Influence of Portland Cement Class on the Corrosion Rate of Steel Reinforcement in Cement Mortar Caused by Penetrating Chloride and Sulfate from the Environment

摘要

The influence of portland cement class on the corrosion rate of steel reinforcement in cementmortar caused by penetrating chloride or sulfate from the environment in already hardenedcement mortar is investigated in this paper. Three classes of portland cement have been usedfor the tests, PC 35, PC 45 and PC 55. Cylindrical samples of cement mortar with steel reinforcementin the middle were treated 6 months at room temperature in the following solutions:w(SO42–) = 2.1 % and w(Cl–) = 5 %. Two techniques have been used for testing corrosion rateof steel reinforcement in cement mortar: Tafel extrapolation technique and potentiodynamicpolarization technique. Investigations were conducted by potentiostat/galvanostat PrincetonApplied Research 263A-2 with the software PowerCORR?. The results of both techniques indicatethe most active corrosion of steel reinforcement in the samples prepared from cement PC35 in both treated solutions, while the lowest corrosion of the steel reinforcement was observedin cement samples prepared from cement PC 55. This conclusion was drawn by analyzing theresults shown in Figs. 1–4. Comparing corrosion current density of samples, working electrodes,Figs. 1 and 2, Table 2, the results show the most stable corrosion of steel reinforcement in samplesprepared from cement PC 55, and the most active corrosion in samples prepared from cementPC 35. The most active corrosion in samples prepared from cement PC 35 is evident fromthe positions of the open circuit potentials whose values are less for samples prepared fromcement PC 35 in both the treated solution, Figs. 1 and 2, Table 2. Comparison of the anodicpolarization curves of the working electrodes in both the treated solutions, Figs. 3 and 4, alsoshows that the intensity of corrosion is the largest for the working electrodes prepared fromcement PC 35 and the smallest for the working electrodes prepared from cement PC 55. Investigationresults should be considered as preliminary. To make the recommendations for theconstruction of reinforced concrete structures in the maritime environment the impact ofsulphates on concrete and steel bars should be investigated.