THE COMPACTION SPECIFICATIONS FOR HIGHWAYS FILL: PLACEMENT MOISTURE CONTENT RANGE FIXATION

SUMMARY

Invariably most highways specifications call for placement moisture content of engineered fills and pavement layers geomaterial to be in the range of OMC±2%. Some awarding agencies specify the placement moisture content in terms of percentage of OMC, typically between 75-120% of OMC. These specifications do not consider the moisture sensitivity of some soils, particularly fine-grained soils. A slight increase or decrease in moulding/placement moisture content of the geomaterial can result in a significant loss of strength. This paper examines the compaction and strength of eight soils of different geological formations at a moisture content of OMC±2% using CBR to measure the bearing capacity of the soil. Shortcomings of specifications based on an arbitrary placement moisture content specification of OMC ±2% are illustrated.