US1464482A - Bituminous concrete - Google Patents

Description

G. A. HENDERSON BITUMINOUS CONCRETE Filed March 29 1921 2 Sheets-Sheet 1 Aug. 7 1923.

G. A. HENDERSON BITUMINOUS CONCRETE;

Filed March 29. 1921 2 ShGtS-ShEGt 2 Patented tag. 7, 3923.

GEORGE ASA HENDERSON, or CHARLESTON, wusr vmemm.

BITUMINOUS CONCRETE.

Application filed March 29, 1921. Serial No. 456,563.

To all whom it my concern:

Be it known that I, GEORGE ASA HENDER- SON, a citizen of the United States of America, residing at Charleston, in the county of Kanawha and State of West Virginia, have invented new and useful Improvements in Bituminous Concrete, of which the following is a specification.

My invention relates to improvements in plastic compositions in which pitch (of petroleum or coal origin) or other plastic binder susceptible of becoming a fluid through the influence of applied heat, is used as the cementing agency of mineral or vegetable aggregate, and particularly to products known as bituminous concrete, produced by the mixin method as distinguished from the so-cal ed bituminous macadam produced by the penetration method known to the trade.

The object of my invention is to produce increased density of such products heretofore produced from artificial asphalts or pitch as distinguished from the so-called natural asphalts, such as that known to the-trade as Trinidad Lake asphalt cement.

I have descovered that the product known. as natural Trinidad Lake asphalt, containing as it does approximately forty per cent mineral matter in the form of impalpable dust more or less colloidally suspended in its bitumen content, is the product of asphaltic base petroleum from which through the agency of severe heat from volcanic eru tion the lighter oils were volatilized durin partial dehydration of the mass of aspha tic basepetroleum, containing a clay deposit composed of mineral dust and water,

by which natural operation the dust present in the deposit at the time was, by the action of evolved steam, acting as a carr ing agent, perfectly disseminated throug out the conglomerate in a state of col oidai dispersion. B tests of such natural itch as compared Wllihi tests of the so-called artieight (38) cms. at 77 degrees :Fahn, that the proportion of bitumen soluble in 76 deg. B. naphtha in the case of the artificlal product is 76.7%, while in the case of the natural product that proportion of total bitumen thus soluble is 68.21% on an average of many tests, while on fluxing tests of 100 parts of each, the so-called Ohio residuum in the case of the artificial roduct is nil as compared with 24 parts inthe case of such natural asphalt; that the natural product as compared with the artificial product is more susceptible to changes in temperature, is less.ductile and cementitious and of a lower degree of purity, more affected by the action of water, and, as compared with 100 sq. yds. of 2" asphaltic concrete structures to 2000 lbs. of the natural product, only 64 sq. yds. of 2" structure can be produced when using 2000 pounds of the so-called natural asphalt.

Accordingly I have discovered that while the bitumen content of the natural product is-inferior to that product of asphaltic base petroleum, containing 99.9% pure bitumen, in all essentials'.. to paving structures, for example, nevertheless before the advent of the present invention, such paving structures produced of the natural asphalts containing said impalpable dust in colloidal suspension in extent approximatel 40%, were and are superior to such pro nets of the purer so-called artificial asphalts, and

that this superiority is due solely to the combination of from 30% to 45% of impalpable dust content, so colloidally suspended inthe structure, and to no other cause or agency, viz:

In the prior art of producing paving structures and the like from mineral and other aggregates mixed with a bituminous compound, any excess over ten per cent of impalpable dust, (or that atomic matter that freely passes a 200 mesh sieve) is impracticable of agglomeration in any aggregate when mixed with a heavy bituminous binder (of approximately 50 penetration) as distinguished from a light oily lubricant, (of approximately 100 penetration) and as a, structures inherent strength is measurable by that of its components bound together, impalpable dust in excess of such ten per cent is prohibited in all United States and other standard specifications for bituminous concrete, (except those specifying the use of said Trinidad Lake asphalt) because it is known that no artificial means have been provided for separating each dust particle from its neighbor, in such a structure, by a sufficiently thin film of such heavy bituminous binder (as distinguished from a light o'ily lubricant) to avoid an excess of the binder itself in such structures.

