No abstract

AN electron microscope study was made to determine the effect of mechanical compaction method on the fabric produced in a compacted commercial kaolin. Direct platinumshadowed carbon replicas wore made from horizontal and vertical fracture surfaces within the middle third of cylindrical specimens compacted by static load, impact, and kneading compaction at optimum moisture content and at 3O/o above and below optimum. Replicas were studied in the electron microscope to arrive at a qualitative evaluation of fabric. No oriented fabric or edge-to-face random fabric of individual particles, as postulated by others, was found. Regardless of compaction method the fabric was found to consist of parallel and random arrangements of packets of kaolin flakes. Both impact and kneading compaction produced essentially the same fabric consisting of trajectories of parallel packets, probably the result of shearing deformation during compaction, within essentially randomly oriented zones of packets. Static load compaction produced a fabric in which some tendency of the packets to orient normal to the direction of loading was apparent. For all compaction methods some increase in parallel packet orientation was noted with increase in molding water content. The mode of parallel orientation differed between static load compacted specimens and those produced by either impact or kneading compaction. Results of the study indicate that some revision of concepts regarding particle orientation duo to mechanical compaction should be made.