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Background/Aim. Pericapsular nerve group block (PNGB) does not affect the motor nerve while blocking the obturator and femoral nerves. The aim of the study was to determine the application value of PNGB for hip replacement in the elderly. Methods. Ninety elderly patients who underwent hip replacement from March 2019 to October 2020 were randomly divided into the fascia iliaca compartment block (FICB) group and the PNGB group. FICB and PNGB were performed prior to subarachnoid block (SAB). Their baseline data, operation conditions, incidence of adverse reactions, visual analog scale (VAS) score, heart rate (HR), mean arterial pressure (MAP), plasma cortisol (COR), and epinephrine (E) levels were compared. Results. VAS score, E, and plasma COR levels in the PNGB group were lower than those in the FICB group at time points T2–T4 (T2: 10 min after nerve block; T3: at position changing; T4: after position changing) (p < 0.001). There were no significant differences in HR and MAP between the two groups at any time point (p > 0.05). In the PNGB group, the ultrasonic imaging time was shorter, the time point of pressing patient-controlled analgesia (PCA) for the first time was later, and the numbers of pressing PCA were fewer than those of the FICB group (p < 0.001). No local anesthetic poisoning took place after the nerve block, and no hematoma at the puncture site, nerve injury, nausea and vomiting, dizziness, or delirium occurred. Conclusion. Both FICB and PNGB prior to SAB were highly safe for hip replacement in the elderly; however, PNGB has shorter ultrasonic imaging time, better analgesic effect, and milder oxidative stress, so it is worth applying it clinically.

Marine concrete is a kind of construction material which is seeking its growing application in marine engineering. However, the marine concrete structures are exposed to aggressive environment and harmful ions. Therefore, it is crucial to improve the durability of marine concrete. The concrete structure located in the tidal zone is subjected to the dry–wet cycles caused by tidal action, chloride ion (Cl−) erosion in seawater, and CO2 erosion in air. When these factors work together, they cause great damage to the marine concrete structure. In view of the three environmental factors, namely, Cl− erosion, carbonation, and dry–wet cycles, taking fly ash, fibers, and nanomaterials as examples, this article expounds the research status of durability of marine concrete, introduces the latest research progress, the addition of fibers, fly ash, and nanomaterials can improve the Cl− corrosion resistance and dry–wet cycles resistance of marine concrete, while the addition of fly ash is unfavorable for carbonation resistance. And the future development trend of marine concrete is prospected.

With the rapid development of modern industry, the foundation soil and the underground water in some areas are severely polluted by the corrosive medium affecting the durability of foundation concrete. Sulfate corrosion is one of the major factors leading to the destruction of foundation concrete. The sulfate corrosion resistance of foundation concrete with nano-particles (nano-SiO2 and nano-CaCO3) under the action of dry-wet cycle is experimentally studied, and compared with that of plain foundation concrete. The test results indicate that, under the action of dry-wet cycle, the sulfate corrosion resistance of foundation concrete is significantly improved with the addition of nano-particles. With the increasing content of nano-particles, the sulfate corrosion resistance of foundation concrete gradually rises to its peak and then drops step by step. The sulfate corrosion resistance of foundation concrete with nano-SiO2 is superior to that of foundation concrete with the same amount of nano-CaCO3. When the content of nano-SiO2 and nano-CaCO3 is respectively 2.0 % and 1.0 % by weight of binder, the sulfate corrosion resistance of foundation concrete is the best. Because the pore structure of concrete is improved with the addition of nano-particles, as nano-SiO2 can react with Ca(OH)2 and nano-CaCO3 can react with C3A, nano-particles can significantly enhance the sulfate corrosion resistance of foundation concrete.

The combination of multiple factors in marine environments can accelerate the concrete corrosion. In this work, bending fatigue load, dry–wet cycles and Cl− erosion were experimentally combined to evaluate the endurance of marine concrete incorporating nanoparticles (nano-silica (NS) and nano-titania (NT)). Dry–wet cycles of the nano-concretes were simulated in seawater (5% sodium chloride solution) and bending fatigue loads at stress levels of 0.5, 0.6, 0.7 and 0.8 were applied. The results indicated that the nanoparticles enhanced the resistance to Cl− erosion during dry–wet cycles and bending fatigue load by making the concrete more durable under coupled bending fatigue load, dry–wet cycles and Cl− erosion. The improvements were the most obvious for a NT content of 1% and a NS content of 2%, and the improvement was better with 1% NT than with 2% NS content is 2%. The free Cl− content in the concrete tension zone was larger than in the compressive zone. X-ray diffraction was used to assess the physical phases of the concretes before and after the experiments and to analyse the reasons for the increased concrete durability. The nanoparticles increases the content of hydrated calcium silicate in concrete, changed the orientation of calcium hydroxide and improved the concrete durability. [ABSTRACT FROM AUTHOR]

