IBN AL- HAITHAM J. FO R PURE & APPL. SC I. VOL. 22 (4 ) 2009 Fractio nal Chemical Co mpo sitio n o f Asphalt as a Functio n o f Its Durability A.F.Kassir Departme nt of Chemistry, College of Education Ibn Al-Haitham, Unive rsity of Baghdad A bs t ra c t In order to get better understanding of asp halt p avement p erformance, asp halt from five Iraqi refineries (Qay arah, Nassiriy ah, Baiji, Samawah and Daurah) were analyzed into five chemical fractions includin g asp haltenes, p olar comp ounds, first acidaffins, second acidaff ins and saturated hy drocarbons where the last four fractions called maltenes. Polar compounds /saturated hy drocarbons ratio (PC/S) and the ratio of the reactive to the un- reactive components of the maltenes fraction (durability rating) p arameters were determin ed. The st udy showed that Baiji asp halt has the best durability over other asp halts, while Qay arah asp halt is considered to have the least durability grade. These results confirm the correlation of the chemical co mposition of asp halt as a function of its durability . Introduction Asphalt, is a sticky , black and high ly viscous liquid or semi-solid that is p resent in most crude p etroleums and in some natural deposits termed asp haltum. It is most commonly modeled as a colloid with asp haltenes as the disp ersed phase and maltenes (the chemical fractions of asp halt material excep t asp haltenes) as the continuous p hase [1]. Asphalts lose their p last icity and therefore harden and crack or crumble when they lose their more volatile lower molecule weight constituents or when these constituents are o xidized; this p rocess is known as aging. M oisture from rain and other sources can also invade and damage asp halts p articularly aged or o xidized asp halts because they have a large nu mber of p olar constituents to attract water molecules [2]. Asphalts which are used in the field of construction p avements are sp ecified by using the p enetration gradin g sy st em .The (40-50) p enetration grade asp halts that p roduced from the various refineries in Iraq are most widely used in p aving the roads desp ite Dourah refinery p roduces other types of asp halts in the grades (40-100).Viscosity may also be consider ed as an accep ted system. Table (1) shows some p hy sical p rop erties of original grades of asp halt and asp halt after aging according to ASTM (D1754) [3]. To obtain a prop er idea of asp halt p avement, the chemical prop erties of asp halt are considered. Asphalts p roduced from various refineries are anticip ated to have different fraction comp onents. Asphalt can be sep arated into five fr action comp onents accordin g to ASTM (D2006) [4].These fractions have functions [5] as shown below: 1. Asphaltenes (A): The p ortion that is insoluble in 50 volume of n-p entane. It acts as (body ing agent). 2. Polar compounds (PC): The nitro gen bases, the portion that is soluble in p entane and that reacts with cold 85% sulfuric acid. It serves as p eptizer for asp haltenes (highly reactive resins). 3. First acidaffins (Al): The p ortion that does not react with cold 85% sulfuric acid, but does react with cold concentrated sulfuric acid. It functions as a solvent for p eptized asp haltenes (more reactive-resinous hy drocarbons). 