' In carrying out my process as described in my application Serial No. 212,194, filed Jan. 15, 1918, (Patent No. l,370,815-Henderson) for Letters Patent of the United States and elsewhere of sucking from the interstices between the larger aggregate, and from the surface of a worn macad'am road, that dust thereof ground to impalpability by traffic and of incorporating that dust by mixing it in air suspension with the heavier aggregate in a closure under suction and sufficient sustainedheat, I have discovered that a considerable quantity of such dust is, by-that means alone, entrapped in the heavy mixing method' bituminous compound, with each particle thereof surrounded by such binder; but I have discovered at the same time that a greater quantityof-such dust can be so colloidally interposed in a paving aggregate, in fur-- therance of the present object of this invention, by the additional means hereinafter described in combination with the above described step of the process, viz:

In my United StatesPatent No. 1,187,314, of 1916, (application Serial No. 874,934 filed Nov. 30,1914) and improvements thereover cited in my coending application now filed herein this atent Office for fibrous compositions and process for making the same, I provide means for dehydrating a paving aggregate in the presence of molten bitumen, and in carrying out that process, in the manner described, therein, 1

have discovered that a considerable quantity of impalpable dust in excess of said erete, or that produced by the so-called mixing method, is treated in the manner herein described, by which its fluidity is increased far beyond that possible by the mere agency of applied heat heretofore used exclusively for this purpose, provided such fluidity is of a temporary character, existing only during such mixing operation, without interfering with the consistency of a relatively hard nature of. the bituminous compound, as tested for penetration, in the final product. 7

My invention will be best understood by reference to the accompanying drawing which will now be described, it being premised, however, that various changes may be made in the apparatus by which the process is carried out without departing from the scope of the invention as defined in the appended claims.

Fig. l of the drawings is a view partly in side elevation and partly in vertical section of theapparatus adapted for carrying out the invention, and Fig. 2 is a cross sectional view of the apparatus taken on "the line 2-2 of Fig. 1, showing the shafts and driving gears for the agitators in-the hoppers and tank.

Fig. 3, is a sectional view, taken on line 33 of Fig. 1.

Fig. 4 is a sectional view, taken'on line 4-4 of Fig. 1.

Supported on I-beams constituting the frame work of the machine, rests a bitumen storage tank N, braced internally with the members N N 3 also surrounding externally impregnating drum 0 rigidly anchored within the lines of tank N relatively near its bottom. Tank N is charged/with bitumen preliminarily heated from an auxiliary supply thereof in heaters not shown, by the operation of pump N forcing such heated bitumen into tank N thru inlet vent N. In tank N this bitumen is maintained at the proper temperature, approximately 325 F., by means of steam pipes N connected with boiler Q in which water is heated to produce the steam, by flues Q. The steam from the boiler Q is conducted through pipe Q which pipe enters tank N just above the drum 0 and to the side of conveyor L and extends and empties into manifold Q connected with pipes N and with manifold Q, as shown. Surrounding drum 0. the heated bitumen tends to heat, indirectly, the contents of drum (l, during the carryin out of the process. .Bitumen outlet cock 9 is manually opened, when tank N is to be emptied of its supply of bitumen, for any purpose. \Vhen approximately two-thirds full of the heated bitumen, the pump N connection with the auxiliary supply is disconnected, and connected with influx suction pipe N the pump actingto lift the heated bitumen from the bottom of tank N 'on one side of drum 0, and to move it up and through bitumen supply cock N;\*, and down through pipe N to the reverse sideof drum 0 in tank N at the top of the bitumen supply therein. thus providing a continuous agitation of the heating bitumen in tank N, and to afford ready access ofthe molten bitumen to the scale bucket E hereinafter described.

