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Benefiting from the large interstate spacing, long biexciton Auger lifetime and relatively large acoustic phonon energy, the temperature-insensitive threshold and peak position of near-infrared ASE are achieved in Ag2Se QDs.

Metal nanoparticles have attracted a great deal of interest due to their unique properties of surface plasmon resonance. Metal nanoparticles can enhance the fluorescence emission intensity of quantum dots (QDs) through the local surface plasmon resonance effect, which is mainly determined by the distance between them. Therefore, it is very important to achieve controllable distance between metal and QDs, and study fluorescence enhancement. In this work, the controllable adjustment of the distance between metal nanoparticles and QDs was successfully realized by controlling the thickness of the SiO2 shell of Ag@SiO2 nanoparticles. Firstly, Ag nanoparticles with uniform size distribution and relatively high concentration were prepared, and then the thickness of the SiO2 shell was controlled by controlling the amount of tetra-ethyl orthosilicate (TEOS) in the hydrolysis of TEOS reaction. (3-aminopropyl) triethoxysilane (APS) was used to connect CdS/ZnS QDs with Ag@SiO2 nanoparticles to form Ag@SiO2@CdS/ZnS QD composite nanoparticles. The fluorescence spectra shows that the fluorescence intensity of the Ag@SiO2@CdS/ZnS QD composite nanoparticles is significantly enhanced. Photoexcitation spectra and fluorescence spectra of CdS/ZnS QD and Ag@SiO2@CdS/ZnS QD composite nanoparticles, measured under different energy excitation conditions, indicate that the existence of Ag nanoparticles can enhance the fluorescence intensity of CdS/ZnS QDs. Finally, a further physical mechanism of fluorescence enhancement is revealed.

Portlandite, Ca(OH)2, is a primary product in cement hydration, on which some biases or misconceptions persist, such as portlandite has inferior mechanical properties because of its layered microst...

The development of colloidal near-infrared quantum dot (QD) lasers has been hindered by the high state degeneracy of lead salt QDs. Here, we show that this challenge can be addressed by utilizing orthorhombic Ag2Se QDs. We demonstrate that the lowest quantized states of Ag2Se QDs display a low, 2-fold degeneracy by employing femtosecond transient absorption (TA) spectroscopy. The optical gain threshold is evaluated to be 156 μJ cm−2, corresponding to ∼1.4 excitons per QD on average. Consequently, the amplified spontaneous emission (ASE) threshold of Ag2Se QD films is as low as 183 μJ cm−2. A large modal gain (∼470 cm−1) of the film is observed by variable stripe length (VSL) measurements. We leverage the low-threshold gain of the QDs to produce microlasers that exhibit single-mode near-infrared emission and a low threshold of 163 μJ cm−2 at room temperature. In addition, the cytotoxicity of Ag2Se QDs is remarkably negligible. Our work represents a significant step toward environmental-friendly near-infrared QD lasers.

Temperature sensors are widely used in important fields such as daily home, medical care, and aerospace as a commonly used device for measuring temperature. Traditional temperature sensors such as thermocouples, thermal resistances, and infrared sensors are technically mature; however, they have limitations in the application environment, temperature measurement range, and temperature measurement accuracy. An eye-resolvable surface plasmon-enhanced fluorescence temperature sensor based on dual-emission Ag@SiO2@CdS/ZnS composite nanoparticle film with multiple-parameter detectable signals and high response sensitivity was proposed in this work. The temperature sensor’s x-chromaticity coordinate varied from 0.299 to 0.358 in the range of 77–297 K, while the y-chromaticity coordinate varied from 0.288 to 0.440, displaying eye-resolvable surface plasmon-enhanced fluorescence. The ratiometric response of two isolated photoluminescence (PL) peak-integrated areas located around 446 and 592 nm was found to be significantly temperature dependent, with a thermal sensitivity of 1.4% K−1, which can be used as an additional parameter to measure the precise temperature. Furthermore, the surface state emission peak intensity was linearly related to temperature, with a correlation index Adj. R-Square of 99.8%. Multiple independent temperature estimates can help with self-calibration and improve the measurement accuracy. Our findings show that the designed sensors can detect low temperatures while maintaining stability and reproducibility.

The effect of polyaluminum chloride (PAC) on the durability, microstructure, and corrosion sensitivity of slag–cement pastes was investigated in this research. Various experimental tests we...

The microstructural evolutions of both uncarbonated and carbonated cement pastes subjected to various high temperatures (30 °C, 200 °C, 400 °C, 500 °C, 600 °C, 720 °C, and 950 °C) are presented in this study by the means of mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). It was found that the thermal stabilities of uncarbonated cement pastes were significantly changed from 400 to 500 °C due to the decomposition of portlandite at this temperature range. More large pores and microcracks were generated from 600 to 720 °C, with the depolymerization of C-S-H. After carbonation, the microstructures of carbonated cement pastes remained unchanged below 500 °C and started to degrade at 600 °C, due to the decompositions of calcium carbonates and calcium modified silica gel. At 950 °C, both uncarbonated and carbonated cement pastes showed a loosely honeycombed microstructure, composed mainly of β-C2S and lime. It can be concluded that carbonation improves the high-temperature resistance of cement pastes up to 500 °C, but this advantage is lost at temperatures over 600 °C.

