In this study, the effect of microbead dosages (0%, 5%, 10%, 15%, and 20%) on the carbonation resistance of expanded polystyrene (EPS) concrete was investigated. Five groups of EPS concrete specimens were produced and underwent rapid carbonation testing. The carbonation depth and strength after carbonation of the specimens were measured at different carbonation ages (7 days, 14 days, and 28 days) and analyzed to determine the effect of microbead dosages and compressive strength on carbonation resistance. Results indicated that the carbonation depth increased with the progression of carbonation time. The introduction of microbeads was found to significantly improve the carbonation resistance of EPS concrete, leading to a reduction in carbonation depth of over 50% after 28 days and an increase in strength after carbonation by 18–56%. A relative compressive strength model for EPS concrete after carbonation was developed, which could accurately characterize the growth of compressive strength. Based on the analysis of EPS concrete carbonation depth data, a prediction model for the carbonation depth of EPS concrete with microbead dosage was established through fitting, providing improved accuracy in predicting carbonation resistance. The microstructure of EPS concrete was also examined using scanning electron microscopy to uncover the underlying mechanisms of microbead enhancement on carbonation resistance. These findings have potential implications for future research and engineering applications in the carbonation resistance of EPS concrete.

This study investigated the influence of microbead dosages (0, 5, 10, 15, and 20%) on the frost resistance of expanded polystyrene (EPS) concrete. Five groups of EPS concrete specimens were prepared and subjected to rapid freeze–thaw tests. The freeze–thaw deterioration of EPS concrete was assessed using macroscopic indicators, including mass loss, strength loss, and dynamic elastic modulus loss. The underlying deterioration mechanism was revealed through the analysis of the EPS particle–matrix interface. A concrete damage plasticity model of EPS concrete based on damage mechanics theory was established. The results indicate that the addition of microbeads increased the strength of EPS concrete by 38–53%, reduced the strength attenuation after freeze–thaw damage by 8.1%, and improved the frost resistance level by 10–60 grades. The optimal dosage of microbeads is 15% of the cementitious material. The interfacial transition zone gaps in EPS concrete with added microbeads after freeze–thaw cycles are smaller, contributing to a more complete hydration reaction. The freeze–thaw damage model established in this study accurately reflects the freeze–thaw damage law of EPS concrete and provides a reference for studying the mechanical properties of EPS concrete under freeze–thaw cycles. The research findings of this study can enhance the strength and service life of EPS concrete, expanding its application scope as a structural material. The study provides valuable insights for future research and engineering applications related to the frost resistance of EPS concrete.

To improve the toughness and strength of ceramsite concrete, this study employed three different types of fibers to enhance its performance. It prepared 8 sets of specimens, conducted stress-strain curve and static strength tests, and calculated various performance parameters. Through analysis of the economic performance and failure modes, it is found that high-toughness polypropylene fibers and steel fibers significantly enhanced both the strength and toughness of ceramsite concrete, while carbon fibers, although capable of increasing strength, do not improve toughness. Specifically, high-toughness polypropylene (HTPP) fibers and steel fibers increased the strength of ceramsite concrete by 32.8% and 49.0%, respectively, resulting in corresponding improvements in strength-to-weight ratio by 33.0% and 39.8%. While the toughness index W_cu^0.85 increased by 20.0% and 85.1%, respectively, W_cu^0.5 increased by 29.0% and 257.6%. The failure mode exhibited ductile fracture. Additionally, HTPP fibers were more cost-effective in increasing the strength and toughness of ceramsite concrete. Finally, based on SEM test results, we explained the mechanisms through which the three types of fibers enhance the performance of ceramsite concrete from the perspective of fibers surface characteristics. These research findings provide theoretical support for the optimization design of ceramsite concrete and are of significant importance for its application as a structural material.

With the increasing prevalence of deep foundation pit projects in modern urban construction, the deformation control of the associated support structures is crucial to ensuring construction safety. Despite the growing importance of this issue, research on deep foundation pit excavation in soft soil areas near the sea is limited. This study investigates the deformation characteristics and impact of a geometrically complex deep foundation pit project in Taizhou, utilizing both long-term in-situ monitoring and numerical simulation. The results of this study indicated that the maximum horizontal displacement of the foundation pit was approximately within the depth range of 5 m, with a value of 34.5 mm. The maximum settlement of both the top of the pit and the surrounding structures were determined to be less than 25 mm, confirming the safety of the excavation process. The excavation process of the foundation pit was simulated and analyzed by the Midas GTS finite element software. The results showed a similar variation pattern to the measured results, but the numerical results were generally lower than the measured values. This study provides valuable insights into the deformation characteristics of deep foundation pit excavation in soft soil areas and serves as a reference for future projects in similar conditions.

The aim of this study is to enhance the carbonation resistance of fully recycled aggregate concrete through diverse measures in an effort to enhance solid waste disposal, reduce the consumption of natural aggregates, and broaden the utilization of recycled aggregate concrete. Six sets of fully recycled aggregate concrete specimens were prepared and subjected to rapid carbonation tests. Carbonation depth and compressive strength measurements were taken at different ages (3, 7, 14, and 28 days). Subsequent calculations and analyses were conducted on both parameters for each set of specimens. Results indicate that the incorporation of microspheres and high-toughness polypropylene fibers (HTPP) substantially improves the carbonation resistance of fully recycled aggregate concrete, leading to a 48% reduction in carbonation depth by the 28th day. Furthermore, a relative compressive strength model for fully recycled aggregate concrete post-carbonation was established based on the strength data of each specimen group. This model accurately depicts the growth pattern of compressive strength after carbonation. Additionally, a carbonation depth prediction model was developed through fitting analysis of carbonation depth data, effectively foreseeing the depth of carbonation in fully recycled aggregate concrete. Based on the carbonation depth, the carbonation life of fully recycled aggregate concrete was predicted. The carbonation life of recycled aggregate concrete with added microspheres and HTPP fibers can be increased by up to 278%. Finally, scanning electron microscopy (SEM) was employed to examine the microstructure of fully recycled aggregate concrete, revealing the mechanisms by which various methods enhance its carbonation resistance. The carbonation resistance improvement technology of fully recycled aggregate concrete is selected through this study characteristics such as simplicity, convenience, and cost-effectiveness, which are crucial for the widespread application of recycled aggregate concrete in building structures.

Expanded polystyrene concrete (EPSC) is increasingly utilized in buildings as a green building material. To investigate the effect of high-tenacity polypropylene (HTPP) fibers on the carbonation resistance (CR) of EPSC, five groups of EPSC specimens with HTPP fiber volume fractions of 0%, 0.6%, 0.9%, 1.2%, and 1.5% were prepared. Rapid carbonation tests were conducted to measure the carbonation depth (CD) and uniaxial compression strength (UCS) of the specimens at different carbonation ages (3, 7, 14, and 28 days). The CD and UCS of the specimens were calculated and analyzed. The results indicated that the HTPP fibers dramatically improved the CR of EPSC, with a decrease in the CD of up to 29.5% at 28 days. A model for predicting the CD of EPSC was developed. The model for the strength after carbonation also showed good agreement with the experimental results. Scanning electron microscopy (SEM) was used to examine the microstructure of the HTPP-reinforced EPSC, while the mechanism of HTPP fibers to enhance the CR of EPSC was elucidated. The findings of this study provide valuable insights for the application of EPSC as a structural material.