Effects Of Revibration On Early Age Retarded
Concrete
Author(s)
M. M. Kassim
Abstract
In this study, the influence of revibration on the compressive strength of retarded
concrete is examined at late lag time intervals before and after the initial and
final setting times. The time lag intervals ranged from about 2 hrs to 8 hrs and
the retarder dosages of the used cement weight ranged from 0.5% to 1.5%.
Results from this study indicate that the maximum compressive strength is
achieved when the concrete is revibrated after 2 hrs 35 min with 0.5% of retarder
dosage for any workability. Furthermore, higher dosages of the retarder do not
reduce the compressive strength of the concrete when it is revibrated at late lag
time intervals even near its final setting time. The use of setting retarder in high
doses and revibration of the concrete reduces the air-voids in hardened concrete.
Keywords: revibration, retardation, workability, fresh concrete, compressive
strength.
1 Introduction
It is essential to place concrete continuously to avoid cold joints in structures
such as beam-column intersection and large constructions (bridge decks and
turbine foundations). In these types of structures, micro transverse cracks could
form in the fresh concrete because of the changes in deflection and rotation over
supports during construction due to the dead weight of the concrete.
Additionally, theses cracks might result from a lapse in time between revibration
and the final setting of the earlier poured layers of concrete. (CCAA Report [1]
and Krishna et al. [2]).
Previous studies indicate that revibration improves many of the qualities of
hardened concrete since it is carried out within about 4 hours from the mixing
time. Compressive strength increases approximately 14%. Water tightness and
Keywords
revibration, retardation, workability, fresh concrete, compressive
strength.
Related Book
Other papers in this volume
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