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Buffer material has been shown to be effective over the long term for radionuclide diffusion retardation and is used as the final artificial barrier of the multi-barrier system in the high-level waste disposal repository. The method of disposal raises the possibility of radionuclides escaping and returning to the biosphere when ground water enters the natural geological barrier, risking the repository's long-term stability and safety. Bentonite was chosen as the basic material in the integrated buffer material due to its low permeability, high swelling, and self-healing ability. Meanwhile, attapulgite served as an auxiliary, and pyrite served as a mineral additive. The buffer material B7AP was created by combining three materials, namely bentonite, attapulgite, and pyrite, with a mass ratio of 63:27:10. The diffusion of uranium in samples with a dry density of 1.70 g/cm3 was studied using a constant source diffusion experiment. The results showed that the B7AP buffer material had a good uranium retardation effect, with an apparent diffusion coefficient of 4.07 × 10−12 m2/s. In addition, using the theory of porous media contaminant migration, a simplified convection-dispersion-adsorption equation for uranium migration on integrated buffer material B7AP was established. MATLAB software was used to simulate time scales, seepage velocity, apparent diffusion coefficient, and retardation factor. The current study provides scientific evidence for improving retardation performance, screening, and optimizing the formula design of radioactive waste repository buffer materials. [ABSTRACT FROM AUTHOR]

The filter mud in molasses has a significant inhibitory effect on biological activity and cannot be utilised by organisms; therefore, before molasses are biotransformed, the filter mud will be separated and directly discarded in the environment. In this study, the filter mud was used as the retarder of cement concrete OPC 42.5 for the first time. It was found that when 0.2–0.8% filter mud was added to fresh cement concrete OPC PC 42.5, the hardening time of cement slurry was significantly prolonged due to the synergistic retarding effect of sugar, colloid and total cellulose in the filter mud. In addition, the compressive strength of cement concrete mixed with the filter mud in the early stage (<10 days), middle stage (10–100 days) and later stage (180 days) was significantly higher than that of cement concrete and cement concrete mixed with commercial asphalt lignosulfonate. These results showed that the filter mud in molasses could realise harmless and resource utilisation, which could promote the comprehensive utilisation of molasses. [ABSTRACT FROM AUTHOR]

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The estimation of fatigue crack growth for a ship structure is a complicated subject, especially when loads vary. Several researchers studied fatigue crack growth under varying loads with simple block loads, and many models have been proposed. More research is required to properly evaluate the storm loads, representing complex actual loads a vessel experience on the sea. This study proposes a new simple fatigue crack growth model that incorporates only two parameters of the stress ratio factor and the load history factor taking account of the underload effects using empirical data in the literature. The procedures for formula modification and optimum model selection are introduced. The new model is optimized and validated by comparing it with several simple block load tests and existing fatigue crack growth models. Generally, the new model shows competitiveness and a good agreement with the experiment results. The proposed model is expected to be a potential solution, with a simple formula, to estimate fatigue crack growth under variable loads including the storm loads.

The filter mud in molasses has a significant inhibitory effect on biological activity and cannot be utilised by organisms; therefore, before molasses are biotransformed, the filter mud will be separated and directly discarded in the environment. In this study, the filter mud was used as the retarder of cement concrete OPC 42.5 for the first time. It was found that when 0.2–0.8% filter mud was added to fresh cement concrete OPC PC 42.5, the hardening time of cement slurry was significantly prolonged due to the synergistic retarding effect of sugar, colloid and total cellulose in the filter mud. In addition, the compressive strength of cement concrete mixed with the filter mud in the early stage (

This study is aimed at analysing the effect of static torsion on Mode I fatigue crack growth behaviour. Experiments have been conducted under constant torque or constant twist angle with different load ratios on SAPH440 and DP780 strip steels. The experimental results showed that the application of the static torsion or twist angle extended the fatigue life of the specimens in all cases. The fatigue life showed a positive relationship with the applied torque or twist angle until some critical value. No additional improvement in fatigue life was found after the critical value. The mechanism of the retardation due to static torsion was discussed and supported by the microscope fractography analysis. An effective stress intensity factor expression was proposed based on the fractography analysis to estimate the fatigue crack growth under constant torque in the low torque condition. The parameters introduced in the expression were found to have relationships with the dimensionless quantity related to torque, tensile load, and specimen geometry. The proposed expression achieved reliable estimates of the SAPH440 and DP780 constant torque experimental results. [ABSTRACT FROM AUTHOR]

The synthesis, characterization and properties of novel amphoteric polycarboxylate superplasticizers (PCs) are highlighted in this work. Specifically, two classes of amphoteric PCs were prepared through the addition of isobutenyl polyethylene glycol, acrylic acid and synthesized amphoteric monomer. The fluidity and fluidity retention of cement pastes containing these PCs and their adsorption behavior were investigated. In addition the cement hydration heat was measured, while X-ray diffraction and thermogravimetric behavior were also characterized. Consequently, the results indicated that these amphoteric PCs exhibited good dispersion performance and enhanced adsorption onto the cement. Furthermore, the results revealed that the PCs exerted a retardation effect during the early stages of cement hydration and subsequently accelerated this process, without affecting the subsequent cement hydration. These findings highlight the potential applications of these amphoteric PCs in concrete engineering. The PCs exerted a retardation effect during the early stages of the cement hydration, and then accelerated this process. Impressively, the presence of the PCs did not affect the subsequent cement hydration. In comparison with other PCs, PC-5 exhibited a more significant retardation effect during the early stages of the cement hydration. [ABSTRACT FROM AUTHOR]

The aim of this research work is to shed more light on performance-based design through a computational framework that assesses the residual strength of damaged plate-type configurations under overloading. Novel expressions are generated to analyze the power of crack-like stress raisers coupled with retardation effects. Analytical outcomes show that careful consideration of the overload location and crack size can be quite effective in improving safety design and failure mode estimation.

Impacts of β-cyclodextrin (β-CD) on hydration of white-Portland-cement (WPC) are studied by calorimetry, ICP-OES, TOC, TG, XRD and time domain NMR. Strong retardation effect of β-CD has been confirmed in both WPC and pure C 3 S pastes. Much stronger retardation in C 3 S pastes suggests the aluminate phases (C 3 A and ettringite) in WPC pastes mitigates the retardation effect of β-CD on C 3 S hydration, probably by adsorbing β-CD molecules and thus reducing β-CD concentration in the aqueous solution. Together with precipitation experiments of pure CH and C-S-H, it is concluded that β-CD remaining in the aqueous solution of the WPC pastes blocks CH and C-S-H formation and the induction period is remarkably extended as additional time is needed to clean up the aqueous solution by slowly formed hydrates e.g., AFt. NMR results suggest high dosage of β-CD promotes C-S-H precipitation directly in aqueous solution in acceleration period, besides the surface of cement grains. [ABSTRACT FROM AUTHOR]

The influence of flaxseed gum ( FG) on the retrogradation of maize starch ( MS) was investigated in this study. Based on the results of rapid visco-analyzer ( RVA), differential scanning calorimetry ( DSC), X-ray diffraction ( XRD), Low field nuclear magnetic resonance ( LF- NMR) and scanning electron microscopy ( SEM), FG has a retardation effect on the retrogradation of MS. With the addition increasing, the more significant the retardation effect was observed ( P < 0.05). However, when the concentration of FG was up to 0.4%, the change of retrogradation ratio showed no significant difference ( P > 0.05). FG could wrap around starch granules, suppress the recrystallisation of amylose and amylopectin, increase the water mobility and decrease the water loss. In summary, the overall results suggested that FG could be used as a natural inhibitor of the retrogradation of starch in food industry. [ABSTRACT FROM AUTHOR]

The usage of chemical admixtures, such as starch-based materials, is a common approach to addressing the thermal cracking problem of cementitious materials. Capsule-based controlled release technique enables the adjustable action time of loaded chemical admixture and thus reveals the potential on inhibiting the exothermic process of cement hydration. Three types of silica-based nanocapsules loaded with 53–63% sucrose retarder are firstly prepared by interfacial polymerization in water-in-oil (W/O) emulsion. The release characteristics of three types of nanocapsules are precisely tuned by varied preparation conditions. The effects of nanocapsules on the exothermic process of cement hydration have been investigated through calorimetry measurements. All prepared nanocapsules not only delay the appearance of the main hydration peak as the retardation effect but also reduce the maximum heat flow of the main hydration peak, to some extent, as the depression effect. The depression and retardation effects are improved with the increased dosage and slower release rate of added nanocapsules. The relationship between the two effects and the action time of loaded sucrose suggests the importance of persistently inhibiting the cement hydration over the entire accelerating and decelerating processes, which can be estimated by the time window between the action of sucrose (50% release time) and occurrence of main hydration peak. [Display omitted] • A series of controlled-release silica nanocapsules containing sucrose were successfully prepared and characterized. • The nanocapsules of diverse release behaviors affect the appearance time and maximum heat flow of the main hydration peak. • The depression and retardingretardation effects dependent on the release characteristics of nanocapsules are deeply investigated. • The inhibiting mechanism is proposed as sucrose's continuous release and adsorption onto early precipitated C-S-H. [ABSTRACT FROM AUTHOR]

