High-strength engineered cementitious composites with nanosilica incorporated: Mechanical performance and autogenous self-healing behavior

It is highly desirable to achieve better self-healing performance of high-strength engineered cementitious composite (ECC) incorporating hydrophobic polyethylene (PE) fibers. This work demonstrated that admixing nanosilica was able to make the ECC matrix denser and strengthen the interfacial bond between PE fiber and matrix. The nano-modified mixtures achieved enhanced mechanical performances, narrowed the crack width and facilitated autogenous self-healing of PE-ECC. For instance, at 28 days, admixing nanosilica at 1 wt% improved the tensile strength, first-cracking strength, and strain capacity of M1 series ECC by 24.5%, 23.4%, and 58.1%, which reached 9.97 MPa, 7.03 MPa and 5.17%, respectively. The incorporation of 1 wt% NS also reduced the average crack width of PE-ECC by 59.5% and 59.4%, which reached 58.1 mu m and 23.3 mu m, for the M1 and M2 series, respectively. The narrower crack widths facilitated autogenous self-healing of PE-ECC specimens subjected to 30 wet-dry cycles, where particle-shaped product (mainly calcite) and dense product (mainly C-S-H gel) formed on the M1 and M2 series PE-ECC, respectively. It is intriguing that the high-volume fly ash PE-ECC (M2-1%) achieved the compressive strength of 80.7 MPa and 97.9 MPa at 28 days and 90 days, respectively. This environmentally sustainable mixture also achieved the first-cracking strength, tensile strength and strain capacity of 3.98 MPa, 7.78 MPa, and 5.28%, respectively, at 28 days of age.