Civil Engineering Reference
In-Depth Information
55
50
45
40
35
30
25
20
Plain concrete (w/c: 0.61)
HVNP concrete (w/cm: 0.45 with Pozzolan no. 8)
HVNP concrete (w/cm: 0.45 with Pozzolan no. 9)
HVFA concrete (w/cm: 0.45)
15
10
5
3 7
28
91
Age, days
7.4
Compressive strength development of HVNP and HVFA concrete
(adapted from Uzal et al., 2007).
7.6.5 Modulus of elasticity
The modulus of elasticity of HVNP concrete made with a zeolitic natural
pozzolan is somewhat lower than that of the control concrete made with the
same w/cm ratio (Uzal, 2007). However, it is known that the modulus of
elasticity of HVFa concrete is higher than that of Portland cement concrete
with comparable strengths (Malhotra and Ramezanianpour, 1994). This
difference between HVFa and HVNP concrete mixtures could be related to
differences in microstructure of the interfacial transition zone, but it requires
further study. In both types of high-volume pozzolan concretes, the modulus
of elasticity is close to or higher than 30 GPa at 28 days, and thus they are
suitable for structural applications.
7.6.6 Resistance to chloride-ion penetration
Investigations into the resistance of HVFa and HVNP concretes to penetration
by chloride ions, as measured by ASTM C 1202 test method, indicated that
their chloride ion permeability is very low (Malhotra and Ramezanianpour,
1994; Bouzoubaa et al., 2000; Uzal et al., 2007; Uzal, 2007). ASTM C
1202 (2005) test method is based on the measurement of the total electrical
charge, in coulombs, passed through a concrete disc subjected to a potential
