Concrete durability of the new Panama Canal: Background and aspects of testing

Abstract

The Panama Canal, vital to international trade, connects the Pacific Ocean and the Caribbean Sea, through the Gatun inland lake (which is almost entirely freshwater). The canal is now 100 years old. Since 2011, new lanes and locks have been or are being built, which will greatly enhance capacity and accommodate vessels with a much deeper draft. This is being done under the Panama Canal Authority (ACP) by a consortium named Grupo Unidos por el Canal, (GUPC), whose engineering division is headed by the firm Sacyr, S.A. Although the concrete on the earlier existing canal is not reinforced, the design for the new canal structures calls for reinforcing steel as an anti-seismic precaution. In its specifications, the ACP requires a 100-year service life for the concrete in all members, which is defined to mean conformity with the 1000-C electrical charge requirement of ASTM C1202, and an application of a reliable method for calculating service life. This chapter describes the tests performed on cores drilled from the old canal and the working program developed with GUPC for demonstrating the requirements, together with complementary test methods. The main tests were the measurement of concrete resistivity, as well as natural chloride diffusion found by ponding. The model used was the LIFEPRED numerical model, using the natural diffusion coefficients. The ageing of the diffusion coefficient was also measured through the resistivity evolution with time. The relationship between electrical charge and resistivity values is shown, along with the variation in these parameters over time. Also given are the chloride diffusion values obtained in four concrete mixes used as examples and their ‘age factor’, which proved to have an even more critical effect on predictions than the diffusion coefficient itself.