Civil Engineering Reference
In-Depth Information
Maximum nominal size of aggregate, in.
handling aggregates much larger than 50 mm (2 in.) may
offset the savings in using less cement. Furthermore,
aggregates of different maximum sizes may give slightly
different concrete strengths for the same water-cement
ratio. In some instances, at the same water-cement ratio,
concrete with a smaller maximum-size aggregate could
have higher compressive strength. This is especially true
for high-strength concrete. The optimum maximum size
of coarse aggregate for higher strength depends on factors
such as relative strength of the cement paste, cement-
aggregate bond, and strength of the aggregate particles.
The terminology used to specify size of coarse aggre-
gate must be chosen carefully. Particle size is determined
by size of sieve and applies to the aggregate passing that
sieve and not passing the next smaller sieve. When speak-
ing of an assortment of particle sizes, the size number (or
grading size) of the gradation is used. The size number
applies to the collective amount of aggregate that passes
through an assortment of sieves. As shown in Table 5-5,
the amount of aggregate passing the respective sieves is
given in percentages; it is called a sieve analysis.
Because of past usage, there is sometimes confusion
about what is meant by the maximum size of aggregate.
ASTM C 125 and
ACI 116
define this term and distinguish
it from nominal maximum size of aggregate. The maxi-
mum size of an aggregate is the smallest sieve that all of a
particular aggregate must pass through. The nominal
maximum size of an aggregate is the smallest sieve size
through which the major portion of the aggregate must
pass. The nominal maximum-size sieve may retain 5% to
15% of the aggregate depending on the size number. For
example, aggregate size number 67 has a maximum size of
25 mm (1 in.) and a nominal maximum size of 19 mm (
3
⁄
4
in.). Ninety to one hundred percent of this aggregate must
pass the 19-mm (
3
⁄
4
-in.) sieve and all of the particles must
pass the 25-mm (1-in.) sieve.
The maximum size of aggregate that can be used
generally depends on the size and shape of the concrete
member and the amount and distribution of reinforcing
steel. The maximum size of aggregate particles generally
should not exceed:
3/16
3/8
1/2
3/4
1
1
1
/
2
2
3
4
3
/
8
300
500
Non-air-entrained concrete
400
200
300
Air-entrained concrete
200
100
100
Slump approximately 75 mm (3 in.)
w/c ratio: 0.54 by mass
0
0
450
700
400
Non-air-entrained concrete
600
350
300
500
Air-entrained concrete
250
400
Slump approximately 75 mm (3 in.)
w/c ratio: 0.54 by mass
200
4.75
9.5 12.5
19.0 25.0 37.5 50.0
75.0 112.0
Maximum nominal size of aggregate, mm
Fig. 5-9. Cement and water contents in relation to maximum
size of aggregate for air-entrained and non-air-entrained con-
crete. Less cement and water are required in mixtures having
large coarse aggregate (
Bureau of Reclamation 1981
).
37.5 mm
25.0 mm
19.0 mm
12.5 mm
9.5 mm
4.75 mm
2.36 mm
1.18 mm
(1
1
⁄
2
in.)
(1 in.)
(
3
⁄
4
in.)
(
1
⁄
2
in.)
(
3
⁄
8
in.)
(No. 4)
(No. 8)
(No. 16)
0 to 15
—
0 to 5
—
—
—
—
—
0 to 15
—
0 to 5
—
—
—
—
—
35 to 70
0 to 15
—
0 to 5
—
—
—
—
—
35 to 70
—
10 to 30
—
0 to 5
—
—
90 to 100
20 to 55 0 to 15 —
0 to 5
—
—
—
95 to 100
—
35 to 70
—
10 to 30
0 to 5
—
—
100
90 to 100
20 to 55
0 to 10
0 to 5
—
—
—
100
90 to 100
40 to 85
10 to 40
0 to 15
0 to 5
—
—
100
95 to 100
—
25 to 60
—
0 to 10
0 to 5
—
—
100
90 to 100
20 to 55
0 to 15
0 to 5
—
—
—
100
90 to 100
—
25 to 55
0 to 10
0 to 5
—
—
—
100
90 to 100
40 to 70
0 to 15
0 to 5
—
—
—
—
100
85 to 100
10 to 30
0 to 10
0 to 5
