Study of the Influence of Cement Type, Cement Content, and Concrete Cover Thickness on the Resistance and Durability of Concretes Subjected to Chloride Ion Aging

摘要

Reinforced concrete structures constructed in coastal zones have constantly been threatened by environmental damaging elements. The chloride ion is known as one of the most aggressive of these elements, causing, among other damages, corrosion of the steel reinforcement and degradation of concrete. The goal of this work was to determinate the influence of the cement type and cement content, as well as the concrete cover thickness, in the resistance and durability of reinforced concrete elements exposed to aging in a 3.4% sodium chloride aqueous solution. Many concrete mixtures were made using CPII-F32 (with filler), CPII-Z 32 (pozzolanic mixture) and CPV-ARI RS (sulfur resistance) portland cements, with contents of about 290 and 350 kg/m~3 (490 and 590 lb/yd~3), and with the concrete cover thicknesses of 10, 15, 25 and 30 mm (0.394, 0.591, 0.984 and 1.18 in). The evaluation of the concrete behavior was taken from the results of physical and mechanical tests of cylindrical concrete samples and electrochemical tests―mainly the electrochemical impedance spectroscopy (EIS)―of small prismatic reinforced concrete samples. The results are presented for each combination of cement type and content, in terms of the aging time. Half cell potential measurements show that concretes made with CPV-ARI RS cement presented the best results, with longer periods necessary to produce electrical change in the samples. The concrete made with CPII-Z 32 cement and cement content of 288 kg/m~3 (485 lb/yd~3) was the mixture with the worst durability, with some samples showing fracture after 110 days of aging.