seawater corrosion of rebar in SRC

seawater corrosion of rebar in SRC specimens was found much lower as compared to in
OPC specimens. DMS further decreases the corrosion rate of rebars in SRC cement. On
the contrary, in the case of OPC cement after 100 days corrosion increases with the
addition of microsilica. This rise in the negative potential does not show parabolic
behavior up to 230 days. The negative potential of rebars in specimens of OPC with
UDMS was found much high than all the concrete mixes from fifth day of the
immersion till 230th day. On the basis of these results it appears that DMS, which does
supress the corrosion of rebars when added to OPC and SRC in chloride environment,
shows adverse effect on the corrosion protection behavior of OPC in seawater. UDMS
appears to be further harmful if added to OPC in seawater environment. The following
observations can be generalized from the above study:

(i) In chloride environment, plain OPC and SRC concretes show higher
negative potential indicating poor corrosion protection to the rebars as
compared to microsilica added concretes.

(ii) In seawater environment, OPC concrete specimens show much higher
negative potential than SRC specimens indicating poor corrosion protection
of OPC as compared to SRC.

(iii) In seawater environment blending of OPC concrete with densified or
undensified microsilica lowers down the potential to more negative values
indicating further deterioration in their protection behavior. In blended SRC
the potential values are much less negative indicating suppression of
corrosion in rebars.

A better corrosion protection behavior of SRC as compared to OPC in seawater
indicates that in the presence of chlorides, sulfate attack is retarded. Similar results have
been reported by Kind [1956], Yagonibali [1984] and Harrison [1990]. Kind [1956]
reported increased sulfate resistance in some cements in sulfate solutions containing
high chloride concentrations. He attributed this effect to: