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The corrosion and oxidation mechanisms of steel in chloride-contaminated environment were studied through the utilization of reactive molecular dynamics simulations with self-developed force fields under various applied electric fields and temperatures. The impact of variations in the external electric field on the thickness of the oxide layer and the dissolution of iron during the corrosion reaction process was scrutinized. The results reveal that under an electric field strength of 10 MV/cm, marginal corrosion was observed within the iron matrix during the simulation period. The surface lattice of the iron matrix retained a relatively intact and regular arrangement. However, under alternative external electric field conditions, as the strength of the external electric field increased, the corrosion behavior of iron in chloride ion solutions became increasingly severe, leading to deeper oxidation levels. Additionally, localized pitting on the iron matrix surface gradually evolved into larger corroded spots. Simulation results within the temperature range studied (278 K, 298 K, 318 K) suggest that temperature elevation amplifies the thermodynamic energy of chemical reactions on the iron surface, consequently leading to a reduction in the bond strength of Fe-O and increase in the corrosion extent. • The Fe-Cl ReaxFF reactive force field for steel corrosion in chloride-contaminated electrolyte environment was established. • MD simulations were employed using self-developed reactive force field to investigate steel corrosion submitted to chloride. • High temperature amplifies the thermodynamic energy of chemical reactions and leads to a reduction in bond strength of Fe-O. [ABSTRACT FROM AUTHOR]

MicroRNAs are involved in the regulation of the autophagy and proliferation in several diseases. This study aims to verify the role of miR-25-3p in the proliferation and autophagy of renal cells in polycystic kidney disease (PKD). We found that kidney to body weight and blood urea content were increased in PKD mice. Cystic dilations were increased in kidney tissue from PKD mice, and autophagy-related protein ULK1 and the ratio of LC3-II/LC3-I were decreased, indicating autophagy was inhibited in PKD mice. In addition, miR-25-3p was upregulated in PKD mice, and inhibition of miR-25-3p decreased cystic dilations in kidney tissues, increased ULK1 expression and the ratio of LC3-II/LC3-I, indicating inhibition of miR-25-3p enhanced the autophagy in PKD. Besides, inhibition of miR-25-3p suppressed the proliferation of renal cells and downregulated E2F-1 and PCNA expressions. Importantly, miR-25-3p targetedly suppressed ATG14 expression in PKD cells. Finally, silencing ATG14 abolished the inhibition effect of miR-25-3p inhibitor on renal cell proliferation, and reversed the inhibition effect of miR-25-3p inhibitor on E2F-1 and PCNA expressions in in vitro and in vivo experiments, which suggested that ATG14 was involved in the regulation of miR-25-3p-mediated kidney cell proliferation. Therefore, inhibition of miR-25-3p promoted cell autophagy and suppressed cell proliferation in PKD mice through regulating ATG14. [ABSTRACT FROM AUTHOR]

Cement powder shapes have a pivotal role in particle packing and microstructural development, while its effect on capillary pore structure formation in three-dimension has not been fully understood. In this study, the modified CEMHYD3D model building on previous work of irregular-shaped cement particles is firstly used to simulate the evolution of capillary pore structures in cement pastes at various water-to-cement ratios. Pore networks at different curing time and degree of hydration are extracted and visualized. Subsequently, some home-made programs for determining three-dimensional pore structure characteristics including porosity, pore size distribution, pore connectivity and pore tortuosity are carried out on these simulated pore network extractions in hardened cement pastes. The results indicate that shape-induced larger surface area in more non-equiaxed irregular-shaped cement particles can improve pore structure parameters in hardened cement pastes, but this effect will be slight in the later curing period and at a low water-to-cement ratio. In addition, the less considered geometric difference plays a role in pore structure evolution especially for extremely non-equiaxed cement particle. However, the geometric attribute has a weak effect on pore structure parameters overall. It can also be concluded that the pore-to-solid ratio is still the most pronounced influence factor for pore structure parameters in hardened cement pastes. [ABSTRACT FROM AUTHOR]

Depassivation and corrosion of reinforcing steels submitted to chloride in simulated concrete pore solution was studied with electrochemical methods. Measurements included half-cell potential (HCP), linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS). Three different equivalent circuits, i.e., R(QR), R(QR)(QR) and R(Q(R(QR))), were proposed to fit and elucidate the EIS data, respectively. Results showed that large-scale depassivation and corrosion of steel occurred when chloride content exceeded 0.05 mol/L. All the three equivalent circuits revealed a good fitting degree of Nyquist plots at early stage, while only circuit R(Q(R(QR))) still retained a most appropriate fitting at severe corrosion stage, of which the chi-square ranged from 3.1E−4 to 8.5E−4 throughout the whole exposure test. Verification could be obtained that circuit R(Q(R(QR))) with two time constants was effective to fit and explain the depassivation process in regard to steel corrosion induced by chloride in simulated concrete pore solution. [ABSTRACT FROM AUTHOR]

• A new avenue to prepare rubber aggregate with excellent interfacial adhesion and compatibility was developed by combining ultrasonic mechanochemistry and a modified slurry coating. • The interface between rubber particles and cement matrix was improved and the mechanical properties were vastly enhanced. • The modification of rubber powder significantly improved the abrasion resistance of crumb rubber concrete. • The abrasion mechanism of CRC was systematically analyzed and the abrasion mechanism models of the rigid and semi-rigid body were established. • The interface between rubber particles and cement matrix played an important role in controlling the abrasion resistance of CRC. The abrasion resistance of crumb rubber concrete (CRC) has always been a research hotspot. However, the large reduction in the mechanical properties of CRC limits the improvement of its abrasion resistance. In this study, a new method of modifying waste rubber powder (WRP) combining mechanochemical action, ultrasonic energy accumulation and the coating effect of the modified slurry was proposed. The mechanical properties of CRC with rubber volume fractions of 0%, 15%, 25% and 35% were determined. The abrasion resistance of CRC was studied by the ball bearing and ball milling methods. The abrasion mechanism of CRC was analysed, and abrasion mechanism models of the rigid and semirigid bodies were established. The results showed that the compressive and flexural strengths of modified CRC (MCRC) were increased by 74.2% and 45.7% respectively, compared with CRC. The abrasion resistance of concrete first increases and then decreases with increasing rubber content. Compared to the control concrete, the abrasion resistance of CRC and MCRC was increased by 14.9% and 24.8%, respectively. The mass loss rates of CRC and MCRC were 29.78% and 24.98% respectively, under the same volume replacement. The enhancement of abrasion resistance of the CRC is mainly due to the absorption of wear energy by rubber. The rubber-cement matrix (R-CM) interface played an important role in controlling the abrasion resistance of CRC. [ABSTRACT FROM AUTHOR]

Electrochemical measurements of open circuit potential, linear polarization and electrochemical impedance spectroscopy (EIS) were utilized to investigate the corrosion behavior and chloride threshold value (CTV) of reinforcing steels submitted to chloride and sulphate attack in simulated concrete pore solution in this study. Determination of corrosion initiation was made by combining half-cell potential (E corr ) with corrosion current density (I corr ) as well as EIS curves. Results showed that electrochemical measurements were effective in detecting corrosion behavior of steels. CTV of steels was 0.5–0.6 mol/L in simulated concrete pore solution contaminated by chloride ions while threshold value of steels submitted to sulphate ions was 0.2–0.3 mol/L. The concomitant presence of chloride and sulphate ions led to higher corrosion current density which indicated sulphate ions accelerated the corrosion of reinforcing steels in simulated concrete pore solution. [ABSTRACT FROM AUTHOR]

Fruit polyphenols are beneficial to human health as antioxidants, but high levels of these compounds diminish fruit appearance and flavor. In this study, we aimed to understand the variations in polyphenol variation and composition in Malus , including cultivars of the domesticated apple ( Malus domestica ). We quantified polyphenols in the flesh of ripening fruits from 20 Malus species (142 accessions), using high-performance liquid chromatography. We also analyzed dynamic changes in the levels of major polyphenols, procyanidin and chlorogenic acid, during fruit expansion. Total polyphenol concentrations (including chlorogenic acid and procyanidins) differed significantly across species and accessions, but intraspecific genetic diversity was the primary source of variation in polyphenol contents and compositions. We also found an effect of development. As fruit weight increased during fruit expansion, chlorogenic acid and procyanidin concentrations decreased continuously per unit fresh weight, but per-fruit concentrations either increased or remained constant. Finally, significant variability in fresh-cut browning positively correlated with chlorogenic acid and procyanidin concentrations, suggesting that these compounds can be targeted to decrease unfavorable apple appearance. In conclusion, the genetic diversity in M. domestica provides sufficient variation for the selection of future cultivars that are both visually appealing (less fresh-cut browning) and nutritious (higher levels of antioxidants). [ABSTRACT FROM AUTHOR]

