Penetration Grade

About Bitumen 

Bitumen is a dark brown to black viscous liquid or solid, consisting essentially of hydrocarbons and their derivatives.

It is soluble in trichloroethylene, is substantially non-volatile, and softens gradually when heated. Bitumen is obtained by refining petroleum crude oil, although it is also found as a naturally occurring deposit.

Penetration Grade of Bitumen

The penetration grading system was developed in the early 1900s to characterize the consistency of semi-solid asphalts. This test is carried out to know the hardness or softness of bitumen used in road construction by measuring the distance in tenths of millimeter to which a standard needle will penetrate vertically into a sample of bitumen under the stipulated conditions of temperature, loading and time. Penetration grading’s basic assumption is that the less viscous the asphalt, the deeper the needle will penetrate. The bitumen grade is specified in terms of penetration value. For instance, the bitumen of grade 80/100 means that the range of penetration value of the material is between 80 and 100. Depending upon the climatic conditions and type of construction, bitumens of different grades are used.

This test is almost applied exclusively for bitumen and it is not intended for softer materials like tar or cutback which are usually Standard penetrometer graded by the viscosity test

In general, it can be stated that for hot climates, lower penetration grades of bitumen are preferred and for cold climates, higher penetration grades of bitumen are preferred.

Lab Tests on Penetration Grade Bitumen to Check Quality

Various tests are conducted on bitumen to assess its consistency, gradation, viscosity, temperature susceptibility, and safety.

There are a number of tests to assess the properties of bituminous materials. The following tests are usually conducted to evaluate different properties of bituminous materials.

1. 1. Penetration test ;                                   ASTM D-5
   2. Ductility test;                                          ASTM D-113
   3. Softening point test ;                            ASTM D-36
   4. Specific gravity test;                             ASTM D-70
   5. Loss on Heating test;                           ASTM D-6
   6. Flash point test;                                    ASTM D-92
   7. Drop in Penetration after Heating;     ASTM D-6 & D-5
   8. Solubility in CS2;                                   ASTM D-4
   9. Spot test;                                               A.A.S.H.O.T.102

 

EN Standards for Penetration Grades

Harmonised European standards exist for most types of bituminous binders, the applicable specifications for bituminous binders in Europe are:

• EN12591 – Specifications for paving grade bitumen
• EN13924 – Specifications for hard paving grade bitumen

Bitumen gardes according to EN standard is calssified as below ;

• Bitumen Grade  35/50
• Bitumen Grade  40/60
• Bitumen Grade  50/70
• Bitumen Grade 70/100
• Bitumen Grade  100/150

Application

Over 80% of the 100 million tonnes of worldwide annual bitumen penetration grade consumption is used for paving applications in the construction and maintenance of roads. The remainder is used for various purposes. The use of bitumen in road maintenance can be up to four times its use in road construction.

The penetration grade bitumen is also used for Manufacturing of bitumen emulsions, polymer modified binders ,cutback bitumen and as a tack coat during surface dressing and for the manufacture of hot mix asphalt.