Ciria Report 108 Concrete Pressure On Formwork -
CIRIA Report 108, "Concrete pressure on formwork," serves as a foundational guide for calculating the lateral pressure exerted by fresh concrete on temporary formwork structures, accounting for variables like rate of rise, temperature, and mix composition. It provides specific formulas to determine maximum pressure ( Pmaxcap P sub m a x end-sub
Apply reduction factors where appropriate: For slower placement and mixes that set quickly (or when using accelerators), designers may apply pressure-reduction factors based on empirical curves or charts (as provided in the report) that relate casting rate, concrete properties, and time since placement to lateral pressure. ciria report 108 concrete pressure on formwork
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A. Clarity of Presentation
The report utilizes clear charts and tables to derive coefficients ($C_1$, $C_2$) based on concrete temperature and cement type. For a site engineer or temporary works coordinator, the workflow is logical and easy to follow. The pressure diagrams (showing hydrostatic head vs. the design envelope) visually explain why the pressure is calculated the way it is. CIRIA Report 108, "Concrete pressure on formwork," serves
Project:
12-story reinforced concrete core wall, London Formwork: Crane-lifted gang forms, 2.8 m tall panels Concrete: C35/45, slump 80 mm, rate of placement 3 m/h, temperature 18°C "CIRIA Report 108 PDF" "concrete lateral pressure charts
CIRIA R108 was a landmark publication because it moved away from purely prescriptive tables and provided a rational, semi-empirical method for calculating pressure based on the specific properties of the pour. Despite its age, it remains a cornerstone document referenced in the Temporary Works Forum (TWf) guidance and is often preferred over the Eurocode methods for its clarity.
Advantages of Using CIRIA 108:
Consider time-dependent load cases: Check formwork both for the peak pressure during casting and for reduced pressures as concrete sets; bracing and ties must resist transient peak loads.
The formula above does not apply infinitely. CIRIA 108 imposes two absolute limits: