Eventhough the process is generally subject
to temperature at 40 – 100 degree Celsius but the range that produces the best
output is at 65 – 80 degree Celsius. In addition, temperature range is
basically attributable to requirement of strength development and ultimate
strength. With high temperature, compressive strength will relatively increase whilst
the ultimate strength will oppositely be low. For low temperature, ultimate
strength rather be applicably enhanced but reduce the rate of strength
development. In Figure 10.3 clearly shown the relationship of those mentioned.
In spite of curing temperature, the most
important thing is time consumption, which involves gradual increase of
temperature, the actual optimum temperature and reduction towards normal
temperature. As Figure 10.4, shows the process of controlling temperature.
After casting, concrete should be left at normal temperature approximately 2 –
6 hours prior to steaming so as to pre-stimulate the hydration reaction. Rate
of increase should not exceed beyond 30 degree Celsius/hour. Further more, when
concrete is subject to maximum temperature; it dominates the increase of
strength as it relies upon relationship of multiplied product of time and
temperature so called “Maturity” as shown in Figure 10.5. On the contrast, the
rate of reduction seems immaterial to this process due to concrete itself has
highly gained the strength. In general, rate of reduction is at 20 – 30 degree
Celsius/hour.
In many occasions, low pressure steam curing is
carried out for just concrete to reach the strength that is safe to be mobilized;
subsequently it will be cured by normal steam procedure until required strength
is acquired.
