Civil Engineering Reference
In-Depth Information
FIGURE 7.38
Measuring the spread dur-
ing the slump flow test.
earlier. In this slump flow test, the slump cone is completely filled, without
consolidation. The cone is lifted, and the spread of the concrete is measured,
as shown in Figure 7.38. The flowability is measured by the spread, or slump
flow. The spread typically ranges from 455 to 810 mm (18 to 32 inches), de-
pending on the requirements of the project. The resistance to segregation, or
stability, is measured with the visual stability index (VSI). The VSI is estab-
lished on the basis of whether bleed water is observed at the leading edge of
the spreading concrete or aggregates pile at the center. VSI values range from
0 for “highly stable” to 3 for unacceptable stability.
During the slump flow test, the viscosity can be measured by the rate at
which the concrete spreads. The time taken for the concrete to reach a spread
diameter of 50 cm (20 inches) from the moment the sump cone is lifted up
is measured. This is called the measurement and typically varies
between 2 and 10 seconds for SCC. A value indicates a more vis-
cous mix, which is more appropriate for concrete in applications with con-
gested reinforcement or in deep sections. A lower value may be
appropriate for concrete that has to travel long horizontal distances without
much obstruction.
T
50
1
T
20
2
T
50
1
T
20
2
T
50
1
T
20
2
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7.6.2
Flowable Fill
Flowable fill is a self-leveling and self-compacting, cementitious material
with an unconfined compressive strength of 8.3 MPa (1200 psi) or less.
Flowable fill is primarily used as a backfill material in lieu of compacted
granular fill (Figure 7.39). Flowable fill is also commonly referred to as con-
trolled low-strength material (CLSM), controlled density fill (CDF), flowable
compacting fill, lean fill, unshrinkable fill, flow mortar, fly ash flow, and liquid
dirt (NRMCA).
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