The effect of PCE-type SP on zeta potential of particles, spread flow, hydration kinetics, setting time, autogenous shrinkage and chemical shrinkage of UHPC pastes is investigated, as well as the spread flow, slump life and early-age strength development of UHPC. Furthermore, the dispersing and fluid-retaining ability of SP, retardation effect of SP, physical and chemical process effects are analysed. The results show that the dispersing ability of PCE-type SP is determined by its chemical structure, which shows an exponential relationship between the flowability of pastes and SP dosages. The fluid-retaining abilities of UHPCs are sensitive to the water-to-powder ratio, while the further addition of SP will not enhance the slump life after excessing the saturation dosage. Both the adsorbed PCE and the PCE remaining in the aqueous phase contribute to retardation effect. A linear correlation between the final setting time ( t final ) and the time of maximum heat flow rate ( t Q ¨ = max ) is derived. The types and dosages of SP primarily influence the absolute chemical shrinkage of pastes within 1 day, but have a great effect on the autogenous shrinkage due to different physical coagulation and chemical process. [ABSTRACT FROM AUTHOR]

We investigated an improved Kramers-Kronig analysis (KKA) routine for measuring the dielectric function of α-Al2O3, avoiding the retardation effect arising in electron energy-loss spectroscopy (EELS). The EELS data differed from the optical data in the energy range of 10-20 eV due to the retardation effect, even though Cerenkov loss was thoroughly suppressed. The calculated differential cross-section indicates that the influence of the retardation appears at scattering angles less than 0.2 mrad in the loss energy range of 10-15 eV. Using the improved KKA routine, we obtained the correct dielectric function that agreed with the optical data. The present technique is especially useful in measuring the dielectric function by EELS with a small collection semi-angle. [ABSTRACT FROM AUTHOR]

In this study, the fatigue behavior of aluminum alloy 2024T3 v-notched specimens repaired with composite patch under block loading was analyzed experimentally. Two loading blocks were applied: increasing and decreasing at two stress ratio: R = 0 and R = 0.1. Failed samples were examined under scanning electron microscope at different magnifications to analyze their fractured surfaces. The obtained results show that under increasing blocks, the crack growth is accelerated for both repaired and unrepaired specimens. This is attributed to the increase of the loading amplitude in the second block. A retardation effect was observed for decreasing blocks loading in unrepaired specimens. However, this retardation effect is attenuated by the presence of the patch which lead to lower fatigue life for repaired specimens. [ABSTRACT FROM AUTHOR]

The effect of four industrial tea derivatives (tea polyphenols [TPS], tea water-soluble extracts [TSE], tea polysaccharides [TSS], and green tea powder [GTP]), on the retrogradation of wheat starch was investigated using texture profile analysis (TPA), differential scanning calorimetry (DSC), rapid viscosity analysis (RVA), and the α-amylase–iodine method. The addition of the four tea derivatives resulted in decreased hardness and increased cohesiveness of the starch gel as shown by the TPA test. The DSC data demonstrated an increase in the enthalpy change of starch gelatinization and a decrease in the enthalpy change of starch recrystallite dissociation. The RVA results indicated that the peak viscosity, representing the intermolecular forces of wheat starch, was reduced after addition of TPS, TSE, and TSS, respectively, but was increased by GTP. Furthermore, the half crystallization time in the Avrami equation almost doubled after the separate addition of the tea derivatives. [ABSTRACT FROM AUTHOR]

Cement-asphalt mortar (CA mortar) is an inorganic-organic composite, which combines both advantages of the mechanical property of cement and flexibility of asphalt. Therefore, it has been widely applied in high-speed railway and used as a kind of semi-flexible pavement material. Cement hydration process can affect the rheological property of fresh cement-asphalt paste as well as the mechanical and durability properties of the hardened cement-asphalt paste. Whereas, the interaction of emulsifier and cement particles will significantly affect the hydration process. Hence, the influence of emulsifier on cement hydration was investigated though measuring of setting time, hydration heat, ions concentration and electrical resistivity. It is indicated that the cement hydration process was retarded with the addition of emulsifier according to the results of the setting time and the hydration heat, and meanwhile, the hydration process was delayed gradually with the increasing dosage of emulsifier. The mechanism of the retardation effect can be attributed to the occupation of emulsifier at the active sites of cement particles, therefore, the delaying of cement hydration was further confirmed by the results of the lower ions concentration of the paste mixed with emulsifier. More specifically, for the cement mixed with emulsifier, a protective layer formed around the cement particles and this protective layer hindered the releasing of ions. As is well known, electrical resistivity is an indicator parameter which can indicate the cement hydration process and the formation of micro-structure effectively, thus, the variation law of the electrical resistivity can also reflect well the retardation effect of emulsifier on cement hydration. [ABSTRACT FROM AUTHOR]

