STRENGTH OF DRIED CLAY - A REVIEW

A COMPREHENSIVE REVIEW OF THE LITERATURE ON FRACTURE MECHANISMS AND STRENGTH CHARACTERISTICS OF DRY OR NEARDRY CLAYS IS PRESENTED. FRACTURE INVOLVES THE BREAKING OF BONDS BETWEEN CRYSTALS OR CRYSTALLINE AGGREGATES, RATHER THAN WITHIN THE CRYSTALS THEMSELVES. HYDRATED OR DEHYDRATED IONS, CRYSTALLIZED SALTS, CEMENTITIOUS IMPURITIES INCLUDING GEL- FORMERS, AND THE SURFACE TENSION AND VISCOSITY OF THE INTERSTITIAL LIQUID, CAN BE INVOLVED IN BONDING. VAN DER WAALS FORCES MAY BE LESS SIGNIFICANT. A STRONG BOND CAN RESULT IN AN OPENTEXTURED WEAK TEST PIECE. ISOTROPIC AND ANISOTROPIC STRENGTH IS RELATED TO FLAWS IN THE MICROSTRUC- TURE. CERTAIN FLAWS RESULT FROM OSBORNE REYNOLDS DILATANCY OR ARISE IN SLIP BANDS WHICH DEVELOP DURING PLASTICE DEFORMATION. NONPLASTICS IN LIMITED ANOUNTS MAY INCREASE STRENGTH BY BLOCKING CRACK-PROPAGATION ALONG SLIP BANDS. STRENGTH CAN BE TREATED THERMODYNAMICALLY WITHOUT DIRECT REFERENCE TO BONDING MECHANISMS OR MICROSTRUCTURES. /ACSB/