One of the primary purposes of the innovative development of ethnomedicines is to use their excellent safety and significant efficacy to serve a broader population. To achieve this purpose, modern ...scientific and technological means should be referenced, and relevant national laws and regulations as well as technical guides should be strictly followed to develop standards and to perform systemic research in producing ethnomedicines. Finally, ethnomedicines, which are applied to a limited extent in ethnic areas, can be transformed into safe, effective, and quality-controllable medical products to relieve the pain of more patients. The innovative development path of ethnomedicines includes the following three primary stages: resource study, standardized development research, and industrialization of the achievements and efforts for internationalization. The implementation of this path is always guaranteed by the research and development platform and the talent team. This article is based on the accumulation of long-term practice and is combined with the relevant disciplines, laws and regulations, and technical guidance from the research and development of ethnomedicines. The intention is to perform an in-depth analysis and explanation of the major research thinking, methods, contents, and technical paths involved in all stages of the innovative development path of ethnomedicines to provide useful references for the development of proper ethnomedicine use.
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•At the initial cracking load, the macroscopic crack-zone length increased with increasing fiber-volume fraction, whereas the fracture-process zone (FPZ) length decreased.•At the ...FMOR, the macroscopic crack and FPZ lengths of specimens were approximately 62.47 and 22.12 mm.•At the 30% FMOR, the macroscopic crack and FPZ lengths of specimens were approximately 75.99 and 18.90 mm.•A linear relationship between fiber pull-out number and equivalent bending stress, as well as between total fiber pull-out length and toughness, was established.•The tension softening curves obtained from the bi-linear softening curve analysis underestimated the experimental results.•The trilinear softening curve analysis exhibited good agreement with the experimental results.
Here, the mechanical properties and crack propagation nalysing of functional gradient ultra-high-performance concrete (FGUHPC) were nalysin using the digital image correlation (DIC) method. The fiber layer thickness (0, 25, 50, 75, and 100 mm) was varied to evaluate the impact on the FGUHPC. A quadratic equation was introduced to evaluate the compressive strength of FGUHPC, and a numerical model based on nonlinear fracture mechanics was established to predict the load crack opening displacement (COD) relationship. Results indicated that the maximum contribution of fibers to flexural strength occurred with a fiber layer thickness of 75 mm. The strength enhancement factor (ξ) was 1.139 and the fracture factor (KIC) was 1.5. The crack propagation nalysing of FGUHPC displayed an increasing curvilinear trend as the fiber layer thickness increased. The mid-span vertical displacement and crack opening displacement had a linear relationship, and the scale factor was 0.549. The fiber layer thickness had a limited effect on the fiber dispersion coefficient (α) and the orientation distribution (ηθ). The two-parameter exponential function proposed accurately evaluated the probability of fiber distribution. The trilinear matrix softening accurately predicted the load-COD curves. Compared to a fiber layer thickness of 100 mm, the specimen with a thickness of 75 mm reduced cost by 13.3% while only decreasing strength by 4.4%, demonstrating the potential of FGUHPC for practical engineering applications.
•Double-layer structured cement-based composites including matching layer and loss layer were designed and fabricated.•The design of the double-layer structure is conducive to improving the absorbing ...properties.•The double-layer structured cement-based composite in this work showed inspiring microwaves absorbing property and mechanical strength.
Double-layer structured cement-based composites, including matching layer and loss layer, were designed and fabricated. Matching layer composed of hollow glass microspheres was used to improve the impedance matching of cement-based composites and attenuate microwaves through complicated channels. Loss layer made up of single-particle sand (1.25–2.5 mm) and carbon powder absorber were designed to absorb microwaves by porous structure and resistive losses. It was found that the absorbing properties of cement-based composites were significantly improved by using the double-layer structure design. For the cement-based composite containing 10 wt% hollow glass microspheres in the matching layer (thickness = 20 mm) and 3 wt% carbon powder in the loss layer (thickness = 10 mm), the reflectivity was below −9 dB in the whole testing frequency ranges and the lowest reflectivity was −12.4 dB at 8.9 GHz, and the absorption bandwidth below −10 dB was 5.2 GHz in the frequency ranged 8–13.2 GHz. The compressive and flexural strength were higher than 42.5 MPa and 4.6 MPa, respectively. In comparison with the ones in literature, the fabricated double-layer structured cement-based composites showed excellent mechanical strength at the same microwaves absorbing level.
•M–S–H gels were found in MgO/SF pastes cured at room temperature.•Mg/Si ratio of M–S–H gels lay in the range of 0.67–1.0.•Mg(OH)2 rapidly formed in first 3days, then M–S–H gels were generated ...afterward.•The pH value of pore solution played a key role on the formation of M–S–H gels.•Reaction process of MgO–SiO2–H2O system at room temperature was summarized.
In order to clarify the reaction process of the MgO–SiO2–H2O system, the heat evolution, pore solution chemistry and reaction products of reactive MgO/silica fume (SF) pastes cured at room temperature were characterized. Based on the thermodynamic calculations and the experimental results, the final products tended to be M–S–H gels (magnesium silicate hydrates) rather than Mg(OH)2, and the Mg/Si ratio of M–S–H gels was in the range of 0.67–1.00. The pH value was increased with the dissolution of MgO and a large amount of Mg(OH)2 generated in the first 3days. M–S–H gels were generated gradually afterward until SF or Mg(OH)2 were consumed completely. It should be noted that the pH value of pore solution played a key role on the formation of M–S–H gels. A proper pH value of pore solution (about 10.5) led to a high concentration of Mg2+ (0.18mmol/L), eventually resulting in a high formation rate of M–S–H gels.
•Focus on damage process and crack propagation of functionally graded ultra-high-performance cementitious composite (FGUHPCC) with different layers (two and three layers) and fibers types (steel ...fibers and PVA fibers) through four-point bending test.•The evolution process of surface displacement and strain of the sample was analyzed by digital image correlation (DIC) technology.•The ultimate flexural strength and Load-COD curve of the specimen are obtained, and the evolution of COD, crack length, and the strain field of the specimen surface is analyzed by DIC.•Investigates the influence of the top layer, middle layer and bottom layer of FGUHPCC on the flexural performance by RFPA3D program. The AE distribution with various steel fibers content on each layer is discussed.
This study investigates the damage process and crack propagation of functionally graded ultra-high-performance cementitious composite (FGUHPCC) with different layers (two and three layers) and fibers types (steel and PVA) through four-point bending test. The evolution process of surface displacement and strain of the sample was analyzed by digital image correlation (DIC) technology, and the influence of the top, middle and bottom layers of FGUHPCC on the damage pattern are also investigated by RFPA3D program. The results indicate that functionally graded design improves the equivalent flexural strength and deflection capacity of the specimens compared with the UHPCC with single layer design. FGUHPCC with three layers and mixed steel and polyvinyl alcohol fibers exhibited best flexural behavior. According to the recorded DIC data and corresponding analyses, the crack opening displacement (COD) profile of functionally graded design with three layers is mutable and nonlinear, and the maximum crack propagation speed is 0.096 L/s, which is the lowest compared with other tested specimens, and the largest crack area ratios are about 0.04% and 0.147% at LOP and MOR, respectively. Based on RFPA3D results, with the change of fiber content, the cumulative AE energy growth rate (k) of bottom layer is about 2.7 times and 1.5 times of that of the middle layer and the top layer, respectively.
•For the fresh mortar with WGP, Modified Bingham model is more suitable for estimating the yield stress (τ0) and H-B model is more appropriated to interpret the plastic viscosity.•The flow index (n) ...remains relatively minor scatter and change slightly, ranging from 0.6 to 0.88; the plastic viscosity varied with a little fluctuation with the scope of 4.0 Pa·s to 5.94 Pa·s.•The contents of the WGP had great influences on the autogenous shrinkage of the mortar, the tremendously change mainly taken placed in the rapidly increase stage.•The addition of WGP can further reduce the heat of hydration of the hardened cement paste, and the rate of hydration heat peaked at about 20 h, there is no reaction occurred for 49.38 μm WGP with calcium hydroxide (CH).
