Experimental Study on the Effect of Proster®21 Formwork on the Load-Bearing Capacity and Failure Mechanism of Short Square Columns under Concentric Compression

Abstract

The Proster®21 permanent formwork system represents a technical solution that goes beyond the traditional concept of formwork systems. Unlike removable formwork, its role is not limited to shaping the geometry of the element, but becomes an integral part of its load-bearing structure, which alters the stress-strain state of concrete under load. However, the absence of approved calculation methods that account for this effect hinders its widespread adoption in design practice. In this study, an experimental comparison was conducted between two centrally loaded square columns made of B25 concrete with a cone slump of P2 and identical reinforcement. One column was constructed using traditional removable formwork, while the other was constructed using the Proster®21 permanent formwork system. Tests showed that the use of the Proster®21 system provides a 14.0 % increase in load-bearing capacity without changing the cross-sectional geometry or reinforcement. Based on the analysis of deformation characteristics and failure modes, it was found that this type of formwork also had a notable effect on the failure mechanism and altered the stress distribution in compressed elements, confirming its structural role in the performance of the column under load.