Manitoba’s Cold Experience
Jan 03, 2012
What happens to compaction when the air temperatures are hovering around freezing and trucks may sit for over an hour before placement? Manitoba Infrastucture and Tranportation gave McAsphalt Industries, our partners to the north, some excellent feedback from their trial using Evotherm warm mix asphalt technology this past construction season.
As often happens on jobs, some trucks sat for up to 1.5 hours prior to being placed. The mix still had good workability behind the paver after this time, meeting all volumetric properties including air content and VMA. The average density in most cases was 96.5-97%. Compaction effort at the reduced temperatures remained the same as a HMA project: double steel breakdown, pneumatic rubber, steel finishing.
The atmospheric temperature when paving took place was -3 C (27 F). Mix temperatures for haul distances greater than 50 km (31 mi) stayed at typical HMA mixing temperatures of 145-150 C (293-302 F). For shorter hauls, mixing temperatures were reduced to 135 C (275 F) because at the higher temperatures the mix behind the paver was holding heat too much and impacted compaction procedures.
Normally, Manitoba's temperature specifiction for surface paving is 6 C (43 F) and rising with less than a 40 km haul. For greater haul distances or when winds are over 10 km/h (6 mph), temperatures must be at least 10 C (50 F) and rising. For this project, the temperature requirements were modified to -5 C (23 F) and rising with no wind velocity specifiecation.
Author: Mark Wiese, McAsphalt Industries