4. Second acidaffins (A2): The p ortion that does not react with cold concentrated sulfuric acid but does react with cold fuming (30% free SO3) sulfuric acid. Silica gel is substitut ed for fumin g acid p recipitation. It acts as a solvent for p eptized asp haltenes (less reactive- slightly unsaturated hy drocarbons). 5. Saturated hydrocarbons (S): The paraffin, the p ortion that does not react with cold fuming sulfuric acid or it is t hat one that is not adsorbed on silica gel, while all other comp onents are adsorbed on silica gel. It serves as a gelling agent for t he asp halt comp onents. Asphaltenes are soluble only in the p olar compounds. First acidaffins and se cond acidaffins act as a medium to disp erse the dissolved asp haltenes, and the saturated hy drocarbons (p araffin) develop the setting char acterist ics of t he entire solution [6]. IBN AL- HAITHAM J. FO R PURE & APPL. SC I. VOL. 22 (4 ) 2009 Asphalts can be also separated into four fractions accordin g to ASTM (D4124) [7] defined as Saturates, Nap hthene Aromatic, Polar Aromatics and nC7 Asphaltenes, but the first procedure is considered as one of the unco mplicated methods for analyzing asp halts [8]. Apparatus and Materials 1. Adsorp tion Column, an 813mm (32 in.) Len gth of 20 mm o.d glass tubing with one end drawn to approximately 8 mm was constructed and prepared. A cotton absorbent p lug was tamp ed in the bottom of the column followed by 43 g of silica gel; p ore size 22°A, 28 to 200 mesh, 15 g of silica gel; p ore size 140°A, 60 to 200 mesh and finally 3-4 g of silica gel; p ore size 140°A, 4 to 10 mesh. Each of them was t app ed to settle resp ectively. 2. Dist illing Ap p aratus (Rost ler-Sternberg) was made of borosilicate glass. 3. Boiling water bath. 4. Water-cooled condenser. 5. Vacuu m source, cap able of reducing p ressure in dist illing app aratus to 15 mm Hg within 3 minutes. 6. Pentane, Sulfuric acid (98% reagent grade), Sod ium hy droxide pellets. All of these reagents and materials were p rovided from BDH Comp any. Procedure Five samples were taken from the refin eries of Qay arah, Nassiriy ah, Baiji, Samawah and Daurah for the work and analyzed according to ASTM (D2006) [4]. De termination of Asphal tenes. 1±0.1 g sp ecimen was we ighed into 100 ml we ighing flask, war med to d istribute the sp ecimen, cooled to room temp erature, then 50 ml of n-p entane was added, swirled and allowed the mixture to stand for 15 hours. The mixture was filtered, rinsed with 10-20 ml p entane three times until the filter p aper showed no oily ring. The filtrate was transferred into a p reviously weigh ed bulb and distilled. When the distillation of solvent had ceased, the condenser was disconnected from the distillin g app aratus while the bulb st ill immersed in the boilin g b ath, a vacuum suction was carefully applied to t he app aratus till the foaming subsides. T he bulb was separated, dried, cooled and weighed. The residue R1 is the pentane-soluble portion of the sp ecimen. De termination of Polar Compounds 1±0.1 g of sp ecimen was weighed, dissolved in 5 ml n-p entane and transferred quantitatively to 100 ml cylinder by rinsing with n-p entane until the vo lume of the solution was 20 ml then 2.5 ml of 85% H2SO4 was added. The cy linder was glass st opp ered, covered with a cloth p ad, grasp ed tightly and shaken hardly for 3 minutes. The acid sludge was settled from the pentane solution by allowing the cylinder to stand for 2 hours. The n-p entane solution was then decanted into 250 ml flask, rinsing the cylinder twice with n-p entane and decanting into the 250 ml flask while the acid sludge was discarded. 