Ciria Report 108 Concrete Pressure On Formwork Repack -
Properly rigid formwork prevents bowing, deflection, and grout loss, ensuring the finished concrete meets tight architectural tolerances. CIRIA 108 vs. CIRIA Report R108 vs. CS 164
Pmax=ρ⋅g⋅Hcap P sub m a x end-sub equals rho center dot g center dot cap H (Where is density, is gravity, and is the pour height).
The report accounts for the specific components of the concrete matrix:
): Measured in degrees Celsius at the time of placing. Lower temperatures delay the chemical hydration process, causing the concrete to remain fluid longer and exert higher pressure. Characteristic Stiffening Time ( ciria report 108 concrete pressure on formwork
Formwork is a critical component in concrete construction, providing a mold for the concrete to take shape. However, the pressure exerted by the concrete on the formwork can be substantial, and if not properly understood and managed, it can lead to accidents, damage, and costly repairs. CIRIA Report 108, "Concrete pressure on formwork," provides valuable guidance on this critical aspect of concrete construction.
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 (
CIRIA Report 108 moved away from overly simplified hydrostatic assumptions by identifying specific variables that dictate how fresh concrete exerts force: Rate of Concrete Rise ( CS 164 Pmax=ρ⋅g⋅Hcap P sub m a x
The core of Report 108 is a set of empirical equations designed to determine the maximum lateral design pressure ( Pmaxcap P sub m a x end-sub
CIRIA Report 108 (1985) establishes the standard UK methodology for calculating lateral concrete pressure on vertical formwork, utilizing factors like placement rate, temperature, and mix composition to determine maximum pressure. Referenced in BS 5975:2019, the report addresses both hydrostatic and reduced pressure scenarios to optimize formwork design. Purchase the report at the CIRIA Official Bookshop . Concrete pressure on formwork - BS5975:2019 - Prontubeam
Concrete with higher workability (slump) generally causes higher pressures. 3. The CIRIA Report 108 Calculation Model Characteristic Stiffening Time ( Formwork is a critical
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.
CIRIA Report 108: Concrete Pressure on Formwork (1985) is a seminal industry standard used to calculate the lateral forces exerted by fresh concrete on vertical formwork. It replaced the older CIRIA Report 1 (1965) to better account for modern developments like chemical admixtures and blended cements. Core Calculation Methodology
). Instead of assuming a uniform hydrostatic distribution, the report utilizes a bilinear or tri-linear pressure envelope to model reality accurately. Step 1: Determine the Materials and Blends Factor ( C1cap C sub 1 The coefficient C1cap C sub 1
The report enforces a baseline minimum pressure to account for localized surges during bucket discharging, pump pressure pulses, and accidental over-vibration. Practical Comparison: CIRIA 108 vs. Other Standards Feature / Parameter CIRIA Report 108 ACI 347 (American Standard) BS EN 1993 / DIN 18218 (Eurocode aligned) Primary Region United Kingdom and Commonwealth North America / International Concrete Technology Adaptation
Consequently, modern European practices have gradually transitioned toward and modern Eurocode framework documents for temporary works.