Evaluation of compression self-healing performance of a smart cementitious composite SMA-ECC

A two-stage compressive test was adopted to study the self-healing performance of a smart cementitious composite SMA-ECC under compression. The ultrasonic pulse and sorptivity tests were used to track self-healing ability and resistance to internal damage, respectively. A total of 32 groups of specimens, including 28 groups of SMA-ECC specimens and 4 groups of ordinary ECC specimens, were tested with various fiber contents and preloading levels. The strength recovery rate, relative dynamic elastic modulus recovery rate before and after self-healing, and cumulative water absorption were measured during the tests. It was found that the strength recovery rate of the SMA-ECC increased by 29.2% to 37.2% compared to the ordinary ECC. The elastic modulus recovery rate after self-healing of the SMA-ECC is approximately 3 to 10 times that of the ordinary ECC, and SMA-ECC with a 0.9% fiber content exhibits the best healing effect, with a remarkable 194% increase in elastic modulus recovery rate compared to ECC. As for internal damage, an increase in fiber content corresponds to a decrease in relative sorptivity coefficient (η) in most cases. Notably, for SMA-ECC specimens featuring a 0.9% fiber content, η reaches its nadir, hovering around 0.7. The situation takes an unexpected turn when fiber content hits 1%, as the relative sorptivity coefficient experiences a 14.9% increment compared to the SMA-ECC with 0.9% fiber content. Based on the test results, it is concluded that the SMA-ECC has excellent compressive recovery performance and the ability to resist internal damage. The optimal SMA fiber content for the self-healing performance of the SMA-ECC is determined to be 0.7% to 0.9%.