Grading system in paving bitumen – an indian scenario


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Grading system in paving bitumen – an indian scenario

  1. 1. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME208GRADING SYSTEM IN PAVING BITUMEN – AN INDIAN SCENARIOApparao G1*, Rajesh G2, Gopala Raju S.S.S.V11Civil Engineering Department, GITAM University, Hyderabad-5023292Assistant Manager, AARVEE Associates, Hyderabad. - 500072ABSTRACTIn India almost 90 per cent road network is occupied by bituminous pavements only.Because bitumen is extensively used as the binding material and it prevents waterpenetrating in to the structures. That to a rapid rate of development in every aspect of lifeand it was dominated by construction boom, it resulted in increased traffic volumes,pavement temperatures and higher than the design load magnitude; leads to the failure ofbituminous pavements. In fact, there is a huge gap in India between proper characterizationof bitumen and its execution in the industries true to the specifications and the aspirationalplanning of creation of important public assets in the road sector whose durability andserviceability is very important socioeconomic improvement of the country. This papergives an overview of paving bitumen grading system, characterization and the newviscosity graded (VG) bitumen specifications has been compared with the old penetrationgraded bitumen specification.KEY WORDS: Bitumen, Flexible Pavements, Viscosity gardening, and Penetration.1.0 INTRODUCTIONIn India Viscosity Grading (VG) system has bee n adopted for paving bitumen since2006. And at the same time, the Bureau of Indian Standards has issued IS 73:2006paving bitumen – specification (Third Revision), which specifies paving bitumen byviscosity at 60 °C and 135 °C rather than the old system of grading paving bitumen bypenetration at 25 °C. But still in the specifications given in the Ministry of Road Transportand Highways (MoRTH), so called orange book, does not revise its highway specificationsrelated to base and surface of bituminous grading. This paper gives an idea of characterizationof bitumen, merits and demerits of penetration and viscosity grading systems, and need to bechanges incorporated in the Ministry of Road Transport and Highways (MoRTH)specifications.INTERNATIONAL JOURNAL OF CIVIL ENGINEERING ANDTECHNOLOGY (IJCIET)ISSN 0976 – 6308 (Print)ISSN 0976 – 6316(Online)Volume 4, Issue 2, March - April (2013), pp. 208-214© IAEME: Impact Factor (2013): 5.3277 (Calculated by GISI)www.jifactor.comIJCIET© IAEME
  2. 2. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME2092.0 CHARACTERIZATION OF BITUMENBitumen is available in variety of types and grades. To judge the suitability ofbitumen binders are most commonly characterized by their physical properties rather than itschemical properties. For engineering and construction purposes, normally three physicalproperties of bitumen are important;2.1 ConsistencyConsistency is the term used to measure its degree of stiffness a b i l i t y t o f l o w .Bitumen is thermoplastic material which means it liquefy when heated and solidifywhen cooled and its state of solidness (stiffness) or liquidness (i.e., ability to flow)is very much temperature sensitive. Consistency of bitumen can be judged by someempirical tests such as penetration, softening point, ductility etc. and also by testing thefundamental property of bitumen such as viscosity.2.2 PurityPure bitumen is completely soluble in solvents like carbon disulphide and carbontetrachloride. Hence any impurity in bitumen in the form of inert minerals, carbon etc. couldbe quantitatively analysed by dissolving the samples of bitumen in any of the abovementioned solvent.2.3 SafetyBitumen materials leave out volatiles at temperatures depending upon their grade.These volatiles catch fire causing a flash. The definition of flash and fire points as given bythe Indian standards are as follows:The flash point of a material is the lowest temperature at which the vapour of asubstance momentarily takes fire in the form of a flash under specified condition of test. Thefire point is the lowest temperature at which the material gets ignited and burns underspecified conditions of test.Thus, it can be concluded that there is no point to grade bitumen on purity and safetyaspect. It is the consistency property of bitumen by which it can be graded.3.0 OVERVIEW OF BITUMEN GRADING IN INDIAThe first Indian standard on the bitumen was first published in 1950 as“Specification for asphaltic bitumen and fluxed native asphalt for road making purpose”: IS73 which was revised in 1961 to change the grades of material and incorporate themethods of test as per IS 1201 to IS 1220:1958 ‘Methods for testing tar and bitumen’.In the first revision, the grades of fluxed native asphalt were deleted and essentially thepaving grades were included. Based on the revised methods of test in IS 1201 to IS1220:1978 ‘Methods for testing tar and bituminous materials (first revision) and the additionaldata that had become available, second revision was prepared in 1992. In this third revision(IS: 73-2006) grading of bitumen’s is changed from penetration grade to viscosity grade. Thevariability in performance at high temperatures can be addressed by adopting a viscosity-graded bitumen specification (based on viscosity at 60°C) in lieu of the current penetration-graded specification (based on penetration at 25°C). Since the viscosity-graded bitumenspecification has a requirement of minimum viscosity at 135°C, it will also be helpful inminimizing the tender mix problems in the field.