Vegetable particles ofthe character denatured in accord with the process described in my United States Patent No. 1,187,314 for fibrous compositions and processesfor making the same, are elevated by conveyor B to bins therefor provided, such as C. In the case of vegetable aggregate, the same is preliminarily dried to a residual moisture content of approximately 20%, that moisture residing at this stage of the process within the innermost pores of the vegetable particles. In the case of the mineral aggregate, the same shall contain atmospherically absorbed moisture, and in both cases the aggregate is so handled at this stage of the process, when it is of atmospheric temperature, and unheated otherwise. v

Mineral or other dust of impalpability is elevated via conveyor K to the bins R and R respectively, from a supply of such dust preliminarily provided at the base of the machine. This dust is of atmospheric temperature at this stage of the process, and may contain atmospherically absorbed moisture.

Before placing the premelted bitumen in tank N the furnace QF' to boiler Q, preferably-equipped with fuel oil burners. is operated by the lighting of the fuel supply, and motive power X, of any approved make or construction, shall operate in operate the moving. members of the apparatus. viz: The revolution of driving shaft X acts thru the cogs shown to revolve the drum 0' central shaft 0' suitably hung in proper bearings and as shown, and to revolve side longitudinal shaft X in turn acting to operate thru pulley Xhbelts X and X exhauster X P thru pulley connection X pulley X, with connection to ump driving pulley X", cog X with connection X to pug mixers cog KJ acting to reciprocally operate cogs K, K and J and Jf, carrying interdigit-ating blades in the pug mixers and J, designed to mix the ingredients the-reinto deposited in the manner hereinafter described; cog X, revolving, by the connections shown, screw conveyor L, pulley and connections X and X to operate the revolving shaft, with agitating blades in dust and water mixer R at pulley 11", and to revolve gate valve R from the bin R supplied with dust thru measuring scale bins R to be deposited, thru. chute R, inthe manner hereinafter described.

The operation of exhauster P acts in lieu of a stack to the furnace of boiler Q, to cause a draft of the hot air together with the products of combustion from said furnace, thru the flues of the furnace Q, all emptying into dust chamber R, and thence thru the drum 0 from the point 0 to the dis charge chamber N at the point and out of the stack as shown. I

The exact temperature of the drum 0, and its contents, is fixed by (a) the temperature of the bitumen in tank N, regulated by the relative degree of heat supplied to steam pipes N, and (b) by the directheat to said drum 0' contents from the furnace, sucked .therethru by the exhauster P. At the point marked R is provided an air inlet valve, manually operated, to cause an influx of air of atmospheric temperature from the outside, into dust chamber R, where, being mixed in the desired proportion with the hot air sucked thereinto from the furnace in the manner described, the temperature of the hot air-to drum 0 is thus fixed at suflicient merely to raise the temperature of the mass in drum 0 at 250 deg. Fahn, as registered by approved thermometer stationed in the wall of the drum within sight of the operator.

Two operators are roposed to be stationed on working lat orm V, one on either side of the pug mixers K and J, shown in the drawing. In charging the machine, which operates to discharge the material prepared in accord with this process, in a continuous flow thru discharge chamber N at the screw conveyor to the atmosphere, operator No. 1 opens cock N to discharge a pre-determined quantity of bituminous compound from tank N thru said cock into weigh bucket E equipped with scale beam, designed to travel on trolley D by being manually pushed by the operator back and forth for the purpose of discharging. when the proper quantity of said bituminous compound has been measured thereinto,'-*approximately one-half of said charge into pug mixer J and one half into pug mixer K. Simultaneously a predetermined quantity of the larger mineral or vegetable aggregate, or the two mixed together, containing residual moisture and. of atmospheric temperature, is by the manipulation of lever D deposited into weigh bin D, pivoted and hung by the member D on trolley D in such a manner that the same may be, when the locking device, not shown, is released by the operator, tilted to discharge the contents of measuring bin D into pug mixer J to be therein mixed by revolving inte-rdigitating blades with the moltenbitumen therein contained. Simultaneouslyoperator No. 2 discharges, after measuring predetermined quantities of dust of impalpability, from bins R- and R into weigh-bins, equipped with scale beams, R approximately one-half of the designed proportion into mixer R" while simultaneously depositing therein water th'ru cock W, in quantity suflicient to produce a plastic composition of dust and water, which, being agitated sufliciently in'mixer R by the revolution of its shaft R, carrying agitating blades in the mixer, not shown,