The pathological damage of mesangial cells serves an important role in the occurrence and development of diabetic nephropathy. Ellagic acid has been reported to possess antioxidant, antitumor, antiviral and anti-inflammatory properties in several diseases, but the roles of ellagic acid in diabetic nephropathy are unclear. The main aim of the present study was to investigate the effect of ellagic acid on high glucose-induced mesangial cell damage. The results revealed that high glucose could induce the hyperproliferation of mesangial cells, decrease the activity of superoxide dismutase, increase the malondialdehyde content, the level of reactive oxygen species, the secretion of inflammatory factors (TNF-α, IL-1β and IL-6) and the synthesis of extracellular matrix (Fibronectin, MMP-9 and TIMP-1) and activate the PI3K/Akt/FOXO3a signaling pathway. Ellagic acid could attenuate the injury of mesangial cells induced by high glucose in a concentration-dependent manner and its effect was consistent with that of a PI3K inhibitor (LY294002). Moreover, a PI3K agonist (740Y-P) reversed the protective effect of ellagic acid on mesangial cells induced by high glucose. In conclusion, ellagic acid protected mesangial cells from high glucose-induced injury in a concentration-dependent manner. The mechanism may be associated with ellagic acid inhibiting the activation of the PI3K/Akt signaling pathway and reducing the expression levels of downstream transcription factor FOXO3a. [ABSTRACT FROM AUTHOR]

• Effect of saturation degree on water absorption of concrete was investigated. • Effect of volume fraction and particle size of coarse aggregates on water absorption were studied. • A model for predicting the rate of water absorption of concrete was established. Better understanding of water transport in concrete is of great significance to assess the durability and predict service life. In this study, effects of water to cement ratio (W/C), volume fraction of coarse aggregate (V a) and particle size of coarse aggregate on water absorption of concrete were investigated. Besides, more attention was paid to the effect of saturation degree (θ) on water absorption of concrete. The results showed that the process of water absorption can be divided into two stages: rapid absorption and steady absorption. The rate of water absorption increases with the increasing W/C of concrete. An increase of V a reduces the water absorption of concrete; however, the particle size of coarse aggregate has no effect on the water absorption of unsaturated concrete. The initial rate of water absorption decreases with the saturation degree of concrete increasing. According to experiment results, a model for predicting the initial rate of water absorption of concrete with any saturation degree is established. From that, the initial rate of water absorption of concrete with any saturation degree can be calculated. [ABSTRACT FROM AUTHOR]

• Nano X-CT combined with metal centrifugation porosimetry (X-MCP) is developed. • The 3D pore structure is visualized by the novel X-MCP and CEM3D simulation methods. • The pore parameters obtained by X-MCP and CEM3D are evaluated by the traditional MIP. • The critical pore diameters obtained by X-MCP and CEM3D are higher than those by MIP. • The porosity values obtained by the three methods are accordant with each other. Cementitious material is a vital composite for infrastructure, its 3D pore-structure determines its cement hydration as well as structural performance. However, the quantitative characterization of 3D pore-structure has yet been investigated in depth. In this study, the 3D pore-structure in hardened cement-paste is investigated systematically using innovative experiment and simulation methods. The experiment implements nano X-ray techniques combined with metal centrifugation porosimetry (X-MCP) for visualizing the 3D pore-structure and compared to that obtained by CEM3D-based model. The 3D pore-structure parameters containing the critical pore-diameter (d c) and porosity by X-MCP and CEM3D are counted and compared to those by mercury intrusion porosimetry (MIP). The results show that the d c values by X-MCP and CEM3D are both higher than those by MIP, and the porosity values obtained by the three methods agree with each other. [ABSTRACT FROM AUTHOR]

Accurate prediction of transport properties for cementitious materials remains a challenge since it is difficult to experimentally obtain the realistic three-dimensional (3D) pore network of cement paste. In this study, the 3D pore network of cement paste is quantitatively characterized using nano X-ray microtomography coupled with the metal centrifugation porosimetry (MCP). First, the MCP technique is carried out to impel the liquid metal into the pore network of cement paste. Subsequently, the 3D pore network of cement paste with the intruded metal is reconstructed using high-resolution X-ray microtomography. Finally, based on the X-ray microtomography images, the transport properties of cement paste including ionic diffusivity and fluid permeability are simulated using a set of lattice Boltzmann transport models. The results show that the metal alloy can significantly enhance the contrast between the pore network and solid phase, and the realistic 3D pore network can be successfully reproduced. For the cement pastes with water-to-cement (w/c) ratios of 0.5 and 0.6, the transport properties are dramatically increased with the improving w/c ratio. A similarly dramatic growth evolution of transport properties also occurs when the effective porosity of cement pastes raises from 27.56% to 36.11%. [ABSTRACT FROM AUTHOR]

As a type of silica-alumina solid waste, fly ash can be utilized to prepare ceramic proppants by partially substituting bauxite due to a similar chemical composition. However, the heavy metal elements in fly ash including Zn and Cd are subjected to be released during high-temperature calcination, causing harm to some extent. In this study, migration, transformation, solidification, and volatilization of heavy metals in proppant at elevated temperatures are systematically studied by various experimental characterization methods. The results show that the solidification effect of the prepared ceramic proppant on the Zn and Cd elements is favorable, with solidification ratios up to 77.16% and 74.34%. The addition of Cd improves the bulk density and strength of the ceramic proppant, while the addition of Zn significantly reduces the strength and increases the water absorption. Additionally, the majority of doped Zn will combine with Al 2 O 3 to form a new phase, zinc spinel ZnAl 2 O 4 , which hinders the formation of the inherent mullite phase. On the contrary, the addition of Cd does not change the phase composition, and the Cd element is mainly solidified in the form of lattice substitution. Finally, the distributions of volatile Zn and Cd in gas- and solid-phase were quantitatively determined by the in situ continuous collection system. In addition, a mathematical model was used to predict the volatilization of heavy metals during the proppant calcination process. [ABSTRACT FROM AUTHOR]

3D printing technique is an opportunity for the development of architecture industry altered by the emergence of 3D printing concrete ink that shows unconventional characteristics mainly originated from its geometric design. In this paper, a novel 3D printing concrete ink that has good fluidity during movement and satisfying standing behavior at static state due to the structural rebuilding of cement paste advanced by the addition of nano clay (NC) and silica fume (SF) was specially designed to be extruded through a nozzle to print layer-over-layer components for an innovative additive manufacturing process. The buildability, rheological properties (viscosity, yield stress and thixotropy), workability, green strength, open time and hydration heat of the fresh 3D printing concrete were systematically investigated. Results indicated that the buildability of this concrete with a small quantity of NC or SF were increased by 150% and 117%, respectively, and remarkably enhances the thixotropy and green strength. The double-doped NC and SF optimize the buildability. [ABSTRACT FROM AUTHOR]

In this study, a novel type of lime-based low carbon cementitious material (LCM) was designed and prepared using low contents of hydrated lime and Portland cement and a high content of mineral admixtures. The mechanical properties, workability, heat of hydration, hydration degree, porosity, hydration products, and microstructure of LCM were systematically investigated. The test results indicated that LCM showed good mechanical properties and workability compared with conventional blended cement. The compressive strength of LCM can achieve 50–60 Mpa at curing 28 d and more than 70 Mpa at curing 180 d. The hydration products of LCM were mainly composed of ettringite, portlandite, and C–(A)–S–H gel according to X-ray powder diffraction results. Analysis suggests that a small amount of Portland cement in LCM accelerated the pozzolanic reaction of mineral admixtures due to the alkalinity, and the Ca 2+ ion concentration in the pore solution increased. Meanwhile, the hydrated lime reacted with mineral admixtures in long-term hydration and increased the mechanical property of LCM. In addition, LCM exerted a notable reduction in carbon emission, energy consumption and environmental burden compared with Portland cement. The quantitative calculation suggested that the energy intensity and carbon emission of the LCM are only approximately 24–45% and 13–38% that of Portland cement, respectively. [ABSTRACT FROM AUTHOR]

