Using Geotechnical Sensors to Measure and Analyze Lateral Pressure of Concrete on Vertical Formwork: Field and Laboratory Experiments

This study investigates the distribution of lateral pressure exerted by fresh concrete on vertical formwork using geotechnical instrumentation. Existing specifications provide a variety of predictive formulas for lateral pressure of concrete. However, the previous studies found that indirect pressure measuring instruments used in the experiments on which the existing specifications are based are not well suited for fresh concrete. In its early stages, concrete behaves as a water-saturated granular material, similar to soil. In view of this, a geotechnical approach was adopted here, using a Null gauge, which is a direct measuring device capable of accurately capturing fresh concrete pressure. A laboratory experiment and four field experiments were conducted. The laboratory experiment was performed on a 2.3-m-high column with a cross-section of 0.3 × 0.3 m, using Null gauges to measure lateral pressure. The field experiments, conducted on an active construction site, were performed on a wall 4.8 m high and 0.35 m thick, using both Null gauges and conventional tension gauges. Although comparisons with existing models and conventional measurement instrumentation revealed general agreement with respect to upper-form pressure values, maximum measured pressures were consistently lower, and their peak formation heights were reduced compared to standard predictions. The results also highlighted the substantial influence of vibration, particularly at greater depths within the formwork, underscoring the need for precise vibration control to mitigate excessive pressure buildup. Thus, by facilitating a more accurate analysis of concrete behavior and hardening, the Null gauges proved to have a clear advantage over conventional tension gauges for measuring pressure exerted by granular and thixotropic materials such as fresh concrete.