Proposed durability parameters for reinforced concrete structures with design service life between 50 years and 100 years in Brazil

Abstract

The main system of a construction is the structure. Its replacement is most of the times unfeasible and its repair or demolition generates waste that is often difficult to recycle, reuse or dispose of. In this way, structures with longer design service life (DSL) will generate lower environmental impacts, in addition to being financially more interesting for their users. Reinforced concrete is one of the most used types of structure, and commonly suffers with attacks of chloride ions and carbon dioxide that can facilitate the corrosion of the reinforcement. Concrete structures also suffer effects from the passage of time, as probability of accidental load increase, creep and shrinkage. The objective of this study was to determine durability and time effect parameters for DSLs between 50 and 100 years. The durability study was conducted through a review of reference studies, a selection of DSL models based on characteristic forms of environmental aggressiveness and comparison with international standards, using DSLs between 50 and 100 years and the following parameters: w/c ratio, compression strength, minimum cement usage and minimum cover. The time effect study considered Brazilian standards and their probability for accidental loads, creep, shrinkage and variations of the compressive strength, using DSLs between 50 and 100 years. The durability results were compiled in a table with practical recommended dimensional parameters. Despite some proposed parameters being higher or lower than standard values, the differences in performance were accounted through other parameters in order to maintain safety levels and to obtain minimum cover thicknesses. Variable vertical loads presented increments of 4.29% for 75 years and 7.22% for 100 years and wind velocity demonstrated a variation of 5.08% increase at 75 years and 9.84% at 100 years. Compression strength of concrete, creep coefficient and specific shrinkage deformation did not present significant variations. FBM: conceptualization, formal analysis, methodology, writing; BFT e FLB: data curation, formal analysis.

Proposed variations in nominal reinforcement cover based on the environmental aggressivity class (EAC) of concrete exposure

“…To highlight the discrepancies, the maximum differences between these values were of 6.16 mm and 4.1 mm for T1 under EAC III and T4 under EAC IV, respectively. The variation in the required protection level of structures under different EAC was also evaluated by Mumberger et al [47] and longer service life periods required corresponding adequate cover levels. The analysis format of the standard AS 3600 [9] is used in Table 8 to present a summary of the necessary reinforcement cover with respect to compressive strength across EACs.…”