Effect of water-to-cement ratio on service life of reinforced concrete structures in chloride environment

Cracking of concrete induced by rebar corrosion is a main cause for deterioration of reinforced concrete structures especially for those exposed to chloride environment. In all of the parameters influencing the service life of concrete structures, water-to-cement ratio is a very important one for it determines the resistance of concrete against chloride aggression and corrosion-induced damage. In this paper, the parameters in corrosion process influenced by water-to-cement ratio of concrete (w/c) are screened all-round which include concrete tensile strength f(t), elastic modulus E-c, porous zone thickness delta(0), corrosion current density i(corr), critical chloride content C-cr, and chloride diffusion coefficient D-cl. The influences of w/c on the chloride penetration stage and the corrosion damage stage are studied. The first stage is expressed by Fick's second law, and the second stage is calculated using a commonly used analytical model, i.e. the thick-walled cylinder model. It is found that with the increase of w/c, the change of some parameters (f(t)up arrow, C-cr up arrow, D-cl down arrow, i(corr)down arrow) will induce increase of the service life, while the change of the others (E-c up arrow, delta(0)down arrow) will induce decrease of the service life. The diffusion stage and damage stage both shorten with the increase of w/c, and thus the total service life decreases with the increase of w/c. These results show that the increase of w/c presents a negative effect on the service life of concrete structures in total. In addition, with the increase of w/c, the service life for various concrete cover thicknesses and rebar diameters decrease in a similar tendency. For probability analyses, it is found that the probability density curves under different w/c are almost symmetric but show a little left-skewed, and the total service life for various w/c fluctuates about 0.6 to 1.0 year.