Abstract
Measurements have been made with mortar specimens with light aggregates (LWA) and the cements Norcem HS65 and MP30, corresponding to CEM I and CEM II. The w/b ratio was 0.30 and 0.40 and in one mix prewetted LWA was used. The silica fume addition was 8%. The specimens have two sets of electrodes consisting of a 10 mm reinforcing steel and a 10 mm rod of stainless steel.
In the start of the experiment the chloride penetration was accelerated by applying a voltage between a negatively charged steel plate within the salt solution and a positively charged net of stainless steel embedded in the concrete above the reinforcing steels. This caused some problems and the set‐up was changed to using a Plexiglas brim and a solution of calcium hydroxide and sodium chloride was applied. In the solution, a titanium net was placed and a positive voltage of 12 V was applied between the embedded steels and the net with the titanium net as the positive pole.
Measuring galvanic currents, electrochemical potential and polarisation resistances have presented a good picture of the corrosion activity of the embedded steels. There is a distinct effect of the humidity upon the corrosion activity registered by the electrochemical measurements.
There is a good relation between the electrochemical measurements and the observed corrosion attacks at the end of the experiments.
The LWA concrete with water saturated aggregates showed more corrosion than the corresponding LWA concrete with dry aggregates. The rates of corrosion measured both as a galvanic current and as a function of the polarisation resistance showed that the concrete with watered aggregate concrete had a corrosion rate about twice as high as the corresponding LWA concrete with dry aggregates.
There are marked differences in the chloride penetration for the different cements. Effects have been observed on the chloride content of the different concretes. Lower w/b ratio, MP30 cement compared to HS65 and no prewatering of the LWA gave less chloride penetration.