1.4 Performance of Blended Cements in Chloride and Sulfate Environment
The deterioration of concrete structures exposed to marine environment and in contact
with soil and/or contaminated ground water is quite a common phenomenon. The
sulfate ion reacts with hydration products of cement, namely C3A and Ca(OH)2
resulting in deterioration of concrete structure. In such environments, ASTM C150
Type V cement with a low C3A has been recommended.
In marine environment including saline subkha soil and ground water, there is
concomitant presence of chloride and sulphate; the role of chloride in durability
performance of concrete is not very well understood. The conjoint presence of Cl-
and
SO4
=
in concrete particularly when it is fresh, influences reinforcement corrosion by two
mechanisms namely by a reduction in the chloride binding capacity of cements and by
decreasing the electrical resistivity of concrete. The rate of reinforcement corrosion in
the concrete specimens contaminated with Cl-
+SO4
=
was on an average 1.4 to 2.0 times
that in the concrete specimens contaminated with only chloride [Maslehuddin et al.,
1996]. Studies were carried out on the effect of SO4
=
, and SO4
=
and Cl-
environments
on the expansion as well as reduction in strength of plain and blended cements [Al-