Docstoc

GRADING SYSTEM IN PAVING BITUMEN – AN INDIAN SCENARIO

Document Sample
GRADING SYSTEM IN PAVING BITUMEN – AN INDIAN SCENARIO Powered By Docstoc
					   INTERNATIONAL JOURNAL OF CIVIL (IJCIET), ISSN 0976 6308
  International Journal of Civil Engineering and TechnologyENGINEERING–AND
  (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME
                              TECHNOLOGY (IJCIET)
ISSN 0976 – 6308 (Print)
ISSN 0976 – 6316(Online)
Volume 4, Issue 2, March - April (2013), pp. 208-214
                                                                            IJCIET
© IAEME: www.iaeme.com/ijciet.asp
Journal Impact Factor (2013): 5.3277 (Calculated by GISI)                 © IAEME
www.jifactor.com




   GRADING SYSTEM IN PAVING BITUMEN – AN INDIAN SCENARIO

                        Apparao G1*, Rajesh G2, Gopala Raju S.S.S.V1
            1
                Civil Engineering Department, GITAM University, Hyderabad-502329
                  2
                    Assistant Manager, AARVEE Associates, Hyderabad. - 500072


  ABSTRACT
          In 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 water
  penetrating in to the structures. That to a rapid rate of development in every aspect of life
  and 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 of
  bituminous pavements. In fact, there is a huge gap in India between proper characterization
  of bitumen and its execution in the industries true to the specifications and the aspirational
  planning of creation of important public assets in the road sector whose durability and
  serviceability is very important socioeconomic improvement of the country. This paper
  gives an overview of paving bitumen grading system, characterization and the new
  viscosity graded (VG) bitumen specifications has been compared with the old penetration
  graded bitumen specification.
  KEY WORDS: Bitumen, Flexible Pavements, Viscosity gardening, and Penetration.
  1.0 INTRODUCTION
          In India Viscosity Grading (VG) system has b e e n adopted for paving bitumen since
  2006. And at the same time, the Bureau of Indian Standards has issued IS 73:2006
  paving bitumen – specification (Third Revision), which specifies paving bitumen by
  viscosity at 60 °C and 135 °C rather than the old system of grading paving bitumen by
  penetration at 25 °C. But still in the specifications given in the Ministry of Road Transport
  and Highways (MoRTH), so called orange book, does not revise its highway specifications
  related to base and surface of bituminous grading. This paper gives an idea of characterization
  of bitumen, merits and demerits of penetration and viscosity grading systems, and need to be
  changes incorporated in the Ministry of Road Transport and Highways (MoRTH)
  specifications.

                                               208
International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME

2.0 CHARACTERIZATION OF BITUMEN

       Bitumen is available in variety of types and grades. To judge the suitability of
bitumen binders are most commonly characterized by their physical properties rather than its
chemical properties. For engineering and construction purposes, normally three physical
properties of bitumen are important;
2.1 Consistency
       Consistency 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 solidify
when 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 some
empirical tests such as penetration, softening point, ductility etc. and also by testing the
fundamental property of bitumen such as viscosity.
2.2 Purity
        Pure bitumen is completely soluble in solvents like carbon disulphide and carbon
tetrachloride. Hence any impurity in bitumen in the form of inert minerals, carbon etc. could
be quantitatively analysed by dissolving the samples of bitumen in any of the above
mentioned solvent.
2.3 Safety
        Bitumen 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 by
the Indian standards are as follows:
        The flash point of a material is the lowest temperature at which the vapour of a
substance momentarily takes fire in the form of a flash under specified condition of test. The
fire point is the lowest temperature at which the material gets ignited and burns under
specified conditions of test.
        Thus, it can be concluded that there is no point to grade bitumen on purity and safety
aspect. It is the consistency property of bitumen by which it can be graded.

3.0 OVERVIEW OF BITUMEN GRADING IN INDIA

        The first Indian standard on the bitumen was first published in 1950 as
“Specification for asphaltic bitumen and fluxed native asphalt for road making purpose”: IS
73 which was revised in 1961 to change the grades of material and incorporate the
methods 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 the
paving grades were included. Based on the revised methods of test in IS 1201 to IS
1220:1978 ‘Methods for testing tar and bituminous materials (first revision) and the additional
data 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. The
variability 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 bitumen
specification has a requirement of minimum viscosity at 135°C, it will also be helpful in
minimizing the tender mix problems in the field.
                                               209
International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME

        Adoption of viscosity-graded paving bitumen specification will also reduce the
number of total tests to 7, which will reduce the cost of testing bitumen. This will result from
eliminating empirical tests/parameters such as – penetration ratio, paraffin wax content, and
Fraass breaking point without compromising the quality of bitumen.
        Since high penetration values are desirable for pavement durability, requirement for a
minimum penetration value is adequate and has been retained in the viscosity-graded
specification. Specifying a maximum value for penetration is undesirable and will reject
some good quality bitumen’s unreasonably.

