Based on the preparation of grouting materials with high-volume mineral admixtures, the effects of chemical admixtures including early-strength components and retarding components on the grouts with ...volume mineral admixtures were investigated. The results show that early-strength components have little effect on the grouts with high-volume mineral admixtures. Retarding component sodium gluconate does not play a great role for the grouts with high-volume mineral admixtures. However, the incorporation of borax and sodium tripolyphosphate can greatly improve the properties of the grouts, mainly due to their composite effect. The appropriate compound content is 0.4 wt% borax and 0–0.2 wt% sodium tripolyphosphate of cementitious materials. When 0.4 wt% borax and 0.2 wt% sodium tripolyphosphate were added to the grouts with volume mineral admixtures, initial fluidity and 30-min fluidity are 340 mm, and 1-, 3-, and 28-day compressive strength are, respectively, 41.6, 57.1, and 81.5 MPa. These values far exceed the standard requirements. It also shows that early-strength components and sodium gluconate can be neglected when high-volume mineral admixtures are added to the grouts.
Traditional tone burst excitation cannot attain a high output resolution, due to the time duration. The received signal is much longer than that of excitation during the propagation, which can ...increase the difficulty of signal processing, and reduce the resolution. Therefore, it is of significant interest to develop a general methodology for crack quantification through the optimal design of the excitation waveform and signal-processing methods. This paper presents a new crack size quantification method based on high-resolution Lamb waves. The linear chirp (L-Chirp) signal and Golay complementary code (GCC) signal are used as Lamb wave excitation signals. After dispersion removal, these excitation waveforms, based on pulse compression, can effectively improve the inspection resolution in plate-like structures. A series of simulations of both healthy plates and plates with different crack sizes are performed by Abaqus CAE, using different excitation waveforms. The first wave package of the S0 mode after pulse compression is chosen to extract the damage features. A multivariate regression model is proposed to correlate the damage features to the crack size. The effectiveness of the proposed crack size quantification method is verified by a comparison with tone burst excitation, and the accuracy of the crack size quantification method is verified by validation experiments.
•Three efficient aryl-OPFRs-degrading bacterial consortia were enriched from China.•These consortia exhibited excellent environmental adaptation (15–40 ℃, pH 5.0–12.0).•Strain Rhodococcus sp. YC-JH2 ...could utilize TPhP as sole carbon source for growth.•Strain Sphingopyxis sp. YC-JH3 could efficiently degrade TPhP (96.2% within 7 days).
Three bacterial consortia, named YC-SY1, YC-BJ1 and YC-GZ1, were enriched from different areas of China. Bacterial consortia YC-SY1, YC-BJ1 and YC-GZ1 could efficiently degrade triphenyl phosphate (TPhP) (100 mg/L) by approximately 79.4%, 99.8% and 99.6%, tricresyl phosphate (TCrP) by 90.6%, 91.9% and 96.3%, respectively, within 4 days. And they could retain high degrading efficiency under a broad range of temperature (15–40 ℃), pH (6.0–10.0) and salinity (0–4%). A total of 10 bacterial isolates were selected and investigated their degradation capacity. Among these isolates, two were significantly superior to the others. Strain Rhodococcus sp. YC-JH2 could utilize TPhP (50 mg/L) as sole carbon source for growth with 37.36% degradation within 7 days. Strain Sphingopyxis sp. YC-JH3 could efficiently degrade 96.2% of TPhP (50 mg/L) within 7 days, except that no cell growth was observed. Combined with 16S diversity analysis, our results suggest that the effective components of three bacterial consortia responsible for TPhP and TCrP degradation were almost the same, that is, bacteria capable of degrading TPhP and TCrP are limited, in this study, the most efficient component is Sphingopyxis. This study provides abundant microorganism sources for research on organophosphorus flame retardants (OPFRs) metabolism and bioremediation towards OPFRs-contaminated environments.