Concrete repairing, rehabilitation and prolonging the effective service-life of structures plays an important role in building field worldwide. The polymer-modified cementitious material dominated by different resins has been widely applied in repairing and reinforcing, wherein the epoxy resin is a material with excellent comprehensive properties. The waterborne resin gets a better compatibility and coupling effects with the cement hydration. In this paper, the effect of two waterborne epoxy resins on the hydration of cement and the microstructure of paste have been studied. The mechanical properties, mesoscopic morphologies after mixing and curing, the hydration products, chemical bonds and three-dimensional structures of the cement paste with emulsion type epoxy resin (EEP) and non-emulsion type epoxy resin (NEP) (with content of 5%–80% wt.) are studied by optical microscopy, field emission scanning electron microscopy, X-ray diffractometer, Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray computed tomography. The results show that EEP and NEP have a significant effect on the formation of portlandite crystals at an early stage. NEP is more effective than EEP on the toughening effect with the content of 40% wt. The stress–strain curve of non-emulsion epoxy cement paste (NEPC) manifests an obvious secondary step, and the fracture strain value rises from 0.6% to 1.2–1.3% which proves the NEP enhances the resistance to cracking. The resin in NEPC mainly consists of a layered network structure with the continuous phase in the transverse direction. [ABSTRACT FROM AUTHOR]

The corrosion of steel fibers is a direct cause of the deterioration of steel fiber-reinforced concrete in chloride environments. This study mainly investigated the corrosion behavior of steel fibers exposed to NaCl solutions with pH=7 , 10, 11, 12, and 13. The corrosion rate of the steel fibers was calculated according to the change of the diameter and ultimate tensile load. The electrochemical parameters of the steel fibers corrosion were continuously monitored. The morphology of the steel fibers affected by chloride attack was observed by scanning electron microscope (SEM). The results reveal that the corrosion rate of the steel fibers decreased as the pH of the NaCl solution increased from 7 to 13, and it was very small at pH≥12. According to the open circuit potential, corrosion potential, corrosion current density, and electrochemical impedance spectroscopy, the steel fibers exhibited a high corrosion tendency and corrosion rate when exposed to NaCl solutions with pH≤12. However, they exhibited low corrosion tendency in the chloride solution with pH=13. The surface roughness of the steel fibers exhibited only a slight increase after exposure to the NaCl solution with pH=13 for 180 days. [ABSTRACT FROM AUTHOR]

Cement‐based sensors (CBSs) have demonstrated potential in structural health monitoring (SHM) despite rare applications due to their poor flexibility and sensing accuracy/protection with robustness. Herein, a promising strategy is reported to design a waterborne epoxy resin (WEP)‐modified cement‐based composite coating sensorcapable of simultaneous stable SHM and durable protection. The interpenetrating network (IPN) formed by WEP within cement paste is bionic to the toughness and crack resistance of biological muscle tissue and balances the ion permeation performance and polarization of hydration products. The polymerization‐redispersion progress and mechanism of calcium silicate hydrate (C‐S‐H) gel modified with [3‐(2‐aminoethylamino)‐propyl]trimethoxysilane silsesquioxane (C‐POSS) are characterized and revealed. The results show that the muscle‐like IPN increases the cement‐based coatings' maximum deflection angle to 30° and improves the monitoring accuracy of compressive, tensile, and fatigue microchanges of concrete structures to more than 95%. The POSS···Ca2+···C‐S‐H interaction in C‐POSS partially transferred the intra‐adhesive hydrogen bonds surrounding the nanoconducer into electrostatic bridging ones to maintain an excellent electromechanical conductive dispersion. [ABSTRACT FROM AUTHOR]

Flue gas desulphurization (FGD) gypsum is a kind of industrial solid waste containing impurities (i.e., heavy metal ions Zn2+ and Ni2+), which may lead to threats to the ecological environment and public health. To safely use the FGD gypsum, this study investigated the mechanical strength, releasing property of SO42- and leachability of heavy metal ions of a series of FGD gypsum (40%) based mortar with various cement to slag ratios. The hydration process, pore structure, and morphology of the sample were then characterized and analyzed by isothermal calorimetry, H1 low-field nuclear magnetic resonance (NMR), and scanning electron microscope with energy dispersive X-Ray analysis (SEM-EDx). It was found that the highest mechanical strength could be obtained when the C/S ratio was 1:5, and the decrease of C/S ratios from 4:2 to 1:5 leads to less SO42- releasing from the mortar. The heavy metal leachability of the mortars is lower than that of the limitation of solid waste stipulated by the specification of GB5085.3-2007, and less of the heavy metal are leached from the sample as the C/S ratios decrease. The heat flow for the paste sample with 40% of FGD gypsum was delayed as the cement to slag ratio decreased from 5:1 to 2:4. In addition, the released amount of Zn2+ ions linearly decreases with the pore size of gel pores and capillary pores but increases with the pore size of macropores, and the ettringite in the paste exhibits the transformation from the needle to the clubbed shape when smaller cement to slag ratio was used. This work helps to understand how to reduce the heavy metals leachability of FGD gypsum from cementitious material and provides baseline for safely using the FGD gypsum for the preparation of building materials. [ABSTRACT FROM AUTHOR]

The effects of three commonly used superplasticisers (SPs) - sulfonated naphthalene formaldehyde (SNF), sulfonated acetone formaldehyde (SAF) and polycarboxylates (PCB) - on the hydration process, products and microstructure of tricalcium aluminate (C3A) pastes in the presence of gypsum were systematically investigated using isothermal calorimetry, x-ray diffraction, environmental scanning electron microscopy, infrared spectroscopy and magic angle spinning-nuclear magnetic resonance spectroscopy. The results show that the hydration reaction rate of C3A paste at the initial stage (0-2 h) was promoted by the incorporation of SPs, especially in the C3A-SNF paste. Hydration was rapidly reduced at the early stage (2-12 h), but an acceleration in C3A-SNF/PCB pastes occurred again at the late stage. The morphology of the C3A-SNF/SAF paste changed from thin needle-shaped crystals at the initial stages to thick and coarse rod-like crystals at late stages. In the C3A-PCB paste, very few crystals occurred at an early age, while a large amount of prismatic crystals were observed at the later age. Chemical environment studies revealed that the SPs did not visibly change the position or shape of the characteristic bands of aluminates, but only influenced their relative intensities. A predominant resonance, assigned to six-coordinated aluminium as [AlO6] type, was observed for all the pastes with and without SP. The interaction mechanism between SP and C3A was also explored. [ABSTRACT FROM AUTHOR]

In this study, based upon the investigation of its effect on workability and the mechanical property of cementitious materials, the Box–Behnken design was adopted to establish models describing self-healing performance on mechanical properties of cementitious materials with polymethylmethacrylate (PMMA)/epoxy microcapsule in terms of healing rate of peak strength (Y1), the recovery rate of peak strength (Y2), the healing rate of Young's modulus (Y3), the recovery rate of Young's modulus (Y4), the healing rate of peak strain (Y5), and recovery rate of peak strain (Y6). This was performed under the influence of the four factors, including microcapsule size (X1), microcapsule content (X2), pre-loading (X3), and curing age (X4). The results showed the four factors significantly affect the healing rate and recovery rate of the peak strength, Young's modulus, and peak strain, except the healing rate on peak strain. Moreover, the interaction between the factors showed some influence as well. The numerically optimised values of X1, X2, X3, and X4 are 203 nm, 5.59%, 43.56%, and 21 days, respectively, and the self-healing cementitious materials with desirable mechanical characteristics (Y1 63.67%, Y2 145.22%, Y3 40.34%, Y4 132.22%, Y5 27.66%, and Y6 133.84%) with the highest desirability of 0.9050 were obtained. Moreover, the porosity of the specimen confirmed the healing performance of PMMA/epoxy microcapsules in cementitious materials. [ABSTRACT FROM AUTHOR]

