Long-term behaviors of fiber reinforced alkali-activated composite cured at ambient condition: Mechanical characterization

This paper focused on investigating the long-term behaviors of alkali-activated fiber reinforced composites (AAFRCs) cured at ambient temperature. Three sets of curing ages (1d, 28d, and 365d) were prepared. The Compression test, uniaxial tensile test, three-point bending test, single crack tensile test and digital image correlation (DIC) test were performed, along with the microscopic characterizations of SEM (scanning electron microscope) and XRD (X-ray diffraction). The results demonstrate that the AAFRC in this study has early strength characteristics, and the compressive strength and tensile strength of 1d is 34.6 MPa and 2.66 MPa, respectively. The compressive strength tended to be stable after 28 days, The compressive strength of 28d and 365d was very similar, 74.9 MPa and 74.4 MPa, respectively. It is worth noting that the tensile strength and tensile strain reached the highest value at 365d, and the tensile strain remained at a high level of more than 4% after 28d. DIC analysis cloud maps visually describe the formation and propagation of cracks, which can be applied to predict reliably the direction and location of cracks to a certain extent. The variation in tensile strain is explained by insufficient index margins of σoc/σcr and Jb′/Jtip. Embodied energy and carbon emissions of solid waste-based materials are calculated to assess the sustainability. AAFRC shows less energy consumptions and lower carbon emissions compared to concrete classic engineered cementitious composites (ECC, M45-PVA) and LC3-ECC. Scanning electron microscopy (SEM) analysis showed that the failure modes of fibers at different ages explained the tensile strength and tensile strain of the corresponding age specimens, and energy dispersive spectroscopy (EDS) showed that the primary polymerization products were C-(A) -S-H gel and N-A-S-H gel.