The plasticity-induced crack shielding effect is evaluated during fatigue crack growth using transmission photoelasticity. The proposed methodology is based on the evaluation of the stress intensity factors calculated from the analysis of the isochromatic fringe patterns observed at the vicinity of a crack tip. Four different mathematical models describing the crack tip stress fields (namely models based on Westergaard’s, Williams’s, and Muskhelishvili’s equations and a new model called Christopher–James–Patterson) have been employed. Thus, a comparative study to evaluate which of the models is more suitable for fatigue crack shielding evaluation has been performed. A set of fatigue experiments on polycarbonate middle-tension specimens at different R-ratios have been conducted. Experimental results reveal the presence of plasticity-induced crack shielding on growing fatigue cracks for specimens tested at a low R-ratio. In addition, a retardation effect on the fatigue growth rate has been observed due to the shielding effect induced by the plasticity generated both at the crack tip and along the crack flanks. All these results highlight the enormous potential of transmission photoelasticity for the evaluation of plasticity-induced crack shielding on growing fatigue cracks. [ABSTRACT FROM AUTHOR]

Cross-termination in bulk reversible addition-fragmentation chain transfer (RAFT) polymerization is characterized by defining a new parameter, RM, in terms of the polymerization rates with and without an externally applied magnetic field (EAMF). For the bulk RAFT polymerization (RAFTP) of styrene (St), mediated by (2-cyano-2-propyl)dithiobenzoate (CPDB) and S-1-dodecyl-S′-(α, α′-dimethyl-α′′-acetic acid)trithiocarbonate (DDMAT), an RM of 0.534 and 0.382 is obtained respectively, showing a sensible dependence on the RAFT agent. It is also found that RM has a close relationship with the strength of the EAMF and the concentration of the RAFT agent. Detailed discussion reveals that RM can be used as a characteristic parameter to measure the extent of cross-termination in RAFTP. The experimental technique offers an efficient way to quantitatively probe the cross-termination in situ, and sheds light on the mechanism of RAFTP. [ABSTRACT FROM AUTHOR]

Co diffusion in Cu was studied by electron probe microanalysis (EPMA). The samples were annealed at the temperature range 600–800 °C (0.65–0.8 T m – Cu melting temperature). The Co concentration was measured along grain boundary (GB) in adjacent to GB region and far from it. It was shown that Co concentration does not depend on the distance from GB at the same depth. This result indicates the absence of the accelerated GB diffusion. The possible reasons for such unexpected result can be connected with the gradient of GB surface tension as the additional driving force for GB diffusion. The last effect is related the increasing of Cu GB surface tension on Co concentration. [ABSTRACT FROM AUTHOR]

In a previous study, a synergistic retardation effect of 1,4-cyclohexanediol and 1,2-hexanediol on percutaneous absorption and penetration of metronidazole (MTZ) was discovered. A complex formation between 1,4-cyclohexanediol and 1,2-hexanediol was proposed to be responsible for the observed effect. The objective of this study was to investigate the necessity of hydroxyl group and the ring structure in 1,4-cyclohexanediol on percutaneous absorption and penetration of MTZ. Eleven formulations were studied in an in vitro porcine skin model using glass vertical Frans Diffusion Cell. 1,4-Cyclohexanediol was changed into 1,4-cyclohexanedicarboxylic acid, trans (and cis)-1,2-cyclohexanediol and 1,6-hexanediol, respectively, to study if H-bonding or ring structure would influence the retardation effect. MTZ was applied at infinite dose (100 mg), which corresponded to 750 μg of MTZ. Based on modifier ratios (MR) calculated by the flux values, the retardation effect on percutaneous absorption and penetration of MTZ was found in the formulations containing 1,4-cyclohexanedicarboxylic acid or cis-1,2-cyclohexanediol (MR values were 0.47 for which only contains 1,4-cyclohexanedicarboxylic acid, 0.74 for the formulation containing both 1,4-cyclohexanedicarboxylic acid and 1,2-hexanediol, and 0.90 for the formulation containing cis-1,2-cyclohexanediol and 1,2-hexanediol, respectively). The results showed that the hydroxyl group and structure of 1,4-cyclohexanediol played a significant role in retardation effects and provided valuable insight on the mechanisms of retardation effect through structure-activity relationships. [ABSTRACT FROM AUTHOR]

Abstract: In order to prevent the initiation of a brittle crack in a marine structure, fatigue crack propagation from potentially hazardous embedded weld defects must be evaluated under the realistic seaway loading using certain clustered loading patterns. We first simulate the fatigue crack propagation under the random sequence of clustered loading so-called storm model. The numerical simulation is carried out by a method considering the plastic wake on the crack surfaces, which may cause the retardation effects after high amplitude of loading. Furthermore, fatigue crack propagation under the effect of slam-induced whipping stress is examined by a series of experiments using CT specimens and by simulations. [Copyright &y& Elsevier]