3.1 Grading Systems
        Bituminous binders are most commonly characterized by their physical properties.
The challenge in physical property characterization is to develop physical tests that can
satisfactorily characterize key asphalt binder parameters and how these parameters change
throughout the life of an HMA pavement.
        Rather than refer to an extensive list of its physical properties, asphalt binders are
typically categorized by one or more shorthand grading systems. These systems range from
simple penetration grading to complex Superpave performance grading and represent an
evolution in the ability to characterize asphalt binder.

3.1.1 Penetration Grading
        The penetration grading system was developed in the early 1900s to characterize
the consistency of semi-solid asphalts. Grading of bitumen by penetration test at 25 °C was
adopted by the American Society for Testing and Materials (ASTM) Committee D04 on
Road and Paving Materials in 1903. To quantify the Penetration grading the following
asphalt concrete characteristics are to be evaluated as per the standard IS: 73-1992;

            Penetration depth of a 100 g needle; 25° C
            Flash point, °C
            Softening point °C
            Penetration ratio
            Ductility at 25 °C, cm
            Paraffin wax content
            Fraass breaking point
            Solubility in trichloroethylene
            Loss on heating (TFOT)
            Retained penetration after Thin Film Oven Test (TFTO)
            Viscosity at 60 °C and 135 °C
            Water content
            Specific gravity at 27 °C

       Penetration grading basic assumption is that the less viscous the asphalt, the deeper the
 needle will penetrate. This penetration depth is empirically correlated with asphalt binder
 performance. Therefore, asphalt binders with high penetration numbers (called "soft") are
 used for cold climates while asphalt binders with low penetration numbers (called "hard")
 are used for warm climates.


                                              210
International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME

       In figure 1, there are three, bitumen A, B & C whose penetration at 25oc is
       same i.e., 65. But these bitumen are having different stiffness values at higher (say
       60oC) temperature and at lower (say 4oc) temperature

       The slope of the stiffness Vs. temperature curve is called temperature susceptibility.
       Steeper is the slope, more will be the temperature susceptibility of the bitumen. In
       fig 1, bitumen ‘C’ is most temperature susceptible , in other words more prone
       to rutting at high temperature and more prone to cracking at low
       temperatures (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 low
                                   service temperatures

3.1.2 Viscosity grade
       In the early 1960s an improved asphalt grading system was developed that
incorporated a rational scientific viscosity test. This scientific test replaced the empirical
penetration test as the key asphalt binder characterization. To quantify the Viscosity
grading the following asphalt concrete characteristics are evaluated based on the as
per IS: 73 - 2006;
       Absolute viscosity at 60 °C, poises
       Kinematic viscosity at 135 °C, cSt
       Flash point
       Solubility in trichloroethylene
       Penetration depth of a 100 g needle; 25° C
       Softening point
       Tests on residue from thin film oven tests/RTFOT;
       viscosity ratio at 60 °C and Ductility at 25 °C, cm

                                             211
International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME

        Viscosity is defined as inverse of fluidity. Viscosity thus defines the fluid property of
bituminous material. Viscosity is the general term for consistency and it is measure of
resistance to flow. Many researchers believe that grading of bitumen should be by absolute
viscosity in it’s instead of the conventional penetration units.
        By measuring consistency at three different penetration, the range (minimum and
maximum temperatures (Figure 2) and specifying the ranges, values) for absolute viscosity
at 60oc, and the slope of temperatures Vs. stiffness curve i.e., the temperature
susceptibility of bitumen can be bound in a specified range which is the key for better
performances. Minimum value for kinematic viscosity at 135oc have been specified, which
are more rotational. As per given the in the table 1 the specifications of the Indian standard
which is IS: 73-2006 needs to be modified shortly.
     Defining the range (minimum and maximum values) for penetration at 250C, minimum
value for absolute viscosity at 600C, and minimum value for kinematic viscosity at 1350C, the
temperature susceptibility of bitumen can be controlled in a better way towards better
performance. However, in ASTM D 3381 specification for viscosity graded asphalt binders,
the minimum value only for penetration, the range (minimum and maximum values) for
absolute viscosity at 60oc, and the minimum value for kinematic viscosity at 135oc have been
specified, which are more rotational. As per given the in the table 1 the specifications of the
Indian standard which is IS: 73-2006 needs to be modified shortly.




