2,5,'2:- THE POTENTIAL USE OF TAR SAND BITUMEN AS PAVING ASPHALT J. Claine Petersen Distinguished Scientist Western Research Institute larami e • Wyomi ng . INTRODUCTION The amount of asphalt used annually is about 30 million tons of which about 24 million tons is used in paving. Thus, the potential exi sts for util i zati on of si gnifi cant amounts of tar sand bi tumen in paving if the bitumen were commercially available and if the properties of tar sand asphalts were suitable for paving use. The commerci a 1 application of tar sand bitumen as a paving material has been limited to the direct use of the tar sand as a surfacing material. Tar sands from the Asphalt Ridge,U~ah, deposit are quarried and blended with dry sand to pave county roads, parking lots, and driveways. Petroleum asphalt is added to limestone tar sands from the Uvalde, Texas, deposit to prepare a pa vi ng materi a 1. Through the 1930' s, crushed tar sand from the Santa Rosa, New Mexico, deposits were used to pave roads, streets, and airport runways as far away as Seattle, Washington; and during the 1940's tar sands from deposits in Utah, California, and Kentucky were quarried for application as paving materials. The tar sands as obtained from quarri es, however, do not meet exi sti ng specifi cati ons as a hi ghway construction material. In thi s paper, several past studi es (l-.!) desi gned to evaluate recovered tar sand bitumen as a pavi ng materi a 1 are revi ewed and the Prepared for presentati on at the 1987 Summer Meeti ng of the Interstate Oil Compact Commission, Coeur d'Alene, Idaho, June 22-24, 1987. 1 results of the studies compared. Considerable data interpretation and some additional data are supplied by the author. The properties of tar sand asphalts prepared from recovered bitumen are compared with those of petroleum asphalts. The properties evaluated are those used for the specification of paving asphalts together with additi.onal properties deemed important to the performance of asphalt in pavements. MATERIALS EVALUATED Tar sand asphalts prepared from different material sources and by different recovery methods are discussed in this paper. They are 1) an aspha lt prepared from sandstone deposi ts near San Lui s Obi spo, California (Edna), and recovered using a light oil-assisted, hot (alkaline) water separation process U); 2) two asphalts prepared by a similar process from Asphalt Ridge tar sand deposits near Price (Sunnyside) and Vernal (Asphalt Ridge), Utah (~); 3) two asphalts prepared from bi tumen recovered duri n g the Larami e Energy Technology Center's U.S. DOE in situ combustion project (TS-2C) (il conducted at Utah's Northwest Asphalt Ridge deposit (Vernal); and 4) two asphalts prepared from bi tumen recovered duri ng the Larami e Energy Technology Center's U.S. DOE in situ steamflood recovery project (TS-IS) (~), also conducted at the Utah Northwest Asphalt Ridge deposit. The two asphalts prepared from the in si tu combusti on bi tumen were prepared to grade by the author and supplied to the subsequent investigators (~) for evaluation. Several representative petroleum asphalts, identified in the text, were used for property compari sons. Experimental details 2 necessary for clarity are briefly provided as needed in the text. For additional detail the reader is referred to the original papers. COMPARISON OF THE TAR SAND AND PETROLEUM ASPHALTS BASED ON PROPERTIES OFTEN USED FOR SPECIFYING PAYING ASPHALTS Before discussing the specific properties of the tar sand asphalts, a few comments will be made regarding paving asphalt specifications. These specifications, which have evolved over the years, deal with easily measured asphalt properties that define the asphalt's suitability for use in paving mixtures. Consistency measurements (e.g., viscosity or penetrati on) are probably the most important pri mary specifi cati on considerations because they are important in determining the properties of the pa vi ng mi xture duri ng preparati on and duri ng pavement construc­ tion as well as the properties of the finished pavement. Some specification tests may not be functional with regard to pavement performance. Many important performance properties of paving asphalts such as long-term durabil ity and factors related to pavement moi sture damage are not adequately defined by standard specifications. Thus, additi ona 1 speci a 1 tests are often necessary; however, these speci a 1 tests have not been standardized for use in current paving technology. Although