In this work, a strategy for hybrid treatment was proposed, aiming to present a hybrid impregnation agent including lignin-derived resin (LR) and surface-modified montmorillonite (GMMT) to treat ...fast-growing poplar wood. The treating agents could penetrate the wood, fill the cavities of the wood interior, and strengthen the cell wall structure. The optimal WPG of 36.2% was obtained upon the response surface methodology (RSM) at the conditions of 34% LR, 1.8% GMMT, 1.2 MPa impregnation pressure, and 99 min impregnation time. The density, water uptake (WU), modulus of rupture (MOR), modulus of elasticity (MOE), and compressive strength (CS) of the samples were tested to evaluate the enhancement of the physical and mechanical properties. In addition, these samples were investigated via cone calorimeter (CONE), Fourier Transform Infrared spectrometer (FTIR), and X-ray diffraction (XRD). The results showed that the density of the treated samples increased significantly up to 0.72 g/cm3. Compared with 134.8% of the control, the WU of the treated wood sample could decrease to 60.3%. In addition, the MOR and MOE of the resulting samples reached up to 131.8 MPa and 18.14 GPa, respectively, which were 62.3% and 77.7% higher than the control. Notably, the CS was 84.7 MPa with an increase of up to 94.7%. Moreover, the peak heat release rate (HRR) of the treated sample was obviously reduced to 231.33 kW/m2, a decrease of 17.5% compared to the control (271.71 kW/m2).
In this article, the low-field nuclear magnetic resonance was used to measure the moisture content (MC) and MC profiles in poplar wood during real-time drying. The T
2
distribution curve at each ...drying stage measured using the Carr-Purcell-Meiboom-Gill pulse sequence provided detailed information in the dynamic change of free water as well as bound water of the whole wood sample. In addition, a new developed SE-SPI pulse sequence was first used to evaluate the spatially resolved T
2
distribution of the successive nondestructive sliced layer of wood. Combined with the area integration method, the moisture content in each layer was calculated, and the change of MC profiles within wood at the MC above and below fiber saturation point was well reflected.
This study used environmentally friendly nano-xylan to enhance the drug loading and preservative performance (especially against white-rot fungi) of pine wood (
), determine the best pretreatment, ...nano-xylan modification process, and analyze the antibacterial mechanism of nano-xylan. High-temperature, high-pressure steam pretreatment-assisted vacuum impregnation was applied to enhance the nano-xylan loading. The nano-xylan loading generally increased upon increasing the steam pressure and temperature, heat-treatment time, vacuum degree, and vacuum time. The optimal loading of 14.83% was achieved at a steam pressure and temperature of 0.8 MPa and 170 °C, heat treatment time of 50 min, vacuum degree of 0.08 MPa, and vacuum impregnation time of 50 min. Modification with nano-xylan prohibited the formation of hyphae clusters inside the wood cells. The degradation of integrity and mechanical performance were improved. Compared with the untreated sample, the mass loss rate of the sample treated with 10% nano-xylan decreased from 38 to 22%. The treatment with high-temperature, high-pressure steam significantly enhanced the crystallinity of wood.
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•The dual-crosslinked nanocellulose-borax-PVA hydrogel is constructed.•The excellent shape controllability, flexibility, and transmittance are realized.•The hydrogel achieves a high ...healing efficiency after 300 s of self-healing.•The hydrogel can act as a green platform for strain sensors and antibacterial agents.
High stiffness of hydrogen-bond network generally endows cellulose hydrogels with weak mechanical flexibility and shape uncontrollability, imposing restrictions on their application scopes. Herein, a flexible polyvinyl alcohol (PVA) network is penetrated through the rigid network of bamboo cellulose, inducing the formation of a dual-crosslinked hydrogel with superior flexibility and shape controllability. Besides, the borax crosslinker offers the bamboo nanocellulose-borax-PVA hydrogel with remarkable self-healing ability and high ionic conductivity. The hydrogel achieves a minimum sensing weight of 5 g (gauge factor: 1.47) and has a stable sensing sensitivity in both hot and cold environments (i.e., 0 and 60 °C). When fixed to the wrist of human, the hydrogel can regularly sense the motion signals, verifying the potential of the hydrogel for the development of next-generation wearable products. More importantly, the hydrogel can serve as a green platform to integrate with amoxicillin to create an effective composite to inhibit the growth of Escherichia coli and Staphylococcus aureus, which provides an effective route to develop eco-friendly and powerful functional composites. The drug-loaded hydrogel displays a negligible cytotoxicity and favorable biocompatibility towards human skin.
