NERI, K. D.; http://lattes.cnpq.br/7605887176195246; NERI, Kátya Dias.
Résumé:
The corrosion of reinforcing steel is of great concern in the construction, because the most
common cause of deterioration in reinforced concrete. Initially, the embedded steel from
corrosion and naturally protected by high alkalinity of the concrete structure. However, this
passive state can be broken by destroying the passive film by aggressive ions (chlorides,
sulfates). In this paper, we study the behavior of three types of concrete over the water /
cement ratio (0.4, 0.5, 0.6) subjected to chemical attack of a solution consisting of only
ehlotide (NaCl) and two 1M increased by 0.4% and 2% H2S04 , respectively. To evaluate the
critical chloride content in concrete. For the tests we used the electrochemical technique of
linear polarization resistance (LPR) to measure the corrosion potential (Ecorr) and corrosion
current density (icorr) after their bodies depassivation proof-of-test and were removed from
the ruptured for visual evidence of corrosion in the steel and determination of the levels of
OH- and CI- total and free, Na + Ca +2, K + and SO4. The leaching method was employed to
determine pH. The leaching efficiency was assessed by measuring the pH of the sample
despassivada and that obtained by titration. We used the potentiometric titillation to determine
the chloride content retained in the concrete. And with the pH and concentration of CI
determined the ionic relations [C1-] / [OH-], referring to the contents retained in the concrete
in the induction process of corrosion. The concentrations of sulfate were determined by
turbidimetric method and the alkali (Na K Ca ~2) by rlame photometry. In this research
can be observed that the water / cement ratio and aggressiveness of the solutions were
determining factors for the corrosion of steel The concrete of higher water / cement ratio
(0.6) subjected to NaCl solution + 2% H2SO4 as the first to despassivarem, had the lowest
value of compressive strength and greater retention of chlorides. We obtained an average
difference between the results of pH titration and pH meter to about 3% with standard
deviation of ± 0.06, a total CI- content (1.07 - 2.5)% by weight of cement and an average ratio
of[Cl-]/[OH-](0.1-0.33).