ESEM observations of compacted bentonite submitted to hydration/dehydration conditions

ESEM observations clearly show that the mechanical compaction influences the textural behavior when the bentonite MX80 is submitted to a hydration/dehydration cycle. In general, the inter-aggregate pores are open during hydration stage and sometimes there is an aggregate cracking. This phenomenon is more significant when mechanical compaction increases since the cohesion force of inter-aggregates at high mechanical compaction “49 and 63 MPa” limits the free swelling of MX80 bentonite. In addition, Hg-porosimetry shows that only the macro-porosity (porous size >50 nm) and eventually the meso-porosity (porous size between 2 and 50 nm) are affected by the mechanical compaction. In fact, the total porosity decreases when the mechanical compaction increases. On other hand, BET measurements and adsorption isotherms of water vapour show a non-significant impact on the microporosity.