Fly ash is an industrial by-product that is widely used in the cement industry. Traditional methods used to investigate the influence of fly ash on the hydration behavior of cement are destructive and cannot accomplish a continuous tracing of the hydration process. In this study, the influence of fly ash incorporation on the hydration process of cement is evaluated using measured electrochemical data obtained from the electrochemical impedance spectroscopy approach. A novel equivalent circuit model that considers the electrochemical characteristics of cement during the hydration process is proposed to investigate the electrochemical property of the blended cement. The resistance parameter of the model, Rct1, was found to have a positive correlation with hydration degree and compressive strength during hydration. With this parameter, the method can be used to non-destructively trace and characterize the effects of fly ash incorporation on the cement hydration process.

In this paper, a novel capillary absorption model is proposed to investigate the capillary absorption process of cementitious materials. This model mainly consider the influence of tortuosity of the capillary pores of cement paste, which is the key factor affecting the capillary absorption process. The proposed model is verified by the capillary absorption process of paste samples with different water/cement ratios. The absorption height and water content profile of testing samples are measured by X-ray computed tomography. The results show that the proposed capillary absorption model that takes the tortuosity of capillary pores into consideration is suitable for investigating the capillary absorption process of water in cementitious materials.

In this study, the chemical composition of cement pastes, exposed to accelerated carbonation using different concentration of CO2 (3%, 10%, 20%, 50%,100%), have been determined and compared with those of natural carbonation (0.03%). Quantitative X-ray diffraction (QXRD) and( 29)Si Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) were used for characterisation and quantitative analysis of the carbonated phases. The obtained QXRD results revealed that the complete carbonation was hardly attained. Calcite, aragonite and vaterite were in co-existence after accelerated carbonation, while vaterite was dominant. The preferential polymorphic precipitation of the three crystal forms of calcium carbonate was affected by the carbonation degree of C-S-H and the duration of the carbonation process, but not by the concentration of CO2. The NMR results indicated that C-S-H gel was strongly decalcified, and calcium modified silica gel was formed after carbonation. The C-S-H decalcification, under all the accelerated carbonation conditions, was clearly more pronounced than that under the natural carbonation conditions. When the concentration of CO2 was in the range of 3%-20%, the ratio of decalcified to remaining C-S-H was similar, in a range of 5-6, while under the higher concentration of CO2 this ratio was increased to > 8. Therefore, in consideration of both acceleration rate and measurement uncertainty, the higher concentration, up to 20%, of CO2 in an accelerated carbonation should be applicable.

Bimetallic Janus nanostructures (JNs) have been revealed to be valuable materials because they have unique intermetallic interfaces that enable their potential use in a range of applications. However, with the increasing miniaturization of electronic devices, particle sizes influence the structure and orientation of these heterointerfaces, which plays a significant role in their application. Our in situ annealing experiments with high-resolution transmission electron microscopy have shown that for particle sizes in the sub-10 nm range, CuAg JNs preferentially show a Cu(100)/Ag(100) interface, differing from the larger CuAg JNs, where the Cu(111)/Ag(111) interface is favored. We discuss a feasible atomic motion mechanism to explain the effect of particle size on the formation of different heterointerfaces. Our results reveal the presence of a novel sub-10 nm heterostructure with a unique Cu(100)/Ag(100) interface and also provide crucial insights into understanding the role of particle size in interfacial evolution during thermal annealing of heterostructures.

Ordinary cement concrete is a popular material with numerous advantages when compared to other construction materials, however, ordinary concrete is also criticized from the public point of view due to the CO2 emission (during the cement manufacture) and the consumption of natural resources (for the aggregates). In the context of sustainable development and circular economy, the recycling of materials and the use of alternative binders which have less environmental impacts than cement are challenges for the construction sector. This paper presents a study on non-conventional concrete using recycled aggregates and alkali-activated binder. The specimens were prepared from low calcium fly ash (FA, an industrial by-product), sodium silicate solution, sodium hydroxide solution, fine aggregate from river sand, and recycled coarse aggregate. First, influences of different factors were investigated: the ratio between alkaline activated solution (AAS) and FA, and the curing temperature and the lignosulfonate superplasticizer. The interfacial transition zone of geopolymer recycled aggregate concrete (GRAC) was evaluated by microscopic analyses. Then, two empirical models, which are the modified versions of Feret’s and De Larrard’s models, respectively, for cement concretes, were investigated for the prediction of GRAC compressive strength, the parameters of these models were identified. The results showed the positive behaviour of GRAC investigated and the relevancy of the models proposed.

