Title:
Effect of Prolonged Mixing on Compressive
Strength of Concrete with and without Fly
Ash and/or Chemical Admixtures
Author(s):
Dan Ravina
Publication:
Materials Journal
Volume:
93
Issue:
5
Appears on pages(s):
451-456
Keywords:
chemical admixtures; compressive
mixing time; prolonged mixing; retempering.
strength; concretes ; fly ash;
DOI:
10.14359/9849
Date:
9/1/1996
Abstract:
The effect of prolonged mixing-up to 180 min without retempering-on the compressive strength of non-air-entrained concrete with and without fly ash and/or chemical admixtures (water-reducing and retarding or high-range water reducers) at the age of 3, 7, 28, and 90 days was studied. It was found that the compressive strength of such concretes increased with mixing time up to a certain point. The increase was linear up to 135 min, differing for the various concrete groups: reference, fly ash (as partial sand replacement), WRR, and HRWR; after 90 min it amounted to 4 to IO percent and after 135 min it amounted to 6 to 1.5 percent. In the 135 to 180 mini-interval, the increase (except for the reference concrete) was very small-about I percent, and in some mixes, an actual strength decrease was observed.