down of more stable emulsions after contact with the coarse particles may be readily accomplished ticles in place thereon.

by accelerating the speed of the drum. Uniform distribution of the bitumen and fine particles in the mix may be obtained by regulating the sprays.

By completely eliminating the fine particles of the aggregate and treating the coarse particles with kerosene or oil, either separately or combined or accompanied by fine material such as hydrated lime, stone dust, etc., before spraying the coarser particles with the bituminous emulsion, a fairly satisfactory material is also produced in accordance with this invention. This material may be improved by steaming the same after the application of the bituminous emulsion. Kerosene, oils or other substances may also be added to the bituminous emulsion before the latter is sprayed onto the coarser particles in order to ensure satisfactory results when the coarse particles are porous or dirty. When the aggregate consists of glassy and dust free stone satisfactory results have been obtained by merely directing streams of bitumen onto the particles instead of employing the sprays previously described since, in this case, the fine spraying of the bitumen is not always necessary.

From the foregoing it will be apparent that the method described herein comprises the following essential steps: (1) separating the aggregate into coarse and fine particles; (2) uniformly coating the coarse particles with bitumen preferably applied in the form of a spray; and (3) spraying the coated coarse particles with the fine particles to retain the bitumen coating of the coarse par- In this process the dividing point between the coarse and fine particles of the aggregate is predetermined so that none of the coarse particles are fine enough to cause the bitumen to congeal, set or break when sprayed thereon. At the same time these coarse particles are small enough to prevent undue running off of the bitumen from the surfaces to which it is applied. The distribution and atomization of the sprays is regulated so that the coarse particles are provided with a uniform bitumen coating of the required thickness. Atomization of the bitumen may be effected by placing the bitumen under the required pressure or by the use of compressed air, steam or any other means capable of close regulation. By suitably regulating the spraying of the fine particles of the aggregate it is possible to congeal,

s'tlt, or; :breakithe, bitumen or .bituminoius emulsion :j ust: sufficiently topreserve the uniformityof;the finishedimixiwithout destroy ing the plasticity necessary messy transportatiomandjlayingiof'tlie-mixn -.T!i"f Having thus described our invention,- whatawezclaimiisrf 1. A methodino'fapreparing' bituminous road surfacing materials which comprises applying a coating of bituminous emulsion to coarse aggregate particles of such size as to prevent breaking or excessive running off of the emulsion when applied to said particles and then applying fines to the bituminous coatings of the coarse particles with sufficient impact to cause the bitumen of the emulsion to separate out and adhere to the coarse particles.

2. A method of preparing bituminous road surfacing materials which comprises (1) coating coarse particles of an aggregate with a bituminous emulsion applied in the form of a spray while subjecting the particles to gentle agitation suflicient to cause all surfaces of the particles to be exposed to the coating action of the spray, the size of said particles being predetermined to prevent breaking or excessive running off of the emulsion as it is applied to said particles and (2) then subjecting the coated coarse particles to a spray of finer particles directed thereon with sufiicient force to break down the emulsion by impact so that the bitumen of the emulsion is caused to separate out and adhere to the coarse particles to provide the latter with a uniform bitumen coating stabilized by incorporation of the fine particles therein.

3. A method of preparing bituminous road surfacing materials which comprises (1) separating from an aggregate the finer particles which would tend to break down a bituminous emulsion applied to said aggregate (2) coating the remaining coarse particles of the aggregate with a bituminous emulsion and (3) applying the finer aggregate particles of the initial separation to the coated coarse particles with sufiicient impact to cause the bitumen of the emulsion to separate out and adhere to the coarse particles.

4. A method of preparing bituminous road surfacing materials which comprises (1) removing from an aggregate the finer particles which would tend to break down a bituminous emulsion applied to said aggregate (2) coating the remaining coarse particles of the aggregate with a bituminous emulsion applied in the form of a spray while subjecting said particles to gentle agitation sufficient to cause all surfaces of the particles to be exposed to the coating action of the spray and (3) then spraying the finer aggregate particles of the initial separation onto the"dated'coars?pai-ticles"wivith siifli v cient impact to caus the bitumdm 'of thw j emulsion tos'eparate'dut and adhere fid=th I coarseparticles. 1' 11 In Witness whereofiwehave 'lie're'unto Setoun handsi FREDERICK 05cm :wAknzul nbomsp v. i DANIEL MACKAY- Lo'omx s.-..-:

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