Hard paving grade bitumens

Hard paving bitumens have very high stiffness modulus values and are used for the construction and maintenance of road and airport pavements or other kinds of bitumen surfaces. Hard paving bitumens constitute an extension of common paving bitumens. They are usually used in locations with very high daily traffic flow, when annual ambient temperatures are intermediate or high. 

Hard bitumens, according to CEN EN 13924 (2006), are designated by a range of penetration values, at 25°C. Sometimes, they also bear the discreet letter H or HB . 

Source Reproduced from CEN EN 12591, Bitumen and bituminous binders - Specifications for paving grade bitumens, Brussels CEN, 2009. With permission ( CEN). 

Viscosity grade (grading based on original asphalt) 

Source Reprinted from ASTM D 3381, Standard specification for viscosity-graded asphalt cement for use in pavement construction, West Conshohocken, Pennsylvania, US ASTM International, 2012.With permission ( ASTM International). 

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The bitumen and bituminous binders may be divided into three general groups (a) the paving grade bitumens, (b) the hard paving grade bitumens and (c) the oxidised bitumens. 

Table 3.6 Specifications for hard paving grade bitumens... 

These additional properties are not part of the mandated essential characteristics but have been considered useful in specification of hard paving grade bitumens in some cases. Important - a restricted softening point range, of 5°C about a midpoint, shall be declared by the supplier the overall range shall be within the range in the table. 

The binder of HiMAs is hard paving grade bitumen 15/25 or 10/20, in accordance to CEN EN 13924 (2006), or very low paving grade bitumen 20/30, in accordance to CEN EN 12591 (2009). Modified bitumen may also be used provided the mixture s fundamental property requirements have been satisfied. 

Hence, as in paving grade bitumen, a 10/20 dmm hard paving bitumen denotes that the penetration is expected to range between 10 and 20 dmm. 

The binder material for empirically or fundamentally specified AC mixtures can be conventional paving grade bitumen, modified bitumen or hard bitumen. The conventional... 

The only difference with points referred to in Section 5.4.1.1 is that, in MA, when paving grade bitumen is used, only grades between 20/30 and 70/100 are selected, and when a hard grade bitumen is used, it should be from grades 10/20 and 15/25. 

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