Internal vibration and the lateral pressure exerted by fresh concrete

Abstract

The design of formwork for vertical surfaces is dependent upon the magnitude of the lateral pressure assumed to act on the form face. This paper describes an experimental investigation to determine the variation of the lateral pressure exerted by fresh concrete with depth of immersion of the vibrator, duration of vibration, and power of the vibrator while keeping the rate of pour, form dimensions, and slump nominally constant and measuring the temperature.It was concluded that the lateral pressure is dependent upon the vibration parameters of depth of immersion of the vibrator, duration of vibration, and power of the vibrator and varies inversely with the temperature of the concrete mix.The experimental results were compared with the CIRIA (Civil Industries Research and Information Association, United Kingdom) and ACI (American Concrete Institute) design recommendations. It was concluded that the CIRIA arching criterion should be used with caution as it was not conservative for low friction formwork surfaces, and that both the CIRIA stiffening criterion and the ACI recommendations are conservative.