Performance Grade bitumen is a type of bitumen which is graded according to its Performance at different alternating temperatures. There is a tendency to divide PG grade into two divisions of high temperature and low temperature pavement services.
Here comes the major issue for high temperature performance which is rutting, that normally takes a while to amass. Thus, the temperature is measured within a week and the highest is considered to be the high climatic temperature. On the other side, there is a possibility for thermal cracking at low temperature. For both high and low temperature, PG grades are graded in 6 ºC (43 ºF) rise. The average seven day maximum pavement temperature typically changes from 46 ºC (114 ºF) to 82 ºC (180 ºF) and the minimum pavement temperature changes from –46 ºC to –10 ºC. For instance, bitumen PG 64–10 meets performance factor at an average seven day maximum pavement temperature of 64 ºC (147 ºF) also at a minimum pavement temperature of –10 ºC.
Performance Grading Should:
• Include measures describing stress
– Strain Relationships under field loading.
• Consider the pavement conditions
– Temperature, traffic speed, traffic volume, and pavement structure.
• Include acceptance limits derived from experience and actual field performance.
Variables that affect Binder Selection:
• Geographic Area:
– Air Temperature, Solar radiation
– Pavement Temperature: Max & Min
• Traffic volume: High, Medium, Low
• Traffic speed: Fast, Slow
• Pavement Structure: Strong, Weak
– Stress and strain
Methods of Selection:
• Select base grade based upon:
– Geographic Area
– Air Temperature
– Pavement Temperature
• Adjust base grade based upon:
– Traffic Speed
– Traffic Volume
Mind the point that maximum pavement temperature is usually higher than the air temperature by about 20 ºC (68 ºF) because the dark color of pavement absorbs the heat and keep it. As PG grades are mainly divided into: (1) Modified and (2) Unmodified bitumen types, keep in mind the following hint which helps to differentiate the mentioned types.
To distinguish the modified from unmodified bitumen, we add both low and high temperature grades together. If the sum is greater than 90, the substance is likely to be a polymer modified binder. As an example, a PG 76–22 is considered as a polymer–modified binder since the sum is 98. Another example, a PG 64–10 is an unmodified binder.
Application of Performance Grade (PG) Bitumen:
- PG52–28 is primarily used in paving for both new construction and pavement rehabilitation and in both dense–graded and open graded “Hot Mix Asphalt” (HMA). This product could also be used for sealing of edges of new to told paving and crack sealing. Other uses include spray applications for bridge deck and pavement protective membrane with fabrics.
- PG58–22 is primarily used in paving for both new construction and pavement rehabilitation and in both dense–graded and open graded “Hot Mix Asphalt” (HMA). This product could also be used for sealing of edges of new to told paving and crack sealing. Other uses include spray applications for bridge deck and pavement protective membrane with fabrics.
- PG58–28 is primarily used in paving for both new construction and pavement rehabilitation and in both dense–graded and open–graded HMA. Other uses include spray applications for bridge deck and pavement protective membrane with fabrics.
- PG58–28 is generally used in very cold areas.
- PG58–34 is generally used in the upper half of Eastern Washington and on higher elevation roadways. PG58–34 is paving asphalt cement primarily used for the production of Hot Mix Asphalt (HMA). This product could also be used for sealing the edges of new to old paving and crack sealing. PG58–34 is used in paving for both new construction and pavement rehabilitation in both dense–graded and open–graded HMA.
- PG58–40 is primarily used on the high elevation roadways. PG58–40 is paving asphalt cement for the production of Hot Mix Asphalt (HMA). This product could also be used for sealing of edges of new to old paving and crack sealing.
Standard Specification Of Performance Grade: