Reliability and durability assessment of recycled aggregate concrete under chloride ingress: Design optimization and service life implications

Abstract

This paper presents a reliability analysis of chloride penetration in concretes with varying replacement levels of natural aggregate (NA) by recycled aggregate (RA) at 25 % and 50 % by weight. Time-dependent Monte Carlo simulations (MCS) were performed to determine the probability of failure due to chloride ingress, which promotes corrosion initiation in reinforcements over time, and a superficial treatment made of silane was considered to improve the response of concretes in marine environments. The results indicate elevated failure probabilities for concrete containing RA, especially at 50 % replacement level. Furthermore, the reference concrete exhibited inadequate durability at design cover thicknesses of 20 mm and 30 mm. The sensitivity analysis using Sobol Indices (SI) identified cover thickness and chloride concentration threshold as the most significant parameters that influence the output of chloride penetration reliability predictions. A comparative examination between reliability-based design optimization (RBDO) and deterministic design optimization (DDO) revealed that deterministic approaches can underestimate the required cover thickness by up to 180 %. Assuming an admissible failure probability of 10 % over 50 years of exposure, concretes with RA required cover thicknesses ranging from 1.28 to 2.0 times greater than those of NA concrete. This study contributes to the development of standard prescriptions for minimum cover thickness in RA concretes, considering a reliability-based service life estimate.

Keywords

• Recycled aggregate
• Chloride
• Service-life
• Reliability analysis
• Reliability-based design optimization
• Sobol Indices