Civil Engineering Reference
In-Depth Information
5
HIGH-STRENGTH CONCRETE
700
Standard cure
The definition of high strength changes over the years as
concrete strength used in the field increases. This publica-
tion considers high-strength concrete (HSC) to have a
strength significantly beyond what is used in normal prac-
tice. For example, today about 90% of ready mixed con-
crete has a 28-day specified compressive strength ranging
from 20 MPa (3000 psi) to 40 MPa (6000 psi), with most of
it between 28 MPa (4000 psi) and 35 MPa (5000 psi).
Therefore, HSC considered here has a design strength of at
least 70 MPa (10,000 psi).
Most high-strength concrete applications are designed
for compressive strengths of 70 MPa (10,000 psi) or greater
as shown in Tables 17-3 and 17-5. For strengths of 70 MPa
(10,000 psi) and higher, stringent application of the best
practices is required. Compliance with the guidelines and
600
4
Insulating Blanket
500
3
400
300
2
200
1
100
0
0
18 hours
24 hours
3 days
Time
Fig. 17-4. Effect of blanket insulation on fast-track concrete.
The concrete had a Type I cement content of 421kg/m
3
(710
lb/yd
3
) and a water to cement ratio of 0.30 (
Grove 1989
).
Table 17-5 (Metric). Mixture Proportions and Properties of Commercially Available High-Strength Concrete
(
Burg and Ost 1994
)
Mix number
Units per m
3
1
2
3
4
5
6
Cement, Type I, kg
564
475
487
564
475
327
Silica fume, kg
—
24
47
89
74
27
Fly ash, kg
—
59
—
—
104
87
Coarse aggregate SSD (12.5 mm
crushed limestone), kg
1068
1068
1068
1068
1068
1121
Fine aggregate SSD, kg
647
659
676
593
593
742
HRWR Type F, liters
11.6
11.6
11.22
20.11
16.44
6.3
HRWR Type G, liters
—
—
—
—
—
3.24
Retarder, Type D, liters
1.12
1.05
0.97
1.46
1.5
—
Water to cementing materials ratio
0.28
0.29
0.29
0.22
0.23
0.32
Fresh concrete properties
Slump, mm
197
248
216
254
235
203
Density, kg/ m
3
2451
2453
2433
2486
2459
2454
Air content, %
1.6
0.7
1.3
1.1
1.4
1.2
Concrete temp., °C
24
24
18
17
17
23
Compressive strength, 100 x 200-mm moist-cured cylinders
3 days, MPa
57
54
55
72
53
43
7 days, MPa
67
71
71
92
77
63
28 days, MPa
79
92
90
117
100
85
56 days, MPa
84
94
95
122
116
—
91 days, MPa
88
105
96
124
120
92
182 days, MPa
97
105
97
128
120
—
426 days, MPa
103
118
100
133
119
—
1085 days, MPa
115 122 115 150 132 —
Modulus of elasticity in compression, 100 x 200-mm moist-cured cylinders
91 days, GPa
50.6
49.9
50.1
56.5
53.4
47.9
Drying shrinkage, 75 by 75 x 285-mm prisms
7 days, millionths
193
123
100
87
137
—
28 days, millionths
400
287
240
203
233
—
90 days, millionths
573
447
383
320
340
—
369 days, millionths
690
577
520
453
467
—
1075 days, millionths
753
677
603
527
523
—