Solid wastes have become used to manufacture high ferrite cement clinker (HFCC). However, the behavior and effect of common heavy metal in solid wastes, i.e., lead during calcination process are still lacking. And understanding the solidification behavior of lead and its action mechanisms on phase reconstruction and hydration processes is crucial for rational utilization of lead-containing solid waste. Hence in this study, the distribution and solidification form of lead during HFCC calcination are explored and the effect of solidified lead in clinker on mineral phase composition, liquid phase properties, microstructures, and hydration properties of HFCC are systematically studied using various experimental and modelling methods. Results indicate that nearly all the Pb ions are solidified in the inherent phase structures, among which the majority are dissolved in the silicate phase. Due to the unstable phase configurations formed by lead substitution and the unmatched electronic structure, the Pb elements are subject to enter C 3 S, C 2 S, and C 4 AF in the form of interstitial solid solution. The solidification preference of the Pb element in the single crystal is C 2 S > C 4 AF > C 3 S as a result of the larger interstitial voids of C 2 S. The solidified Pb elements in HFCC mainly affect the mineral phase composition by varying the liquid phase properties. The formation of a eutectic mixture reduces the viscosity and formation temperature of the liquid phase, resulting in an increased interstitial phase content. Additionally, the high-energy-activated state of the Pb-formed interstitial solid solution increases the hydration activity of HFCC and the Pb elements in the voids of the tetrahedral silicate phase will not be released through chemical bond rupture. Thus, the solidification of Pb ions in clinker accelerates the hydration reaction of HFCCs and eventually leads to a higher ultimate hydration heat and the postponing effect on induction period is relatively low. • The mechanism of Pb element participating in high-temperature mineral phase reconstruction was revealed. • Most Pb ions solidified in the voids of the tetrahedral silicate phase in the form of an interstitial solid solution. • The high-energy-activated state of the Pb-formed interstitial solid solution increases the hydration activity of HFCC. • The low dissolution content of solidified Pb ions results in a low postponing effect on induction period. [ABSTRACT FROM AUTHOR]

In this paper, the effects of recycled powder content, fly ash content, and different mixing ratios of recycled powder and fly ash on the hydration process of cement were systematically studied by isothermal calorimetry, and the evolution of its mechanical properties was explored. Additionally, a variety of modern analytical testing techniques were used to quantitatively characterize the content of hydration products and the evolution of microstructure. The results showed that the recycled powder can accelerate the early hydration rate, while the fly ash reduces the early hydration heat release rate and delays the hydration process. Both recycled powder and fly ash can reduce the total heat of hydration. The increase of recycled fine powder and fly ash content leads to a decrease in mechanical properties. In the ternary system, when the total substitution rate of recycled powder and fly ash is 30%, and the rate of the two is 1:1, the mechanical properties are optimal; with the increase of the content of recycled powder and fly ash, the content of hydration products of the specimen decreases and the porosity increases. When the ratio of recycled fine powder and fly ash is 1:1, the content of hydration products of the specimen increases, the pore size is refined, and the porosity decreases, which indicates that there is a synergistic effect between recycled fine powder and fly ash. • Research on the hydration process of recycled powder-cement binary system. • Study on the synergistic effect of recycled powder and fly ash in cement-based materials. • The microstructure evolution law of recycled powder in cement-based materials. [ABSTRACT FROM AUTHOR]

An innovative apparatus guided by a proposed theoretical-model was developed for evaluating the radial gas-permeability of cement-based materials under steady-state flow. The testing condition is of higher inlet-gas pressure in an annular concrete cavity to monitor the pressure decrease over time. The gas-tightness for the cavity was effectively enhanced and quantitatively characterized by an ingenious silicone-rubber washer with embedded flexible sensors. The radial gas-permeabilities of the annular concrete with different water-to-cement (w/c) ratios of 0.35–0.55 were measured using various inlet-gas pressures (1.0 bar–30.0 bars) and compared to those obtained by the traditional axial-direction method. The results show that the concrete gas permeability in radial-direction reaches stable permeability zone (SPZ) with inlet-gas pressure exceeding 6.0 bars, which is faster than the SPZ with inlet-gas pressure exceeding 15.0 bars of the axial-direction gas permeability obtained by the traditional method. Under the same inlet-gas pressures of 6.0 bars–10.0 bars, the intrinsic permeability values in the radial and axial directions are near to each other with the standard deviations of 2.83%~9.90% while the apparent permeability values in the radial direction are lower than those in the axial direction by reductions of 3.69%~21.89%. The evolution of apparent gas permeability in radial-direction obeys well the typical model with the low coefficients of variation from 1.01% to 12.55%, indicating that the as-obtained apparatus combined with the proposed theoretical-model can quantitatively and accurately evaluate the radial-direction gas permeability of cement-based materials. • A device is initiatively designed for radial-direction gas permeability measurement. • Theoretical modeling is established for guiding the apparatus application. • By comparison, radial-direction inlet-gas mainly affects apparent gas permeability. • Apparent gas permeability evolution in radial-direction obeys well the typical model. [ABSTRACT FROM AUTHOR]

Apparent gas-permeability (k a) of concrete highly depends on pore-structure and medium. However, the effects of gas-medium on permeability have yet been investigated in depth. In this work, concrete with various water-to-cement ratios and fly-ash/slag dosages is prepared for k a testing. Various gas-mediums (CO 2 and O 2) are applied for analyzing their effects on the k a. Meanwhile, pore-structure characteristic, inner gas-pressure, and gas-absorption in concrete are observed for exploring permeation mechanism. The results illustrate that the narrowing pore-scale effect and surface-diffusion contribution derived from gas-absorption of CO 2 and O 2 both have minor impacts on the k a. The k a of O 2 (k O2) is higher than that of CO 2 (k CO2) and their relative permeability (k O2 / k CO2) ranges from 1.18 to 2.29. These deviations are mainly caused by significantly different Knudson diffusion occurring in the area near the concrete outlet-gas side (approximately 5%). • Gas permeability of concrete is measured by various osmotic-mediums (CO 2 and O 2). • Inner gas-pressure distribution of concrete is obtained under steady-state flow. • The apparent gas-permeability of concrete tested by O 2 is higher than that by CO 2. • Gas absorption of CO 2 and O 2 has minor impacts on apparent gas-permeability. • The deviation of apparent permeability is mainly caused by Knudson diffusion. [ABSTRACT FROM AUTHOR]

• A new avenue to prepare rGO suspension with excellent comprehensive was developed. • The mechanical and functional properties of samples were significantly improved. • The percolation threshold of rGO was determined by comparing different performance. • The functional mechanism of rGO to mortar was analyzed by comparing different model. For modern concrete materials and structures, how to realize the multifunctional application is still a challenge. The introduction of functional components into concrete materials is the most effective method. The present study successfully develops a new avenue to prepare rGO suspension with excellent dispersibility and stability through the combination of dispersant and ultrasonic pre-dispersion. This rGO suspension is added to the cement-based material, resulting in the improvement of mechanical and functional properties. The compressive and flexural strength of mortar are increased by 45% and 50% at 3 days, respectively. Meanwhile the hydration heat and pore structure are improved up to doping 2.00 wt% rGO. Moreover, the resistivity and thermal conductivity of mortar are decreased by 45% and increased by 23%, while the electromagnetic shielding effectiveness of cement paste is increased by 45%. In addition, the pressure-sensitive property of mortar increases first and then decreases with the increases of rGO content, wherein the largest stress and strain sensitivity coefficient can reach up to 1.28%/MPa and 147.80 with 2.00 wt% rGO. These results demonstrate that doping rGO is a promising approach to the improvement of the functionality of cement-based materials resulting from the doping rGO is attributed to, the formation of a conductive network structure with the continuous phase in the cement matrix when rGO content reached percolation threshold. [ABSTRACT FROM AUTHOR]

