Paving in today''s climate is a balancing act. Contractors have a desire to lay high tonnages of material per day. Yet with current mix designs like Superpave and SMA (Stone Matrix Asphalt), there''s a tipping point between paving speed and quality. Whether dictated by spec or company pride or policy, sometimes the paving crew must slow down to deliver the desired mat quality.

For contractors who want to lay more tons of material in a day, there is a right way and a wrong way to deliver high mat quality. High speeds using only a paver can create a hurry-up and wait paving sequence as the paver runs out of asphalt before the next truck arrives. "This makes it difficult to maintain a constant head of material at the screed, so smoothness suffers," says Mark Hunt, general manager of Terex Roadbuilding''s Asphalt Group.

Establishing a continuous paving process will deliver a smoother mat, but it takes a great deal of planning and coordination between plant production, trucking needs and the paving train''s speed. Sometimes it''s difficult to continuously lay material with a paver alone, as truck exchanges are slow and hopper capacity is limited. "It''s not recommended for the paving crew to run the hopper dry as this can lead to truck-end segregation," says Bill Rieken, paver application specialist for Terex Roadbuilding. "So this limits the surge capacity of the hopper and the distance that can be paved before the next truck arrives."

A number of machines are available to help bridge this gap and deliver more paving time between truck exchanges. Material transfer devices (MTDs), like windrow and mat smoothness machines, and material transfer vehicles (MTVs) deliver the additional surge capacity to help contractors better establish a continuous paving process to produce a higher quality, smoother mat.

Selecting the right machine for the paving train depends on a number of factors from production goals and mix designs to truck availability and state specifications.