Paving Asphalt from California Crude Oil A
troleum asphalt exclusive of road oils had risen to 8,000,000 tone, almost ten times the quantity of natural hard bitumens used ( 2 7 ) . Of this figure only about 20y0was produced on the Vest Coast. I n spite of the important part played by California eludes in introducing petroleum asphalt to the paving market, the major expansion of asphalt production has been in the East. This is largely attributable to the fact that by far the greater part of the paving grade asphalt has been and still is consumed in the East. In past years so-called Mexican asphalt made from highly asphaltic Mexican crude supplied much of this eastern market, but with the introduction of asphaltic and semiasphaltic Wyoming, Arkansas, and west Texas crudes the supply of domestic asphaltic residuum has become more than adequate. At the present time only about 30y0 of the straight-run petroleum residua is actually processed into solid or semisolid asphalts. The remainder is cracked down to petroleum coke or sold as cheap "black" fuel oil, because of an insufficient market for asphalt.
SPHALT is one of the oldest and most widely used materials of engineering construction. I n about 3800 B.C. preBabylonian peoples in the Euphrates valley were using natural asphalts to waterproof wicker boats and as an adhesive ( 1 4 ) and a few centuries later it first found use in building construction and floor surfacing (15). However, about the beginning of the Christian era the material fell into disuse and it was not until 1852 that the first modern asphalt road was constructed in France ( 1 ) . Eighteen years later the first such roadway in the United States was laid in front of the City Hall in Newark, N. J. ( 2 ) . Although the innovation was a success, the demand for hard-surfaced roads at that time was slight and i t was not until the era of extensive rural paving in the early 1920's that American asphalt production experienced a large scale expansion to the rate of 1,000,000 tons per year. The Pennsylvania, Ohio, and Indiana fields which furnished crude for the first refineries in the United States produced a paraffin-type oil which yielded only a small quantity of liquid asphaltic residue, and this Tas not suitable for paving application. Consequently, Trinidad natural asphalt was used almost exclusively for early asphalt paving in this country. The discovery of oil in California late in the 19th century, however, made available a crude from which semisolid and solid residual asphalts could be obtained and by 1902, 20,000 tons of petroleum asphalt reached the paving material market. Within ten years the production of the petroleum product exceeded importations of natural hard bitumens ( 8 ) . By 1946 the consumption of pe-
ASPHALTIC PAYING
Petroleum asphalt is now unquestionably the principal paving material in most parts of the country. Asphalt Institute figures show that as of January 1, 1945, there were 216,309 miles of bituminous surfaced highways in the state and national highway networks as against 87,064 miles of cement surface. This predominance of asphaltic pavements is rapidly increasing. In 1937, 80% of the new highway construction was bituminous. By 1939 the percentage had increased to 867,. In 1945, 10,743 miles of
Schematic Flow Sheet of Asphalt nfanufacturing Process
548
A Staff-Industry
Collaborative Report. M. L. KASTENS,
a
Associate Editor
In collaborationwith
CALIFORNIA ASPHALT CORPORATION AND CALIFORNIA RESEARCH CORPORATION
new bituminous ro* were constructed compared to 369 miles in mncrete-ahcat %yoin asphalt, T b i s p ~ m i n e n c e i s a t r i b u t e to asphalt's B B B ~and economy of construction and maintenance and -tional performance. Army tests during the recent indicat.4 thst automobile tires last 4 to 5% longer on 88. p W m concrete highways W). hsphsltie produets are also Gnding increased application in nonpvbg we.. b 6 n g compounds of various typee account for aS to 30% of ssphalt production-less than half the amount used for p v b g but large compared to other minor mea. Nalural ssphalts 818 consumed in large quaotitiee by aranufncturen, of Boor coverings and lithographic inks. Manufacturers of laminaupsperproducteand manuIactureraofmolddproducts mch ra battery boles account for sigoi6eant quantities of petroleum
-
asphalt. TUREI3 TYPES OF PglROLELM ASPIMLT
Petroleum ssyhalta cnn be divided into three 0laSst.a: cracked. blown, and Straight-run. h - o As-. Cracked asphalts, often called cracked tam, are the d u e from thermal cracking operations. They have lower aversge molecular weights than other commerrial ssphalts and 818 believed to have a larger percentage of aromatic ewstituenta (9). However, mme invmigstors believe that the increased ammaticity ia in the oily Irwtion of the residue rathcr thsn in the asphaltene portion. Cracked tnre exhibit extreme in M t y with changiog temperature. This high "temperature ausoeptibility" combined with their low oxidation mistance relatively rapid deterioration of pavements in which they are wed. Beesuse of this characteristic many highway commissions prohibib their use or'restfict it to very small mardmum percantagenin r o d surfacing. However, in some eblown cracked m i d u e is used on mcondary roads. Crackedasphaltsfromcertain units have considerable hardow, high mft~icgpoint,and high ductility at 77' F.. and this has led to their utiliration in the manufacture of molding compositiom for storsge battery e8888 and similar products (J6). However, these u ~ e sare not suiiicient to consume all of the residue
Pchp-Chem Furnam 549