The effects of type-F fly ash (FA) on the performance of Portland limestone cement (PLC) under sodium sulfate or magnesium sulfate attack at 5°C were evaluated. The degree of damage to the ternary blended cement exposed to 5 wt% sulfate solutions was assessed based on the evolution of the blended cement's appearance, compressive strength and volume. The sulfate product compositions from the blended cement under sulfate attack were analysed by Fourier transform infrared spectroscopy and quantitative X-ray powder diffraction. The results indicated that the PLC containing 40 wt% type-F FA was more resistant to sulfate attack than the control specimen without FA with similar mechanical properties, which was tested at a low temperature. The PLC containing 20 wt% type-F FA showed few effects in terms of improved resistance to sulfate attack. Analysis suggested that active aluminium in the FA glassy phase weakened the blended cement's resistance to sulfate attack because more ettringite was easily formed during the attack, which might accelerate thaumasite formation by means of the woodfordite route at low temperature. Therefore, the effects of type-F FA containing high contents of aluminium phase on the sulfate attack of PLC at low temperature need to be carefully evaluated and studied. [ABSTRACT FROM AUTHOR]

This study focused on the modification of a mixture of a lime-based composite cementitious material (LCM) by using chemical admixtures to increase the mechanical performance of the LCM. The different types and amounts of chemical admixtures including NaOH and Na 2 SO 4 were used as activators to prepare the novel modified LCM. The mechanical strength, hydration kinetics, assemblage of hydrates and microstructure of the modified LCM were systemically explored and compared to conventional LCM. The experimental results indicated that Na 2 SO 4 had better effects on the improvement of LCM strength compared to NaOH when used alone as the activator. The composite activator that was composed of Na 2 SO 4 and NaOH showed the optimal effects on the increase of the LCM strength. The composite activator effectively increased the hydration rate of the LCM, and more hydrates were formed during the hydration process of the LCM. Furthermore, the U-phase was formed only in the hydration products of the LCM containing the composite activator. A large amount of U-phase as crystals effectively occupied and filled the space in the LCM paste and led to the formation of a compact microstructure with fewer macro-pores. Thus, the presence of U-phase in the paste increased the strength of the LCM. [ABSTRACT FROM AUTHOR]

• Using X-CT combined with MIP is a reliable method for investigating the pore feature in printed concrete interlayer interface. • The bond strength in the middle interface of the printed element is higher than that of the upper and bottom interfaces. • The pores in the bottom interface tend to be interconnected or continuous due to the pressure of upper printed layers. 3D printed concrete is an emerging intelligent construction method, and it has been attracting an exponential attention in this sector. However, one of the major issues in printed concrete is the cold joint between the neighbor layers. In this study, an experimental study on the relation between the number of stacked layers vertically and the interlayer adhesion of 3D printed element was conducted. Splitting method was carried out to test the interlayer bond strength, mercury intrusion porosimetry (MIP) and X-ray computed tomography (X-CT) scanner were used to investigate the pore structure of the interlayer zone. The experimental results indicated that a markable influence of the stacked layers vertically on the interlayer adhesion is found. The interlayer bond strength in the middle interface of the printed element is higher than that of the upper and bottom interfaces, especially the bond strength in the bottom interface is the least. Such result is also reflected in the results of the MIP test: the lower total pore volume and total pore surface area existed in the middle interfaces. The X-CT results showed that a large number of elongated and flat pores present in the interlayer zone, the pores in the bottom interface tend to be interconnected or continuous due to the pressure of upper printed layers. An empirical model was proposed to account for the formation of the irregular pore and the change of bond strengths between the vertical neighbored layers of 3D printed element. [ABSTRACT FROM AUTHOR]

Abstract To reduce the carbon footprint and energy consumption from the cement manufacturing industry, lime-based low carbon cementitious materials (LCM) has caught strong attention. LCM as a novel low-carbon cement shows impressive performance and promising prospects; however, its mechanical properties are inferior to those of ordinary Portland cement (OPC). In this study, different dosages of sulfate sodium was incorporated into LCM to investigate the effects of sodium sulfate on LCM performance. The properties and hydration of LCM with and without sulfate sodium were systemically investigated and analyzed. The results revealed that LCM blending with 2–3 wt% sodium sulfate showed the best mechanical performance. The compressive strength of LCM containing 3 wt% sodium sulfate was increased by 57.0% and 20.8% relative to the plain LCM at 3 d and 90 d, respectively. Microstructural characterization showed that a great amount of ettringite had formed at 3 d, which effectively improved the mechanical performance of LCM at early stage. Moreover, the addition of sodium sulfate effectively accelerated the hydration of the solid waste in LCM, and more hydrated lime was consumed in the hydration process. The ettringite became embedded in C(A)SH gel with increasing curing age, which resulted in a dense microstructure of hydrated paste with fewer coarse pores and an enhancement in the mechanical performance of LCM. Thus, the sodium sulfate effectively increased the strength of LCM at both early and later stage. [ABSTRACT FROM AUTHOR]

Highlights • A high-thixotropy 3D printing concrete has been successfully developed. • Such concrete had lower drying shrinkage, normal elastic modulus and Poisson's ratio. • The rheological properties and anisotropy of such concrete were systematically investigated. • A series of large-scale components industry–scale were applied into public transportation. Abstract 3D printing is a promising technology in construction industry. Unlike conventional construction process, 3D printing buildings are extruded by a nozzle layer-over-layer without the requirement of formwork. This paper investigates the rheological and harden properties of the high-thixotropy 3D printing concrete. Flowability, rheological property (viscosity, yield stress, thixotropy) and open time are considered as critical wet properties to control the printable property (pumpability, extrudability and buildability) of such concrete material. Five different mixtures are systematically investigated to obtain the optimum mix and then it's used to study the harden property, such as anisotropy (compression and flexural), elastic modulus and drying shrinkage. At last, a large-scale components-bus station preliminarily was prepared by using this technology. [ABSTRACT FROM AUTHOR]

Highlights • The sodium hydroxide enhanced the mechanical properties of LCM at the early age. • The increase of strength of LCM with sodium hydroxide was little at the later stage. • The C-(N)-A-S-H gel formed in the paste due to the Na uptake in the C-A-S-H gel. Abstract To increase the recycling of industrial solid waste in cement-based materials, lime-based low carbon cementitious materials (LCM) as green binder materials have shown bright prospects. To further improve the properties of LCM, different dosages of sodium hydroxide as alkali activators were mixed with LCM in the test, and this study focused on the influence of sodium hydroxide on the performance and hydration of LCM. The strength, workability, hydration and microstructure of LCM in the presence of sodium hydroxide were investigated in detail and compared to those of the original LCM. The test results indicated that the minor amounts of sodium hydroxide remarkably improved the mechanical properties of LCM at early ages (3 and 7 days). Additionally, the further hydration of mineral admixtures was affected by the presence of sodium hydroxide, which resulted in a slight improvement of the mechanical properties of LCM at the later stage. The formation of ettringite in the hydrates of LCM was suppressed by the addition of sodium hydroxide. Moreover, the Ca/Si ratio of the C-(A)-S-H gel formed in the sodium hydroxide activated LCM was lower than that in the plain LCM, and a minor amount of C-(N)-A-S-H gel formed in the hydrated paste due to the Na uptake in the C-A-S-H gel. Therefore, sodium hydroxide modified the composition of hydrates in the LCM to a certain extent during the hydration process. [ABSTRACT FROM AUTHOR]