20 g of sodium hy droxide p ellets were added, swirled and allowed to st and a min imum of 20 minutes. The solution was filtered, rinsed with n-p entane until filter p aper showed no oily ring. The solvent was distilled as mentioned p reviously (asp haltene determination).The residue R2 is the fraction not reacting with 85% H2SO4 . De termination of First Acidaffins 1±0.1 g of sp ecimen was weighed, d issolved in 5 ml n-p entane then 2.5 ml of concentrated sulfuric acid was added, shaken, settled, decanted, neutralized with 20g of sodiu m hy droxide p ellets and finally distilled and evaporated to dry ness and weighed as above. The r esidue R3 is the fraction not reacting with concentrated sulfuric acid. De termination of Se cond Acidaffins and S aturated Hydrocarbons 1±0.1 g of sp ecimen was we ighed, dissolved in 20 ml n-p entane then p assed into the silica gel at the top of the adsorption column and the effluent was received at the bottom of the column. The upper part of the column was rinsed with n-p entane till 100 ml of t he eff luent was co llected. The collected n-p entane solution was distilled as above and the residue R 4 is the saturated p ortion of the sp ecimen. IBN AL- HAITHAM J. FO R PURE & APPL. SC I. VOL. 22 (4 ) 2009 C a l c ul a t io ns Q 1= (R1/ S1 ) x 1 0 0 ………………………………….(1) Where Q1= p ercentage soluble in pentane R1= weight of p entane-soluble fraction, g S1= weight of sp ecimen used, g Q2= (R2/S2) x 1 0 0 …………………………………... (2) Where Q2 = p ercentage not reacting with 85% H2SO4 R2= weight of fraction not reacting with 85% H2SO4, g S2= weight of sp ecimen used, g Q3= (R3/S3) x 1 0 0 … … … … … … … … … … … … . ( 3) Where Q3= p ercentage not reacting with concentrated H 2 SO 4 R3= weight of fraction not reacting with concentrated H2SO4, g S3= weight of sp ecimen used, g Q4= (R4/S4) x l 0 0 … … … … … … … … … … … … . (4) Where Q4= p ercentage not adsorbed on silica gel R4= weight of fraction not adsorbed on silica gel, g S4= weight of sp ecimen used, g Therefore the weight p ercentage of the comp onents is as follows: - Asphaltenes, % by weight= 100-Q1 - Polar Comp ounds, % by weight= Q1-Q2 - First Acidaffins, % by weight= Q2-Q3 - Second Ac idaffins, % by weight= Q3-Q4 - Saturated Hy drocarbons, % by weight= Q4 Results and Discussion Table (2) demonst rates t he results of chemical composition of the gr ades for both the original and aged asp halts. The p recision and accuracy were calculated and exp ressed by the relative st andard deviation (RSD %) and the relative error (RE %). The results show that Qay arah asp halt with high asp haltenes content and relatively low- content of p olar comp ounds exhibits a gel st ructure, while Nassiriy ah asp halt with lower asp haltenes and high er content of p olar comp ounds y ields sol typ e asp halt. Sy neresis, which is the incomp atibility of asp haltenes with t he acidaffins and saturated hy drocarbons, is gov erned by the ratio PC/S (p olar comp ounds/ saturated hy drocarbons). T herefore, asp haltenes content and the ratio of PC/S are consider ed resp onsible for the rheolo gical p rop erties of asp halt sol-gel characterist ics [9, 10]. It was reported that during aging p rocess an incr ease in the asp haltene fraction of asp halt is occurred except Baiji asp halt (almost constant), and as a