), while CIRIA 108 seamlessly unifies walls and columns under a single generalized structural equation using the minimum section dimension ( 7. Summary Checklist for Formwork Designers
Modern mixes: Self-compacting concrete and special admixtures can produce pressures exceeding traditional hydrostatic assumptions in some cases; designers should treat such mixes cautiously and may need more recent research or testing.
Pmax=D⋅[C1⋅R+C2⋅K⋅H−C1⋅R]cap P sub m a x end-sub equals cap D center dot open bracket cap C sub 1 center dot the square root of cap R end-root plus cap C sub 2 center dot cap K center dot the square root of cap H minus cap C sub 1 center dot the square root of cap R end-root end-root close bracket
The construction of concrete structures requires safe, efficient, and economical temporary support systems. Formwork failure represents one of the most common and catastrophic risks on a construction site, often leading to structural collapse, injuries, and significant financial loss. To mitigate these risks, engineers must precisely calculate the lateral pressure exerted by fresh concrete against the vertical or inclined faces of the formwork. ciria report 108 concrete pressure on formwork
The six examples included in the report are:
It is written with the authority of research but the pragmatism of the construction site. For any engineer designing vertical formwork, R108 remains an indispensable tool, serving as a sanity check against more complex modern standards.
Published in 1985 by the Construction Industry Research and Information Association (CIRIA), "Concrete Pressure on Formwork" (Report R 108) has remained a cornerstone reference for calculating the maximum lateral pressure exerted by freshly placed concrete against vertical formwork surfaces. This comprehensive article explores the origins of R 108, its detailed calculation methodology, practical applications through worked examples, and its evolving relevance in the era of Self-Compacting Concrete (SCC) and modern construction. ), while CIRIA 108 seamlessly unifies walls and
The formula assumes standard internal poker vibration restricted to the top 1 to 2 meters of the freshly placed layer. Deep, continuous revibration of lower layers breaks early crystallization, rendering the formula invalid and driving pressures toward full hydrostatic limits.
Document frameworks needed alignment with European standards (such as BS EN 12812 for temporary works).
The standard simplified equation for the maximum concrete pressure is often expressed as: Formwork failure represents one of the most common
Limit internal poker vibration depth to the freshly deposited upper layer. Vibrating deeper, partially stiffened layers re-liquefies the concrete, instantly spiking the lateral pressure back to hydrostatic levels.
Managing lateral concrete pressure involves both accurate design calculations and strict quality control during field operations.
Moderate (Uses chemistry factors for cement type and accelerators) High (Uses consistency classes and setting time tEt sub cap E Accounts for cross-sectional dimensions ( Ignores section size (assumes infinite wall width) Focuses primarily on setting time and pour height Hydrostatic Cutoff Explicitly applied based on pour height Explicitly applied based on pour height Applied based on consistency and setting thresholds Modern Relevance and the Transition to CIRIA Guide C751
The report was written before the widespread use of highly fluid Self-Compacting Concrete (SCC). SCC typically requires designing for full hydrostatic pressure unless specialized testing proves otherwise.