Numerical service-life modeling of chloride-induced corrosion in recycled-aggregate concrete

This paper presents the theoretical development, validation, and implementation of a 1D numerical service-life prediction model for reinforced recycled aggregate concrete exposed to internal and external sources of chlorides. The model accounts for the inclusion of supplementary cementitious materials (SCMs), namely (a) fly ash, (b) slag, (c) silica fume, and (d) metakaolin, and recycled aggregates (i) with and (ii) without initial chloride contamination from previous in-service exposure. The model is used to predict time to corrosion-induced cracking for reinforced recycled aggregate concrete in five case-study applications, namely structures in a marine splash zone (Zone I), a marine spray zone (Zone II), within 800 km of coastline (Zone III), within 1.5 km of coastline (Zone IV), and parking structures at locations greater than 1.5 km from the coastline (Zone V) in Los Angeles, California and Anchorage, Alaska. The effects of recycled aggregate size, aggregate replacement ratio, degree of aggregate pre-contamination, water-to-cement (w/c) ratio, and SCMs on time-to-cracking of reinforced recycled aggregate concrete are elucidated herein. The potential for SCMs to improve the service life of recycled aggregate concrete is investigated by estimating additions required to meet a target service life of 50 years. Results indicate that, in addition to geographic location, temperature, and severity of exposure, w/c ratio and aggregate replacement ratio exhibit the greatest impact on time to chloride-induced cracking in reinforced recycled aggregate concrete. Furthermore, initial aggregate chloride contamination and aggregate size impart minimal effects on expected service life. Finally, the results illustrate that the use of either fly ash or slag is most viable in achieving a 50-year service life for the recycled aggregate concretes in chloride-laden environments considered in this work.