is the total pour height. This is the absolute physical limit of pressure).
However, CIRIA 108 remains the foundational logic taught in temporary works coordinator (TWC) courses globally. Its equations are still embedded in the background code of modern proprietary formwork calculation software used by industry giants like Doka, Peri, and Paschal. Conclusion
). If the calculated empirical pressure is greater than the hydrostatic pressure, the hydrostatic value is used as the design maximum.
CIRIA Report 108 addressed these deficiencies by synthesizing extensive field data and laboratory research. The report introduced a comprehensive design framework that evaluates how the physical and chemical characteristics of a concrete mix interact with site conditions and placement methods. Core Mechanics: Hydrostatic vs. Real Pressure
CIRIA Report 108 transformed temporary works design from a discipline of guesswork into an accurate science. By carefully balancing environmental factors like temperature with construction factors like the rate of rise and concrete chemistry, it allows temporary works designers to optimize formwork layouts. This optimization lowers material costs, speeds up construction cycles, and guarantees site safety. Whether utilizing the historical Report 108 guidelines or its modern successor, C751, understanding the underlying mechanics of lateral concrete pressure is essential for successful structural concrete delivery. ciria report 108 concrete pressure on formwork
The vertical speed at which the concrete rises in the formwork (measured in meters per hour, m/hr). A faster pour rate means more concrete is placed before the underlying layers begin to stiffen, resulting in higher lateral pressures. Concrete Temperature (
When utilizing the principles of CIRIA Report 108, always verify the exact cement composition, pour temperature, and placement speed. For standard OPC mixes with traditional slump profiles, the historical CIRIA 108 curves offer excellent conceptual insights, but modern execution should leverage the updated Concrete Society CS030 guide to align with current Eurocodes and modern admixture behaviors.
The CIRIA 108 method recognizes that lateral pressure is not determined by depth alone. It evaluates a matrix of site variables: Rate of Rise (
, formally titled Concrete Pressure on Formwork , is a foundational technical document published by the Construction Industry Research and Information Association (CIRIA). It has long served as an essential reference for formwork designers, engineers, and concrete contractors, particularly in the UK and Europe, helping them calculate the lateral pressure exerted by fresh concrete on vertical and near-vertical formwork. is the total pour height
While highly versatile, CIRIA Report 108 is an empirical framework developed under specific criteria. Designers must be aware of its boundaries:
How do you turn CIRIA 108 into actionable formwork design?
Introduced precise mathematical limits based on rising rate ( 5. Modern Status: From 108 to Guide CS030
The methodology relies on empirical formulas developed from extensive field testing. Rather than treating concrete strictly as a fluid, CIRIA 108 calculates a maximum design pressure ( Pmaxcap P sub m a x end-sub ) based on the interaction of the variables listed above. Step 1: Determine the Pure Hydrostatic Pressure Its equations are still embedded in the background
Often used internationally, ACI provides slightly different empirical formulas for maximum pressure based on placing rate and temperature.
CIRIA Report 108 (1985) provides a standard, non-hydrostatic method for calculating lateral concrete pressure on vertical formwork by accounting for placement rate, temperature, and concrete mix design. The model determines the maximum pressure based on either full hydrostatic pressure or a formula covering the "arch effect," which is widely recognized in standards like BS 5975. For more information, visit the official CIRIA R108 overview Concrete pressure on formwork (R108) - CIRIA
Before Report 108, engineers relied heavily on hydrostatic assumptions or early formulas that failed to account for modern concrete technology, such as chemical admixtures and high-frequency vibration. Overestimating pressure leads to over-engineered, expensive formwork. Underestimating it leads to catastrophic formwork bursts, safety hazards, and financial loss. Core Philosophy
This article explores the origins, the core formula, and the lasting impact of this essential guide. We'll break down its science into plain English, exploring the key parameters that govern formwork design and showing why this report remains relevant in today's world of high-tech concrete.