Study of the Freeze–Thaw Resistance for Composite Fiber Recycled Concrete with Sulphate Attack Exposure

The exposure of recycled concrete (RCA) to a sulphate environment in cold regions makes it crucial to overcome the freeze–thaw cycling effects of recycled concrete. Based on steel and basalt fiber reinforced recycled concrete, the freeze–thaw cycle resistance of recycled concrete was studied by exposure to a sulphate environment. The mass loss, dynamic elastic modulus loss and compressive strength loss of the specimens were studied through freeze–thaw cycle experiments. SEM techniques were used to explore the effect of fiber distribution on the freeze–thaw resistance of recycled concrete. The freeze–thaw mechanism of the basalt fiber and steel fiber recycled concrete exposed to a sulphate environment has also been summarized. The results show that, based on the sulphate environment, the composite fiber recycled concrete has a higher stability in terms of mass loss and relative dynamic modulus of elasticity than single fiber concrete. The compressive strength of S0.9RC (recycled concrete with 0.9% steel fibers) and BF5.5RC (recycled concrete containing 5.5 kg/m3 basalt fibers) increased by 8.62% and 13.62%, respectively, compared to normal recycled concrete after 28 days of maintenance; and after 150 freeze–thaw cycles, the compressive strength increased by 41.39% and 47.54%, respectively; compared to ordinary natural aggregate concrete, the compressive strength of S0.9RC and BF5.5RC increased by 32.90% and 27.36%, respectively. The compressive strength of the S1.5BF7.5RC (recycled concrete with 1.5% steel fibers and 7.5 kg/m3 basalt fibers) composite basalt fiber–steel fiber concrete also increased by 42.82%. SEM techniques indicated that the basalt fiber in the recycled concrete exhibited fracture damage, which inhibited the development of microcracks within the concrete. When the recycled concrete is subjected to coupled sulphate and freeze–thaw cycles, freezing occurs from the outside in, with ice crystals extending along the cracks into the matrix. Prior to freezing, a negative pressure is created by the compression of the air and the contraction of the salt solution, which pulls the external solution inwards. The brine is in a state where ice and water coexist during the continuous cooling process. The salt solution migrates from the inside to the outside during heating and melting

Effect of Graphene Oxide and Fly Ash on Frost Resistance of the Steel Fiber Reinforced Concrete

The addition of graphene oxide (GO) and fly ash (FA) to SFRC (steel fiber reinforced concrete) increases frost resistance. Based on the analysis of the amelioration of GO on the frost resistance of SFRC, the improvement mechanism and the effects of GO and FA on the durability of SFRC were studied in depth. The test blocks’ compressive strength, relative dynamic modulus of elasticity, and mass-loss rate were tested through experiments. The pore distribution and morphological characteristics of concrete were captured by industrial CT scanning technology. The effects of GO and FA on the pore distribution and morphology of the SFRC are discussed. The results show that the compressive strength of GO-SFRC(graphene oxide and steel fiber reinforced concrete)with GO proportion of 0.03% is 28.20% higher than that of ordinary SFRC without freezing and thawing; after 100 freeze-thaw cycles, the compressive strength of the G0.03S25 increased by 31.70% compared with the compressive strength of the G0.00S25, and pore shape of G0.03S25 presents a spherical shape and an elliptical spherical shape; based on the data analysis of the strength loss, relative dynamic elastic modulus loss and mass-loss rate, it is considered that the properties of ordinary SFRC are the worst under freezing and thawing; as FA admixture increases, the porosity decreases; with FA of 30% and GO of 0.03%, the GO-FA-SFRC has the best frost resistance, as well as most of the pores are closed which resemble spheres and ellipsoids

Effect of Graphene Oxide and Fly Ash on Frost Resistance of the Steel Fiber Reinforced Concrete

The addition of graphene oxide (GO) and fly ash (FA) to SFRC (steel fiber reinforced concrete) increases frost resistance. Based on the analysis of the amelioration of GO on the frost resistance of SFRC, the improvement mechanism and the effects of GO and FA on the durability of SFRC were studied in depth. The test blocks’ compressive strength, relative dynamic modulus of elasticity, and mass-loss rate were tested through experiments. The pore distribution and morphological characteristics of concrete were captured by industrial CT scanning technology. The effects of GO and FA on the pore distribution and morphology of the SFRC are discussed. The results show that the compressive strength of GO-SFRC(graphene oxide and steel fiber reinforced concrete)with GO proportion of 0.03% is 28.20% higher than that of ordinary SFRC without freezing and thawing; after 100 freeze-thaw cycles, the compressive strength of the G0.03S25 increased by 31.70% compared with the compressive strength of the G0.00S25, and pore shape of G0.03S25 presents a spherical shape and an elliptical spherical shape; based on the data analysis of the strength loss, relative dynamic elastic modulus loss and mass-loss rate, it is considered that the properties of ordinary SFRC are the worst under freezing and thawing; as FA admixture increases, the porosity decreases; with FA of 30% and GO of 0.03%, the GO-FA-SFRC has the best frost resistance, as well as most of the pores are closed which resemble spheres and ellipsoids

