Civil Engineering Reference
In-Depth Information
Table 6.1
Chemical/physical properties and standard specification of pozzolans
Requirements
Standard specification
Natural
pozzolan,
Class N,
ASTM C618
Fly ash,
Class F,
ASTM C618
Silica fume,
ASTM
C1240
Chemical
requirements
SiO
2
+Al
2
O
3
+Fe
2
O
3
, %
min, 70
min, 70
-
SiO
2
-
-
min, 85
Sulphur trioxide (SO
3
), %
max, 4
max, 4
-
Moisture content, %
max, 3
max, 3
max, 3
Loss on ignition, %
max, 10
max, 10
max, 6
Physical
requirements
Amount retained when
wet-sieved on 45
m
m
sieve, %
max, 34
max, 34
max, 10
Strength activity index,
at 7 days, percent of
control
min, 75
min, 75
-
Strength activity index,
at 28 days, percent of
control
min, 75
min, 75
-
Accelerated strength
activity index, at 7 days,
percent of control
-
-
min, 105
Water requirement,
percent of control
max, 115
max, 105
-
Autoclave expansion or
contraction, %
max, 0.8
max, 0.8
-
Specific surface, m
2
/g
-
-
min, 15
this, the AsTM C311 abandons discussion of the pozzolan Psd (particle
size distribution) and only demarcates the percentage passing 45 mm.
6.4.2 ASTM C1240
originally it was intended to consider silica fume in AsTM C618; however,
this suggestion was rejected and silica fume is covered in AsTM C1240 -
first introduced in 1993 (ACI 234R, 1996). ASTM C1240 addresses physical
and chemical requirements of silica fume for cement replacement (see Table
6.1). The prominent requirements are: (1) the amount of sio
2
, and (2) the
accelerated strength activity index, defined in ASTM C311, considering that;
the amount of silica fume replacement in binary cement is 10%, the amount
of water in tested mortar is regulated with super-plasticizers to be identical
with control mortar, and specimens are stored at 65 °C for 6 days.
