Ciria Report 108 Concrete Pressure On Formwork
CIRIA Report 108 is a classic example of industry research that successfully transferred into daily practice. While it requires careful application when dealing with modern, highly fluid concrete mixes (like SCC), it remains the "go-to" document for standard concrete pours.
While CIRIA Report 108 remains widely cited in project specifications, temporary works engineers must note its historical trajectory. In 2014, CIRIA released . Why was the standard updated?
Pmax=C2KHcap P sub m a x end-sub equals cap C sub 2 cap K the square root of cap H end-root (Where C2cap C sub 2 relates to the form geometry, is a temperature/blending factor, and is the total fluid height).
To safely and economically design formwork today:
Four decades after its publication, CIRIA Report 108 remains the most practical, research-backed tool for predicting concrete pressure on formwork. It has saved the construction industry billions in material costs and prevented countless formwork failures. Whether you are designing a retaining wall, a dam, or a high-rise core, understanding and applying is a non-negotiable skill for the modern engineer. ciria report 108 concrete pressure on formwork
), which often led to massive over-designing of formwork. CIRIA 108 recognized that concrete is not a perfect fluid; it undergoes stiffening, hydration, and internal friction during the pouring process, which limits the maximum pressure exerted at the bottom of a tall pour. 2. Key Factors Influencing Formwork Pressure
Let's break down what each term means.
When concrete is poured into a tall, vertical formwork system, it initially behaves like a fluid—exerting hydrostatic pressure. However, as hydration begins and the concrete loses workability, it begins to set and "stiffen." The formwork does not have to support the full fluid weight of the column forever; it only needs to withstand the pressure until the concrete gains enough shear strength to support itself.
) and design coefficients for walls and columns to prevent formwork failures. For more details, visit CIRIA. Construction and Building Materials CIRIA Report 108 is a classic example of
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
While C766 focuses heavily on thermal cracking, it works alongside modern structural execution standards like BS EN 1992 (Eurocode 2) and BS EN 13670 , which govern the modern execution of concrete structures.
is the total pour height. This is the absolute physical limit of pressure).
: A coefficient accounting for the size and shape of the formwork cross-section. Step 3: Apply the Core Formulas The maximum lateral pressure Pmaxcap P sub m a x end-sub (expressed in kPak cap P a ) is taken as the of the following three criteria: Hydrostatic Pressure Head: In 2014, CIRIA released
) based on concrete density, rate of rise, and temperature coefficients, distinguishing between wall and column applications. Detailed information on the 1985 report is available at CIRIA . Concrete Pressure Analysis per CIRIA 108 | PDF - Scribd
CIRIA 108 is often considered more flexible for low- to moderate-rate pours, while EN 12812 is more prescriptive for safety-critical applications. Many formwork manufacturers now produce load tables that directly reference loading.
The emergence of advanced superplasticizers and stabilizers altered early-age concrete behavior beyond the original mix classifications of Report 108.