Civil Engineering Reference
In-Depth Information
Table 7.5
Setting time of HVNP pastes and concretes
Cementitious
system
Pozzolan
Setting times (minute)
Reference
Initial
Final
Reference PC paste
-
155
180
Uzal and
Turanli (2003)
HVNP paste
Pozzolan no. 1
157
190
HVNP paste
Pozzolan no. 2
98
140
Reference PC paste
-
150
188
Turanli et al.
(2004)
HVNP paste
Pozzolan no. 3
197
295
Reference PC paste
-
175
215
HVNP paste
Pozzolan no. 4
103
157
Reference PC paste
-
160
189
HVNP paste
Pozzolan no. 5
115
144
Reference PC paste
-
218
245
Uzal and
Turanli (2012)
HVNP paste
Pozzolan no. 6
112
185
HVNP paste
Pozzolan no. 7
54
164
Reference PC concrete -
265
375
Uzal et al.
(2007)
HVNP concrete
Pozzolan no. 8
280
425
HVNP concrete
Pozzolan no. 9
185
395
Note: PC = Portland cement
due to incessant absorption of free water by the natural pozzolan, due to
their high specific surface area.
7.6.4 Strength
Strength development in HVPC mixtures varies significantly depending on
the type (fly ash or natural pozzolan) and source of the pozzolan used. HVFA
and HVNP concrete mixtures exhibit sufficient strength values for structural
applications both at early and later ages (Malhotra and Ramezanianpour, 1994;
Uzal et al., 2007). Since HVFa concrete mixtures are typically made with
lower w/cm values compared to HVNP mixtures, HVFa concrete generally
shows a higher rate and extent of strength development, especially in the
early stages. However, for the same w/cm, some HVNP concrete mixtures
exhibit comparable or higher compressive strength development for up to
28 days when compared with the identical HVFa concrete mixture. Beyond
28 days, HVFa concrete is again stronger than the HVNP concrete (Uzal
et al., 2007). Compressive strength development of the HVFA and HVNP
concrete mixtures made with the same w/cm is illustrated in Fig. 7.4 (Uzal
et al., 2007). Splitting-tensile strengths of the HVFa and HVNP concrete at
28 days are approximately 10-15% and 8-10% of the corresponding 28-day
compressive strength, respectively (Malhotra and Ramezanianpour, 1994;
Uzal et al., 2007).
