To investigate the mechanical properties of polyvinyl-alcohol (PVA)-fiber-reinforced rubber concrete, 13 groups of PVA rubber/concrete specimens with PVA volume fractions of 0%, 0.5 vol%, 1.0 vol%, and 1.5 vol% and rubber particles with volume replacement sand ratios of 0%, 10%, 20%, and 30% were prepared, and the uniaxial compression full curve test was performed. The findings indicate that the bridging effect of PVA, as well as the synergistic effect of PVA and rubber particles, can improve the compressive properties of concrete, and the failure of the specimens demonstrates obvious ductile characteristics. Furthermore, PVA has a better impact on rubber concrete’s bearing capacity, crack propagation of the failure surface, and compressive strength in the latter stages. PVA-fiber-reinforced rubber concrete is thought to be a six-phase composite made up of the aggregate phase, mortar matrix, PVA fiber, rubber particles, aggregate–mortar interface, and rubber–mortar interface on the mesoscale. To simulate the entire process of concrete with varying PVA rubber/content from integrity to damage and cracking, a meso-numerical model of PVA rubber/concrete was constructed. The simulation results and test results are in good agreement, demonstrating the validity of the mesomodel and offering a theoretical foundation for the structural analysis and design of this type of concrete.

Amphiphilic Silane coupling agent (SCA) improves the weak bond between the two phases of rubber and hydration products, fills the interfacial gaps and effectively repairs the interfacial defects between rubber and hydration products. The addition of PVA fibers mainly improves the cracking performance and durability of concrete. However, most of the studies addressing this issue have been limited to phenomenology, ignoring the mechanism of action at the atomic structure level. Therefore, this study investigates the strengthening mechanism of the interfacial properties of KH-560 coupling agent-reinforced PVA fiber-rubber concrete from the multi-scale analysis of macro-mechanical properties, micro and fine structure, chemical composition and nano-optical level. Based on the results of macro-mechanical tests, it was found that the KH-560 coupling agent could improve the compressive, flexural and shear strength of PVA-rubber concrete, so that the damage morphology also changed from brittle damage to plastic damage, and the compressive strength of concrete was slightly reduced due to the addition of PVA, but the durability and cracking resistance were enhanced. XRD (X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy) and SEM (scanning electron microscopy) tests observed the presence of some gels and polymers that filled the interfacial slits and effectively repaired the interfacial defects. The two-phase interface was simulated by molecular dynamics at the nano level, and it was found that KH560 molecules could be closely connected with C-S-H gel collectively through Si-O-Si chemical bonding, and KH560 molecular bonds were unevenly distributed between the C-S-H and rubber interfaces, while the addition of modifier KH560 and PVA fibers caused more hydrogen and ionic bonds at the interface, which enhanced the interfacial interaction energy. Systematic experiments were conducted on PVA fiber-rubber soil materials before and after SCA modification under macroscopic, microscopic, fine and nano-level multi-scale analyses, which ultimately lead to the design and performance improvement of SCA modification of PVA-rubber cement-based materials in a multi-scale framework. The graphic summary is shown in Figure 1. GRAPHICAL ABSTRACT

The feasibility of PVA fiber rubber concrete modified by modifier in the structure was investigated using the portal frame as the research object. The basic mechanical properties of modified PVA rubber concrete materials were tested mechanically first, and then ABAQUS was used to establish the ordinary concrete portal frame model, and after confirming the model’s rationality, the rubber concrete, PVA rubber concrete, and modified PVA rubber concrete models were established on this basis, and the displacement and strain comparison analysis with ordinary concrete was carried out. The simulation results show that using PVA rubber concrete material in the concrete frame structure can improve the large deformation of rubber concrete, and using PVA rubber concrete treated with a modifier can improve structural strength and deformation even more.

Expanded polystyrene (EPS) foam concrete is attractive for lightweight building applications, yet its practical use is often limited by weak EPS–cement interfacial bonding, which promotes interfacial debonding and crack propagation and thereby compromises mechanical performance. Although nano-SiO₂ (NS) has been reported to improve EPS–cement compatibility, the interfacial strengthening mechanism is still not fully clarified across scales, especially the molecular-level interactions that govern the formation of a robust interfacial transition zone (ITZ). Herein, EPS particles were modified with NS and a multi-scale framework (macro tests, micro-characterization, and molecular dynamics (MD) simulations) was employed to establish a mechanistic linkage between interfacial chemistry/structure and macroscopic performance. The results show that an optimal NS dosage of 9% (by cement mass) increases the 28-day compressive strength and flexural strength of EPS concrete by up to 18.3% and 11.2%, respectively, compared with the unmodified system. SEM, XRD, and FTIR collectively indicate a denser interfacial microstructure, increased hydration-product accumulation near the EPS surface, refined interfacial porosity, and the occurrence of condensation-related reactions involving NS. MD simulations further reveal that NS facilitates the formation of molecular bridges between EPS and C–S–H through hydrogen bonding and ionic interactions, which enhances interfacial adhesion and contributes to improved ITZ thermal stability. This study provides a cross-scale mechanistic understanding for designing high-performance EPS foam concrete via targeted interfacial engineering. MD simulations further suggest that NS enhances interfacial bonding by increasing the occurrence of hydrogen-bond networks and ionic associations at the EPS/C–S–H interface, as evidenced by the intensified interaction-related distributions and peaks in the simulation outputs.