Highlights • The various regular- and irregular-shaped aggregates are constructed using a pixel-based method. • The effects of aggregate characteristics on elastic and diffusive properties of concrete are investigated. • The aggregate characteristics apart from the aggregate type, play a slight role in the elastic properties of concrete. • The aggregates characteristics have a significant influence on the diffusive properties of concrete. Abstract Concrete is a complex three-phase composite material at a mesoscale, thus its overall elastic and diffusive properties strongly depend on that of each component. However, the effects of aggregate characteristics are little considered, especially the aggregate shape effect. In this study, a set of numerical methods is employed to evaluate the effects of aggregate characteristics on the elastic and diffusive properties of concrete. Firstly, a concrete representative volume element (RVE) is constructed using a pixel-based method by packing aggregates surrounding a soft interlayer as ITZ in a homogeneous mortar matrix. The different aggregate characteristics including morphology, fineness and type, are respectively considered. Subsequently, a set of the finite element-based and finite difference-based numerical method that is designed for the pixel-based concrete structure, is applied to predict the elastic modulus and the diffusion coefficient of concrete. The simulated results indicate that aggregate characteristics apart from aggregate type play a negligible role in the elastic modulus of concrete, while the effects of aggregate characteristics on the diffusion coefficient of concrete are pronounced. The aggregates with less regularity or coarser size can decrease the diffusion coefficient of concrete. Furthermore, the property of ITZ is another pronounced factor for the elastic and diffusive properties of concrete in addition to aggregate area fraction. The weaker ITZ can significantly decrease the stiffness and increase diffusivity of concrete. The modelling results are expected to guide the design of concrete materials from the perspective of aggregate characteristics. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a centrifuge device is proposed to facilitate the intrusion of a low-melting point metal alloy into the pore space of hardened cement paste. X-ray microtomography is combined with metal centrifugation porosimetry (MCP) to quantitatively investigate 3D pore structure. The low-melting-point metal alloy is melted and introduced into pore space in pastes with water cement ratio of 0.5 and 1.0 at a temperature of 65 °C. 3D pore structure is quantitatively analyzed by X-ray microtomography after the molten metal alloy has been consolidated. A new threshold value segmentation method for pore space was proposed using conversion coefficient on region of interest (ROI). Porosity and pore size distribution are tested by MCP and compared with the results based on mercury intrusion porosimetry (MIP). The results show that the contrast between pore space and solid phase in the X-ray microtomography device image is improved. The total porosity obtained by MCP was found to be consistent with the results obtained by MIP. Highlights • Metal alloy was intruded into pore space to enhance the contrast in imaging. • 3D pore structure of hardened cement paste investigated with X-ray microtomography. • 3D pore structure of cement paste successfully imaged and quantitatively analyzed. [ABSTRACT FROM AUTHOR]

A novel green cement which was prepared with superfine Portland cement and high volume solid wastes (fly ash and blast furnace slag) was investigated in this study. The mechanical performance, heat of hydration, particle packing density, evolution of hydration products and microstructure of this novel blended cement were studied and compared to the conventional blended cement. Moreover, the energy consumption and carbon emission of novel green cement were calculated. The effects of superfine cement in blended cement were systematically studied and compared to Portland cement (PC). Test results showed that a notable improvement in the mechanical properties of novel green cement was achieved compared to conventional blended cement. Even the mechanical properties and workability of novel green cement were very close to PC. The calculation based on mixtures indicated that the energy consumption and carbon emissions of novel green cement containing 70 wt% mineral admixtures only reached 47.3% and 40.9%, respectively, of those of PC. The analysis suggested that the superfine cement increased the packing density of blended cement and effectively accelerated the hydration of mineral admixtures to form a refined and dense microstructure, which is key for preparing high-performance green cement. This research provided guidance for developing low carbon and environmentally friendly cement. [ABSTRACT FROM AUTHOR]

The use of solid waste to produce low carbon, high ferrite cement clinker (HFCC) with favorable durability delivers potential application prospects. However, the semivolatile heavy metals Zn and Cd in solid waste not only restrict its utilization ratio but also cause potential environmental pollution. In this study, the migration and solidification behavior of Zn and Cd during calcination and their action mechanisms on phase reconstruction are systematically studied. The reaction sequence and conditions of Zn were revealed by experimental tests and phase diagram simulation. Zn2+ will firstly solidify in the C 2 S phase by the solid-phase reaction. After liquid phase forms, Zn2+ is more inclined to substitute Fe3+ in the C 4 AF phase with 4-coordination in the [FeO 4 ]. Only a small amount of Zn2+ enters the C 3 A and C 3 S phases in the form of interstitial solid solution. Zn promotes the formation of the liquid phase and C 3 S phase. And HFCCs indicate a favorable solidification effect on Zn. While due to low volatilization temperature and high volatility of Cd, even at a low sintering temperature, the HFCC cannot greatly reduce the volatilization of Cd. Cd2+ mainly exists in HFCC by substituting Ca2+ in the C 3 S, C 2 S and C 4 AF phases with a 6-coordination number in [CaO 6 ] to form the spatial configuration of octahedral complexes. • Reaction sequence and reaction condition of Zn during sintering were revealed. • Compared with OPC, high ferrite cement clinker (HFCC) has a stronger solidification ability for Zn. • Solidification priority depends on liquid phase content, elements volatilization and lattice distortion. [ABSTRACT FROM AUTHOR]

To investigate the relationship between morphology and specific ion transport properties in low-density (LD) and high-density (HD) calcium-silicate-hydrate (C-S-H), a numerical method of directly achieving diffusivities is developed. Firstly, a multiscale structural model is proposed to reconstruct C-S-Hs in which self-similarity and quantitative physical properties are compared to experimental results. Subsequently, electrical double layer (EDL) theory is introduced into analysis of ion transport in pore solution. The quantitative analysis of various influence factors of EDL on ion diffusivities in pore solution is carried out and average diffusivity in pore solution is also obtained. Moreover, a numerical method for solving Fick’s first law equation is performed on the simulated C-S-H structures to obtain numerous diffusivities of common ions in C-S-H. Finally, the significant parameter for durability in reinforcement concrete, chloride diffusivity in hardened cement paste, is predicted using simulated diffusivities in C-S-Hs, based on a multiscale method. It is found that compared to the atomic force microscope image and surface area of C-S-H, this self-similar model can well reconstruct real C-S-H structures. In addition, the influence factors of EDL including overlapping diffuse layer, relative potential, cation/anion, valence, zeta potential and bulk solution have great effects on ion diffusivities, which demonstrates EDL effects cannot be ignored when investigating ion transport behavior in C-S-H. Furthermore, using an appropriate case of pore solution with diffusivities of 8.2 × 10 −12 m 2 /s in LD C-S-H and 2.0 × 10 −13 m 2 /s in HD C-S-H, estimated chloride diffusivities in cement pastes agree well with measured values, which can indirectly indicate this modelling work is reasonable. [ABSTRACT FROM AUTHOR]

To investigate the relationship between morphology and specific ion transport properties in low-density (LD) and high-density (HD) calcium-silicate-hydrate (C-S-H), a numerical method of directly achieving diffusivities is developed. Firstly, a multiscale structural model is proposed to reconstruct C-S-Hs in which self-similarity and quantitative physical properties are compared to experimental results. Subsequently, electrical double layer (EDL) theory is introduced into analysis of ion transport in pore solution. The quantitative analysis of various influence factors of EDL on ion diffusivities in pore solution is carried out and average diffusivity in pore solution is also obtained. Moreover, a numerical method for solving Fick’s first law equation is performed on the simulated C-S-H structures to obtain numerous diffusivities of common ions in C-S-H. Finally, the significant parameter for durability in reinforcement concrete, chloride diffusivity in hardened cement paste, is predicted using simulated diffusivities in C-S-Hs, based on a multiscale method. It is found that compared to the atomic force microscope image and surface area of C-S-H, this self-similar model can well reconstruct real C-S-H structures. In addition, the influence factors of EDL including overlapping diffuse layer, relative potential, cation/anion, valence, zeta potential and bulk solution have great effects on ion diffusivities, which demonstrates EDL effects cannot be ignored when investigating ion transport behavior in C-S-H. Furthermore, using an appropriate case of pore solution with diffusivities of 8.2 × 10 −12 m 2 /s in LD C-S-H and 2.0 × 10 −13 m 2 /s in HD C-S-H, estimated chloride diffusivities in cement pastes agree well with measured values, which can indirectly indicate this modelling work is reasonable. [ABSTRACT FROM AUTHOR]

• The saline soil does not change the internal degradation mechanism of mortar, and the degradation products are still mainly composed of gypsum and ettringite. • The degradation rate of saline soil containing sodium sulfate to mortar is faster than that of sodium sulfate solution. It is contrary for saline soil containing magnesium sulfate. • When the mortar is degraded by sulfate, an obvious movable corrosion interface is observed in mortar along corrosion direction. The sulfate attack of salt solution and saline soil on concrete structures is an essential factor threatening their durability. The degradation of saline soil to concrete structures has attracted more attention than the salt solution in recent years. Thus, the degradation of mortar buried in saline soil containing sulfate ions was investigated in this study. Combined with the macro and micro degradation results, the saline soil does not change the internal degradation mechanism of mortar because the degradation products are also mainly composed of gypsum and ettringite. The degradation rate of soil containing sodium sulfate to mortar is more vital than that of the corresponding salt solution. However, the results are contrary for soil containing magnesium sulfate and the corresponding salt solution. An evident and movable degradation interface in the eroded mortar is observed based on a color difference along the direction of degradation; The fly ash with a high replacement (60 wt%) is unfavorable to the resistance of the mortar under sulfate attack, because it contains a high aluminum phase to form ettringite. The slag can increase the resistance of the mortar under sulfate attack due to its smaller content of aluminum phase and higher activity. [ABSTRACT FROM AUTHOR]