- permeates and completely coats each atom of the dust with the water. The other halfof the said dust charge is, simultaneously with the above operation deposited by operator No. 2 into chamber R from which chamber it is designed, by gravity, to fall into one of the four compartments of gate valve R, revolved at 20% of 1 R. P. M. to deposit within dust chute R one-half of the aforesaid dust charge within five minutes time. This dust is precipitated, gradually, by gravity, into dust chamber R, and is in said dust chamber constantly lifted by the spoon shaped agitating blades R and dropped "ertically therein, until all of that dust is, in air suspension, sucked in a heated condition, with the hot air and 'fumes from the furnace, directed into said dust chamber through the end of the boiler Q fines emptying thereinto, through said dust chamber and into drum 0 in a continuous flow, to be thereentrapped by its adhering to the revolving blades 0 anchored. to central shaft 0' in drum 0, and by the larger aggregate being therein manipulated in the manner hereinafter described.

- In case there exists in the dust precipitated into chamber R, any particles too heavy or large to be carried in said air suspension to drum 0, these are accumulated at the bottom of chamber R, from whence they are manually removed from time to time, by the instant opening and closing of sliding gate R, precipitating them to chamber R from which they are removed and discarded at the end of each day, or oftene-r if need be, manually. I

The apparatus is designed to operate automatically to the extent of providing the proper proportion of the ingredients through the measuring devices, above described, to the pug mixers, and otherwise, to provide for'the continuous operation of the various units of the ap aratus reciprocally, as for example: The dirum 0, when of a fixed capacity of 1000 sq. yds. of 1% paving compacted in place per 8-hour day, of weight 100 pounds to the sq. yd. of finished product, is constructed of volume capacity to manipulate within five minutes and to discharge within that time through 12 feet of its length 1000 pounds of the material by the revolution of central shaft 0, carrying 36 agitating blades 0 of dimensions 6" at greatest (end) width'tapering to 2" at the shaft-sleeve is fixed at 14 R. P. M., it being discovered by me that when set as shown in the drawing, these blades have a play each of 4" of the longitudinal length of said drum, and the material is moved by each blade 2" instead of four inches at each stroke, by reason of the tendency of approximately half of .the material dropping vertically, and not being moved longitudinally more than 50% of the effective capacity of the blades ends. When for example such material is mixed in the proportions, viz, containing in the final product in pounds and by per cent weight, sulfochlorinated bitumen 22, denatured wood particles 12.5, broken stone 52.2 and keiselguhr 13, (gwhen the respective weights of said ingre ients are as follows: Bituminous compound, per cu. ft. vol. cold, lbs, keiselguhr per cu. ft., uncompacted, 15 lbs.,. dry wood fiber, uncompacted, uncontracted,-. per cu. ft. 10 lbs, and stone per cu. ft, of sizes 1" to 11, 100 lbs), 1000 pounds of the aggregate on the basis of the final product, with proper allowance being made for the initial moisture content at beginning of the operation, shall be weighed and manipulated through the aforesaid pug mixers, leading through screw conveyor L to drum 0 in a continuous flow per five minutes of the plants operation, viz:

The mixers K and J simultaneously mix for not exceeding one minute the proper proportions of the materials,v deposited therein in the manner aforesaid. In mixer J, the residuaLmoisture content of the aggregate reduces the temperature of the bitumen from approximately 325 tn 250deg. at which it is deposited in the mixer J, in combination with the cooling influence of the said aggregate of atmospheric temperature, to a degree that results in the temperature of the mixture, within one minute in said mixer J being approximately 175 deg. F., or under that temperature at which the moisture within the pores of the wood or of the stone becomes steam. However, in mixer K, where the dust mixed with water inthe form of clay is deposited with 325 deg. Fahr. bitumen, in the proportions above given (with consideration given to the fact that but one-half of the proposed charge of dust passes thru this mixer, the

