Performance and water-resistance mechanisms of wood chips-modified magnesium oxychloride cement composites

To realize the utilization of wood waste, the composites using wood chips as aggregate and modified magnesium oxychloride cement as binder was prepared. The mechanical properties, durability, and microstructure were systematically investigated. The results showed that the compressive strength progressively decreased from 74.8 MPa to 27.7 MPa and the flexural strength decreased from 18.9 MPa to 15.2 MPa with growth of the wood chip replacement. The 7th softening coefficient (The ratio of the compressive strength in the water-absorbed saturated state to the compressive strength in the dry state) improved from 0.63 to 0.74 with growth of the wood chip replacement. The incorporation of water-based acrylic emulsion (AE) or polycarboxylate superplasticizer (PCE) modifiers can reduce the amount of 5Mg(OH) 2 ⋅MgCl 2 ⋅8 H 2 O (phase 5) and increase the content of MgO crystals, which tend to form a film-like structure. This structural evolution significantly impacts the mechanical properties and water resistance. The highest compressive strength of composites with the AE or PCE can exceed 31.0 MPa, while the flexural strength almost unchanged. Furthermore, both AE and PCE can improve the water resistance of the composites. The softening coefficient of unmodified composites is from 0.63 to 0.74. With the wood chips increasing, the softening coefficient of modified composites gradually decreased. The softening coefficient of PCE composites can be higher than unmodified composites. This research can provide theoretical basis for the utilization of wood waste. • The effects of two chemical additives on the performance of Wood Chips-Modified MOC composites was compared. • The mechanisms of the different effects of two additives on Wood Chip-Modified MOC composites were analyzed. • Wood chips reduce the erosion of the 518 phase in the composite by water molecules. • The state of 518 phase is affected by wood chips and two chemical additives.