A recent survey has showed the prediction of the long-term deflection of existing concrete bridges after several decades is a great challange in civil engineering. The crux is to predict the creep deflection of a concrete structure after several decades from laboratory tests carried out over few months. This work aims at combining microindentation tests and as short as possible Uniaxial Compression Creep Test (UCCT) to characterize the modulus $C$ and the characteristic time ${\tau }_{ch}$ of the compliance function of basic creep used in modern design codes.

First, concrete samples made of cement paste, mortar and concrete with a water-to-cement ratio of 0.6 were cured and loaded in sealed condition at a age of 90 days under UCCT for a duration of 1 year. A convergence study showed that the duration of UCCT which is needed to accurately estimate the characteristic time ${\tau }_{ch}$ and creep modulus $C$ is about 30 days and 300 days, respectively. Then, the creep modulus $C$ was measured by microindentation tests on the cement paste and homogenized at the scale of mortar and concrete by micromechanics. Finally, the compliance creep function obtained by the proposed two-scale method was compared to experimental results which are available in open literature and other ones of existing design models, such as the model code 2010 and the well-established B4 model. As main result, the proposed simplified method which combines short (2-month) UCCT and rapid microindentation tests showed to be practical and accurate to characterize the basic creep compliance function of concrete.

最近的一项调查表明，预测现有混凝土桥梁几十年后的长期挠度是土木工程中的一个巨大挑战。关键是通过几个月的实验室测试预测混凝土结构在几十年后的蠕变挠度。这项工作旨在结合微压痕测试和尽可能短的单轴压缩蠕变测试 (UCCT) 来表征模量$C$ 和特征时间 ${\tau }_{CH}$ 现代设计规范中使用的基本蠕变的顺应函数。

首先，由水泥浆、砂浆和水灰比为 0.6 的混凝土制成的混凝土样品在 UCCT 下在密封条件下养护 90 天，持续时间为 1 年。收敛性研究表明，准确估计特征时间所需的UCCT持续时间${\tau }_{CH}$ 和蠕变模量 $C$分别是30天和300天左右。那么蠕变模量$C$通过对水泥浆的微压痕测试测量，并通过微力学在砂浆和混凝土的尺度上均质化。最后，将所提出的两尺度方法获得的柔量蠕变函数与公开文献和其他现有设计模型（如模型代码 2010 和完善的 B4 模型）中可用的实验结果进行了比较。作为主要结果，所提出的结合短期（2 个月）UCCT 和快速显微压痕测试的简化方法表明，在表征混凝土的基本蠕变柔量函数方面是实用且准确的。