result, the ratio of maltenes to asp haltenes is reduced causin g dry and britt le asp halt and this may be clue to the conversion of maltene co mponents to asp haltene comp onents [5]. The PC/S ratio of original and aged asp halt p roduced from the various refineries is shown in table (3); it varies between (0.76-2.58) for or iginal asp halt. Baiji asp halt shows t he lowest ratio while Nassiriy ah and Daurah asp halts show t he highest. Aft er aging the (PC/S) ratio is altered to range between (1.08-2.60).The ratio PC/ S must be 0.5 or gr eater to assure these components will not sep arate [6, 11]. The Durability Rating (Rost ler and White parameter), (PC+A1/S+A2), defined as the ratio of the more reactive to the less reactive fractional comp onents in asp halt is shown also in table (3). The Durability Rating values vary between (0.83-1.92) for original asp halt, but altered to (1.02- 1.78) after aging. The asp halt durability increases with the decrease in Durability Rating .The Qay arah asp halt is considered as t he least durability grade. Rost ler and White, mentioned that asp halt with Durability Rating not exceed ing (1.5) is considered to be satisfactory [12]; while the issue of TRICOR Refining, LCC and the sp ecification of the City of Lafayett e (USA) considered the limitation between (0.2-1.2) to assure good aging p rop erties [5,11]. IBN AL- HAITHAM J. FO R PURE & APPL. SC I. VOL. 22 (4 ) 2009 Conclusion The analysis covers determination of the comp osition of asp halt in terms of comp onents that are characterized by sp ecific chemical r eactivity . The determination of second acidaffins and saturated hy drocarbons by the adsorption method has been found to be suitable for asp halt. The five group s of components (asp haltenes, p olar comp ounds, first acidaffins, se cond acidaff ins and saturated hy drocarbons) give bett er understanding of (PC/S) ratio, asp halt durability and rheolo gical prop erties of asp halt. The durability of asp halt depends up on the ratio (PC+Al/S+A2) as determined by ASTM method D2006. During the p rocess of aging, the ratio of maltenes (the remainder of the asp halt material left after p recipitation of the asp haltenes) to asp haltenes is reduced, resulting in bein g dry and brittle asp halt p avement. Re ferences 1. Wikipedia, The free ency clop edia, "Asp halt", http ://en.wikipedia.org. (2008). 2. M ichael Freemantle, (1999), Am erican Chemical So ciety , Chemical and Engineering News, 77(47), 81-83. 3. Annual book of ASTM st andards D1754, (1986). 4. Annual book of ASTM st andards D2006, (1976). 5. Boy er, R.E., Transp ortation sy stems (2000) (T S2K) workshop , San Antonio, Texas. 6. Tricor refining, LCC issue, (2005). 7. Annual book of ASTM st andards D4124, (1986). 8. Little, (1986), Proceedings AAPT, 55, 314-322 9. Philip s Petroleum Company , (1975), US patent 3900692 10. Loeber, L. ; M uller, G.; M orel, J. and Sutton, O., (1998), Bitumen in collo id science: a chemical, st ructural and rheological ap p roach, INIST-CNRS France. 11. City of Lafayette standard sp ecifications, T-39, (2002). 