Civil Engineering Reference
In-Depth Information
Fig. 6-10. Plasticized, flowing concrete is easily placed in
thin sections such as this bonded overlay that is not much
thicker than 1
1
⁄
2
diameters of a quarter. (69874)
(3-in.) slump concrete can easily produce a concrete with a
230-mm (9-in.) slump. Flowing concrete is defined by
ASTM C 1017 as a concrete having a slump greater than
190 mm (7
1
⁄
2
in.), yet maintaining cohesive properties.
ASTM C 1017 has provisions for two types of admix-
tures: Type 1—plasticizing, and Type 2—plasticizing and
retarding. Plasticizers are generally more effective than
regular or mid-range water-reducing admixtures in pro-
ducing flowing concrete. The effect of certain plasticizers
in increasing workability or making flowing concrete is
short-lived, 30 to 60 minutes; this period is followed by a
rapid loss in workability or slump loss (Fig. 6-11). High
temperatures can also aggravate slump loss. Due to their
propensity for slump loss, these admixtures are some-
10
250
TC
TN
TM
TB
TX
8
200
Fig. 6-9. Flowable concrete with a high slump (top) is easily
placed (middle), even in areas of heavy reinforcing steel
congestion (bottom). (47343, 69900, 47344)
6
150
4
100
free of excessive bleeding or segregation. Following are a
few of the applications where flowing concrete is used:
(1) thin-section placements (Fig. 6-10), (2) areas of closely
spaced and congested reinforcing steel, (3) tremie pipe
(underwater) placements, (4) pumped concrete to reduce
pump pressure, thereby increasing lift and distance capac-
ity, (5) areas where conventional consolidation methods
are impractical or can not be used, and (6) for reducing
handling costs. The addition of a plasticizer to a 75-mm
2
50
0
0
0
20
40
60
80
100
120
140
Elapsed time, minutes
Fig. 6-11. Slump loss at 32°C (90°F) in flowing concretes
(TN, TM, TB, and TX) compared with control mixture (TC)
(
Whiting and Dziedzic 1992
).
