In order to investigate the steel fiber parameters on the damage characteristics and crack evolution of cellular concrete materials, uniaxial compression–acoustic emission combined tests were carried out on steel-fiber-reinforced cellular concrete (SFRCC) with different steel fiber contents (0%, 0.5%, 1%, 1.5%, and 2%) and different porosities (10% and 20%). The material damage evolution characteristics were analyzed by acoustic emission parameters and IB values, and the crack types were identified using Gaussian mixture clustering method (GMM) pairs. The results show the following: the inclusion of steel fibers increased the compressive strength of cellular concrete by 19.8~46.3% at 10% porosity, and by 37.1~102.2% at 20% porosity; the addition of steel fibers significantly increased the density and intensity of the acoustic emission signals; the decreasing tendency of the IB value at the peak stress slowed down with the increase in the amount of steel fibers, and the steel fibers could effectively inhibit the crack development; crack classification results show that the proportion of shear cracks in all stages of cellular concrete increased significantly after the addition of steel fibers.

In order to reveal the intrinsic mechanism of the mechanical properties of lime-treated sandy soil from a microscopic perspective, triaxial tests were conducted to analyze the macroscopic mechanical characteristics of sandy soil with different lime contents (0%, 5%, 8%, and 12%). The changes in the microstructure of the lime-treated sandy soil were studied through scanning electron microscopy, energy-dispersive spectroscopy, and mercury intrusion tests, combined with fractal theory for quantitative characterization. The results indicate that the stress–strain curve of lime-treated sandy soil can be divided into four stages: linear elastic, non-linear, failure, and residual strength. With the increase in lime content, the peak stress and cohesion first increase and then decrease, while the internal friction angle first decreases and then increases, suggesting the presence of an optimal threshold for lime content between 5% and 12%. The failure mode transitions from diagonal shear failure to bulging failure, significantly enhancing stability; both the fitted Mohr–Coulomb and Drucker–Prager failure criteria effectively reflect the failure patterns of the specimens in principal stress space. The results based on the three fractal dimensions demonstrate that lime-treated sandy soil exhibits clear fractal characteristics, with the highest fractal dimension value at a lime content of 8%, corresponding to the highest overall strength. In addition, the fractal dimension shows a binomial relationship with pore characteristic parameters and shear strength parameters; it can effectively characterize the complexity of the microstructure and accurately predict changes in shear strength parameters.

To address the detrimental effects of high mud content on cemented sand and gravel (CSG) materials, this study focuses on CSG materials with different contents of alkali-activated rice husk ash (RHA). The microscopic enhancement mechanism of mechanical properties of CSG materials with alkali-activated RHA were studied through the experiments. Based on the changes in microstructure, pore sizes, and mineral composition, the microstructural features of CSG materials are quantitatively characterized using pore characteristic parameters and fractal dimensions, revealing the mechanism by which alkali-activated RHA improves the mechanical properties of CSG materials. The results indicate that alkali-activated RHA effectively enhances the mechanical properties of CSG materials. As the RHA content increases, the compressive strength and elastic modulus initially increase and then decrease, while the failure strain first decreases and then increases. The failure mode transitions from splitting failure to shear failure, with the optimal mechanical performance at 5% RHA content. Microscopic experimental analysis found that adding an appropriate amount of RHA can promote the generation of cementitious substances, improve the internal pore structure, and increase the fractal dimension. However, excessive RHA can adsorb moisture, inhibit part of the hydration reactions and reduce the fractal dimension. Under the action of alkali activators, the activity of RHA is enhanced, generating more cementitious materials and significantly improving the pore-filling effect within the material, especially affecting the capillary pores.

In order to evaluate the effect of steel fiber volume fraction on the anti-explosion performance of cellular concrete, this study analyzed four steel fiber contents of 0.5%, 1.0%, 1.5%, and 2.0%. On this basis, the effects of protective layer thickness and explosive amount on the anti-explosion performance of the structure were further explored. The results show that the protective layer with 1.5% steel fiber content can provide the best protective performance. The influence of explosion shock on the protected structure has been significantly attenuated. The peak pressure at the measuring point and the damage degree of the protected structure are significantly reduced compared with the unreinforced concrete slab. It is found that the SAP20S15 ratio protective layer can still maintain a high energy absorption effect by increasing the amount of explosives, and increasing the thickness of the protective layer can directly and effectively reduce the damage level of the protected structure. Fitting curves are meticulously provided to illustrate the damage degree of the safeguarded structure under the distinct influences of fiber content, explosive mass, and protective layer thickness. These curves enable a rapid evaluation of how these three factors influence the explosion resistance of the protective layer.

This study investigates the blast-protective performance of RC slab strengthened on the blast face with various concrete protective layers under contact-detonation loading. The research focuses on analyzing shock wave propagation characteristics, peak pressures at measurement points, energy absorption capacities of the protective layers, the development of damage, and the governing failure mechanisms of the RC slab. The protective layers used for structural reinforcement include Steel Fiber-Reinforced Cellular Concrete (SFR-CC), Asphalt Concrete (AC), Rubberized Concrete (RBC), and Foamed Concrete (FC). Among these, the maximum support rotation angle of the structure strengthened with the SFR-CC concrete layer (T-1) is 0.20°, indicating significantly less damage and deformation compared to other protective schemes. Based on the damage coefficient calculated from the remaining sectional moment of inertia of the protected RC slabs, the destruction grades of the structures at different concrete protective schemes were classified. Among these, the SFR-CC layer exhibits the most effective attenuation of shock wave peak pressure. Additionally, the maximum support rotation angle of the structure strengthened with the SFR-CC concrete layer is 0.20°, indicating significantly less damage and deformation compared to other protective schemes. Damage grades were assigned according to a coefficient derived from the residual sectional moment of inertia of the protected RC slabs. The SFR-CC configuration (T-1) gives the lowest damage index, 0.178, approximately 64.5% below that of the NC scheme, and is classified as slight damage. In contrast to the severe damage sustained by the protected RC slabs strengthened with the NC concrete scheme, those strengthened with the AC, RBC, and FC protective layer schemes exhibit only a moderate damage grade. Empirical formulas predicting the damage index of protected structures under the combined effects of varying blast charges and concrete layer thicknesses were further developed for rapid damage assessment.