  3. 3. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME210Adoption of viscosity-graded paving bitumen specification will also reduce thenumber of total tests to 7, which will reduce the cost of testing bitumen. This will result fromeliminating empirical tests/parameters such as – penetration ratio, paraffin wax content, andFraass breaking point without compromising the quality of bitumen.Since high penetration values are desirable for pavement durability, requirement for aminimum penetration value is adequate and has been retained in the viscosity-gradedspecification. Specifying a maximum value for penetration is undesirable and will rejectsome good quality bitumen’s unreasonably.3.1 Grading SystemsBituminous binders are most commonly characterized by their physical properties.The challenge in physical property characterization is to develop physical tests that cansatisfactorily characterize key asphalt binder parameters and how these parameters changethroughout the life of an HMA pavement.Rather than refer to an extensive list of its physical properties, asphalt binders aretypically categorized by one or more shorthand grading systems. These systems range fromsimple penetration grading to complex Superpave performance grading and represent anevolution in the ability to characterize asphalt binder.3.1.1 Penetration GradingThe penetration grading system was developed in the early 1900s to characterizethe consistency of semi-solid asphalts. Grading of bitumen by penetration test at 25 °C wasadopted by the American Society for Testing and Materials (ASTM) Committee D04 onRoad and Paving Materials in 1903. To quantify the Penetration grading the followingasphalt concrete characteristics are to be evaluated as per the standard IS: 73-1992;Penetration depth of a 100 g needle; 25° CFlash point, °CSoftening point °CPenetration ratioDuctility at 25 °C, cmParaffin wax contentFraass breaking pointSolubility in trichloroethyleneLoss on heating (TFOT)Retained penetration after Thin Film Oven Test (TFTO)Viscosity at 60 °C and 135 °CWater contentSpecific gravity at 27 °CPenetration grading basic assumption is that the less viscous the asphalt, the deeper theneedle will penetrate. This penetration depth is empirically correlated with asphalt binderperformance. Therefore, asphalt binders with high penetration numbers (called "soft") areused for cold climates while asphalt binders with low penetration numbers (called "hard")are used for warm climates.
  4. 4. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME211In figure 1, there are three, bitumen A, B & C whose penetration at 25oc issame i.e., 65. But these bitumen are having different stiffness values at higher (say60oC) temperature and at lower (say 4oc) temperatureThe slope of the stiffness Vs. temperature curve is called temperature susceptibility.Steeper is the slope, more will be the temperature susceptibility of the bitumen. Infig 1, bitumen ‘C’ is most temperature susceptible , in other words more proneto rutting at high temperature and more prone to cracking at lowtemperatures (sue to higher stiffness) compares to bitumen ‘B’ and ‘A’.Figure 1: Three 60-70 penetration grade bitumen’s with different stiffness’s at high and lowservice temperatures3.1.2 Viscosity gradeIn the early 1960s an improved asphalt grading system was developed thatincorporated a rational scientific viscosity test. This scientific test replaced the empiricalpenetration test as the key asphalt binder characterization. To quantify the Viscositygrading the following asphalt concrete characteristics are evaluated based on the asper IS: 73 - 2006;Absolute viscosity at 60 °C, poisesKinematic viscosity at 135 °C, cStFlash pointSolubility in trichloroethylenePenetration depth of a 100 g needle; 25° CSoftening pointTests on residue from thin film oven tests/RTFOT;viscosity ratio at 60 °C and Ductility at 25 °C, cm
  5. 5. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME212Viscosity is defined as inverse of fluidity. Viscosity thus defines the fluid property ofbituminous material. Viscosity is the general term for consistency and it is measure ofresistance to flow. Many researchers believe that grading of bitumen should be by absoluteviscosity in it’s instead of the conventional penetration units.By measuring consistency at three different penetration, the range (minimum andmaximum temperatures (Figure 2) and specifying the ranges, values) for absolute viscosityat 60oc, and the slope of temperatures Vs. stiffness curve i.e., the temperaturesusceptibility of bitumen can be bound in a specified range which is the key for betterperformances. Minimum value for kinematic viscosity at 135oc have been specified, whichare more rotational. As per given the in the table 1 the specifications of the Indian standardwhich is IS: 73-2006 needs to be modified shortly.Defining the range (minimum and maximum values) for penetration at 250C, minimumvalue for absolute viscosity at 600C, and minimum value for kinematic viscosity at 1350C, thetemperature susceptibility of bitumen can be controlled in a better way towards betterperformance. However, in ASTM D 3381 specification for viscosity graded asphalt binders,the minimum value only for penetration, the range (minimum and maximum values) forabsolute viscosity at 60oc, and the minimum value for kinematic viscosity at 135oc have beenspecified, which are more rotational. As per given the in the table 1 the specifications of theIndian standard which is IS: 73-2006 needs to be modified shortly.Figure 2: Graphical representation of viscosity-graded AC-30 (VG-30) bitumen