       Figure 2: Graphical representation of viscosity-graded AC-30 (VG-30) bitumen

                                              212
International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME

                    Table 1: Requirements for Paving Bitumen as per IS: 73-2006

                       Characteristics                         VG-10    VG-20   VG-30     VG-40
Absolute viscosity, 60 °C, poises, min                           800     1600    2400       3200
Kinematic viscosity, 135 °C, cSt, min                            250    300     350       400
Flash point, °C, min                                             220    220     220       220
Solubility in trichloroethylene, %, min                         99.0     99.0    99.0     99.0
Penetration at 25 °C                                           80-100   60-80   50-70      40-60
Softening point, °C, min                                        40      45      47         50
Tests on residue from thin film oven test/RTFOT:
Viscosity ratio at 60 °C, max                                   4.0     4.0     4.0       4.0
Ductility at 25 °C, cm, min, after thin film oven test          75      50      40         25



4.0 CONCLUSIONS

         The existing penetration grading system of bitumen has been replaced by viscosity
         grading system in India based on improvement in the durability and serviceability
         condition of the desired extent. For this, issues regarding improvement of the
         specification and also manufacturing of bitumen true to that specification need to be
         addressed.
         In view of modification and improvement of the current specification of IS : 73
         (specification for paving grade bitumen), sample of bitumen are being collected from
         all 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 the
         MoRTH for section 500 which is guidelines for base and surface course of bituminous
         layers given based on the penetration grading only. Though in the recent revision, these
         specifications have been revised as per viscosity grading.

5.0 REFERENCES

1. SSSV Gopala Raju (2007), “Reuse of polyethylene waste in road construction”, Journal
   of Environmental Science and Engineering, Vol.49, No.1, pp.67-70
2. SSSV Gopala Raju(2010), Utilization of building waste in road construction”, Indian
   Journal of Science and Technology, Vol.3, No.8,pp. 894-896
3. Prithvi Singh Kandhal, P.S (2007), An overview of the viscosity grading system
   adopted in India for paving bitumen “Indian Highways.
4. Rajib Chattaraj (2011) “Bitumen Grading system – from penetration grading to viscosity
   grading – A step towards better quality control” ,“INDIAN HIGHWAYS”
5. MoRTH (Ministry of Road Transport and Highways) (2001). “Specification for Road
   and Bridge Works”. Indian Roads Congress, New Delhi, Section 500, Bases and surface
   courses for bitumen.
6. Kandhal, P. S (2005),“ Selection of Bitumen for Paving Highways”, Indian Roads
   Congress, Indian Highways

                                                         213
International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME

7. Kandhal, P.S., L.D. Sandvig, and W.C. Koehler (1973), “ Asphalt Viscosity Related
    Properties of In-Service Pavements in Pennsylvania”, ASTM Special Technical
    Publication 532..
8. Kandhal, P.S. and M.E.Wenger (1975), “ Asphalt Properties in Relation to Pavement
    Performance”, 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 Pavement
    Performance”, ASTM Special Technical Publication 628.
11. Kandhal, P.S (1988)., “Low-Temperature Properties of Paving Asphalts”, TRB State-
    ofthe- Art Report 7
12. Kandhal, P.S. and W.C. Koehler (1987), “Effect of Rheological Properties of Asphalts on
    Pavement Cracking”, ASTM Special Technical Publication 941.
13. Kandhal, P.S., L.D. Sandvig, and M.E. Wenger (1973), “ Shear Susceptibility of Asphalts
    in Relation to Pavement Performance”, Proc. Association of Asphalt Paving
    Technologists, Volume 42.
14. Kandhal, P.S (1980), “Evaluation of Low-Temperature Cracking on Elk County Research
    Project”, TRB, Transportation Research Record 777.
15. Kandhal, P. S (2006), Quotations for Supply of Vacuum Viscometer Equipment from
    Indian 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 using
     Cement 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 for
     Geotextile 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.




                                           214

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:0
posted:4/29/2013
language:Latin
pages:7