CIRIA 108 assumes internal vibration is stopped 1.5m below the current concrete level. If you over-vibrate (running the head too deep), you liquify the stiffened concrete, resetting the pressure to hydrostatic at that depth.
CIRIA Report 108, 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 108 is not for SCC (Self-Compacting Concrete). For SCC, assume full fluid pressure (( \rho gh )) until the HPC (High Performance Concrete) has a measured yield stress > 300 Pa.
Your turn: Do you still use the CIRIA 108 nomographs, or have you moved to pressure sensors and digital monitoring?
#ConcreteConstruction #Formwork #CivilEngineering #CIRIA108 #ConstructionSafety #ConcretePressure
Suggested Image for the Post: A graph showing "Lateral Pressure (kN/m²)" on the Y-axis vs "Height (m)" on the X-axis, with two lines:
Alt Text: Comparison graph of concrete pressure on formwork showing CIRIA 108 plateau vs hydrostatic pressure.
CIRIA Report 108: Concrete Pressure on Formwork - An In-Depth Review
Introduction
Formwork is a crucial component in the construction industry, particularly in the building of concrete structures. The temporary structure is used to hold and shape concrete until it sets and gains sufficient strength. One of the primary concerns with formwork is the pressure exerted by the concrete on the formwork, which can lead to deformation, instability, or even collapse. CIRIA (Construction Industry Research and Information Association) Report 108, titled "Concrete Pressure on Formwork," provides a comprehensive guide on the subject. This report aims to summarize and expand on the key findings and recommendations of CIRIA Report 108.
Background
The pressure exerted by concrete on formwork is influenced by several factors, including:
Key Findings
CIRIA Report 108 provides a detailed analysis of the factors influencing concrete pressure on formwork. Some of the key findings include:
Design Methods for Concrete Pressure on Formwork
The "H" method, as presented in CIRIA Report 108, is a widely used approach for estimating concrete pressure on formwork. The method assumes a linear pressure distribution with depth, with the maximum pressure occurring at the bottom of the pour. The pressure (P) at any point is calculated using the following equation:
P = (ρ × g × h) × (1 + (α × V))
where:
Case Study
A case study was conducted on a recent high-rise building project in London. The project involved pouring a large concrete slab using a climbing formwork system. The CIRIA Report 108 method was used to estimate the concrete pressure on the formwork. The results showed that the maximum pressure occurred at the bottom of the pour, with a value of 65 kN/m². The formwork was designed to withstand this pressure, and the pour was completed successfully without any incidents.
Recommendations and Best Practices
Based on the findings of CIRIA Report 108, the following recommendations and best practices are proposed:
Conclusion
CIRIA Report 108 provides a comprehensive guide on concrete pressure on formwork, highlighting the key factors influencing pressure and recommending best practices for design and construction. By understanding and applying the principles outlined in this report, engineers and contractors can ensure the safe and efficient construction of concrete structures.
References
Appendices
The appendices provide additional information and examples to support the report's findings and recommendations.
This report aims to provide an interesting and informative review of CIRIA Report 108. It is essential to consult the original report for detailed information and guidance on concrete pressure on formwork.
CIRIA Report 108, "Concrete pressure on formwork," serves as a foundational guide for calculating the lateral pressure exerted by fresh concrete on temporary formwork structures, accounting for variables like rate of rise, temperature, and mix composition. It provides specific formulas to determine maximum pressure ( Pmaxcap P sub m a x end-sub
) and design coefficients for walls and columns to prevent formwork failures. For more details, visit CIRIA. Construction and Building Materials
In the world of construction, few forces are as misunderstood—or as dangerous—as fresh concrete pressure on formwork. Every year, projects face blowouts, bulging forms, and even catastrophic failures because engineers and contractors underestimate the liquid-like pressure exerted by newly placed concrete. For decades, the industry struggled with inconsistent guidelines until a groundbreaking document changed everything: CIRIA Report 108, "Concrete Pressure on Formwork."
Published by the Construction Industry Research and Information Association (CIRIA), Report 108 remains the gold standard for calculating lateral pressure exerted by fresh concrete on vertical and inclined formwork systems. Despite being originally released in the 1980s (with updates in subsequent years), its principles continue to inform modern design codes, including ACI 347 and EN 12812.
This article provides a comprehensive breakdown of CIRIA Report 108—its history, key formulas, practical applications, and why it remains indispensable for safety and efficiency in concrete placement. ciria report 108 concrete pressure on formwork