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Different crumb rubber (CR) particle sizes affect asphalt performance differently. To improve the performance of CR in SBS/CR composite modified asphalt (SBS/CRMA) and to study the enhancement of SBS/CRMA performance with varying ratios of composite CR particle sizes. This study employed three different configurations of SBS/CRMA composite ratios. Several tests and analyses were conducted, Brookfield viscosity measurements, conventional performance tests, storage stability, high- and low-temperature rheology, LAS, Fourier transform infrared spectroscopy (FTIR) and fluorescence microscopy (FM) analysis. The results indicated that, in the composite CR particle size ratio, a finer particle size of CR demonstrated more significant benefits in improving the high- and low-temperature performance of asphalt. However, with aging, the role of a coarse particle size of CR gradually became more prominent. Furthermore, compared to a single CR mesh SBS/CRMA, the 3 S + 5R-6:2:2 composite CR particle size ratio of SBS/CRMA exhibited superior high- and low-temperature deformation and fatigue resistance. Considering the microscopic analysis, it can be observed that the fine particle size of CR exhibited superior compatibility and anti-aging performance compared to the coarse particle size. In the composite CR particle size ratio, adjusting the proportion of coarse and fine CR particle size will improve the performance of SBS/CRMA significantly. Contrary to common belief, it was not necessarily true that a higher ratio of coarse CR particles leads to a better modification effect in SBS/CRMA. On the other hand, the composite CR particle size ratio proved significantly advantageous, thereby providing valuable guidance for enhancing the performance of SBS/CRMA.

An orthogonal test of the component design of aerated concrete was carried out to solve the problems of low strength, easy cracking, and high water absorption of aerated concrete. The influences of cement content, water-binder ratio, foaming agent content, and polypropylene fiber content on the performances of aerated concrete including dry density, compressive strength, and thermal conductivity were investigated. Furthermore, the optimal composition of aerated concrete was determined. The test results showed that the dry density, compressive strength, thermal conductivity, and water absorption of aerated concrete were greatly influenced by the dosage of the foaming agent. Additionally, the water-binder ratio was found to significantly influence the apparent porosity of aerated concrete. Based on the experiment, the optimal combination of components for aerated concrete was 65 wt.% cement and 35% wt.% mineral admixture with a fly ash to slag ratio of 3:1. Meanwhile, the content of water-binder ratio, foaming agent, and polypropylene fibers were 0.4, 4 wt.%, and 0.4 wt.% of the total cementitious material, respectively. Among the mix proportions in this study, aerated concrete prepared by using the above mix proportion had the best performances. Subsequently, the influence of ceramsite content on the strength, dry density, and thermal conductivity of aerated concrete was analyzed. The results showed that the dry density and thermal conductivity of ceramsite aerated concrete increased with the increase of ceramsite content, but the change law of the water absorption was the opposite. Moreover, the compressive strength increased first and then decreased with the increase of ceramsite content, while the apparent porosity was the opposite. The optimal ceramsite content in ceramsite aerated concrete was 20 wt.%.

The solar temperature field and its temperature effects on the straddle monorail tourist transportation system (SMTTS) significantly affect its mechanical performance. To investigate the distribution law of the daylight temperature field of the unpaved steel beams, the daylight temperature fields of box-type and I-sectional steel beams in different regions were measured and simulated. With the simulation results, the vertical temperature gradient curves of the unpaved steel girders were determined. Afterward, with the historical meteorological data as variables, the parameters of the extreme value model of generalized extreme value (GEV) distribution were obtained, and the representative values of temperature differences in China, based on the recurrence period, were analyzed. By analyzing the temperature difference values in 34 cities in China, an empirical prediction formula for the representative temperature difference value with three parameters was proposed, and the temperature gradient partition was established. The results indicated that the vertical temperature gradients of closed-section steel box girders are about 2–3 °C greater than that of open-section I-beams. Moreover, there are apparent geographical differences in the temperature difference values of steel girders.

To investigate the fatigue and freeze-thaw properties of the geotextile isolation layer in CRTS III ballastless track, a new type of disc multi-point load distribution device was manufactured. The experimental study was carried out on the geotextile isolation layer subjected to the fatigue load and freeze-thaw cycles. The results showed that the mechanical properties of the geotextile isolation layers were affected by the harsh environment and cyclic load. With the increase of fatigue loading cycles, the dynamic stiffness of the geotextile isolation layers increased and tended to be stable, and the nonlinear performance of the geotextile isolation layer gradually weakened. The freeze-thaw cycle greatly influenced the dynamic stiffness of the geotextile isolation layer compared with the fatigue loadings, and the freeze-thaw cycle action could accelerate the elastic loss of the geotextile isolation layer. Under the fatigue load and freeze-thaw cycles, the tensile strength of the geotextile isolation layer decreased and caused damage to the geotextile isolation layers, which should be paid attention to in long-term service.

