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Compaction factor test

Compaction factor test used to measure the degree of compaction for a given concrete mix. this test is more precise than the slump test but it is less common. the size of the apparatus makes it difficult to conduct the test at the field. this test suitable for concrete with very low workability. compaction factor test developed by Road Research Laboratory in United Kingdom. 

Test apparatus

  • compaction factor apparatus: the compaction factor apparatus consist of upper hopper, bottom hopper, cylinder, and tamping road. the dimensions of the apparatus are shown in figure below.

  • balance: tolerance should be with 1 g only.

Test procedure

The test will be done in two stages. first stage fill the upper hopper gently with fresh concrete then open the trap door. remove the stuck concrete gently using the tamping rod then open the door for the bottom hopper. cut the excess concrete from the cylinder using trowel and level the concrete at top of the cylinder. clean any concrete stuck outside the cylinder and weight it (W1). this knows as the weight of partially compacted concrete. 
the second stage of the test: the cylinder will be filled in layers. each layer shall not exceed 5 cm and it must be compacted heavily using tamping rod or vibration to achieve full compaction. the exceesive concrete at cylinder top shall be removed and the weight of cylinder measured. this weight knows as fully compacted concrete (W2).

compaction factor=(W1-W)/(W2-W)

W is the weight of empty cylinder

The bulky apparatus and the need for balance limit the using of the test at construction fields. the using of hand compacting may not reflect the field condition and produce less effective results. however, the test is more precise compared to slump test and it is a dynamic test providing more information about concrete compactability


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