The coupling effect of bending load and salt spray erosion during the service of a sea-crossing bridge accelerates the deterioration and durability of concrete and dramatically reduces the load-carrying capacity of the bridge. The effects of nanoparticles on the durability of marine concrete exposed to bending loads and salt spray erosion were studied. In this paper, nano-SiO2 and nano-Fe2O3 were mixed into plain concrete. Free chloride ions (Cl−) were titrated at different concrete depths using a four-point loading device and a self-developed salt spray erosion test chamber. Test results showed that chloride ion levels in the tensile and compressive zones for both nanoconcretes were lower than plain concrete at the same timepoint. The optimal mixtures of the two nanoparticles were 2% and 1%, and the improvement of nano-SiO2 was more significant than nano-Fe2O3. Due to the special properties of nanomaterials, they effectively improved the microstructure of concrete and the composition of cement hydration products. This allowed concrete to become more compact, reduced crack generation, increased the difficulty of Cl− migration inside the concrete, and improved the overall durability of marine concrete upon exposure to bending loads and salt spray erosion.

AbstractThis paper investigated the role of nano-particles in the resistance of marine concrete to chloride ion (Cl-) corrosion under the combined influence of flexural fatigue load and freeze-thaw cycles. We analyzed the nano-particles to improve the mechanism of Cl- attack resistance of the concrete. The results indicated that the combined effect of freeze-thaw cycles and flexural fatigue load promoted the migration of Cl- into the concrete. The free Cl- content in the compressive zone of concrete initially decreased and subsequently increased with the increasing stress level and combined action stage. In the tensile zone of concrete, the free Cl- content increased significantly with the stress level and combined action stage. The nano-SiO2 and nano-CaCO3 could effectively improve the Cl- attack resistance of concrete and the optimal amounts of nano-CaCO3 and nano-SiO2 were 1% and 2% (Nano-particles were substituted for equal amount of cement), respectively. According to the SEM and XRD results, nano-particles could help cement hydrate and lower the size and orientation of Ca(OH)2 in the interfacial transition zone (ITZ). Nano-SiO2 exhibited a good pozzolanic effect, while the pore structure and ITZ of concrete with nano-SiO2 was denser compared to the concrete with nano-CaCO3. [ABSTRACT FROM AUTHOR]

In the northern region of China, freeze–thaw cycles and chloride ion (Cl−) penetration are the primary factors affecting the durability of marine concrete. To investigate the influence of nanoparticles on the Cl− penetration resistance of marine concrete under the action of freeze–thaw cycles, nano-SiO2 and nano-Fe3O4 were added to plain concrete in different amounts. The Cl− penetration resistance of concrete under the action of freeze–thaw cycles was measured in a 5% NaCl solution. The relative dynamic modulus, mass loss rate, and Cl− content at different depths in concrete were measured to evaluate the salt-scaling resistance. The test results show that under salt freeze–thaw cycles, the relative dynamic modulus, bound Cl− content, and Cl− binding capacity of concrete with nanoparticles were higher than those of plain concrete. However, the mass loss, total Cl− content, and free Cl− content in concrete with nanoparticles were lower than those of plain concrete. With increasing nanoparticle content, the relative dynamic modulus, bound Cl− content, and Cl− binding capacity of the concrete first increased and subsequently decreased. However, the mass loss rate, total Cl− content, and free Cl− content first decreased and subsequently increased. The optimum amount of nano-SiO2 and nano-Fe3O4 in the concrete was 2%. The improvement effect of nano-SiO2 on the salt-scaling resistance of concrete was superior to that of concrete with the same amount of nano-Fe3O4. The addition of nanoparticles can accelerate the formation of hydrated products, enhance the chemical binding capacity and physical adsorption capacity of hydrated products to Cl−, and reduce the free Cl− content in concrete. This can improve the Cl− penetration resistance of marine concrete under the action of freeze–thaw cycles. This study provides a reference for the durable design of marine concrete in the northern region. [ABSTRACT FROM AUTHOR]

Geopolymers are amorphous, quasi-crystalline, three-dimensional networked gel structures formed by the reaction of aluminosilicate raw materials and alkali activators and are composed of silicon-oxygen tetrahedrons and aluminum-oxygen tetrahedrons. They have excellent mechanical properties, durability and environmental friendliness and can be used as a substitute for Portland cement in civil engineering. In this paper, the current research achievements of geopolymers are reviewed, including the structure type, preparation process, mechanical performance, durability and application of geopolymers in civil engineering. When compared with those of ordinary Portland cement, the mechanical properties of geopolymers not only meet the specification requirements but also show carbonation resistance, acid resistance and high temperature resistance. In addition, the raw materials of geopolymers, such as fly ash and blast furnace slag, are all derived from industrial waste; the use of geopolymers can realize waste recycling, which has extremely high economic benefits. This paper introduces its applications in soil stabilization and silt solidification, curing heavy metals, pavement repair materials and so on. The shortcomings in the current research of geopolymer are also briefly analyzed. This article reviews geopolymers from multiple perspectives, trying to give a more comprehensive understanding of geopolymers. [ABSTRACT FROM AUTHOR]

