Towards Accurate In-Situ Static Yield Stress Measurement for 3D Concrete Printing (2025-05)¶

The accurate measurement of static yield stress is crucial for the success of 3D concrete printing (3DCP), ensuring the stability and buildability of printed layers. Traditional methods, like rotational rheometry, face limitations in applicability for 3DCP due to issues with portability. This paper introduces a novel fast penetration test approach for determining static yield stress of cement-based printing materials, using an automatic, portable device tailored for in-situ measurements. The influence of key test parameters, including penetration speed and probe geometry are investigated. Different theoretical frameworks including force equilibrium, fluid dynamics, and solid plasticity models are evaluated for calculating static yield stress from penetration force. The optimal penetration speed was found to be 0.5 mm/s, achieving the highest correlation with traditional rheometer test results (R2 = 0.96). Both conical and spherical probes demonstrated acceptable correlations with vane test results (R2 = 0.96 and 0.95, respectively) with no significant difference. While the force equilibrium and fluid dynamic methods overestimated yield stress by 240% and 140%, respectively, the solid plasticity approach emerged as the most accurate, aligning within 12% of static yield stress values obtained from the vane rheometer.