550
INDUSTRIAL AND ENGINEERING CHEMISTRY
USES O F
TOTAL PETROLEUM
-4SPHALT PRODUCTION IN
(Short tons) 1546 % Solid and semisolid (less t h a n 200 penetration) Paving 1,594,621 Roofing Waterproofing Rubber compounding 28,715 Mastic a n d binders Pipe coating 31,774 Molding conipounds 51,316 Miscellaneous 177,028 Semisolid Flux a n d liquid Paving Roofing Cutback asphalt’ Emulsified asphalt Paints a n d finishes Miscellaneous Total
26.2
1945-46
9%
1545 ( 2 6 ) 1,904,002
27.7
0.4 0.7 2.3
17,965 44,818 175,976
0.3 0.6 2.6
288,229 866,842 1,908,344 06917 68:355 107,347
3.7 11.3 25.2 0.7 0.9 1.4
225,084 745,354 1,861,773 69’943 46,189 145,508
3.3 10.9 27.2
7,614,367
100 . O
6,850,984
100.0
0.4
0.7 2.1
Vol. 40, No. 4
that a certain amount of esterlike compounds and anhydrides is formed (11), oxygen analysis reveals no appreciable fixation of oxygen (2%) in the asphalt. The asphalts that result i‘rom these operations range from tacky “roofing tars” to glassy products used in printing inks. Theyhave a relatively low temperature susceptibility and a greater elasticity than is found in asphalts produced by other processes. STRAIGHT-RUP; ASPHALT. The most important type of asphalt from a volume standpoint is the straight-run material produced primarily for use in road surfacing composit,ions where it mag be used unaltered (paving grade or “penetration” asphalt) or cut back with lighter fractions (liquid asphalts). This product is produced by distilling off the lighter fractions of a pet,roleum oil to produce a residue of predetermined penetration containing the heaviest compounds present in the charge. This distillation may be conducted a t atmospheric or reduced pressure, with or without the introduction of steam or some other foreign gas. When the distillation is carried out a t atmospheric pressures it is usually necessary to “blow” the residue in order t o obtain the desired hardness or “penetration.” In modern practice only a negligible amount of polymerization occurs and no free carbon is
produced in thermal cracking operations. -4s thermal cracking is replaced by catalytic processes in the production of light fuel fractions from cracked residues w,ill become less important as asphaltic raw materials. The highly polymerized formed. The charge to the distillation tower may be topped cruderesidues formed in the neby processes are burned in the regenerathat is, crude from which the lightest fractions have already been tion of the catalyst and are not available for recovery. B~~~~ A ~ Asphalts ~ that~ are to ~be used ~for roofing ~ .removed-or high asphalt crude such as is found in .the central California fields, in which the asphalt content may run above 40% and pipe coverings .as well as certain other industrial and the naphtha Or gasoline fraction less than 1 In general, applications must have, in addition to w-eather resistance, a high straight-run asphalt has a temperature susceptibility intermedisoftening point and low flow at high atmospheric temperatures ate between the cracked tars and the blown bitumens. HOW~ ~ For these and yet must not become brittle a t 1 0 temperatures. ever, this property varies from crude to crude. applications a blown asphaltic bit,umen is used. This type of The variation in properties b e h e e n asphalts produced by idenmaterial is made by passing air through a liquid residuum obtical techniques from different crudes may be inferred on examitained from either straight distillation towers or thermal cracking nation of the composition of the residuums. Analysis of 100units. Moderately high temperatures (400” t o 600” F.) are maintained and blowing periods range from 3 to 24 hours a t Fates of 3 to 20 cubic feet per gallon per hour, dependCHARICTERISTICS O F h P H . 4 L T s BY TYPES ing on the properties desired in the end BLOWK E~ R A I G H T - R T J N CRACKED product, The reaction is exothermic Black Color Brownish-black t o Black and requires external cooling after the black Cniform to gritty Variable Homogeneity Uniform t o gritty initial phase. Bright t o dull and Variable Bright t o dull Appearance of surface after one-week Several processes utilizing catalysts, greasy aging indoors Soft grades do not Conchoidal ............ Fracture notably heavy metal chlorides, t o profracture. Hard grades fracture duce a similar end product have been conchoidally investigated. Catalytic processes have Variable Bright t o dull Bright t o dull Luster Black Brownish-black t o Brownish-black Streak on porcelain a much shorter reaction time but entail black 1.00-1.17 0.50-1.07 0.90-1.12 increased expenditure for equipment Specific grav ity a t 77O F 0-150 25-200 50-110 Penetration a t 77” F. and catalyst in addition to introducing 5-100 2-30 ..., . , .. . . Consistency a- t_770 . . -P. Variable Variable 2-125 + Ductility a t 77’ F., em. solvent-insoluble salts into the finished 0.5-10.0 Variable Tensile strength a t 77“ F. 40-60 8-40 asphalt. Standard of California is pro. . . . . . . . . . Susceptibility index 80-225 80-400 90-125 + Fusing point (K. & S. method), F. ducing “blown” asphalt by a catalytic 100-260 100-426 110-126 + Fusing point (R. R. B. method), F. 400-600 350-500 340-530 Flash ppint. F. process a t its Richmond refinery. This 450-700 400-650 400-650 Fire point F. Variable 1-12 plant has been in operation for five years 1-20 Volatile d a t t e r , 500” F.for 5 hours, % 85-100 95-200 98 Solubility in carbon disulfide, 70 and is believed to be the only producSolubility in petroleum naphtha a t 25-85 50-90 ? 3 G7 80-99 ing catalytic blowing unit in the counvu ., / D 0-5 0-15
