Mechanical Behavior of RC and SFRC Precast Tunnel Lining Segments under Chloride Ions Exposure

Abstract

The structural integrity of precast concrete tunnel lining (PCTL) segments largely depends on its durability performance. The ingress of chloride ions into PCTL segments can induce reinforcement corrosion, which has been the primary cause that jeopardizes the structural safety of PCTL. This study explores the mechanical behavior of specimens extracted from full-scale PCTL segments made with conventional steel-rebar-reinforced concrete (RC) and steel-fiber-reinforced concrete (SFRC) for a subway tunnel in Canada and subjected to chloride ions exposure. Test specimens were subjected to chloride ion (Cl−) solutions with various concentrations (3.5 and 1.%) for up to 16 months, combined with weekly wetting and drying cycles. The mechanical degradation of RC and SFRC specimens was assessed after every 4 months of chloride ions exposure. Initially, an increase in concrete mass by .84 and .35% was observed for RC and SFRC PCTL segments, respectively, after 4 months of 3.5% Cl− exposure. However, after 8 months of Cl− exposure, a decreasing trend in mass was observed for both the RC and SRFC specimens. Furthermore, results indicated that the mechanical properties of conventional RC PCTL segments were more vulnerable to chloride-induced damage compared to that of SFRC PCTL segments. For instance, 19 and 47% decreases in compressive and flexural strengths, respectively, were observed in RC specimens after 12 months of exposure to 3.5% Cl− solution. Exposure to 1% Cl− solution led to a greater reduction in the mechanical properties of RC specimens compared to that of 3.5% exposure. No significant decrease in compressive and flexural strengths was observed in SFRC specimens due to Cl− exposure. Interestingly, the mechanical performance of SFRC specimens improved when subjected to chloride ions. Experimental results for both the RC and SFRC segments point to the potential of SFRC as a strong contender in the construction of precast concrete tunnel linings.