Polyvinyl alcohol (PVA) concrete is a new green building material. In order to make it more widely used, this study used butylbenzene emulsion (SBL) to modify PVA fiber concrete. The enhancement mechanism of SBL on the PVA/cement interface was systematically investigated at multiple scales, including macroscopic mechanical properties, microstructural characteristics, nano-interface interactions. On a macro scale, the addition of SBL and PVA fibers can significantly improve the shear strength and flexural strength of composite concrete at 7 and 28 days, and SBL can make up for the decrease in compressive strength caused by PVA. On a micro scale, the corresponding polymer cement concrete was tested by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). It was observed that some gels and polymers filled the interfacial gap and effectively repaired the interfacial defects. The SBL brought the two interfaces closer together and described its bonding effect at the micro-interface. On the nano scale, SBL/PVA/C-S-H is modeled by molecular dynamics method. Binding energy, Relative concentrations, Radial distribution function, Mean-square displacement and Time correlation function were analyzed and calculated. The results show that SBL reduces the interfacial effect, enhances the interfacial hydrogen bond, van der Waals interaction, Ca-H coordination bond and stability, improves the interfacial adhesion, and further enhances the weak interfacial bond between organic polymer (PVA) and inorganic silicate (C-S-H).

Rubberized concrete is a novel green building material that enhances many features when rubber particles are incorporated into cement mortar, simultaneously yielding economic benefits through the recycling of waste tires. This study applies styrene–butadiene latex (SBL) for toughening treatment. The investigation delves into the mechanism by which SBL improves the interface between rubber and cement, encompassing macroscopic mechanical properties, microscopic structural characteristics, and nano-scale interfacial interactions. Macroscopic mechanical tests reveal a significant increase in flexural strength, shear strength, and compressive strength of the composite concrete upon the introduction of SBL and rubber. Specifically, the compressive strength improved by 8.8%, shear strength by 13.7%, and flexural strength by 18.9% at 28 days. Through electron microscopy observation of corresponding polymer cement concrete sections, observations reveal that SBL reinforces both interfaces and elucidates its bonding impact at the micro-level interface. Molecular dynamics (MD) modeling of SBL/rubber/CSH is employed at the nanoscale to compute and examine the local structure, dynamic behavior, and binding energy of the interface. The findings indicate that SBL mitigates interface impacts, enhances interface hydrogen bonds, van der Waals interactions, $\mathrm{C}\mathrm{a}-\mathrm{H}$ coordination bonds, and stability, consequently improving interfacial adhesion and fortifying the feeble interface bonding between organic polymers (rubber) and inorganic silicates (CSH).

This study employs polyvinyl alcohol (PVA) fibers and silane coupling agent (SCA) to augment rubberized concrete mechanical prowess. A multiscale investigation delves into the synergistic enhancement mechanism of SCA on the interfaces of PVA/cement and rubber/cement, considering macroscopic mechanical properties, microscopic structural characteristics, and nanoscale interface interactions. Initially, fundamental mechanical performance tests reveal a notable enhancement in compressive and flexural strength with the inclusion of SCA and PVA fibers in rubberized concrete. Subsequently, observations of corresponding composite concrete slices are conducted using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). The results manifest gel and polymer filling interface gaps, with SCA fostering a tighter amalgamation of the two interfaces, effectively rectifying interface defects and elucidating its bonding effects at the microscopic interface. Molecular dynamics (MD) modeling and simulation analyses of PVA/C-S-H and rubber/C-S-H, pre- and post-SCA modification, demonstrate that SCA mitigates interface effects, reinforcing hydrogen bonding, van der Waals interactions, Ca-H coordination bonds, and stability. This augmentation enhances interface adhesion energy, fortifying the weak interface bonding between PVA fibers, rubber, and inorganic silicate (C-S-H). Ultimately, portal frame experiments substantiate that incorporating fiber rubberized concrete into structures not only fails to diminish but marginally enhances the load-bearing capacity of the framework. This research furnishes concrete and innovative solutions for sustainable development while providing a valuable reference for the future application of PVA fiber rubberized concrete materials in practical engineering endeavors.

Due to the organic porous nature of expanded polystyrene (EPS) foam concrete, the bond strength between it and cement is weak, leading to a weakened interface transition zone and low strength. However, most studies on this issue have been limited to phenomenological approaches, neglecting the role of atomic-level mechanisms. Therefore, this study combines macroscopic and microscopic experiments, as well as molecular dynamics, to investigate the mechanisms of a silane coupling agent (SCA) enhancing the interface performance of EPS-concrete. Macroscopic mechanical tests demonstrate that SCA can improve the compressive and flexural strength of EPS concrete. Combined with the test and analysis of variance, the addition of 9% SCA has the best enhancement effect on the mechanical properties of EPS composite concrete. The compressive strength increased by 24% and 17% on day 7 and day 28, respectively, and the flexural strength increased by 39% and 16% on day 7 and day 28, respectively. At the microscopic scale, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy are used to analyze the effects of SCA on the microstructure and functional groups of the EPS-cement interface. Microscopic analysis shows that SCA optimizes the composition of cementitious products, effectively repairing and improving the defects of the EPS-cement interface. Ultimately, molecular dynamics simulations and analysis are conducted on two interface models, one including and one excluding SCA, at the nanoscale. The results indicate that SCA enhances the hydrogen bonding, H-Ca ion bonding, and interface interactions between EPS-C-S-H, resulting in a tighter and more stable bond between the two phases, effectively enhancing the mechanical properties of EPS composite concrete. This study provides valuable insights into the strengthening mechanisms of EPS composite concrete and proposes a promising improvement method.

To address poor rheology, pumping challenges, and interfacial instability during pipe-jacking through sandy-spoil, this study develops a sodium polyacrylate (PAA)-modified bentonite slurry and establishes an integrated macro–micro–nano multiscale analytical framework. At the macroscopic level, an orthogonal design systematically evaluates fluid loss, Su’s funnel viscosity, bleeding rate, and friction coefficient; the results indicate that 12-14% bentonite with 0.3-0.4% PAA simultaneously achieves low fluid loss, near-zero bleeding, and pronounced friction reduction while keeping viscosity within the pumpable range. At the microscopic level, TEM reveals a transition from a dense, agglomerated state to a flexible, lubricated state; PAA forms a coating layer and lubricating film that enhance particle dispersion and flow, strengthen thixotropic recovery, and thereby optimize structural stability and rheological performance. At the nanoscale, MD elucidates a cooperative interfacial mechanism: PAA and water assemble on mineral surfaces into a stable hydrated/lubricating layer, where weak interactions strengthen particle-water-polymer coupling, accounting for the macroscopic improvements in friction reduction and stability. Overall, PAA modification enables coordinated “lubrication-water retention-interface stabilization,” providing experimental evidence and mechanistic support for optimizing pipe-jacking slurry formulations.