This paper deals with the development of a simple, low-cost, fringing field impedance sensor suitable for early age hydration monitoring and setting time determination of hydraulic cement paste. An impedance technique using a double-sided copper-cladded printed circuit board substrate as a sensor is proposed. Different batches of sensors with different probe sizes and substrate thickness have been fabricated and tested for hydraulic cement paste. The cement samples having different water-to-cement ratios (w:c) by weight are considered to study the effectiveness of the sensor. The purpose of this study is to develop a simple yet effective measurement system to determine the change in impedance of the cement paste with hydration time and thus to correlate the impedance change to determine the critical initial and final setting times. Initial and final hydration times of different cement samples are compared with the results of the commercial Vicat apparatus (VA). The values of the setting times closely match the Vicat values (the average value at 100 kHz differs by 4 m). Therefore, the proposed sensor-based system can be used in place of conventional VA to determine the hydration condition. The output of the sensor can be electronically processed further to develop a prototype system.

中文翻译：

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用于混凝土材料水化监测和凝结时间测定的边缘场阻抗传感器

本文讨论了一种简单、低成本、边缘场阻抗传感器的开发，适用于早期水化监测和水硬性水泥浆凝固时间的确定。提出了一种使用双面覆铜印刷电路板基板作为传感器的阻抗技术。已经制造并测试了具有不同探头尺寸和基板厚度的不同批次的传感器用于水硬性水泥浆。考虑按重量计具有不同水灰比 (w:c) 的水泥样品来研究传感器的有效性。本研究的目的是开发一个简单而有效的测量系统来确定水泥浆阻抗随水化时间的变化，从而关联阻抗变化以确定临界初始和最终凝结时间。将不同水泥样品的初始和最终水化时间与商业维卡装置 (VA) 的结果进行比较。凝固时间值与维卡值非常匹配（100 kHz 下的平均值相差 4 m）。因此，所提出的基于传感器的系统可以代替传统的 VA 来确定水合条件。传感器的输出可以进一步进行电子处理以开发原型系统。