Ciria Report 108 Concrete Pressure On Formwork — Newest & Premium

): The temperature of the concrete mix during placing. Higher temperatures accelerate the chemical hydration process, causing the concrete to stiffen faster and reducing the maximum pressure. Cold weather slows setting and increases pressure.

As construction technology advanced, these legacy formulas failed to account for modern concrete behaviors. The introduction of chemical admixtures, diverse cement types, and powerful mechanical vibration demanded a more dynamic calculation model. CIRIA Report 108 addressed these gaps by synthesizing extensive field research and laboratory testing into a reliable, adaptable design framework. Key Factors Influencing Lateral Concrete Pressure

, 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. ciria report 108 concrete pressure on formwork

accounts for the cross-sectional geometry of the structure being poured. Narrow walls or columns restrict concrete flow and introduce boundary friction, which reduces lateral pressure compared to massive, open pours. Step 3: Calculate the Theoretical Maximum Pressure

The report categorizes concrete mixes into groups based on their components and setting characteristics. Engineers look up the constituent materials (OPC, GGBS, Fly Ash) and the presence of admixtures to select the appropriate mix coefficient, which scales the pressure calculations according to the specific chemical behavior of the pour. Step 2: Calculate the Operational Variables Gather the site-specific parameters: : Rate of concrete rise ( : Concrete temperature at placement ( ∘Craised to the composed with power C : Concrete density ( kg/m3kg/m cubed : Total vertical height of the pour ( : Minimum internal dimension of the formwork section ( Step 3: Compute the Empirical Formwork Pressures ): The temperature of the concrete mix during placing

CIRIA Report 108 splits vertical formwork elements into two categories because aggregate arching actions behave differently depending on geometry. Both plan dimensions are less than 2 meters. At least one plan dimension exceeds 2 meters. Arching Action

The section size and shape influence the "archig action" or friction between the concrete and the form face. The report uses the minimum core dimension ( ) or a size factor ( C2cap C sub 2 ) to account for this. Key Factors Influencing Lateral Concrete Pressure , formally

If the form height is 3 m, full hydrostatic would be 72 kN/m². The CIRIA method allows a far lighter formwork system, saving material and labor.

Base weight of the material alters the hydrostatic pressure profile. Size and Shape of the Formwork

Before the widespread adoption of limit state design in temporary works, there was significant ambiguity regarding how to calculate concrete pressure. Previous methods were often overly conservative or failed to account for the specific behavior of modern concrete mixes (particularly those with admixtures and pulverized fuel ash).

Imagine designing the formwork for a wall as if the concrete were a heavy liquid—this is the hydrostatic approach. For a 3-meter-high wall, this would mean designing to withstand over 70 kN/m² of pressure at the base. For decades, up until the mid-20th century, these large and often overly conservative pressures were the standard used for formwork design.