Civil Engineering Reference
In-Depth Information
a given value (criado et al.,
2010) has a beneficial effect on the compressive
strength of these concretes, regardless of the type of ash used.
Drying shrinkage
Mortars made entirely of alkali-activated fly ash exhibit promising shrinkage
properties.
in 2009, Fernández-Jiménez and Palomo (2009) studied shrinkage
in (OPC-free) alkali-activated fly ash mortar and compared the results with
the findings for a series of traditional Portland cement mortars. The fly ash
mortars had very small drying shrinkage values, clearly smaller than found
for the Portland cement mortars (see Fig. 17.10), an indication of their
dimensional stability.
Pull‑out test
Bonding provides for the transfer of stress between the steel and the concrete.
This characteristic is the key to the advantage in combining concrete, which
has a high compressive strength, and steel, which has a high tensile strength,
in reinforced concrete structures. When a steel bar embedded in a concrete
matrix is subjected to tensile force, the stress is transferred from the steel to
the concrete via slanted compressive forces originating at and following the
0.10
M-FA-N
M-CE-A
M-FA-W
M-CE-B
0.08
0.06
0.04
0.02
0.00
0
10
20
30
40
50
60
70
80
90
Time (days)
17.10
Drying shrinkage over time in fly ash mortars (cured at 85 °C)
alkali-activated with two types of activators: NaOH (M-FA-N) and
NaOH +Na
2
SiO
3
(M-FA-W) compared with the values obtained for
traditional Portland cement mortars cured at ambient temperature
(M-CE-A) or at 50 °C (M-CE-B) (Fernández-Jiménez and Palomo, 2009).