each state or local unit may impose unique restrictions or modifications regarding specifications, general specifications have been adopted at the national level and can be found in readily available publications (2.. ~). Specification-type data cited in the discussions in this paper are those generally accepted by most transportation agencies, although all agencies may not use the same types of data. 3 The approach used by a 11 of the i nvesti gators to prepare candi date tar sand asphalts was to first prepare a material, by distillation of oi 1 s if necessary, to meet consi stency specifi cati ons (penetrati on or vi scos;ty). foll owed by the measurement of other properti es to determi ne how these remai ni ng properti escompared wi th those of speci ncati on petroleum asphalts. Tar Sand Asphalts from Hot Water Process In Table 1 the properties of the three tar sand asphalts recovered by the hot water process (from tar sand deposits in Edna, California, and Sunnysi de and Vernal, Utah) are compared with the properti es of three petroleum asphalts prepared from different crude oil sources. The consistency of all three petroleum asphalts was 80 penetration at 77°F (2S·C); penetration values of the Edna, Sunnyside, and Vernal tar sand asphalts were 80, 84, and 64, respectively. Both viscosity and penetration measurements at temperatures other than 77°F (2S0C) for the tar sand asphalts compare favorably with those of the petroleum asphalts and fall within the normal range of variability expected for materials from different sources. Results of the ash determinations, spot tests, and loss on heating measurements for the tar sand asphalts, however, were different than correspondi ng results for the petrol eum asphalts and requi re further di scussi on. As seen in the table, the ash content of the tar sand .. aspha 1ts was consi derab 1y hi gher than that of the petrol eum asphalts. Also, ash determinations by direct ashing of the tar sand asphalts was considerably higher than determinations by a filtration method using an asphalt solution (ASTM D4-42). The lower ash content obtained by 4 Tab 1e 1. Compari son of PrQperti es of Tar Sand Asphalts Prepared from Hot WUet-Separated Bitumen with Properties of Several Petroleum Asphalts L Tar sand asghalts Petroleum as~fia1ts ,~ Edna, Sunnyside, Vernal, Kern Rtver, Oregon Basin, Tampi co, ;- Ca 1i fl Utah 2 Utah 2 Ca 1ifl Califl Mexico 1 '1 1- ! Asphalt yield, % 100 100 94.5 53.0 43.6 72.2 Ash, % 0.53 , 2.04 0.8 3 , 2.14 0.53 , 1.84 03 03 03 I Spot test Positive Posi ti ve Positi ve Negative Negative Negati ve Solubility in carbontetrachloride, % 99.6 100 100 100 100 100 I Specific gravity, 77°F (25°C) 1.087 1.020 1.012 1.012 1.028 1.038 Flash point, of (OC) 505 (263) 460 (238) 505 (263) 550 (288) 570 (299) 510 (266) i Penetration, dmm $ 77°F (25°C), 100g, 5 sec 80 84 64 80 80 80 $• t1l 60°F (15.5°C), 100g, 5 sec 26 32 18 22 26 34 ~ 34°F (1°C), 200g, 60 sec 14 23 11 10 17 26 •il" Viscosity, poise 210°F (99°C) 24.4 62.6 36.7 18.3 33.8 72.6 275°F (135°C) 2.71 7.39 3.93 1.93 3.72 7.31 Ductility, 77°F (25°C), 5 cm/min 100+ 100+ 100+ 100+ Ii § Softening point, of (OC) 116 (47) 123 (51) 121 (49) 111 (44) 116 (47) 121 (49) i Loss on heating, % 0.45 0.40 0.11 0 0 0.2 ,~ 77°F (25°C) Pen of ~ loss on heating residue 66 57 54 71 70 68 1 t '1 1 Data from (1) ~ I 2 Data from ("2) ,/ 3 ASTM 04-42- I 'I Di rect ash j I j ! t I fil trati on ref1 ects the fi neness of the mi nera 1 parti c1 es in the tar sand asphalt. Although most asphalt speci fi cati ons 1 i mi t ash content, sma 11 amounts of mi nera 1 matter in the asphalt may not necessaril y be detrimental. A certain amount of mineral fines are a normal part of a pavement aggregate mixture. Small amounts of ash in tar sand asphalts coul d most 1i kel y be taken into account duri ng the desi gn of the pavement mixtures. The spot test measures the presence in asphalts of components that are not soluble in petroleum naphtha. The test in itself is non­ functi ona 1 wi th regard to pavement performance and was i niti ally deve loped to detect aspha lts that had been thermally cracked duri ng manufacture. Such asphalts often had poor component compatibility that resulted in poor aging and flow characteristics. The tar sand asphalts probably gave a positive spot test because of the presence of the mineral matter just described. As will be seen later, evidence suggests that tar sand asphalts may actually have better aging characteristics than typical petroleum asphalts.