Determination of time-zero is crucial for standardizing autogenous shrinkage measurement, data processing and cracking risk calculation for cementitious materials. The main objective of this study is to assess mainstream methods of time-zero determination and to provide recommendations based on the underlying mechanism and data reliability. In total, nine kinds of determination methods for time-zero were conducted for mortars with different water-to-cement ratios (w/c) including a simplified measurement for the restraint stress generation. The method of combining penetration resistance and capillary pressure is suggested due to its clear mechanism and ease of operation in different cementitious systems. After classification and statistical evaluation, the final setting, the peak rate time of the temperature, the restraint stress generation time and the newly proposed combined method are considered more suitable among the assessed time-zero determination methods. The recommendation is applicable for cement mortars with the w/c 0.3–0.4 and also expected to be extended to more complex cementitious systems.

中文翻译：

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水泥砂浆自收缩零时测定方法的评估


零时间的确定对于标准化水泥材料的自收缩测量、数据处理和开裂风险计算至关重要。本研究的主要目的是评估主流的时间归零确定方法，并根据基本机制和数据可靠性提供建议。总共，针对不同水灰比（w/c）的砂浆进行了九种零时间测定方法，包括约束应力产生的简化测量。建议将渗透阻力和毛细管压力相结合的方法，因为其机理明确且易于在不同水泥体系中操作。经过分类和统计评估，认为最终设置、温度峰值速率时间、约束应力产生时间和新提出的组合方法在评估的零时确定方法中更为合适。该建议适用于水灰比为 0.3-0.4 的水泥砂浆，并且预计还将扩展到更复杂的水泥体系。