Bulletin 80: Assessment of Existing Concrete Structures
About this book
FIB Bulletin 80: Assessment of Existing Concrete Structures, published by the fib (International Federation for Structural Concrete), provides a comprehensive framework for the structural assessment of reinforced and prestressed concrete structures that are already in service — whether for the purposes of confirming continued safe use, evaluating fire damage or accidental loading effects, preparing for change of use, or planning rehabilitation and strengthening work. As the definitive fib guidance document on this topic, Bulletin 80 bridges the gap between the design-centred assumptions of Eurocodes and the reality of assessing structures with known defects, deterioration, and incomplete documentation. The bulletin defines a structured assessment process with five stages: definition of the assessment purpose and scope; collection and review of existing documentation (design drawings, material test records, inspection reports, load history); structural investigation (non-destructive testing, material sampling, geometric survey); structural analysis using updated probabilistic material properties; and assessment conclusion with recommendations for intervention or continued monitoring.
Non-destructive testing methods for concrete assessment are reviewed in detail: rebound hammer testing (Schmidt hammer) for surface hardness as a proxy for compressive strength; ultrasonic pulse velocity (UPV) testing for integrity and crack detection; cover meter and ground-penetrating radar for rebar location and cover depth measurement; half-cell potential mapping for reinforcement corrosion activity; pull-out and pull-off tests for surface bond strength; and carbonation depth testing using phenolphthalein indicator. The bulletin discusses the interpretation of each test result type, the calibration requirements, and the combination of multiple methods for reliable assessment. Deterioration mechanisms and their structural consequences are examined: carbonation-induced and chloride-induced reinforcement corrosion (leading to cracking, spalling, and cross-section reduction), alkali-silica reaction (ASR) causing expansive cracking and strength reduction, freeze-thaw damage, chemical attack, and creep and shrinkage effects.
Assessment methods for each deterioration mode are provided. The updating of structural reliability using Bayesian probabilistic frameworks — incorporating site-specific test data to refine the probabilistic description of material properties — is presented as a rational basis for relaxing conservative code partial factors when assessment evidence supports higher confidence in material quality.