12. Rost ler and White, (1970), Proceedings AAPT, 39, 532-557. Table (1): Some physical properties of original grades of asphal t and asphal t after aging Physical p rop erties of asp halt Qay arah asp halt Nassiriy ah asp halt Baiji asp halt Samawah asp halt Daurah asp halt Original asp halt Penetration; 1/10mm 25°C, l00g, 5 sec 43 41 43 46 45 Absolute Viscosity at 60°C, p oises 5265 4420 4112 3150 2065 Sp ecific Gravity 1.053 1.028 1.028 1.022 1.051 Aging asp halt Penetration; 1/10mm 24 28 22 28 31 Absolute Viscosity at 60°c, poises 10550 9785 9064 5022 2637 M ass Loss, % 0.56 0.02 ------- 0.10 0.58 IBN AL- HAITHAM J. FO R PURE & APPL. SC I. VOL. 22 (4 ) 2009 Table (2 ): Chemi cal fraction of the asphalt grades for both the original and after agin g Chemical Fraction Q ayar ah asp h alt N ass iriy ah asp h alt B aiji asp h alt Sa maw ah asp h alt D aur ah asp h alt O r igin al as p h alt Asp h alt ene 39.95 2 4 .9 1 3 0 .4 1 2 7 .4 3 22.3 R E%± 0 . 15 0 . 12 0 . 21 0 . 20 0 . 31 R SD% 0 . 19 0 . 15 0 . 25 0 . 24 0 . 36 P o lar co mpo un ds 1 6 . 5 1 3 3 .3 4 1 5 .0 7 2 6 .9 6 2 5 .3 1 R E%± 0 . 57 0 . 66 0 . 29 0 . 18 0 . 39 R SD% 0 . 81 0 . 87 0 . 42 0 . 22 0 . 53 First acidaffins 2 3 . 0 3 1 3 . 7 7 1 6 .6 2 1 6 . 37 20.22 R E%± 0 . 15 0 . 49 0 . 30 0 . 21 0 . 56 RSD% 0 . 20 0 . 65 0 . 36 0 . 29 0 . 76 Second acidaffins 7 . 52 1 5 .0 9 18.22 1 4 .7 5 21.80 R E%± 1 . 06 0 . 38 0 . 31 0 . 13 0 . 33 RSD% 1 . 35 0 . 46 0 . 38 0 . 19 0 . 40 Saturates 1 2 .9 9 1 2 .8 9 1 9 .6 8 1 4 .4 9 1 0 .3 7 R E%± 0 . 34 0 . 33 0 . 31 0 . 17 0 . 21 RSD% 0 . 45 0 . 40 0 . 47 0 . 21 0 . 26 Aging asp halt Asphaltene 4 0 .5 3 0 .1 3 2 9 .8 7 3 1 .0 0 2 4 .8 2 R E% ± 0 . 15 0 . 16 0 . 23 0 . 17 0 . 19 RSD% 0 . 19 0 . 22 0 . 32 0 . 20 0 . 26 Polar compounds 2 9 .7 9 2 3 .8 9 2 1 .1 0 3 2 .4 7 2 7 .3 9 RE%± 0 . 16 0 . 11 0 . 32 0 . 18 0 . 17 RSD% 0 . 23 0 . 13 0 . 40 0 . 23 0 . 27 First acidaffins 8 . 35 1 4 .8 7 1 4 .3 7 9 . 44 1 7 .2 1 RE%± 0 . 39 0 . 25 0 . 20 0 . 18 0 . 13 RSD% 0 . 44 0 . 33 0 . 25 0 . 21 0 . 16 Second acidaffins 6 . 41 1 5 .3 7 1 5 .2 8 1 0 .4 1 2 0 .0 5 R E%± 0 . 35 0 . 21 0 . 19 0 . 43 0 . 35 RSD% 0 . 43 0 . 26 0 . 26 0 . 50 0 . 40 Saturates 1 4 .9 5 1 5 .7 4 1 9 .3 8 1 6 .6 8 1 0 .5 3 RE%± 0 . 25 0 . 19 0 . 11 0 . 16 0 . 28 RSD% 0 . 29 0 . 25 0 . 14 0 . 22 0 . 42 Table (3): Parameters of original and oven-age d asphalt produced from va rious refineries Qay arah Nassiriy ah Baiji Samawah Daurah Parameters asp halt asp halt asp halt asp halt asp halt Original asp halt PC/S 1.27 2.58 0.76 1.86 2.44 Durability Rating PC+A1/S+A2 1.92 1.68 0.83 1.48 1.41 Aging asp halt PC/S 1.99 1.51 1.08 1.94 2.60 Durability Rating PC+A1/S+A2 1.78 1.24 1.02 1.54 1.45 2009) 4(22 المجلد مجلة ابن الھیثم للعلوم الصرفة والتطبیقیة التحلیل الكیمیائي التجزیئي لالسفلت دالة لقوة تحمله عبداالحد فرید قصیر ابن الهیثم ، جامعة بغداد-قسم الكیمیاء ، كلیة التربیة الخالصة سفلت المستعمل في أعمال التبلیط فقد أجري التحلیل الكیمیائي التجزیئي لغرض الحصول على مفهوم أفضل الداء اال :التي تضمنت مكونات) القیارة، الناصریة، بیجي، السماوة والدورة(لخمسة نماذج مأخوذة من مصافي العراق الخمسة (asp haltenes, p olar comp ounds, first acidaffins, second acidaff ins and saturated hydrocarbons) maltenesوتدعى المقاطع االربعة االخیرة p تم استخراج كل من olar comp ounds/saturated hy drocarbons (PC/S) ونسبة التحمل التي تمثل نسبة االسفلت لقد بینت الدراسة أن.لكل أنموذج أسفلت maltenesالمقاطع التجزیئیة الفعالة الى المقاطع التجزیئیة غیر الفعالة للـ المنتج في مصفى بیجي كان أفضل أنواع االسفلت تحمال من غیره من أنواع االسفلت االخرى المنتج في باقي المصافي .العراقیة فیما عد أسفلت القیارة أقلهم درجة تحمل سفلت ومن ثم تعطینا ان النتائج المستحصلة أكدت أن العالقة بین المكونات الكیمیائیة لالسفلت تعد دالة لقوة تحمل اال .مفهوما أفضل الداء االسفلت