• Using X-CT combined with CsCl enhancing to study the water uptake in 3DPC filament. • Elongated pore can enhance water uptake rate, compared with molded concrete. • X-CT is a reliable method for investigating the pore feature in printed concrete. The water uptake in 3D printed concrete along the printing direction is experimentally studied using X-CT combined with CsCl enhancing, molded concrete is as reference. The pore feature of the printed and molded concrete is analyzed by re-structuring X-CT images. Results show that in printed concrete quicker ingress of water is acquired, compared with molded concrete. This could be related to the elongated pores along the filament in printed concrete, while almost of all the pores in molded concrete are in spherical shape. [ABSTRACT FROM AUTHOR]

In this study, a new modification method of waste rubber powder (WRP) was proposed to improve the workability and mechanical properties of rubber cement-based materials (RCM). This method combines mechanochemical action, inorganic powder intercalation, and modified slurry coating to obtain modified rubber aggregates (MRA). The modification mechanism and structure properties of the WRP were measured and characterized by NMR and TG-DSC. The effects of the WRP and MRA on the hydration, workability and mechanical behavior of RCM were further studied by an isothermal calorimeter, and rheometer. The ITZ between rubber and the cement matrix (R-CM) was analysed by SEM, Micro-hardness. The result showed that the porosity of the MRA was reduced (24.68 to 17.87) and the stability is increased (mass loss rate was reduced from 64.8 % to 57.5 %) compared with the WRP. WRP delayed the hydration induction and acceleration periods of cement hydration by 9 h, but MRA was only 0.5 h compared with control groups. The yield stress and plastic viscosity of MCRM were decreased by 356.95 % and 154.65 % respectively, compared with CRM. The compressive and flexural strengths of MCRM increased by 159.0 % and 87.5 % compared with CRM. The voids at the interface of R-CM disappeared after modification, and ITZ thickness decreased from about 160 µm to 80 µm. The interfacial adhesion of R-CM is a key factor in improving the failure model and mechanical behavior of RCM. [ABSTRACT FROM AUTHOR]

• A modified random hierarchical bundle model for predicting the permeability of cement-based materials was presented. • The intrinsic permeability of cement-based materials can be accurately simulated. • The apparent permeability and Klinkenberg constant of different gases can be predicted. Permeability is a fundamental property indicating the durability of cement-based materials, predicted according to the material's pore size distribution (PSD). The random hierarchical bundle model is a promising approach based on a random hierarchical assembly of capillary segments to estimate the permeability of porous media. However, the original model neglected the slippage effect during gas penetration—a common occurrence in cement-based materials and other low-permeability porous media. Thus, we considered this effect in a modified model proposed herein, and the permeability of cement-based materials can be directly predicted using the PSD obtained via mercury intrusion porosimetry. Compared with data from experiments and literatures for various mortars and concretes with permeabilities ranging over 3 orders of magnitude, the results revealed that this modified model can accurately predict the intrinsic permeability and Klinkenberg constant. Moreover, this model can predict the intrinsic permeability and apparent permeability of various gases and porous media. [ABSTRACT FROM AUTHOR]

• Using X-CT combined with CsCl enhancing to study the water transport in hardened 3DPC. • Steel fiber alignment can enhance water uptake rate, compared with molded concrete. • Steel fiber can not elevate the sorptivity of printed concrete along the filament. In this study, X-CT combined with CsCl enhancing method is used to investigate the effect of steel fiber on the unsaturated flow in printed concrete along the printing direction, and to contrast the molded concrete. Results indicate that this method could be used effectively to monitor the evolution of water ingress into cementitious materials continuously. The addition of steel fiber slightly reduces water absorption rate in printed specimens. Compared with the molded specimen, the fiber alignment enhances the sorptivity of the printed specimen significantly. [ABSTRACT FROM AUTHOR]

• The self-designed conductometric titrator can test the conductivity of solution and can test the concentration of sulfate. • The conductivity of Na 2 SO 4 and BaCl 2 solution increases linearly in the temperature range of 25–70 °C. • When titrating sulfate in cement-based materials, 0.02 mol/L BaCl 2 , 0.828 mL/s titrating rate of, and 10 mL volume titrated are recommended. The concentration of sulfate ion in cement-based materials is the basic data for the design and evaluation of concrete structures exposed to sulfate lakes and saline soil areas. In this study, a conductivity titrator was developed and used to test the sulfate concentration in concrete corroded by sulfate attack based on the Internet of Things. The theories of conductivity measurement and conductivity titration were described; The main hardware composition and software design of conductometric titrator were introduced; Then, the effects of temperature, concentration, hydroxyl ion and hydrogen ion on the conductivity of solution of sodium sulfate and barium chloride were explored by the titrator; The titration parameters, the influence of hydroxyl and hydrogen ion on sodium sulfate titration were determined by test of sulfate ion titrated by barium chloride with known concentration; Finally, the titrator was used to test the sulfate concentration in cement-based materials after sulfate attack. The results show that the titrator can measure the conductivity of solution with 0.4% accuracy and the concentration of sulfate ion with 0.8% accuracy; During the titration of sulfate ion, the concentration of barium chloride should be twice that of sulfate ion, the titration rate should be less than 0.828 mL/s, and the titration volume should be at least 10 mL; It is found that the influence of hydroxyl ion can be effectively eliminated by adding nitric acid or hydrochloric acid, and the influence of hydrogen ion can be effectively eliminated by adding sodium carbonate. This conductivity meter can accurately test the sulfate concentration in the concrete after corrosion. [ABSTRACT FROM AUTHOR]

• The influence of liquid paraffin/diatomite capsule phase change material on the compressive strength of cement matrix is far less than the flexural strength. • The mass loss of the capsule phase change material cement-based test block after freeze–thaw cycles is reduced by 47% compared with the pure cement paste. • The liquid paraffin/diatomite capsule phase change material has a certain effect on improving the frost resistance of concrete. Freezing-thawing cycles is one of the most common and severe factors to concrete in service. The research focuses on breaking through the bottleneck of passive frost resistance of traditional concrete materials. Based on the principle of phase change heat storage and release, liquid paraffin/diatomite microcapsule phase change material was prepared by controllable assembly method. Its physical and chemical properties and thermal properties were explored by modern characterization methods. At the same time, it is introduced into the cement matrix to explore its specific effects on the thermal conductivity, mechanical properties and frost resistance of concrete materials. The results show that liquid paraffin/diatomite capsule phase change materials (CPCMs) cement-based test block has stable chemical properties and excellent thermal properties. The heat resistance limit is 280 ℃. Adding liquid paraffin/diatomite capsule phase change material will weaken the thermal conductivity and mechanical properties of cement matrix, but at the same time, it will significantly improve the frost resistance of cement matrix. The mass loss after freeze–thaw cycles can be reduced by 47%, the compressive strength loss and flexural strength loss are reduced by 186% and 99%, respectively. The negative effect of liquid paraffin/diatomite capsule phase change material on the flexural strength of the cement matrix is greater than the compressive strength. [ABSTRACT FROM AUTHOR]

• A logarithmic model with three parameters is developed based on the analytical solution of kinetics function of capillary absorption. • The inlet height of capillary bundle increases with the decrease in the maximum pore size, and the capacity of capillary absorption increases with time of absorption. • An interesting phenomenon, capillary oscillations, is found during the test of the capillary water absorption in mortar with different saturation. Capillary water can transmit in capillary tube induced by hydrostatic pressure, which has an important impact on the durability and shrinkage of concrete. In this study, the ultimate height of capillary rise under various conditions was analyzed based on thermodynamic equilibrium of capillary water where capillary water is subjected to six types of force. Subsequently, a logarithmic model of capillary rising with three parameters (Jurins's height h c , permeability coefficient k , characteristic time τ) was proposed according to the analytical solution of kinetics function of capillary absorption. To better understand capillary behavior in capillary bundle with different radius, the spatio-temporal distribution of saturation, and the variation of water content with time and saturation are predicted according to the kinetics of capillary rise in single capillary. Additionally, the kinetics of capillary absorption in porous materials was discussed. Finally, the developed model was verified by testing the true rising height of water in a mortar specimen using X ray computed tomography. The equivalent height of adsorbed water in mortar with varied saturation under different time was obtained by gravimetric method. The results show that the logarithmic model gives a good description of the kinetics data of water absorption in mortar. [ABSTRACT FROM AUTHOR]

