Experimental testing method for plastic shrinkage crack risk assessment

Abstract

Plastic shrinkage cracking significantly affects the durability and performance of cement‐based materials, particularly in 3D concrete printing (3DCP), where environmental exposure and geometrical features exacerbate early‐age deformation. This study proposes a simplified experimental method to assess shrinkage crack risk of 3DCP mixes using cast specimens subjected to controlled environmental conditions. The approach enables monitoring of deformation from approximately 15 minutes after water addition, capturing the critical early‐age response. Shrinkage was continuously measured using a non‐contact laser‐based system, while mass loss and environmental parameters were recorded to quantify evaporation rates. Results show that the initial deformation rate increases with evaporation rate, and three distinct deformation behaviors were identified, depending on cracking occurrence and evolution. A critical condition for cracking was observed at evaporation rates above 0.15 kg/m ² ·h combined with concrete temperatures below 25 °C. The proposed methodology provides a robust, conservative, and practical tool for evaluating plastic shrinkage susceptibility under realistic conditions.