Improvement of device (CMD) for monitoring the consolidation of plastic concrete

The development of an automatic distance gauging system for use in a device (CMD) for monitoring the consolidation of a portland cement concrete pavement is decribed. The capactive distance gauging system measures the air gap between the surface of the pavement and the bottom of a gamma backscatter instrument for density monitoring. The incorporation of the capacitance gauging system has made the density measurement independent of air gap height variations normally encountered as the concrete pavement surface is extruded behind a paving machine. Laboratory and field testing programs are described, and recommendations are made for further development and application of the density monitoring system.