The effects of alumina nano-fibres are investigated in this paper on the mechanical performance of Ultra High Performance Fibre Reinforced Cementitious Concrete and their efficacy in enhancing the durability of the cementitious composite when exposed to extremely aggressive conditions, with main reference to the stimulated autogenous crack sealing and self-healing capacity. A tailored characterization of the flexural and tensile behaviour of the composite has been first of all performed, also with the purpose of validating an experimental and analytical approach for the identification of the tensile stress vs. strain/crack opening constitutive relationship, which makes use of a purposely conceived indirect tensile test methodology, called Double Edge Wedge Splitting test. Secondly the crack sealing and self-healing capacity have been investigated, considering the recovery of both mechanical flexural performance and durability properties (water permeability) and cross analysing the results for a thorough validation. Microstructural investigations have complemented the aforementioned experimental programme to confirm the efficacy of alumina nano-fibres in enhancing the durability performance of the investigated composites. Superior performance of the mix with alumina nano-fibres with respect to parent companion ones has been highlighted and explained through both a nano-scale reinforcing effects which helps in controlling the cracking process since its very onset as well as through their hydrophilic nature which is likely to foster cement and binder hydration reactions, which can usefully stimulate crack sealing and performance healing recovery at both the macroscopic and mesoscopic fibre-matrix interface) level.

本文研究了氧化铝纳米纤维对超高性能纤维增强水泥混凝土的机械性能及其在极端侵蚀条件下增强水泥复合材料耐久性的功效，主要涉及受激自生裂纹。密封和自我修复能力。首先对复合材料的弯曲和拉伸行为进行了量身定制的表征，其目的还在于验证一种用于鉴定拉伸应力与应变/裂纹开口本构关系的实验和分析方法，该方法利用了一种专门设计的间接拉伸测试方法，称为“双边楔裂测试”。其次，研究了裂缝的密封性和自愈能力，考虑恢复机械弯曲性能和耐久性能（水渗透性），并交叉分析结果以进行全面验证。微观结构研究补充了上述实验程序，以确认氧化铝纳米纤维在增强所研究复合材料的耐久性能方面的功效。氧化铝纳米纤维混合物相对于母体同伴的优越性能已经得到了强调和解释，原因是纳米尺度的增强作用从开始就有助于控制裂化过程以及其可能的亲水性，这可能有助于控制裂化过程。促进水泥和粘合剂的水合反应，