other half going to the dust chamber for manipulation in air suspension in the mass later) steam is evolved (which as pericommon knowledgelis approximately 1600 times the volume of the moisture from which it is evolved) with the result that in mixer K, the volume as deposited therein is increased, by ebullition, the steam acting as a carrying agent of the fine dust, to approximately ten times that of the cold paste therein deposited. whereupon, within the space of one minute, both mixers K and F, by manually openin of their bottoms thru the use of lever xJ', dump their contents simultaneously by gravity to within chamber L, from which they are precipitated by gravity thru common open gate onto screw conveyor L which operates to move from the chamber L its entire contents to the drum 0, at the point L within the aforesaid five minutes, the shaft revolved by the cogged connection X-M being fixed at the proper revolution per minute to accomplish this result. This operation being repeated through the batch mixers, as described, every five minutes, there is provided a continuous flow of measured mixed material into drum 0 during the entire time of its operation.

The fumes and vapors from chamber L are sucked out of that chamber and discharged to the atmosphere by the action of exhauster P acting thru outlet pipe L as shown. The fumes and vapors from the bitumen storage and heating tank N, are likewise removedtherefrom by suction of exhauster P by its action in connection with outlet pipe 5 as shown. I

It Wlll be noted that the agitators 0 are designed to be so set on central shaft 0 as to forma perfect screw, to move the material within drum 0 from its front to discharge chamber into which it d10ps*by gravity onto cross screw conveyor 0 stationed at its bottom, and revolved at fixed R. P. M.

b the machines motive power, to discharge t e mixed material either into trucks, not shown, for carting to the previously prepared road base, and thereon spread and compacted, or into molds for the manufacture ofthe product in block form, or otherwise used as hereinafter specified.

The complete dehydration of the mixture is accomplished in theimpregnating drmn 0, it being designed that when therein subjected to the provided suction, shown, under the fixed degreeof sufficient heat,- sufficiently sustained, for the purpose, a thoroughly dry product, in the common acceptation of the term, is produced of initially wet material.

The fluidity, durin mixing, of the bitu minous compound, I produce in thefollowin manner: (a) By mixir. with the aspha tic product of asphaltic base petro leum or pitch, from 6 to 14% of sulfur,

and one-half of 1% of sulphate of copper, and relying on the partial volatilization of the oily constituent, under the influence of heat, to entrap the sulfur and its components within the bituminous compound,

and then adding, to the sulfuretted bitumenv I in the impregnating drum, chlorine by injecting the same, in the form of chlorine gas, in measured quantities, thru dust chamer' R, from a tube containing chlorine therefor provided. I have discovered that and vegetable aggregates for paving, flooring and such purposes, a product of greater cementing qualities, of greater ductility, and

less aifectable by atmospheric temperature changes, than any other such structure of which I have knowledge. Due to the fact that it is the chemical action of the entrapped sulfur and' chloride on the bituminous compound, affecting, in actually vulcanizing, the entire structure, that results in its ductility aforesaid, it is notewortiig that this chemical agency is not volatiliz and lost in time to the atmosphere as is the oily constituent of such bitumens heretofore relied on for continued life of the bituminous ingredient of paving, flooring, insulation, roofing and such products.

In a modified procedure in this regard, I take the fumes of heated sulfur and copper sulfate and pass them by said suction from their source, in the furnace proper, thru the dust chamber to the drum, and in the dust chamber I inject chlorine as, which immediately marries with the su fur product producing sulfur chloride, which in turn mixes, under the influence of such suction in the drum with the bitumen and aggregate while the same is being dehydrated,

producing hydrated sulfo-chlorinated bitumen, during the process of completely dehydrating the aggregate by the removal in the said drum, in the manner above described, .of its residual moisture content, under sufficient heat and suction, and I have discovered that this condition results in thetemporary extreme fluidity of the heavy bituminous compound, only during dehydration thereof, required for its perfect agglomeration, entrapping in true colloidal act apparatus as shown in the drawing illustrating the process; nor to the product of bituminous concrete in sheet and block form hereinabove descri ed, but, after the material is prepared i the manner above described, it may be spread, from the machine of a portable nature as the machine is drawn, over the surface of a worn macadam road, for example, reliance on the machine itself being in thi instance had to accomplish the following results: In lieu of the boiler, and furnace described and shown in the drawing herewith, the furnace of the apparatus mayc'onsist of two steel sides supported on elliptical springs anchored between the sides and the bottom of bitumen storage tank N, the lower edges of Which,

