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| Hardened Concrete |
An important
property of hardened concrete is the compressive strength. It is determined by
a compression test on specially produced specimens (cubes or cylinders) or
cores from the structure.
The main
factors influencing compressive strength are the type of cement, the water/cement
ratio and the degree of hydration, which is affected mainly by the curing time
and method.
The concrete
strength therefore results from the strength of the hydrated cement, the
strength of the aggregate, the bond between the two components and the curing.
Guide values for the development of compressive strength are given in the table
below.
|
Cement
strength class
|
Continuous
storage at
|
3 days
N/mm²
|
7 days
N/mm²
|
28 days
N/mm²
|
90 days
N/mm²
|
180 days
N/mm²
|
|
32.5
|
+20°C
+5°C
|
30…40
10…20
|
50…65
20…40
|
100
60…75
|
110…125
|
115…130
|
|
32.5 R;
42.5 N
|
+20°C
+5°C
|
50…60
20…40
|
65…80
40…60
|
100
75…90
|
105…115
|
110…120
|
|
42.5 R;
52.5 N
52.5 R
|
+20°C
+5°C
|
70…80
40…60
|
80…90
60…80
|
100
90…105
|
100…105
|
105…110
|
1The 28-day
compressive strength at continuous 20°C storage corresponds to 100%.
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