Using ultrafine fly ash to achieve low-carbon, high strength and high toughness engineered cementitious composites LC-HSTC

Conventional green engineered cementitious composites (ECC) with ordinary Grade I fly ash usually show insufficient tensile strength and toughness. To produce a low-carbon, high strength, and high toughness ECC (LC-HSTC), this study used ultrafine fly ash to substitute 80% binder mass. The ultrafine fly ash has an average size of 2.5 um, which is 5 times smaller than that of ordinary Grade I fly ash. A series of comparative tests were carried to investigate the workability, tensile behavior, tensile toughness, flexural property, compressive strength, fiber bridging ability of the LC-HSTC. Results show that the tensile strength, elongation, flexural strength, compressive strength and strain energy density of the LC-HSTC is 11 MPa, 6.5%, 27 MPa, 88 MPa and 500 kJ/m3, respectively, indicating a significant enhancement in the comprehensive performance compared to other similar materials. Sustainability analysis reveals that the cost of LC-HSTC (526.83 $/m3) is comparable to the other green fly ash ECCs and its embodied carbon (348.74 kg/m3) is over 17.75% lower than others. The findings indicate that ultrafine fly ash has significant advantages for the development of high strength and low carbon ECC.