Golden Gate National Recreation Area – Part II
Aug 01, 2011
Last year, Telfer Oil used Evotherm on a section of the Golden Gate National Recreation Area project, constructed by Ghilotti Brothers Inc. The project ran into several problems and delays, due to the weather, unstable sub-base, and other issues, but the mix compacted well despite the challenges. The original blog post is here.
The project continued along about 0.8 miles of another steep stretch of Conzelman Rd. And while similar delays took place again, according to Brian Dobling, Project Engineer for FHWA Central Federal Lands Highway Division, the ability of Evotherm mixes to compact after such delays was not just impressive, but helped to save the project. Throughout construction the heavy fog and strong winds typical of the Bay Area were rolling in (55F and 30 mph).
Dutra Materials produced the mix using 64/-28 PMA binder from Telfer, on 3/4" dense graded design, with binder content target of 4.9%. Temperatures in the drum plant ranged from about 290F – 310F, sometimes getting as low as 270F. Most of the temperatures behind the screed were in the 250F range.
The mix was laid in windrows and spread with a CAT AP-1055D paver with ExtendaMat screed. The breakdown roller was a CAT CB534D, followed by two smaller rollers in static mode. The rolling pattern was established with a Troxler nuclear density gauge, and though not calibrated with core data, the gauge was giving 92 – 93% densities rather consistently using the Rice number from the plant.
I brought the TransTech 380 PQI electromagnetic density gauge with me, and used the device to measure a number of points after the Troxler, and calibrated the PQI to the Troxler. The PQI also has a GPS feature and stores the measurements. It gave what appear to be decent values. These data can be viewed here. The numbers in the blue markers are the recorded density values, calibrated to the Troxler, so they are only relative.
All in all, the many cyclists I saw in the Park are going to be happy with the new road.
Author: Michael Plouff