F. K. Kong MA, MSc, PhD, CEng, FICE, FIStructE, R. H. Evans CBE, DSc, D ès Sc, DTech, PhD, CEng, FICE, FIMechE, FIStructE (auth.)-Reinforced and Prestressed Concrete-Springer US (1987)

Principles of concrete mix design 49
Table 2.6-1 Comparison of workability
measurements
Slump VB time Compacting
(mm) (seconds) factor
0 over 20 0.65-0.75
0-10 20-12 0.75-0.85
10-30 12-6 0.85-0.90
30-60 6-3 0.90-0.93
60-180 3-0 over 0.93
Table 2.6-1 gives some idea of the interrelationship of the three
workability tests. The data apply to the mixes used in the comparisons of
the tests and should not be assumed to be of general validity. Actually,
accurate comparisons of the tests are not possible because each test
measures the behaviour of concrete under a different set of conditions.
The relationships between the slumps and VB times in Table 2.6-1 are
reasonably reliable for a broad range of practical mixes, but the relationships
between the compacting factors and slumps or VB times are much
less consistent.
Table 2.6-2 defines arbitrarily four degrees of workability appropriate
for the principal types of construction where high-frequency vibrators are
used. The slumps given are those for concretes with aggregates having a
nominal maximum size of about 10 mm. For concretes of comparable
workability, the slump increases with the maximum size of the aggregates.
Compacting factors are relatively little affected.
Table 2.~2 Uses of concrete of different degrees of workability-maximum
aggregate size 10 mm nominal (adapted from Reference 32)
Degree of Slump Compacting
workability (mm) factor Type of construction
Very low 0 0.75 Roads or other large sections
Low 0-5 0.85 Simple to normal reinforced
concrete work
Medium 5-25 0.90 Normal to heavy reinforced
concrete work
High 25-100 0.95 For sections with heavily
congested reinforcement. Not
normally suitable for vibration
2. 7 Principles of concrete mix design
As stated at the beginning of this chapter, the aim in mix design is to select
the optimum proportions of cement, water and aggregates to produce a
concrete that satisfies the requirements of strength, workability, durability