Electrochemical Corrosive Behaviors of Fe-Based Amorphous/Nanocrystalline Coating on Stainless Steel Prepared by HVOF-Sprayed

In this study, FeCrMnWMoSi amorphous/nanocrystalline coating was prepared on stainless steel by high-velocity oxygen fuel (HVOF) spraying. In order to thoroughly evaluate this novel material, the corrosion behaviors and corrosive film characteristics of the amorphous/nanocrystalline coating in NaCl corrosive media were studied using electrochemical measurement technologies such as potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). It was found that the corrosion resistance of Fe-based amorphous/nanocrystalline coating could be attributed to the passive film formed, which consisted of Fe, Cr, Mo, and W oxides. pH has an important influence on the corrosion resistance of amorphous/nanocrystalline coating by changing the pitting corrosion mechanism. Under neutral and acidic conditions, the corrosion mechanism of Fe-based amorphous/nanocrystalline coating was mainly local pitting corrosion. However, under strong alkaline conditions, the amorphous/nanocrystalline coating not only had pitting corrosion, but also had the active dissolution of the passive film. Therefore, the anti-corrosion performance of Fe-based amorphous/nanocrystalline coating under alkaline conditions was not as good as neutral and acidic corrosive medium

Pivotal role of mast cells in pruritogenesis in patients with myeloproliferative disorders

Abstract Pruritus is a common symptom in patients with Philadelphia chromosome–negative myeloproliferative disorders (MPDs). The pathophysiology of MPD-associated pruritus is unclear. We have demonstrated that MPD mast cells (MCs) are involved by the malignant process. In the present study, we explored the hypothesis that MCs play an important role in the development of pruritogenesis in MPDs. We found that MPD MCs released significantly greater amounts of pruritogenic factors, including histamine, leukotrienes, and interleukin-31 (IL-31) than normal MCs. Elevated levels of IL-31 were also observed in MPD CD3+ cell-conditioned media. MPD MCs exhibited increased migratory behavior in response to stem cell factor or interleukin-8, which was associated with increased filamentous-actin content. Furthermore, the presence of pruritus in MPDs was statistically correlated with a greater number of MCs being generated by CD34+ cells, a greater number of MC colonies being formed by CD34+ cells, decreased apoptosis and prostaglandin D2 release by cultured MCs, and higher plasma levels of IL-31. These data demonstrate that functional abnormalities of MPD MCs probably lead to pruritogenesis in patients with MPDs. These studies provide cellular and molecular targets for the development of antipruritus drugs for patients with MPDs

Effect of C2H2 flow rate on microstructure, properties, and application in micro-drilling of a-C:H films deposited by PECVD

The drilling of printed circuit board (PCB) using micro-drills is an important processing method in modern industry. A protective film with good lubricating and anti-wear properties is generally applied to improve the processing problems of micro-drills during operation. In this study, the effects of C2H2 flow rate on the microstructure, mechanical, and tribological properties of a-C:H films deposited by plasma enhanced chemical vapor deposition (PECVD) technique were investigated. The results showed that when the C2H2 flow rate was low, varying the flow rate had little effect on the microstructure of the prepared a-C:H films. However, when the C2H2 flow rate was greater than 210 sccm, the increase in flow rate caused large particles of carbon clusters to aggregate on the surface of a-C:H films, which resulting in an increase Ra value. Not only did it reduce the adhesion between the film and the substrate, but it also deteriorated the mechanical and tribological properties of the a-C:H film produced. In addition, a-C:H films were also deposited on the micro-drill, and were used for drilling tests on the PCBs to evaluate its servce capability. The optimal parameters of a-C:H film deposited on the micro-drill surface were obtained by observing the morphology of the micro-drill surface after drilling and the hole accuracy statistics. The results showed that a-C:H film deposited on the surface of the micro-drill showed the best machining performance when the C2H2 flow rate was 180 sccm. The surface wear of micro-drill was minimal, the entanglement of tangled chips was minimal. The value of the process capability index (CPK) after 500, 1000, and 2000 drilling of PCB boards was 5.95, 4.33, and 3.15 respectively, which showed the highest drilling accuracy. This is mainly attributed to the better overall properties of the a-C:H films prepared at C2H2 flow rate of 180 sccm, such as lower surface roughness, lowest residual stress, higher hardness, better adhesion, and lower friction coefficient