In this paper, the mechanical properties of Engineered Cementitious Composites (ECC) with two different fly ash contents after sub-elevated temperature exposure were investigated systematically at multiple scales. At composite level, uniaxial compressive and tensile tests were performed on specimens underwent 20 °C, 50 °C, 100 °C, and 200 °C exposure. The results indicate that, as temperature rise from 20 °C to 200 °C, the compressive strength of both ECC mixtures increased due to the refinement of the matrix pore structure. In term of tensile properties, after exposed to 100 °C and 200 °C, ECC M1 with relatively lower fly ash content shows a substantial reduction in strain capacity, but still retaining strain-hardening behavior, whereas ECC M2 with higher fly ash content exhibits a comparable or even enhanced tensile strength and strain capacity. At micro-scale, ECC matrix toughness was increased and PVA fiber strength was degraded under 200 °C exposure, which deteriorates the tensile properties of ECCs. However, the above negative effects are diminished due to the reduced fiber/matrix interfacial bond. Furthermore, the rather low matrix toughness and fiber/matrix interfacial bond associated with high fly ash content are the main reasons for the highly remained ductility in ECC M2 after sub-elevated temperature exposure.

本文以多种尺度系统地研究了亚高温暴露后两种不同粉煤灰含量的工程胶凝复合材料的力学性能。在复合水平下，对暴露于20°C，50°C，100°C和200°C的样品进行了单轴压缩和拉伸测试。结果表明，随着温度从20°C升高到200°C，两种ECC混合物的抗压强度都由于基质孔结构的细化而增加。在拉伸性能方面，粉煤灰含量相对较低的ECC M1在暴露于100°C和200°C后显示出应变能力的显着降低，但仍保持应变硬化行为，而粉煤灰含量较高的ECC M2则表现出可比甚至更高的拉伸强度和应变能力。在微尺度下，在200°C的暴露条件下，ECC基体韧性增加，PVA纤维强度降低，这会恶化ECC的拉伸性能。然而，由于纤维/基质界面键的减少，上述负面影响得以减小。此外，与粉煤灰含量高相关的较低的基体韧性和纤维/基体界面结合力是在较低的温度暴露后ECC M2仍具有较高延展性的主要原因。