Constitutive relationships and acoustic emission behavior of plant-fiber/magnesium oxychloride cement composites under uniaxial compressive load

Abstract

Plant-fiber/magnesium oxychloride cement composites (PF-MOC) are bio-composite building materials that are produced by mixing magnesium oxychloride cement (MOC) with plant fibers. The application of PF-MOC in construction engineering can not only promote the reuse of bio-waste but also compensate for the shortage of wood. In this study, 33 prismatic specimens of PF-MOC were prepared using the extrusion molding method for the uniaxial compression test. The compression characteristics of PF-MOC under uniaxial compression load were studied by combining the test with acoustic emission (AE). The results illustrated that the apparent density of the PF-MOC ranged from 771 kg/m3 to 1806 kg/m3, and the compressive strength ranged from 4.7 MPa to 44 MPa. PF-MOC uniaxial compressive stress–strain relationship model was established. The compressive strength of PF-MOC with different types and content of plant fiber is closely related to the apparent density, and thus a compressive strength prediction model was developed. The PFC-MOC with bamboo scrap exhibited the highest AE energy near the peak load, indicating greater brittleness. Conversely, the PF-MOC with wheat straw demonstrated a well-distributed energy release throughout the compression process, suggesting lower brittleness in the straw specimens. The utilization of the b-value proved effective in characterizing the crack development and size transformation process of PF-MOC. Furthermore, SEM revealed that straw fibers exhibited the weakest bonding with the MOC matrix, while wood sawdust fibers and bamboo scrap showed superior interactions with the hydration products of MOC.