A concrete suspended slab formwork system is designed for a target concrete pour rate of 1.5 m/h. The concrete mix has a density of 2400 kg/m³ and vibrated concrete is assumed. To determine the maximum lateral pressure on the formwork, which formula is most appropriate under CSA S269.3 guidelines?

Question: A concrete suspended slab formwork system is designed for a target concrete pour rate of 1.5 m/h. The concrete mix has a density of 2400 kg/m³ and vibrated concrete is assumed. To determine the maximum lateral pressure on the formwork, which formula is most appropriate under CSA S269.3 guidelines?

Answer options:

• P_max = ɣh ✅ P_max = 6.44R / (T + 17.8) + ɣh
• P_max = 7.2R / (T + 17.8)
• P_max = 1000 + 7.85R / (T + 17.8)

Correct answer: P_max = 6.44R / (T + 17.8) + ɣh

Explanation: CSA S269.3, Clause 6.4.1 details formulas for lateral pressure. For concrete placed at a rate up to 3 m/h with vibration, the formula P_max = 6.44R / (T + 17.8) + ɣh is used, provided other specific conditions for temperature and concrete density are met, and P_max is less than or equal to ɣH. This considers hydrostatic head (ɣh) and kinetic pressure components.