Assessment of rapid, non-nuclear compaction control devices

To ensure that compacted backfill performs as expected, compaction control is performed in the field by measuring the dry unit weight and moisture content of the compacted fill. The nuclear gauge is the most common device used to make these measurements because it is very rapid and thus does not delay the construction schedule. However, due to increased regulatory restrictions and growing concerns over the safety of using a device with a nuclear source, there is an increased effort to find a possible alternative to the nuclear gauge for compaction control. In this study, four devices were evaluated as potential replacements for the nuclear gauge. These devices include the Clegg Impact Hammer, the PANDA Dynamic Cone Penetrometer, the Moisture Density Indicator (MDI), and the Electrical Density Gauge (EDG). All the devices underwent laboratory testing conducted in large-scale soil specimens of poorly graded sand compacted to a target dry unit weight and moisture content. The MDI and EDG also underwent field testing at several different construction sites in central Texas. All testing includes comparisons between the results from the replacement devices and traditional compaction control devices. Analysis of the data revealed that, at this time, none of the four devices can be recommended to replace the nuclear gauge because they do not always accurately assess the compaction of the soil.