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The second compactor in the paving train was a nine-wheel pneumatic compactor, positioned too far behind the paving train to effectively manipulate the mix to reduce air voids. Both compactors were observed at various times 500 feet to 1,000 feet behind the paver.

Ideally, both compactors should have been working much closer to the paver so that mix temperature remained high and permit greater void reduction. The state's density technician suggested the rollers be moved closer to the paver, but was unsuccessful in changing these operators' rolling technique.

During the next 30 days, this contractor experimented with an assortment of brands and sizes of compaction equipment in an attempt to improve density and achieve the high density incentive for this long-term project.

A second visit to this paving project was made in late September. The contractor was still using a vibratory double drum compactor for breakdown, a nine-wheel pneumatic intermediate compactor, and a double drum vibratory compactor (without vibration engaged) for finish rolling. The first and second compactors were once again too far behind the paver, working on a mix that had already cooled too much to permit achieving target air void content and the agency's high density incentive.

There were also difficulties with mix delivery by the hauling units and a mechanical problem with the MTV that interrupted the paving operation and allowed mix to prematurely cool. However, I demonstrated to the operators that moving the compactors closer to the paver improved in-place density.