, strict monitoring must ensure the placing crew does not accelerate to
The method can be extrapolated to conditions outside existing practice, but designers should exercise caution.
The key takeaway:
Understanding CIRIA Report 108: Concrete Pressure on Formwork ciria report 108 concrete pressure on formwork
) based on factors such as concrete weight density, rate of rise, and temperature, is recognized within BS 5975:2019. For detailed information and to acquire the report, visit CIRIA .
For normal internal vibration (the standard for most construction), the characteristic maximum lateral pressure is given by:
Before the publication of CIRIA Report 108, engineers primarily relied on traditional methods like the American Concrete Institute (ACI) formulas or earlier versions of British Standards (such as CP 110). These early methods were often limited because they treated fresh concrete either as a pure liquid or as a static material with fixed properties. , strict monitoring must ensure the placing crew
While reprinted, the original document reflects an era of transition in UK construction. While largely metric, the explanations sometimes lean on industry norms that have since shifted.
Note: This formula has upper and lower limits. P_max should not exceed the full hydrostatic head (ρgh) nor drop below a recommended minimum of about 25 kN/m² for normal pours.
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 For normal internal vibration (the standard for most
Temperature: Higher temperatures accelerate setting — reducing pressure sooner — but also reduce concrete viscosity, which can increase early pressure during placement.
The report provides excellent guidance on the "kick" or the outward force generated during the placement of the first lift of concrete, and the importance of adequate restraint systems (props and ties). It addresses safety factors and load combinations with a site-focused perspective.