Hixtra Ltd 
Construction & Geotechnical Testing 

Density and Compaction On-Site Testing 

 
Testing to assess the percentage compaction of backfill, earthworks and engineered fill on construction and civil projects 
 
Highways England earthworks specification often calls for testing to monitor the compaction level of placed materials. As this is the 'gold standard' specification, many other earthworks contracts call for the same type of testing, The basic principle is to first determine the maximum dry density that the material can achieve in laboratory conditions. 
 
Depending on the material and the likely compaction methods on-site, this can be tested in various ways and we can advise on which would suit best. Once this laboratory maximum dry density has been determined then site based density tests on compacted material can be undertaken with the on-site density values compared to the maximum laboratory value in terms of percentage. 
 
A common specification requirement would be that the on-site density should be at least 95% of the laboratory maximum density. In summary compaction monitoring would comprise of laboratory maximum density tests and on-site density tests. 
A variety of methods 
We can test for maximum dry density values using a 1 litre or CBR mould, using either a 2.5kg, 4.5kg or vibrating hammer, giving the full range of methods 
Even more methods for on-site density 
We can test on-site density using, core cutters, the sand replacement method and shortly non-nuclear methods. 
Help with specifications 
If you need some advice as to what tests should be done, where and how often then get in touch as we can help. 
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