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.

中文翻译：

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面向 3D 混凝土打印的精确原位静屈服应力测量：新型快速渗透试验研究

静态屈服应力的准确测量对于 3D 混凝土打印 （3DCP） 的成功至关重要，可确保打印层的稳定性和可构建性。由于便携性问题，传统方法（如旋转流变法）在 3DCP 的适用性方面面临限制。本文介绍了一种新颖的快速渗透测试方法，用于确定水泥基打印材料的静态屈服应力，使用专为原位测量量身定制的自动便携式设备。研究了关键测试参数（包括穿透速度和探针几何形状）的影响。评估了不同的理论框架，包括力平衡、流体动力学和固体塑性模型，以计算穿透力的静态屈服应力。发现最佳穿透速度为 0.5 mm/s，与传统流变仪测试结果的相关性最高 （R2 = 0.96）。锥形和球形探针均显示出与叶片测试结果 （R2 = 0.96 和 0.95） 可接受的相关性，没有显著差异。虽然力平衡和流体动力学方法分别高估了屈服应力 240% 和 140%，但固体塑性方法是最准确的，与从叶片流变仪获得的静态屈服应力值相差 12% 以内。