To achieve a much better utilization the medium and small particle size of WGP, this study investigated the effect of WGP with different particle sizes (6.63 μm, 18.33 μm, 30.15 μm and 49.38 μm) and replacement ratios (3.0 %, 6.0 %, 9.0 %, 12.0 % and 15.0 %), as the supplementary cementitious materials, on the performance of the mortar. First, the rheological properties of the fresh mortar was evaluated by using Bingham model, Modified Bingham model, and H-B model; Second, the autogenous shrinkage and dry-wet cycling deformation of the hardened mortar were monitored; Finally, the micromorphology, weight loss and crystalline structure of hydration products were analyzed by SEM, TG and XRD. The results show that, for the fresh mortar with WGP, Modified Bingham model is more suitable for estimating the yield stress (τ0) and H-B model is more appropriated to interpret the plastic viscosity. As the averaged diameter of WGP increased, the yield stress (τ0) emerged a reversed S-shaped variation tendency; the flow index (n) remains relatively minor scatter and change slightly, ranging from 0.6 to 0.88; the plastic viscosity varied with a little fluctuation with the scope of 4.0 Pa·s to 5.94 Pa·s. The contents of the WGP had great influences on the autogenous shrinkage of the mortar, the tremendously change mainly taken placed in the rapidly increase stage; with the condition of same WGP content, the particle size of the WGP has a minimal impact on the autogenous shrinkage; under the drying and wetting cycle environment from 28 days to 140 days, the deformation rate changed in a way of sinusoidal wave. The addition of WGP can further reduce the heat of hydration of the hardened cement paste, and the rate of hydration heat peaked at about 20 h, there is no reaction occurred for 49.38 μm WGP with calcium hydroxide (CH).
Abstract
The ability of the resistivity measurement to study the crack propagation behavior of the ultra‐high‐performance concrete (UHPC) under flexural loading was analyzed, and focused on ...investigating the effects of crack length and the fracture process zone (FPZ) on the change in electrical resistivity in the post‐cracking stage. The results indicated that the strain‐dependent resistivity characteristic was able to drawn by a linear‐fitting equation before the crack initiated (stage I). After the crack initiated, the change in electrical resistance of the UHPC can be good to reflect the crack development in the post‐cracking stages (II and III), then, the relationship between the crack propagation behavior and the fractional change in electrical resistance (FCR) can be quantitative analysis by using an exponential function. It was also found that the evolution of the crack length and FPZ also had an appreciable impact on the variation tendency of the FCR. The crack length increased dramatically at first and then increased smoothly with the increase of FRC, while the FPZ showed the reverse change trend.
Three combinations of single fibers and nine combinations of hybrid fibers were tested to analyze the mechanical properties and crack propagation behavior of ultra-high-performance concrete (UHPC) by ...digital image correlation. It was found that in comparison to single fibers, the long fibers had a more pronounced effect than short fibers. The hybrid combination of medium length fiber (Vf = 0.5%) and long fiber (Vf = 1.5%) generated a better flexural behavior in terms of post-crack strength, deflection, toughness, than the other hybridization series. A digital image correlation (DIC) technique was applied to record the evolution of surface deformation. The hybrid use of longer fiber replaced the shorter fiber, long fiber replaced medium length fiber and short fiber, medium length fiber replaced short at lower replacement ratios (0.5% and 1.0%), the crack shapes were presented linear variation and showed an abrupt change and did not have a constant increment at higher replacement ratios (1.5% and 2.0%).
In the paper, five quaternary ammonium salts derived from rosin were synthesized, characterized and their antifungal activities against different molds were studied. Choline quaternary ammonium salt ...and tetramethylammonium hydroxide were synthesized from dehydroabietic acid and the rosin ethanolamine ester quaternary ammonium salts which are new compounds were synthesized from propylene pimaric acid. Their structures were confirmed by FTIR,
1
HNMR,
13
CNMR, and high resolution mass spectrometry. The antifungal activities of the synthesized quaternary ammonium salts from rosin acid were tested by Oxford cup method, and their minimum inhibitory concentration was determined. The results show that quaternary ammonium salts derived from rosin acid have inhibitory effects on bamboo slices to some extent. Among them, propylene pimaric acid ethanolamine ester quaternary ammonium salts (A
1
and A
2
) showed obvious antifungal activity in the Oxford cup test. The Oxford cup activity test and anti-mildew effect of quaternary ammonium salts (B
1
and B
2
) synthesized from rosin acid are significant, and there are almost no mould growth on bamboo slices. It can be inferred that A
1
, A
2
, B
1
and B
2
are expected to be used as bamboo mildew inhibitors.
Graphical abstract
Five quaternary ammonium salts derived from rosin were synthesized and characterized; and their antifungal activities against different molds were studied.
