Compaction Testing: Find Optimum Moisture and Max Dry Density
The purpose of compaction testing is to determine a material’s Maximum Dry Density (MDD) and Optimum Moisture Content (OMC)—two key parameters for earthworks quality control and performance. The results show the relationship between dry density and moisture content, helping engineers identify the moisture range where a fill material will compact best and achieve the required strength.
There are three common laboratory approaches using the same principles:
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2.5 kg and 4.5 kg methods for cohesive soils (e.g., silts and clays)
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Vibrating hammer method for granular materials (sand, gravel and aggregates)
Why compaction results matter
Compaction testing supports:
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earthworks control—site density results can be compared directly to the lab MDD/OMC to confirm compliance
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improved strength, stability and load-bearing capacity when materials are compacted to target (often ≥95%around OMC)
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reduced settlement and better long-term performance
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preparation of recompacted specimens for other tests such as CBR, shear box, and triaxial testing
Poorly compacted soils can lead to excessive settlement, shear failure, increased permeability, and reduced bearing capacity—all of which can create costly remedial work later.
Why choose The Testing Lab PLC?
At The Testing Lab PLC, we deliver compaction testing with consistent methods and clear, decision-ready reporting so you can control fill quality with confidence. We work closely with clients to match the right compaction method to the material and project specification.
Need compaction testing? Contact The Testing Lab PLC to discuss your samples and turnaround.
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