Page 380 - Handbook of Thermal Analysis of Construction Materials

358 Chapter 9 - Non-Portland Cement Binders and Concrete

Figure 1. Development of rigidity and compressive strength in magnesium oxychloride
cement. [8]

Beaudoin and Ramachandran compared the strengths (in terms of
microhardness) of various cements using microhardness-porosity plots. [9]
Strengths of various cement systems for different porosity values are
indicated in Fig. 2.
The MOC paste has the highest strength values over the porosity
range indicated. Normal portland cement paste has the next highest
values. The magnesium oxysulfate paste has the lowest values. The
strength values of MOC paste, obtained by extrapolating the strength-
porosity curve to zero porosity, exceeds that of the other cement systems.
The curves representing the latter converge to an approximately common
strength value at zero porosity. This suggests that the solids comprising
MOC paste have a higher intrinsic strength. The relative position of the
curve for MOC paste also suggests that the bonding between solid particles
is superior to that for the other cements over the porosity range investigated.
The nature of these bonds was investigated employing compacted speci-
mens prepared from ground MOC pastes. It is apparent that unlike portland
cement the interparticle bonds formed during hydration cannot be remade
by compaction.