Understanding creep in cement-based materials is crucial for durability, yet macroscopic tests are time-consuming and poorly suited for rapid relative humidity (RH) and temperature (T) control, limiting accurate assessment of viscoelastic behavior. This study aims to advance the application of micro-indentation (MI) for evaluating basic creep and creep recovery by introducing an environmental indentation technique with rapid positioning (IT-RP), which enables reliable testing under controlled RH-T conditions while overcoming limitations of conventional approaches. Cement paste systems containing fine limestone filler (LF) were tested using the continuous stiffness measurement (CSM) method to assess elastic modulus and hardness. Critical parameters influencing MI measurements, including maximum applied load, holding duration, and grid size, were systemically optimized. MI creep recovery tests were also conducted to evaluate viscoelastic behavior, including total/reversible/irreversible creep and the recovery index. The results demonstrate that LF increases the elastic modulus and hardness and reduces creep. The recovery index was found to range from 34% to 38%, with higher LF content leading to a slight reduction. Moreover, the coupled hygro-thermal effects were investigated, demonstrating that increasing RH-T reduce the elastic modulus and hardness while increasing creep. A simultaneous increase in RH and T amplifies their weakening effects, with RH exerting a stronger influence than T, highlighting the dominant role of moisture in altering microstructure. Notably, the incorporation of LF mitigates these effects. These findings provide insights into the elastic and viscoelastic behavior of cement paste at micro-scale, contributing to the development of predictive models for long-term deformation under different environmental conditions. • Environmental MI enables fast creep and recovery testing under RH-T conditions. • Critical MI parameters (load, holding time, grid size) were optimized. • Limestone increases elastic modulus and hardness and reduces creep and recovery. • Coupled RH-T conditions increases creep; RH has the strongest weakening effect. • Limestone mitigates the weaking effect of RH-T conditions.
Dargahi et al. (Sun,) studied this question.