Over the years, we've had many contractors describe what they believed to be inferior specifications, but it was hard for us to tell if the problem was widespread. To evaluate a broad sampling of concrete specifications, we visited plan rooms in Baltimore, Denver, Detroit, San Diego, and Seattle and did an in-depth review of 50 specifications.
According to a study funded by the National Cooperative Highway Research Program, initial pavement smoothness significantly affects future pavement smoothness, leading to pavements that remain smoother longer. But what's the best way to get better initial smoothness so that pavements last longer before requiring rehabilitation because of unacceptable ride quality?
A petrographic report is often used in construction disputes or litigation as evidence of poor workmanship by contractors. Contractors may accept these conclusions because they don't understand the limitations of petrographers' techniques. But because of these limitations, some of the conclusions should be challenged.
Longitudinal cracking and low air content due to excessive vibration can cause premature concrete pavement deterioration. Because vibrator frequency is a key controllable factor affecting the consolidation defects that lead to such deterioration, state DOT specifications often require paving contractors to periodically measure the frequency. However, when this requires them to slow or stop the paver and use a hand-held tachometer, it slows production. The solution: Equip the paver's hydraulic vibrators with sensors that monitor frequency and permit a continuous readout.