They failed to account adequately for the rapid advancements in concrete technology, such as the introduction of chemical admixtures and diverse cement replacements.
To address these, CIRIA issued subsequent guidance (e.g., C660 "Formwork Pressure"), but Report 108 remains the foundational reference.
If formwork is designed for a pour rate of
High (Accounts explicitly for GGBS, Fly Ash, and Retarders via mix groups)
Superplasticizers increase workability without immediate stiffening, while retarding admixtures intentionally delay the set time. Both increase the duration of fluid pressure on the formwork. 4. Size and Shape of the Formwork ( ciria report 108 concrete pressure on formwork
cannot theoretically or practically exceed certain physical boundaries. Therefore, the final design pressure is subject to two absolute limits: Pmaxcap P sub m a x end-sub can never exceed the full hydrostatic pressure (
remains the definitive industry standard for calculating the lateral pressure exerted by fresh concrete on temporary structures. Published by the Construction Industry Research and Information Association (CIRIA) in 1985, this document revolutionized formwork design by replacing oversimplified empirical formulas with a comprehensive, scientifically validated methodology. Accurate calculation of concrete pressure is critical for structural safety, cost optimization, and quality control on construction sites. The Evolution of Formwork Pressure Calculation
The expected and minimum ambient temperature on site
Pmax=ρ⋅g⋅Hcap P sub m a x end-sub equals rho center dot g center dot cap H (Where is concrete density, is gravity, and is the pour height). Step-by-Step Engineering Workflow They failed to account adequately for the rapid
To explore how these calculation steps apply to your current project, please let me know: What is your expected and pour height ( ) ? Are you using any cement replacements like Fly Ash or GGBS ?
): The self-weight of the concrete mix creates hydrostatic pressure. Standard concrete typically weighs around 24–25 kN/m³, but heavy aggregate or lightweight mixes must be factored in accordingly. Vertical Formwork Dimension (
Do you still use the CIRIA 108 nomographs, or have you moved to pressure sensors and digital monitoring?
Reduction with time/setting: As concrete stiffens, lateral pressure decreases. The rate of reduction depends on mix chemistry, temperature, and admixtures (notably accelerators or retarders). Both increase the duration of fluid pressure on the formwork
Pressure characteristics and influencing factors
The calculated pressure is subjected to two strict boundary limits to ensure safety and realism:
Formwork bursting or moving during a pour poses severe safety risks to site personnel.