  6. 6. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME213Table 1: Requirements for Paving Bitumen as per IS: 73-20064.0 CONCLUSIONSThe existing penetration grading system of bitumen has been replaced by viscositygrading system in India based on improvement in the durability and serviceabilitycondition of the desired extent. For this, issues regarding improvement of thespecification and also manufacturing of bitumen true to that specification need to beaddressed.In view of modification and improvement of the current specification of IS : 73(specification for paving grade bitumen), sample of bitumen are being collected fromall over the country in Indian Institutes , which are going through rigorous testing.In the specifications for the road and bridge works (fourth revision) addressed by theMoRTH for section 500 which is guidelines for base and surface course of bituminouslayers given based on the penetration grading only. Though in the recent revision, thesespecifications have been revised as per viscosity grading.5.0 REFERENCES1. SSSV Gopala Raju (2007), “Reuse of polyethylene waste in road construction”, Journalof Environmental Science and Engineering, Vol.49, No.1, pp.67-702. SSSV Gopala Raju(2010), Utilization of building waste in road construction”, IndianJournal of Science and Technology, Vol.3, No.8,pp. 894-8963. Prithvi Singh Kandhal, P.S (2007), An overview of the viscosity grading systemadopted in India for paving bitumen “Indian Highways.4. Rajib Chattaraj (2011) “Bitumen Grading system – from penetration grading to viscositygrading – A step towards better quality control” ,“INDIAN HIGHWAYS”5. MoRTH (Ministry of Road Transport and Highways) (2001). “Specification for Roadand Bridge Works”. Indian Roads Congress, New Delhi, Section 500, Bases and surfacecourses for bitumen.6. Kandhal, P. S (2005),“ Selection of Bitumen for Paving Highways”, Indian RoadsCongress, Indian HighwaysCharacteristics VG-10 VG-20 VG-30 VG-40Absolute viscosity, 60 °C, poises, min 800 1600 2400 3200Kinematic viscosity, 135 °C, cSt, min 250 300 350 400Flash point, °C, min 220 220 220 220Solubility in trichloroethylene, %, min 99.0 99.0 99.0 99.0Penetration at 25 °C 80-100 60-80 50-70 40-60Softening point, °C, min 40 45 47 50Tests on residue from thin film oven test/RTFOT:Viscosity ratio at 60 °C, max 4.0 4.0 4.0 4.0Ductility at 25 °C, cm, min, after thin film oven test 75 50 40 25
  7. 7. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME2147. Kandhal, P.S., L.D. Sandvig, and W.C. Koehler (1973), “ Asphalt Viscosity RelatedProperties of In-Service Pavements in Pennsylvania”, ASTM Special TechnicalPublication 532..8. Kandhal, P.S. and M.E.Wenger (1975), “ Asphalt Properties in Relation to PavementPerformance”, TRB, Transportation Research Record 544.9. Kandhal, P.S. and W.C. Koehler (1984), “ Significant Studies on Asphalt Durability:Pennsylvania Experience”, TRB, Transportation Research Record 999.10. Kandhal, P.S (1977)., “ Low-Temperature Ductility in Relation to PavementPerformance”, ASTM Special Technical Publication 628.11. Kandhal, P.S (1988)., “Low-Temperature Properties of Paving Asphalts”, TRB State-ofthe- Art Report 712. Kandhal, P.S. and W.C. Koehler (1987), “Effect of Rheological Properties of Asphalts onPavement Cracking”, ASTM Special Technical Publication 941.13. Kandhal, P.S., L.D. Sandvig, and M.E. Wenger (1973), “ Shear Susceptibility of Asphaltsin Relation to Pavement Performance”, Proc. Association of Asphalt PavingTechnologists, Volume 42.14. Kandhal, P.S (1980), “Evaluation of Low-Temperature Cracking on Elk County ResearchProject”, TRB, Transportation Research Record 777.15. Kandhal, P. S (2006), Quotations for Supply of Vacuum Viscometer Equipment fromIndian Suppliers, 2006.16. “Paving bitumen – specification”, (2ndRevision), IS 73: (1992).17. “Paving bitumen - specification”, (3rdRevision), IS 73: (2006).18. Brijesh Kumar and Nitish Puri, “Stabilization of Weak Pavement Subgrades usingCement Kiln Dust”, International Journal of Civil Engineering & Technology (IJCIET),Volume 4, Issue 1, 2013, pp. 26 - 37, ISSN Print: 0976 – 6308, ISSN Online: 0976 –6316.19. Ravin M. Tailor, Prof. M. D. Desai and Prof. N. C. Shah, “Performance Observations forGeotextile Reinforced Flexible Pavement on Swelling Subgrade: A Case of Surat, India”,International Journal of Civil Engineering & Technology (IJCIET), Volume 3, Issue 2,2012, pp. 347 - 352, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316.