metal of the road. Immediately following. this roller, and within the zone of the aforesaid two sides, (which act to retain in said furnace all supplied heat, without lateral suction of cold .air from the outside) are provided tynes extending approximately 8 feet in width of the roadway under treatment, which act toiscarify the broken road 1 surface to a depth of approximately 2% thereof. Immediately following these tynes,

-,ward and down onto the roads surface approximately 1500 cu. ft. of hot air and flame mixed, per minute. This blast acts to blow out of the loosened interstices of the old roads stone, scarified, all dust and to heat the stone remaining on the road. This dust together with theproducts of the fuel oil combustion, is sucked up through two large flues, extending from the dust chamber R, shown in the drawing, through its bottom, to their opening over the roadway, the furnace above referred to-being composed as follows: its bottom. is[the roads surface; its top is the bottom ofthe bitumen storage tank, and its sides are provided as hereinabove described. No part of the weight of the machine rests on the aforesaid sides, the rear of the machine being supported on two side wheels and the front by the aforesaid roller wheel above described. w

The dust thus removed from the interstices of the heated stone on the roadway,

is sucked into drum 0 shown in the draw ing after being mixed. in said dust chamured quantity, as above described, and mixed sections are with the new aggregate specification described.

At the rear end of the aforesaid furnace is rovided bitumen penetration nozzles, pre erably of the rotary type, supplied with bitumen from an auxiliary supply in a tank on motor driven truck acting as a traction unit of the entire plant, and, under pres sure, being conducted thru a supply pipe from said truck back through the top of said furnace to the aforesaid nozzles, manually operated by an operator stationed there, todeposit, and force within the dust cleared, loose heated stone of the roadway, an adequate quantity of preheated bitumen suflicicnt to coatsaid mineral aggregate on the road during turning of the same, by

prepared as in this tynes placed within the radius of the effecin the'absence of dust, until the larger stonev remaining on the roadway shows on its surface a mosaic-like appearance.

In this manner I produce a 2" to 2-} bituminous concrete wearing surface of mixed material, by-the use of approximately 25% of new material added to the old, in approximate situ.

' In cases where the width of the roadway is in excess of eight feet, two lateral in the above manner constructed, a temporary 'steel curbing being spiked to the old surface in its center, and upon final rolling of the last section constructed, this curb is removed, and the space (about 4 inches) between the two sections, is filled with the new material, and rolling continued until no joint appears between the two.

It will be notedthatthe entire depth of approximately 29; of this structure is prepared while all of the ingredients forming it are hot, and that no dust is present to interfere with penetration of the bitumen thru the nozzles, into the open interstices of the roads stone during this part of the operation. I

The above modification of the present n'ocess to correct the conditions in this regard present inmthe .prionart, viz: It is known that a light oily liquid (known as road' oil) will penetrate a cold road aggregate, and the dust on its surface. as well as,that dust leached, in time, to and within the interstices of such an old road, by permeating it, as would a'similar liquid such as water; but that such a heavy bituminous binder as that standardized for the mixing method (as distinguished from such road oil, dust layer, or lubricant, both known to the trade and prior art) will mat on the top producing paving structures, and merely acts as a lubricant, or temporary dust-layer to be renewed annually, to form a built-up structure of inferior-lasting quality to that herein proposed.

