Chloride transport property is very important for the durability and service life of reinforced concrete structures subjected to marine environments and de-icing salt. In reality, for different reasons, concrete structures are frequently cracked, and cracks can alter the chloride transport properties of concrete. Recently, several studies have been conducted by both experiment and simulation on the influence of cracks on the chloride transport properties of concrete. The aim of this paper is to review these research efforts. The experimental methods and simulation approaches on the chloride transport properties of cracked concrete are introduced. Detailed discussions on the findings from these experimental and simulation studies are given. The chloride transport properties of cracked concrete are influenced by various factors, such as crack geometry, concrete composition, and load condition. Research in this area is still on-going, and many problems need to be settled before proposing reliable models for predicting the service life of real cracked concrete structures in chloride environments. Hence, some further research topics are recommended. The influences of other factors, such as carbonation, freeze-thaw, fatigue, and saturation degree, on the transport properties of cracked concrete should be revealed.

During earthquakes, the response of pile foundations in liquefiable sand reinforced by densification techniques is still a very complex dynamic soil-structure interaction problem. Two shake-table experiments were conducted to investigate the behavior of a reinforced concrete (RC) low-cap pile group embedded in liquefiable soils. Discussion is focused on the behavior of soil-pile-superstructure systems prior to and during liquefaction of the medium-dense and dense sand stratums, which are involved in restoring force characteristics at the superstructure and pile group effect. The test results demonstrated a stiffness reduction and dependent nonlinear behavior appearing in the liquefied medium-dense sand; however, an overall stiffening response was observed in liquefied dense sand. The pile group effect seemed insignificant in liquefied medium-dense sand, but was very significant in the liquefied dense sand.

In research on damage identification, conventional methods usually face difficulties in converging globally and rapidly. Therefore, a fast in-time damage identification approach based on the Kalman filter and energy equilibrium theory is proposed to obtain the structural stiffness, find the locations of damage, and quantify its intensity. The proposed approach establishes a relationship between the structural stiffness and acceleration response by means of energy equilibrium theory. After importing the structural energy into the Kalman filter algorithm, unknown parameters of the structure can be obtained by comparing the predicted energy and the measured energy in each time step. Numerical verification on a highway sign support truss with and without damage indicates that the updated Young’s modulus can converge to the true value rapidly, even under the effects of external noise excitation. In addition, the calculation time taken for each step of the approach is considerably shorter than the sampling period (1/256 s), which means that, this approach can be implemented in-time and on-line.

A numerical model was developed to evaluate the possibility of people walking in a flooding flow on a staircase with rest platforms. Commercial software was used and validated by experimental data for flows on staircases and stepped spillways. The effects of the rest platform, the staircase slope, and the staircase pattern on the flooding flow characteristics are discussed. A comparison of staircases with or without rest platforms shows that the flow velocity increases significantly downstream of the rest platform on a straight-run type, which would have negative effects on the safe evacuation of people walking through a flooding staircase. The slope of the staircase, ranging from 26.6° to 30°, has less effect on safe evacuation. A comparison of flows on straight-run (with or without rest platforms), 90°-turn and 180°-turn staircases (with rest platforms) shows that the rest platforms on the latter two staircases could induce a redistribution of the flow field on the rest platform and downstream. The distribution of evacuation indicators along the longitudinal planes of those staircases indicates that a 90°-turn staircase or a straight staircase without rest platform would be the first choice for trapped people evacuating from underground spaces.

Earthquake-induced-landslides will change the underlying surface conditions (topography, vegetation cover rate, etc.), which consequently may influence the hydrologic response and then change the flash flood risk. The Jianpinggou catchment, located in the Wenchuan earthquake (occurred in Sichuan, China, 2008) affected area, is selected as the study area. The distribution of the landslides is obtained from the remote sensing image data. The changes of topography are obtained from the comparisons among digital elevation models (DEMs) during different periods. A physical-based model, the integrated hydrology model (InHM), is used to simulate the hydrologic response before and after the landslide. The influence of the underlying surface conditions is then discussed based on the simulation results. The results reveal that landslides cause significant effects on the hydrologic response, and the impact is proportional to the proportion of surface flow in the total runoff. The effect of landslides on the runoff is insignificant at the outlet, but obvious in the local area. The larger the rainfall, the more visible the impact, and the impact of landslides will increase rapidly at the threshold of the runoff (the total rainfall of 235 mm in 6 h in the study area), but there is a limit with the further enlarged rainfall. The improved understanding of the impact of landslides on the hydrologic response provides valuable theoretical support for storm flood forecasting.

In this paper, the effect of redispersible vinyl acetate/ethylene copolymer powder (VAE) on the secondary efflorescence of Portland cement-based decorative mortar (PCDM) was evaluated by alkalis leachability. The secondary efflorescence substances were investigated using X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscope (SEM). The mechanism was also analyzed from the aspect of soluble components in PCDM. The results show that the secondary efflorescence level of PCDM can be quantitatively evaluated by alkalis leachability, with a higher alkali leachability indicating more obvious secondary efflorescence. VAE increases the concentrations of free alkalis ions including Ca²⁺, K⁺, Na⁺ of PCDM, improves the capacity of pore water transmitting ions, increases the alkalis leachability of PCDM, and accordingly promotes the secondary efflorescence of PCDM.

The friction and wear properties of nitrile rubber (NBR) against 316L stainless steel pairs were investigated by using a sphere-on-disc test device. The influence of Al₂O₃ particle sizes and the normal load on the tribological behaviors of the pairs were primarily evaluated. The damage behaviors of worn surfaces were analyzed using a scanning electric microscopy (SEM) and a surface profilometer. The results show that the friction coefficient decreased because of particles coming into contact pairs, while particles also play an important role in increasing the wear loss of stainless steel with many furrows on the steel ball surface due to the ploughing effect of hard particles. Large-sized particles could accelerate the wear of rubber, and the micro-cutting scratches of the stainless steel induced by the Al₂O₃ particles embedded in the rubber matrix. However, as the particle’s size decreased, the wear loss of the rubber was gradually mitigated. It is obvious that the normal load affected the wear of the rubber to a larger extent than the stainless steel. Moreover, with large particles, the wear loss of rubber increased sharply with increasing the normal load. In addition, the NBR/stainless steel tribo-pairs presented different wear mechanisms, under different conditions, such as having no particles or varied particle sizes.

To improve aluminum extraction efficiency, a two-step acid leaching process was proposed to dissolve aluminum and aluminum-bearing crystals with sulfuric acid. The first leaching residue (FLR) was obtained through direct leaching of coal ash with sulfuric acid. After roasting a mixture of the FLR and sodium carbonate, the aluminum-bearing crystals in FLR were completely destroyed while sodium silicate was generated. Then the roasted products were leached with water to dissolve the sodium carbonate. X-ray diffraction (XRD) analysis indicated that the water leaching residues (WLR) mainly contained the amorphous phase, which allowed easy aluminum extraction in the second leaching step. In the first leaching test with 10 mol/L sulfuric acid at 120 °C in 2 h and a solid to liquid ratio (S/L) of 1:2, aluminum dissolution from raw coal ash reached 81.72%. In the second leaching step with 5 mol/L sulfuric acid, the aluminum dissolutions from WLR were 87.31% at 20 °C and 99.06% at 100 °C. Total aluminum dissolutions were more than 97%. Moreover, the leaching process produced two by-products, sodium silicate solution and amorphous silicon dioxide, which contained nearly all the silicon from the coal ash.

The original version of this article unfortunately contained one mistake. In p.980, the legend in Fig. 15a was incorrect. The correct version of Fig. 15a is given.