Binderless poplar/bismuth oxide wood alloy is prepared using the warm-press forming technology. The effect of the forming temperatures on color changes and mechanical properties of the poplar/bismuth ...oxide wood alloy is studied. The results show that the surface color of the specimen gradually darkened as the forming temperature increased. There is the most obvious change from 140 to 160 °C. The CIE lightness color coordinate
L*
and chroma coordinate
b*
decrease with the increase of the forming temperature, while chroma coordinate
a*
decreases initially, but later increases with treatment severity. The static bending strength (MOR), the elastic modulus (MOE) and the surface hardness (HV) increase first and then decrease with the increase of the forming temperature. The X-ray diffraction (XRD) analysis shows that the wood underwent carbonization at 180 °C, resulting in a decrease in the density and mechanical properties of poplar/bismuth oxide wood alloy, and a deepening of the surface color. The Fourier transform infrared spectroscopy (FTIR) analysis reveals that the pyrolysis of cellulose and hemicellulose, as well as the pyrolysis and condensation of lignin led to the color of poplar/bismuth oxide wood alloy deepening. The hydroxyl groups between the cellulose molecular chains are reduced and hydrogen bonds are formed at 140 °C, which improve the mechanical properties of poplar/bismuth oxide wood alloy. However, the massive degradation of hemicellulose weakens binding strength with cellulose and lignin at 160 °C above. It greatly reduces the mechanical properties of specimen.
Graphene oxide (GO) membranes have attracted extensive interest due to their ultrathin thickness, high flux, pore size tunability, superior flexibility, and energy-efficient properties for ...transporting ions and molecules through the unique 2D channels. Nevertheless, membrane fouling leading to membrane blocking and poor water flux of GO membranes during long-term use are major obstacles for water treatment or desalination applications. In this work, Ag doped GO/titanate nanotube (Ag/GO/TNT) membranes with enhanced visible light degradation ability were fabricated by a single-step procedure to resolve the fouling problem via integration of photocatalysis with membrane filtration. The results show that the Ag nanoparticles could be highly dispersed on the surface of GO and TNTs. And, the as-prepared Ag/GO/TNT membranes exhibited reasonable ability on photocatalytic degradation of Methylene Blue under visible light. We found that 90% of MB could be effectively degraded after 120 min irradiation with 8 mg of photocatalyst. More importantly, the membrane fouling could be effectively alleviated with visible light irradiation. In coupling the photocatalysis and membrane separation processes, the flux of Ag/GO/TNT membranes with the GO and TNT ratio at 1:3 and Ag content of 6% could be maintained at 34.7 L/m2 h which doubles that of membrane filtration without visible light irradiation. In addition, Ag/GO/TNT membranes possess high acid–alkali resistance stability and good compressive strength. These results have provided a simple preparation strategy to obtain highly dispersed nanoparticles and valuable insight into endowing membranes with visible light degradation ability for solving the problem of GO based membrane fouling.
Creep performance is a crucial factor that must be considered in structural design. This paper aims to investigate the creep failure mode, creep strain, creep compliance, and other creep properties ...of bamboo scrimber under long-term tension in parallel-to-grain. To establish a general creep life prediction method for the full stress level of the bamboo scrimber, a multi-branch Kelvin–Voigt model, a generalized Maxwell model, and a creep finite element simulation were employed. The results showed that the creep strain curve of bamboo scrimber included the unsteady creep stage and the stable creep stage, but not the accelerated creep stage. When the stress ratio was less than 0.3, the residual strength decreased gradually. Below 70% of the ultimate load capacity, the creep characteristics of the bamboo scrimber were linear viscoelastic, and the creep compliance was generally independent of the load level. The creep finite element model of bamboo scrimber could accurately calculate the creep deformation of specimens. Based on this creep finite element model and creep failure rules, a life prediction model for the full stress level of bamboo scrimber was established, which could accurately predict the creep life. This paper provides theoretical guidance for the creep design of bamboo scrimber in engineering structures.
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