This study has investigated the activation of reactivity of fly ash in diff
erent blended cements such as lime-fly ash, lime-fly ash-stag and Portland
fly ash cements. Experimental results have indicated that the addition of N
a2SO4 can significantly increase the strength of all these blended cements.
The activation effect happens mainly during the first 3 to 7 days. The gri
nding of fly ash also increases its activity, but is not as effective as th
e addition of Na2SO4. On the other hand, the combination of grinding and th
e addition of Na2SO4 shows a much higher strength than a single activation
method. Finally, this paper also discusses the feasibility of the addition
of Na2SO4 in different cement and concrete products production processes. (
C) 2001 Elsevier Science Ltd. All rights reserved.