The service environment of concrete in the marine environment is harsh, and demands regarding the durability of marine concrete have increased. Marine concrete in harbor and wharf areas suffers from the combined effect of fatigue load, dry–wet cycles, and Cl− erosion, which can result in spalling of the concrete surface, corrosion of the internal reinforcement, and even concrete damage. This paper reviews recent research results on the durability of concrete and reinforced concrete (RC) under the combined effect of fatigue load, dry–wet cycles, and Cl− erosion. We further assess the variation in Cl− transport properties with fatigue load, the causes behind the reduction in the carrying capacity of RC products under fatigue load, the methods of Cl− erosion on concrete under the pressures imposed by dry–wet cycles, and the damage of the protective layer of concrete due to accelerated Cl− erosion caused by the action of dry–wet cycles. Further studies are needed on the durability of concrete under the action of fatigue load, wet and dry cycles, and Cl− erosion, in addition to the testing of the durability of concrete under the combined effects of the afore-mentioned various factors. [ABSTRACT FROM AUTHOR]

In order to study the influence of nanomaterials on the carbonation resistance of marine concrete under bending loads, an appropriate amount of nano-SiO2 was added to plain concrete, and a self-developed carbonation box and bending loading device were used to conduct a coupling test. Four different stress levels were set to measure the carbonation depth of nano-concrete at different ages. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to analyze the concrete interfacial transition zone. The carbonation depth was used as the test index to evaluate the durability of nano-SiO2-based concrete under the combined action of bending load and carbonation. The test results showed that the compressive and flexural strengths of concrete remarkably improved when the nano-SiO2 concentration was 2%. Compared with regular concrete, the compressive and flexural strengths of nano-SiO2 based concrete improved by 15.5% and 15.3%, respectively. When the stress level was 0.15 and 0.6, the carbonation depths of NS20 were 20.5 and 18.4% lower than those of PC in the tensile zone and 18.9 and 23.7% lower than those of PC in the compression zone. The carbonation depth of the NS20 tensile zone was lower by 31 and 18.4% at 3 and 28 days than that of PC. Compared with PC, the carbonation depth in the compression zone of NS20 decreased by 50 and 23.7%, and the carbonation depth of nano-concrete was significantly lower than that of conventional concrete under the same stress level and age. When the stress level is constant, the carbonation depth of the tension zone and compression zone increases gradually with the increase in age, and the carbonation depth of the concrete in the first 7 d was 50% that at 28 days. Under the same age, the carbonation depth in the tension zone increased with increasing stress levels, while the carbonation depth in the compression zone decreased with increasing stress levels. When the stress level was 0.3–0.45, the slope of the carbonation depth curve significantly increased. SEM and XRD analysis results revealed that nano-SiO2 significantly improved the internal structure of concrete by reducing the width of the microcracks, the number of pores, and the number of microcracks. The number of C3S/C2S and CaCO3 crystals in nano-SiO2 based concrete was significantly less than that in plain concrete, and the amount of C-S-H gel was more than that in plain concrete. Under bending loads, the nano-SiO2 significantly improved the carbonation resistance of concrete. When the dosage of nano-SiO2 was 2%, its improvement effect was the most significant. [ABSTRACT FROM AUTHOR]

The reinforced concrete (RC) frames with masonry infill walls are always subject to in-plane (IP) and out-of-plane (OOP) interaction under earthquakes, and IP damage will affect OOP seismic performance. In order to study IP and OOP interaction of the masonry infill walls with opening in RC frames, we establish a finite element model of RC frame with solid and opening infill walls based on existing tests. We simulated the influence of opening rate and opening aspect ratio on IP and OOP interaction of RC frames with masonry infill walls. The results show that IP damage significantly reduces the OOP stiffness of the RC frames with masonry infill walls; The IP storey drift between 0.5%–2%, the OOP stiffness is reduced by 58.3%–73.7%; Under the same IP damage, the OOP bearing capacity and stiffness of RC frames with masonry infill wall in a larger opening rate has greater degradation level and faster degradation rate; For a given opening rate, the opening with an aspect ratio that closer of infill wall has the least influence on the IP and OOP interaction. Finally, based on the simulation results, a two-parameter exponential equation is found to describe the relationship between the OOP bearing capacity reduction, IP storey drift and the wall opening rate. [ABSTRACT FROM AUTHOR]