Based on the compressive strengths calculated using the
simulation model, the following can be concluded.
High ash content results in a reduction in compressive
strength at early ages. Long-term strength (say after 1 year)
was improved by replacing up to 75 wt.% of the cement
with ash.
An optimum ash content was observed that resulted in
the highest compressive strength for a given porosity, and
this optimum increases with increased age. This optimum
content is dependent on age only and although the porosity
affects the compressive strength it does not affect the
optimum ash/cement ratio.
The trends observed for classified ash (pfa) and
unclassified ash (pozz-fill) were similar, with the pozz-fill
mixtures yielding marginally lower strengths than the mixtures
containing pfa. The pozz-fill mixtures (with up to more
than 70% of the cement replaced with pozz-fill) still
achieved higher long-term strengths than the mixtures containing
no ash.