With the extension of service time, infrastructure is in growing urgency for repair and reinforcement due to its deterioration in safety and durability over the years. Normal cement concrete has shortcomings, e.g., high brittleness and low flexural-tensile strength, that fail to meet the requirements of construction repair. In this paper, a novel waterborne epoxy-concrete composite repair material (WECM) was prepared by using self-synthesized water-based epoxy resin based on the molecular structure-activity relationship. The mechanisms of waterborne epoxy (WEP) and WEP-fiber synergy on the improvement of concrete performance were clarified. The results show that the defects of high brittleness and poor ductility of concrete are significantly improved by WEP and that the ductility of WECM is increased by 300%–600% compared with the control concrete. The fiber and WEP in the WECM exhibited a synergistic effect on the tensile strength, ductility, and crack resistance of concrete in which the fiber coating layer mixed with WEP and embedded cement particles (inlay) provided fiber protection as well as an interfacial bonding enhancement. The P/C of 0.2 is the turning point of the flexural and tensile strength of the WECM, which is related to the continuous phase formation of the WEP-interpenetrating polymer network (WEP-IPN). [ABSTRACT FROM AUTHOR]

Long noncoding RNAs (lncRNAs) have been identified as oncogenes or tumor suppressors that are involved in tumorigenesis and chemotherapy drug resistance. Maternally expressed gene 3 (MEG3) is an imprinted gene located at 14q32 that encodes an lncRNA, and decreased MEG3 expression plays an important role in multiple cancers. However, its biological role in the development of the chemoresistance phenotype of human lung adenocarcinoma (LAD) is unknown. This study aimed to observe the expression of MEG3 in LAD and to evaluate its biological role and clinical significance in the resistance of LAD cells to cisplatin. MEG3 expression was markedly decreased in cisplatin-resistant A549/DDP cells compared with parental A549 cells as shown by an lncRNA microarray. MEG3 overexpression in A549/DDP cells increased their chemosensitivity to cisplatin both in vitro and in vivo by inhibiting cell proliferation and inducing apoptosis. By contrast, MEG3 knockdown in A549 cells decreased the chemosensitivity. Moreover, MEG3 was decreased in cisplatin-insensitive LAD tissues while p53 protein levels were decreased and Bcl-xl protein levels increased. Furthermore, patients with lower levels of MEG3 expression showed worse responses to cisplatin-based chemotherapy. These findings demonstrate that MEG3 is significantly downregulated in LAD and partially regulates the cisplatin resistance of LAD cells through the control of p53 and Bcl-xl expression. Thus, MEG3 may represent a new marker of poor response to cisplatin and could be a potential therapeutic target for LAD chemotherapy. [ABSTRACT FROM AUTHOR]

• In situ tracking water transport at the interlayer zone of 3D printed concrete using X-CT combined with CsCl enhancing. • The percentages of 0.1 mm-0.6 mm and 1 mm-4 mm voids size are observed to have an opposite effect on the water transport. • Connected or continuous voids induce a preferential water transport along the interlayer zone. • The spherical shape, independent and evenly distributed relatively voids were observed in cast concrete, while the irregular shape and interconnected or even continuous voids in 3DPC were detected. 3D printed concrete is a rising technology recently developed for construction industry. Unlike conventional concrete, since 3D printed elements are built by using a layer-deposition process, the distinct void generated between the printed concrete filaments considerably reduce mechanical strength and durability of 3D printed concrete. Using X-CT technology combined with CsCl enhancement, this study aims at investigating the water transport characteristics at different interlayer zones of 3D printed concrete, cast concrete as the reference. Meanwhile, the void characteristics of different interlayer zones are analyzed to establish quantitatively the relationship between the void distribution and the water transport process. It can be found that those voids at the interlayer zone led to a faster water transport along the printed concrete' interlayer zone than that of cast concrete. In addition, the percentages of 0.1 mm-0.6 mm and 1 mm-4 mm voids size are observed to have an opposite effect on the water. [ABSTRACT FROM AUTHOR]

• A structural kinetics model was developed by combining a kinetic equation of the structural parameter λ and the relationships between yield stress τ y. • Yield stress is more suitable to characterize the structural build-up of fresh cement paste than viscosity and rheological index. The test of the yield stress needs to consider the structure of the rheometer. • When the specific area of limestone exceeds 600 m2·kg−1, it can accelerate the establishment rate of the dynamic structure. When the specific area is 400 m2·kg−1, the content of limestone corresponding to the maximum structuration rate is reduced. The structural build-up of fresh cement-based materials is of great significance to the early forming and later performance. A structural kinetics model (SKM) used to indicate the structural build-up was developed by combining a kinetic equation described by structural parameter (λ) and a relationship between yield stress (τ y) and λ in the paper. SKM transforms the structuration rate (A thix ) in linear Roussel model and the characteristic time (t c) in non-linear Perrot model into more specific indicators such as initial solid volume fraction (ϕ 0) , rate of hydration during induction period (α ̇ ind) , and shear rate (γ.). The yield stress (τ y) obtained by RHEOLAB QC rotary viscometer was explored the dynamic and static structural build-up of fresh cement paste. The yield stress of fresh cement paste (W/C = 0.4) exhibits a quasilinear pattern with rate of 0.42 Pa/s for 210 min of mixing, with rate of 0.88 Pa/s for 100 min of resting after 4 min of mixing. The static yield stress of fresh cement paste evolves from linear to non-linear patterns within 100 min of resting after beyond 30 min of mixing. The fitting results show that SKM can well fit the evolution of yield stress including linear and nonlinear phases. Comparing with the dynamic structural build-up, the effect of limestone powder on the static structural build-up of cement paste is more obvious. When the mixing process is longer than 60 min, the content of limestone powder less than 20 wt% is beneficial to the structural build-up of fresh paste. Additionally, a declined rate of cement hydration in the induction period with increasing mixing time indicates that the rising yield stress, in this case, cannot be attributed entirely to the contribution of hydration to structural build-up. [ABSTRACT FROM AUTHOR]

• An extrusion-based 3D printer for concrete with the largest aggregate size of 20 mm was introduced. • The range of ratios of cement and aggregate of printable concrete with coarse aggregate was recommended. • The direction-dependent mechanical properties of 3D printed concrete were investigated. • The voids distribution and the microstructure of interlayer area in 3D printed concrete were studied through X-CT and SEM. Concrete with coarse aggregate in the 3D concrete printing (3DCP) has broad prospects for high strength, low cost and shrinkage. In this study, an extrusion-based 3D printer was designed and utilized to print concrete with the largest aggregate size of 20 mm. Printable concrete with coarse aggregate was designed by different volume ratios of cement to aggregate (C/A). Then the effect of C/A on the printability and direction-dependent mechanical performance was investigated. X-ray micro-computed tomography (X-CT) was used to detect and analyze the voids distribution characteristics of printed specimens. Scanning electron microscope (SEM) investigations of microstructure at the interlayer area were conducted. Results indicated that the initial flowability of printable concrete should be within 178–200 mm, and the recommended printable C/A was within 0.35–0.60. The decrease of C/A improved the maximum printing height and mechanical performance but weakened the shape-stability of the multi-layer structure. X-CT results indicated that reducing excess slurry content caused by the decline of C/A decreased the compactness of the printed structure. The compressive strength and flexural strength of 3D printed specimens showed a direction-dependent characteristic, mainly related to the non-uniform distribution of voids revealed by X-CT. SEM images revealed the "micro-bridging" morphology in the interlayer area and proved that there were carbonation and structural weakening problems at the surface and surrounding of this area. [ABSTRACT FROM AUTHOR]