Another caution expressed by some agencies concerned the aggregate delivery system inside the different Crack Sealing Machine unit. Some Crack Sealing Machine use a hydraulically driven auger to deliver the aggregate to the hose mechanism. Other models use a low-pressure air system. Several of the agencies reported that in using a unit with an auger delivery system, the auger was wearing out because of abrasive aggregate. They recommend using a less abrasive aggregate or a unit with an air delivery system.
Each agency expressed a need to have good operators using the Crack Sealing Machine equipment. They also indicated that there would be a learning curve and productivity gains would not be seen until the operators became proficient. In most cases, they felt that 4-6 weeks would be needed before an operator would feel comfortable with the Crack Sealing Machine equipment.
