Feasibility study of 3D-printed rubberized concrete as a permanent formwork: mechanical properties, interlayer interface and durability

This study proposes 3D-printed rubberized concrete (3DPRC) as an innovative permanent formwork solution that integrates recycled rubber aggregates (RA) with 3D concrete printing (3DCP) technology to resolve interfacial bonding and durability limitations. A systematic evaluation of RA dosage (0-15 %), particle size (30-70 mesh), and surface treatments (water-soaking, cement coating, and heat treatment) demonstrated that 5 % unmodified 50-mesh RA optimizes interlayer adhesion, yielding a compressive strength of 49.78 MPa, flexural strength of 10.59 MPa, exceptional freeze-thaw resistance (>600 cycles), and low chloride ion permeability (diffusion coefficient of 6.99 x 10(-12) m(2)/s). The absorption-desorption process of RA reduces surface water films on printed filaments and facilitates internal curing at interfaces, suppressing elongated pore formation and refining pore geometry. These synergistic effects enhance interfacial bond strength while mitigating mechanical anisotropy, thereby validating 3DPRC's suitability as a high-performance permanent formwork system.