This study investigated the bonding strength between various cement-based grouting materials (CBGM) and high-strength bolts, the flexural and compressive strength variation of different CBGM with curing age, and the failure characteristics of flexural, compressive and bonding strengths. Moreover, the morphological characteristics of bond-slip curves and their similarities and differences were discussed as well. Based on the mechanical property and safety analysis, a calculation model of the critical anchorage length of high-strength bolt in CBGM was proposed. The results indicate that the flexural and compressive strengths increase with the increase of curing age. The strength growth rate is faster at the initial stage of 3 days, which implies that the CBGM has a significant high-early strength characteristic. Depending on the diameter and type of high-strength bolts employed, the bonding strength of specimens can be divided into two failure forms, i.e., splitting and slipping pull-out. The specimens with threaded bolts easily take place a splitting failure form, but the specimens with plain round bolts tend to be destroyed with a slipping pull-out failure form. The ascending section of bond-slip curve is well fitted with the same stage of CEB-FIP 2010. However, a linear relationship can be employed to characterize the bonding strength between CBGM and high-strength bolt. The bond failure capacity is also linear correlation with the strength of CBGM.

According to the assumption of small strains and total strain decomposition of cast iron, the expressions of the inelastic principal strain rate and relative energy dissipation rate of cast iron are derived, and the parameters of the tensile and compressive damage ratio of cast iron in the inelastic phase are proposed. Based on the least energy consumption principle, combined with the above expressions and parameters, the damage ratio strength criterion for cast iron under biaxial stress states is established. The damage ratio variable expression of the cast iron damage ratio strength criterion considering the effect of Lode angle is proposed. Furthermore, the values of the damage ratio variable are verified by the experimental stress–strain curves of cast iron under uniaxial stress states. By comparing the predicted values to 104 experimental data points of cast iron specimens, the failure envelopes of the proposed criterion can represent the failure behavior of cast iron under biaxial loading conditions. To facilitate the practical application in engineering, the further simplified expression of the four-parameter damage ratio strength criterion for cast iron under biaxial stress states is suggested and those empirical parameters are recommended. Compared with some main strength criteria, the simplified criterion is in better agreement with the experimental results under every stress state.

The ultra-high performance concrete (UHPC) was prepared by using the limestone coarse aggregate and ordinary Portland cement. The effects of sand ratio, water to cement ratio (W/C), cementitious materials, type and content of fiber, dosage of water reducer and defoamer on the mechanical and rheological properties of the UHPC were investigated. The correlations among influence factors and performances of UHPC were discussed. Moreover, the internal relationship between loading rate and elasticity modulus of UHPC was also studied. The results indicate that the compressive strength of UHPC first increases and then decreases with the increase of sand ratio, and a maximum compressive strength of UHPC was found at the sand ratio of 41%. The water reducer content of fresh UHPC firstly decreases and then increases with the increase of sand ratio. The compressive strength of UHPC firstly increases and then decreases with the increase of W/C, which also increases with the increase of cementitious materials. The elasticity modulus of UHPC decreases with increase of sand ratio and cementitious materials content, and the compressive strength and elasticity modulus of UHPC cured for 28 d increase with the increase of defoamer dosage. The slump flow of fresh UHPC first increases and then decreases with the increase of water reducer dosage. An optimum fiber content of UHPC can enhance the tensile strength and adhesive property, which can play the restraining deformation and toughening effect.

The fundamental understanding of metal-organic frameworks (MOFs) is crucial since the relationship between the macroscopic properties of these materials and their molecular-level structures allows for the development of technological applications and improvements in current performance. The metal centers and attached functional groups dictate MOFs' dynamics, structure, and porosity. The development of the solid-state nuclear magnetic resonance (SSNMR) technique, capable of providing atomic-level information, enables the non-destructive characterization of the structure and dynamics of MOFs have become essential step in ameliorating our understanding and are often complementary to traditional methods. This review aims to briefly introduce the concepts of SSNMR and the methods employed when investigating the dynamics, structure, and mapping of functional groups of microporous materials, including MOFs. This review highlights the best experimental practices when working with these complex systems. The article scrutinizes the information on framework structures, active center, surface position, host-guest interaction, and intermediate interaction through different SSNMR spectrums. Despite all the recent technological advancements, the SSNMR still faces the challenges of large sample quantities, long experimental measurements and data analyses, and complex isotopic labeling, which are enlightened in this review.

The mix proportion, phase diagram components and mechanical properties of ultra-high performance mortar (UHPM) based on simplex-centroid design method were investigated. The effects of material components, sand/binder ratio (S/B) and water/binder ratio (W/B) on the strength and fluidity of UHPM were studied. Simultaneously, the relationship between water reducer dosage and slump flow of UHPM was investigated as well as the mix proportion design and performance prediction. The results showed that the simplex-centroid design method can be used to determine the relationship between influence factors and performance of UHPM. The differences of strength phase diagram for different mix proportion of UHPM were manifested in central position of minimum strength, strength contours and gradient, and position of maximum strength. There has a quadratic function relationship between water reducer dosage, slump flow and W/B. The slump flow of UHPM increases with the increase of water reducer dosage. The UHPM can be prepared based on simplex-centroid experimental design method.