AS 3600:2018

AS 3600 governs essentially every concrete-element decision TRSC makes. In the context of existing-asset assessment, the standard is applied differently from new design — and the application requires deliberate engineering judgement that the standard itself does not codify. Three points matter in practice. First, AS 3600 durability provisions in Section 4 are written for new construction. They specify exposure classifications (A1/A2/B1/B2/U), corresponding minimum cover, water/cement ratio and concrete grade, that protect new concrete against the design-life chloride and carbonation loading. For existing assets, those provisions are not directly applicable: we measure actual cover, actual chloride profile and actual carbonation depth, then assess whether the in-service durability is adequate against the residual design life of the asset. The 12 Creek Street investigation is a worked example: AS 3600 'minimum cover' provisions would have triggered a conservative facade remediation; measured chloride profiles and carbonation depths against measured cover demonstrated the substrate was performing adequately and a coating-only intervention was appropriate. Second, AS 3600 capacity provisions for shear and punching shear changed materially in the 2018 edition (Modified Compression Field Theory replaced the empirical formulation used in earlier editions). For pre-2018 existing structures, TRSC routinely re-checks capacity against the current edition's provisions because the capacity calculated under earlier methods can be unconservative for high-strength concrete or thin-section elements. Where this matters — typical examples are post-tensioned slab punching shear at column heads, transfer beam shear, and cantilever slab edge connections — we explicitly state the design basis in our investigation and remediation reports. Third, AS 3600 is silent on much of the assessment context. There is no formal AS 3600 'assessment' provision; the standard treats assessment as the inverse of design. TRSC fills this gap with measured-data input (chloride, carbonation, cover, concrete strength from extracted cores, reinforcement section loss from electrochemical surveys) and applies AS 3600 capacity equations to the measured properties rather than assumed-design properties. This evidence-based application is what gives TRSC investigation reports their commercial value: capacity assessed against measured properties is consistently — and often substantially — different from capacity assessed against AS 3600 minimum-design assumptions.