A system for the transport of high solids materials such as concrete includes a positive displacement pump, a pipeline connected to the pump and a valve in the pipeline located downstream from the pump for preventing material flow through the pipeline when the valve is in a closed position. The valve is closed at the end of each pumping stroke to prevent material flow through the pipeline. The pressure of material on the pump side of the valve is sensed. During a subsequent pumping stroke, the valve is opened when sufficient pressure exists on the pump side of the valve to ensure that material will flow in a positive direction through the pipeline.