I claim:

1. The process of manufacturing a bituminous composition, consisting in preheating, while agitating, 'a relatively hard bituminous cement to a temperature of approximately 325 deg. F ahr. then preparing by wetting and comminuting a fibrous vegetable aggregate and then removing therefrom a portion of its water content; then depositing the fibrous material, when at atmospheric temperature and containing its residual moisture into a mixer eqluipped with revolving interdigitating b ades containing the heated bitumen during agitation of the mass therein to reduce the temperature of the bitumen and of the mass to approximately 17 5fdeg. Eahr.;'then subjecting the .mass during contlfiued agitation thereof, to

sufficient heat, sufliciently sustained for the purpose of raising the temperature of the mass to a degree above the boiling point of water, to cause ebullition of the mass by the creation therein of steam from the residual moisture, to act.as a carryin agent of the ingredients, and to separate t e fibers from each other during said agitation of the mass, and continuing. the operation under sustained heat sufficient to produce a thoroughly dry product from the initially wet material; then compacting the same in molds to shape, substantially as described.

2. The process of producing a bituminous conglomerate, the inherent density of which is characterized by colloidal dispersion of mineral dust and vegetable fibers uniformly throughout its mass, consisting in depositing comminuted fibrous vegetable .material containin in excess of 20% moisture and truly coll hidal -keiselguhr, (an impalpable silica so finelydivided as to form atomic matter all of which freely passes a 200 mesh sieve) at atmospheric temperature in a mixer equipped with} revolving interdigitating blades, containing a predetermined proportion of bitumenpreheated to a temperature above 325 deg. Fahr., and subjecting the mass therein to sufficient heat sufficiently sustained, during continuous agitationof the mass, to colloidally disperse the fibers and mineral dust throughout the bitumen during complete dehydration of the mass; then removing the mass from the mixer while hot and compacting the same in molds to shape, substantially as described.

3... The process of producing a fibrous composition for insulation, roofing, paving and other purposes, consisting in introducing into a mixer to preheated bitumen,- moist fibrous material and truly colloidal dust, all passing a 200 mesh sieve, at atmospheric temperature, in proportions of each predetermined and mechanically fixedby measuring devices at the mixer; then subjecting the mass to sufficient heat, sufliciently sustained, to cause ebullition of the mass during continuous kneadin of the same by revolving interdigitating blades until, during the process of complete dehydration of the mass, the fibrous material and filler-dust are in a state of colloidal, dispersion within the bitumen constituting the continuous phase of a thoroughly dry product of initially wet material, substantially as described.

4. The process of producing a dense bituminous composition consisting in reducing a relatively hard bituminous cement to fluidity by heat in the presence of steam acting as its carrying agent while separating, during mechanical agitation of, moist vegetable fibers in the presence of the bitumen in a mixer equipped with revolving interdigitating blades; then cooling the mass to a temperature below the boiling point of water; then reheating the mass in said mixer, subjecting it to sustained heat sufiicient in degree and duration to raise the temperature of the mass to approximately 250 deg.Fahr., during dehydration of the mass required for its perfect agglomeration and entrapping in truly colloidal suspension of from 20 to 45 of added impalpable dust in sizes that all of the particles thereof shall pass a 200 mesh sieve, in the final product by the process of forming steam of the residual moisture in the agitated material; then aggregate throughout, the bitumen acting as the continuous phase of the conglomerate while separating the fibers and dust therein in a state ofcolloidal dispersion, then tilting the mixer to discharge its contents into molds, and then compactlng the same therein to shape substantially as described.

6. A bituminous fibrous composition consisting of hard bituminous cement, fibrous material and in excess vof 40% mineral dust all articles of which are sufiiciently divided to reely pass a 200 mesh sieve, colloidally suspended in the relatively hard bituminous cement which has a ductility over 60 cms. at 77 deg. Fahn, acting as the impregnating coating and binding agent of and as the continuous phase in coloidal dispersion of the separated fibers which reinforces the mass.

'at 77 deg. Fahr., and colloidally suspending keiselguhr in particles all passing a 200 mesh sieve, and acting as the continuous phase in colloidal dispersion of the vegetable fibers. v

I In witness whereof I have hereunto set my hand in the presence of two witnesses this sixteenth day of October, 1920.

I GEORGE ASA HENDERSON. Witnesses:

J. H. DUNLAP,- W. A. BURGESS.

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