Effect of water vapour atmospheres on thermal transformations and mechanical strength of montmorillonite clay compacts

The thermal transformation of montmorillonite clay compacts has been studie d in water vapour (0.4 atm) and dry atmospheres by thermal analysis, XRD, a nd solid state MAS NMR. The water vapour atmosphere decreased the thermal t ransformation temperature by about 200 degrees C and produced a threefold i mprovement in the mechanical properties of the fired clay compacts (crushin g strength and softening coefficient). These effects are attributed to the increased strength at the contact points between the grains due to polycond ensation of silanol groups and may be a general phenomenon in a range of cl ay mineral types. RCT/379. (C) 2000 IoM Communications Ltd.