Luan Congqi, Yuan Lianwang, Wang Jinbang, Zhou Zonghui
Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of Jinan, Jinan 250022, China.
Shandong Hi-Speed Road & Bridge Technology Co., Ltd., Jinan 250021, China.
Materials (Basel). 2023 Apr 28;16(9):3453. doi: 10.3390/ma16093453.
As an admixture of cement-based materials, the reaction of fly ash (FA) usually takes place in the late age of curing, so FA will affect the self-healing ability of long-age cement-based materials. The self-healing potential and the characteristics of self-healing products of cementitious materials before and after crack healing were analyzed by microscopic tests, and the mechanism of the effect of fly ash on the self-healing performance of cementitious materials was revealed. The results showed that the increase in fly ash content promoted the improvement of the self-repair performance of cracked specimens at 28 d, especially when the fly ash dosage was 40%, the crack opened after 30 d of healing in water was completely closed, the UPV value after recovery was close to 3000 m/s, the self-repair efficiency of maximum amplitude and main frequency amplitude was up to more than 60%, and the recovery rate of compressive strength was increased to more than 30%. However, the increase in fly ash content was not conducive to the self-repair of cracked samples at 210 d, and with the increase in fly ash content, the crack closure effect weakened, the UPV value after recovery decreased, the crack repair rate based on ultrasonic transmission decreased to about 20%, and the compressive strength recovery rate increased slightly. In addition, calcium carbonate precipitation was the main repair product of crack filling and healing, including calcite and spherulite. With the increase in fly ash content, the content of element C in the self-repair products of 28-day-old specimens gradually increased, and the size of calcium carbonate crystals gradually decreased, but the filling was denser, whereas the calcium carbonate crystals in the self-repair products of 210 d specimens gradually became fine and loose.
作为水泥基材料的一种掺和料，粉煤灰（FA）的反应通常在养护后期发生，因此粉煤灰会影响长期龄期水泥基材料的自愈合能力。通过微观试验分析了胶凝材料裂缝愈合前后的自愈合潜力和自愈合产物特性，揭示了粉煤灰对胶凝材料自愈合性能的影响机制。结果表明，粉煤灰掺量的增加促进了28 d龄期开裂试件自修复性能的提高，特别是当粉煤灰掺量为40%时，在水中养护30 d后开裂的裂缝完全闭合，恢复后的超声波声速（UPV）值接近3000 m/s，最大振幅和主频振幅的自修复效率高达60%以上，抗压强度恢复率提高到30%以上。然而，粉煤灰掺量的增加不利于210 d龄期开裂试件的自修复，随着粉煤灰掺量的增加，裂缝闭合效果减弱，恢复后的UPV值降低，基于超声波传播的裂缝修复率降至20%左右，抗压强度恢复率略有增加。此外，碳酸钙沉淀是裂缝填充愈合的主要修复产物，包括方解石和球霰石。随着粉煤灰掺量的增加（28 d龄期试件），自修复产物中元素C的含量逐渐增加，碳酸钙晶体尺寸逐渐减小，但填充更致密，而210 d龄期试件自修复产物中的碳酸钙晶体逐渐变细且疏松。
