Civil Engineering Reference
In-Depth Information
Different slumps are needed for various types of con-
crete construction. Slump is usually indicated in the job
specifications as a range, such as 50 to 100 mm (2 to 4 in.),
or as a maximum value not to be exceeded. ASTM C 94
addresses slump tolerances in detail. When slump is not
specified, an approximate value can be selected from
Table 9-6 for concrete consolidated by mechanical vibra-
tion. For batch adjustments, the slump can be increased by
about 10 mm by adding 2 kilograms of water per cubic
meter of concrete (1 in. by adding 10 lb of water per cubic
yard of concrete).
aggregates (crushed stone). For some concretes and aggre-
gates, the water estimates in Table 9-5 and Fig. 9-5 can be
reduced by approximately 10 kg (20 lb) for subangular
aggregate, 20 kg (35 lb) for gravel with some crushed par-
ticles, and 25 kg (45 lb) for a rounded gravel to produce
the slumps shown. This illustrates the need for trial batch
testing of local materials, as each aggregate source is dif-
ferent and can influence concrete properties differently.
Table 9-6. Recommended Slumps for
Various Types of Construction
Water Content
The water content of concrete is influenced by a number of
factors: aggregate size, aggregate shape, aggregate texture,
slump, water to cementing materials ratio, air content,
cementing materials type and content, admixtures, and
environmental conditions. An increase in air content and
aggregate size, a reduction in water-cementing materials
ratio and slump, and the use of rounded aggregates, water-
reducing admixtures, or fly ash will reduce water demand.
On the other hand, increased temperatures, cement con-
tents, slump, water-cement ratio, aggregate angularity, and
a decrease in the proportion of coarse aggregate to fine
aggregate will increase water demand.
The approximate water contents in Table 9-5 and
Fig. 9-5, used in proportioning, are for angular coarse
Slump, mm (in.)
Concrete construction
Maximum*
Minimum
Reinforced foundation
walls and footings
75 (3)
25 (1)
Plain footings, caissons, and
substructure walls
75 (3)
25 (1)
Beams and reinforced walls
100 (4)
25 (1)
Building columns
100 (4)
25 (1)
Pavements and slabs
75 (3)
25 (1)
Mass concrete
75 (3)
25 (1)
*May be increased 25 mm (1 in.) for consolidation by hand methods,
such as rodding and spading.
Plasticizers can safely provide higher slumps.
Adapted from
ACI 211.1
.
Nominal maximum aggregate size, in.
Nominal maximum aggregate size, in.
0
0.5
1
1.5
2
2.5
3
0
0.5
1
1.5
2
2.5
3
250
250
400
400
Non-air-entrained concrete
Air-entrained concrete
350
350
200
200
300
300
150
150
250
250
200
200
100
169
100
169
0
10
20
30
40
50
60
70
0
10
20
30
40
50
60
70
Nominal maximum aggregate size, mm
Nominal maximum aggregate size, mm
Fig. 9-5. Approximate water requirement for various slumps and crushed aggregate sizes for (left) non-air-entrained
concrete and (right) air-entrained concrete. Adapted from Table 9-5,
ACI 211.1
and
Hover
(
1995
and
1998
).
