The Model 3440 gives you the features you need for compaction control, but its enhanced capabilities make it a step above our basic Model 3430. The Model 3440 is used to measure the density of asphalt, soil, aggregate or concrete and the moisture of soil or aggregate. Density can be measured in either the backscatter or direct transmission mode and moisture is measured in the backscatter mode. The backscatter mode is ideal for concrete and hot asphalt, while direct transmission is the choice for 50 – 300 mm (2 – 12 inch) lifts of soil and aggregates. Test results in as little as 1 minute allow additional compactive effort to be applied immediately if necessary.