Actions during hardening 75
is a polycarboxylic ether. Porphyry coarse aggregates have been used, with
particle size between 2 mm and 20 mm. Some silica fume was added.
This reference concrete, with a low water/binder ratio and containing silica fume, shows a high autogenous shrinkage strain, as shown in
Figure 4.3, with a value up to 450 mm/m after 144 hours. Due to this high
autogenous shrinkage in combination with the effects of the heat of hydration, early-age cracking can be expected when this concrete is applied for a
bridge deck (Craeye et al. 2011).
144
120
96
72
Time (h)
48
24
0
–500
–400
–300
–200
–100
100
200
300
400
0
Autogenous Shrinkage (µm/m)
REF
SAP_50
SAP_70
SAP_90
Figure 4.3 Reduction of autogenous shrinkage by means of SAP (Craeye et al. 2011).
Table 4.1 Concrete composition (kg/m³)
Component
REF
SAP50
SAP70
SAP90
Cement CEM I 52.5 R
475
475
475
475
Sand 0/5
588
461
410
359
Porphyry 2/6
482
482
482
482
Porphyry 6/20
677
677
677
677
Silica Fume
25
25
25
25
Super plasticizer
3.125
1.875
1.333
0.667
Water
150
150
150
150
Internal curing water
-
50
70
90
SAP
-
1.11
1.56
2.00