Poly (methyl methacrylate) (PMMA) bone cement is an excellent biological material for anchoring joint replacements. Tensile strength $f_{\mathrm{t}}$ and fracture toughness $K_{\mathrm{IC}}$ have a considerable impact on its application and service life. Considering the variability of PMMA bone cement, a three-parameter Weibull distribution method is suggested in the current study to evaluate its tensile strength and fracture toughness distribution. The coefficients of variation for tensile strength and fracture toughness were the minimum when the characteristic crack of PMMA bone cement was ${\alpha }_{\mathrm{ch}}^{\ast }=8d_{\mathrm{av}}$. Using the simple equation ${\alpha }_{\mathrm{ch}}^{\ast }=8d_{\mathrm{av}}$ and fictitious crack length $\Delta {\alpha }_{\mathrm{fic}}=1.0d_{\mathrm{av}}$, the mean value $\mu$ (= 43.23 $\mathrm{MPa}$), minimum value $f_{\mathrm{t}}^{\min }$ (= 26.29 $\mathrm{MPa}$), standard deviation $\sigma$ (= 6.42 $\mathrm{MPa}$) of tensile strength, and these values of fracture toughness ($\mu$ = 1.77 $\mathrm{MPa}\cdot {\mathrm{m}}^{1/2}$, $K_{\mathrm{IC}}^{\min }$ = 1.02 $\mathrm{MPa}\cdot {\mathrm{m}}^{1/2}$, $\sigma$ = 0.2644 $\mathrm{MPa}\cdot {\mathrm{m}}^{1/2}$) were determined simultaneously through experimental data from a wedge splitting test. Based on the statistical analysis, the prediction line between peak load $P_{\max }$ and equivalent area $A_{\mathrm{e}}^1\left(A_{\mathrm{e}}^2\right)$ was obtained with 95% reliability. Nearly all experimental data are located within the scope of a 95% confidence interval. Furthermore, relationships were established between tensile strength, fracture toughness, and peak load $P_{\max }$. Consequently, it was revealed that peak load might be used to easily obtain PMMA bone cement fracture characteristics. Finally, the critical geometric dimension value of the PMMA bone cement sample with a linear elastic fracture was estimated.

There are long periods of winter construction in China’s eastern and western Alpine regions. The decreased construction temperature adversely affects the workability, mechanical properties, and durability of cement-based materials and alkali-activated materials. Under low-temperature curing conditions, the hydration reaction of these materials slows down, resulting in limited strength development and reduced durability. In response to this problem, researchers have summarized three measures to improve performance: the use of anti-freezing components, nanoparticles, and pre-curing. The effects of anti-freezing components on the mechanical properties and micro-mechanism changes of Portland cement, sulphoaluminate cement, magnesium phosphate cement-based materials, and alkali-activated cementitious materials are organized. Additionally, the improvement of macro-micro properties in cement-based materials through mineral admixtures, nanoparticles, and hydrated calcium silicate seeds is summarized. The influence of pre-curing on the mechanical properties of cement-based materials is analyzed, focusing on the relationship between pre-curing time and the critical strength of frost resistance. Finally, existing research challenges are summarized, and future research directions are proposed, providing valuable references for the further development of materials and engineering applications.

This study numerically investigated how varying pulse durations of water mist systems influence fire dynamics in long, narrow underground enclosures. A Fire Dynamics Simulator (FDS) model was built to represent a pulse-actuated, fine water mist test rig, and simulations of oil pan fires were performed to quantify the evolution of temperature and radiative heat flux. Results show that an 8 s spray followed by an 8 s pause yields the most effective suppression cycle. When spray and pause durations are equal, periodic momentum exchange resonates with the buoyant plume, intensifying the mixing of gas and enhancing cooling near the fire seat. Compared with continuous discharge, pulsed mist generates stronger buoyancy-driven disturbances and delivers superior performance in terms of local heat’s extraction and extinguishment. This study has, for the first time, determined the optimal pulse cycle (8 s spray/8 s stop) for oil pool fires in narrow and long underground spaces through FDS simulation, and revealed the enhancement effect of the gas disturbance resonance mechanism on fire suppression efficiency.

Acid rain can significantly undermine the structural integrity and seismic resilience of concrete structures, posing substantial risks of catastrophic failures and jeopardizing safety. However, studies on the seismic behavior of reinforced concrete (RC) columns affected by acid rain corrosion remain nascent. Therefore, this study explored the impact of acid-rain corrosion extent and axial compression ratio on the seismic behavior of RC columns that experienced flexural failure using an artificial rapid corrosion method and pseudo-static test in sequence. The corrosion-induced damage, weight loss of the reinforcement, failure pattern, hysteretic behavior, load-bearing capacity, deformation capacity, stiffness degradation, and energy dissipation were analyzed. The test observations showed that the acid rain corrosion extent was more pronounced in the column peripheries compared to their central sections. As the number of ARCCs (acid rain corrosion cycles) increased, the damage extent of column specimens was gradually aggravated; the load-bearing, deformation, and energy absorption capacities were significantly reduced. Notably, the column specimen RCZ-4 compared to RCZ-1, with reductions of 14.54% in peak load, 22.58% in plastic rotation, and 28.6% in total cumulative energy dissipation. As the axial compression ratio was increased from 0.3 to 0.5, the column specimens exhibited a 17.12% increase in peak load, alongside a decline in plastic rotation by 25.40% and a reduction in cumulative energy dissipation by 25.85%. Based on the experimental results and the existing theoretical, a calculation formula for the flexural failure skeleton curve characteristic point parameters of RC columns was proposed, considering the impact of acid rain corrosion damage and axial compression ratio. The proposed calculation method could effectively determine the load-bearing and deformation capacity of RC columns under low cyclic loading. The results of this study enable engineers to better understand the seismic behavior of RC columns in an acid rain corrosion environment.