The International Association for Automation and Robotics in Construction
Publications / CCC 2025 - Zadar, Croatia
MEASUREMENT AND ANALYSIS OF CONCRETE LATERAL PRESSURE ON VERTICAL FORMWORK USING GEOTECHNICAL TOOLS: LABORATORY EXPERIMENT
Formwork represents a significant portion of construction costs, with its design and implementation largely dependent on the pressure exerted by fresh concrete. Accurate estimation of this pressure enables the optimization of formwork systems, reducing costs associated with materials, fabrication, labor, and transportation. This study aims to measure and analyze the distribution of lateral pressure exerted by fresh concrete on vertical formwork using geotechnical instrumentation. Existing technical literature and industry specifications provide a range of predictive formulas; however, conventional measurement instruments are not well-suited for fresh concrete. In its early stages, concrete behaves as a water-saturated granular material, analogous to soil. Consequently, this study adopts a geotechnical approach to pressure assessment, utilizing a Null gauge, which overcomes the limitations of previously used measurement devices. Null gauge belongs to the direct measuring methods. The measurement system is based on pressure gauges installed on the casing of the plywood formwork sheathing and come in contact with the concrete poured against the formwork. This measurement concept is based on maintaining zero sensor membrane deflection through a servo-controlled feedback system. A controlled laboratory test was conducted. The test was performed on a 30×30 cm, 2.3-m-high column, allowing for controlled comparisons of theoretical models. Five Null gauges were placed along the column height. Vibration effect on lateral pressure was checked before and after vibrating. The results demonstrated that lateral pressure initially followed a hydrostatic distribution but stabilized as casting progressed. Consistent with the literature, peak lateral pressure was achieved not at the very bottom but slightly higher. The results exhibited high consistency with ACI Guide to Formwork for Concrete, confirming the validity of existing theoretical models. However, a significant difference was observed from other well-documented specifications. Vibration had massive effect on lateral pressure, with a peak increase of 4.4 times compared with pre-vibration pressure.