To appreciate Report 108's place in the industry, it helps to compare it with the American standard, .
): The vertical speed at which the concrete level rises in the formwork (measured in meters per hour). Faster pours increase lateral pressure. Concrete Temperature (
For a typical wall pour:
Pmax=C1Rcap P sub m a x end-sub equals cap C sub 1 the square root of cap R end-root (Where C1cap C sub 1
CIRIA 108 is intended for stationary forms. For slipforming, dynamic pressures are higher—consult separate guidance. ciria report 108 concrete pressure on formwork
Categorized by specific modern consistency classes (F1 to F6). Detailed assessment of modern chemical additives. Not fully covered (developed post-report). Explicitly covers SCC up to full hydrostatic pressure. Integrates SCC characteristics. Limitations of CIRIA 108
Before Report 108, formwork designers relied on empirical rules-of-thumb or overly conservative hydrostatic pressure models. The hydrostatic assumption—that fresh concrete behaves exactly like a liquid (pressure = density × height)—led to massively over-engineered (and expensive) formwork. Conversely, simplified rules like "pressure = 1.5 × height" often proved unsafe for high-slump, fast-pouring conditions.
Published in 1985, CIRIA Report 108 (R108) serves as a primary industry standard for calculating the lateral pressure of fresh concrete on formwork. The report provides an empirical formula to determine maximum pressure based on variables like concrete density, rate of rise, and temperature, which remains relevant for ensuring safe, cost-effective formwork design. For full details, visit CIRIA . Concrete pressure on formwork (R108) - CIRIA
Disclaimer: This article is for informational purposes. Always consult the official CIRIA Report 108 document and relevant local building codes for actual construction projects. If you'd like to dive deeper, I can help you: from CIRIA 108 with ACI 347. Create a sample calculation for a 4-meter wall. To appreciate Report 108's place in the industry,
Pmax=D⋅[C1⋅R+C2⋅K⋅Hi−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 sub i minus cap C sub 1 center dot the square root of cap R end-root end-root close bracket
The speed at which concrete fills the formwork (measured in meters per hour) is the most critical factor. A faster pour rate means a higher column of wet, un-set concrete accumulates, increasing the maximum lateral pressure. Concrete Temperature (
Never exceed the maximum vertical rise rate specified by the temporary works designer. Use a dipstick or laser measure to check the rise over time.
The formula only applies up to the height where concrete begins to set. For very tall walls (e.g., 10 m), multiple lift pours are needed, as the lower concrete will have set before the top is placed. Concrete Temperature ( For a typical wall pour:
This appears complex, but it breaks down logically. Let's examine each variable in detail.
Dependent on the formwork's dimensions and shape; it distinguishes between walls and columns. cap C sub 2 (Material Coefficient):
). Beyond this depth, the pressure remains constant or decreases because the lower layers have begun to stiffen. CIRIA Report 108 focuses precisely on determining this maximum pressure ( Pmaxcap P sub m a x end-sub ) and the height at which it occurs. Key Factors Influencing Lateral Pressure