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Field identification test No 2 – Clay condition

Clays suitable for compaction with pedestrian controlled compaction plant can usually be identified by a simple roll test:


Select a sample of small lumps of the fine material only, at a moisture content representative of the bulk material.

Test – Clay Condition

With clean dry hands, take the sample and squeeze together in one hand and release. If the sample crumbles away and mostly fails to hold together into a ball then the sample is too dry for compaction. If not, break off part of the ball and roll between the palms or between one palm and any convenient clean dry flat surface, for example the back of a spade. Roll out the sample into a long thin cylinder until it fractures or begins to show significant transverse cracks.


If the strand can be rolled into intact or uncracked lengths that are thinner or longer than a typical pencil, i.e. less than 7 mm diameter or more than 175 mm length then the sample is too wet or too plastic for compaction. Any result between the ball and the pencil is acceptable for use provided the bulk of the material consists of lumps smaller than 75 mm.