To investigate the effect of different CO2 concentrations on the carbonation results of slag blended cement pastes, carbonation experiments under natural (0.03% CO2) and accelerated conditions (3, 20, and 100% CO2) were investigated with various microscopic testing methods, including X-ray diffraction (XRD), 29Si magic angle spinning nuclear magnetic resonance (29Si MAS NMR) and scanning electron microscopy (SEM). The XRD results indicated that the major polymorphs of CaCO3 after carbonation were calcite and vaterite. The values of the calcite/(aragonite + vaterite) (c/(a + v)) ratios were almost the same in all carbonation conditions. Additionally, NMR results showed that the decalcification degree of C-S-H gel exposed to 0.03% CO2 was less than that exposed to accelerated carbonation, under accelerated conditions, it increased from 83.1 to 84.2% when the CO2 concentration improved from 3% to 100%. In SEM observations, the microstructures after accelerated carbonation were denser than those under natural carbonation but showed minor differences between different CO2 concentrations. In conclusion, for cement pastes blended with 20% slag, a higher CO2 concentration (above 3%) led to products different from those produced under natural carbonation. A further increase in CO2 concentration showed limited variation in generated carbonation products.

Ground Granulated Blast-furnace Slag (GGBS) can partially replace cement in concrete to improve certain properties. However, some concerns regarding its performance have been raised. This research aimed at investigating the properties of concrete with GGBS, with special focus on its frost scaling and chloride ingress resistance. Concretes with different amounts of GGBS, different efficiency factors, and different air contents have been tested. The effects of other factors, namely the curing temperature, the use of superplasticizer and carbonation, have also been investigated. The results showed that the frost resistance generally decreases with the increase of the amount of GGBS. However, this research showed that it is possible to produce frost resistant concrete with up to 50% of GGBS by changing some properties of the mix (such as increasing the air content). The results also showed a significant improvement of the chloride ingress resistance for concrete with high additions of GGBS.

Two-dimensional (2D) materials have been incorporated into calcium silicate hydrate (C-S-H) gel to enhance its mechanical performance for decades, while the modified C-S-H gel exhibits poor toughness, tensile strength, and ductility. In this work, we report a new design strategy and synthesis route to strengthen C-S-H interface by intercalating a silicene sheet of one atom thickness. The hybrid C-S-H/Silicene gel shows superb mechanical properties, with a remarkable enhancement in strength and other functional properties. By using density functional theory (DFT) and molecular dynamics (MD) simulations, we have demonstrated that Si-O bonds between silicene and C-S-H are stable and covalent, and the interaction energy of this bilayer gel nearly doubles by forming a 3D covalent network with a strong bridging effect. Owing to its better crystallinity enrichment and its induced dislocation dissipation mechanism, the hybrid C-S-H/Silicene gel possesses a higher tensile ductility (∼118% average enhancement and ∼228% in the

Beam-induced heating effect on nanoscale samples is a crucial question as it strongly influences the interpretation of observed unusual behaviors. This question is currently under debate without a convincing conclusion. Here, using silver nitride (Ag 3 N) nanoparticles as temperature labels, we perform an investigation on this heating effect inside a transmission electron microscope (TEM) under normal imaging conditions. Combined with experimental measurements and semi-quantitative calculations, a temperature increase of more than 100 K is estimated and confirmed in the graphite carbon nitride (g-C 3 N 4 ) films. Strong temperature gradients are found to exist in the single-end fixed g-C 3 N 4 films. The influencing factors of heat accumulation are also investigated and discussed. Findings in this paper may shed some light on the understanding of the abnormal behaviors of nano-objects observed inside TEM.

Impressed current cathodic protection and prevention techniques are efficient methods to stop or prevent corrosion in steel reinforced concrete structures. The inevitable side effect of the current exchange is acidification at the anode–concrete interface. Accelerated test methods can be used to investigate the long-term performance of the system. However, a linear relation will not hold between the accelerated and normal conditions because of the influence of the current density. This paper presents results of an accelerated test. A power-relation conversion model is proposed and an acceleration factor is introduced.

Hydrothermal treatment has been widely applied in the synthesis of well crystalline calcium silicate hydrate (CSH), such as tobermorite and xonotlite. However, both morphology and crystallinity of CSH are greatly affected by the conditions of hydrothermal treatment including siliceous materials, temperature increase rate and isothermal periods. In this study, the influence of hydrothermal conditions on the growth of nano-crystalline CSH was investigated based on XRD analysis. Results showed that siliceous materials with amorphous nature (i e, nano silica powder) are beneficial to synthesize pure amorphous CSH, while the use of more crystallized siliceous materials (i e, diatomite and quartz powder) leads to producing crystalline CSH. Results also indicate that the formation of tobermorite and xonotlite is greatly affected by the temperature rise rate during hydrothermal treatment.

Layered GaSe is an important binary semiconductor because of its anisotropic crystallography characteristics, wide band gap and attractive optical and electrical properties. Here, we report the self-catalytic growth of GaSe nanobelts via a simple chemical vapor deposition method. The quality of the as-grown nanobelts have been confirmed by transmission electron microscope and photoluminescence spectra. The field-effect transistors based on these individual GaSe nanobelts have been fabricated and show p-type semiconducting behaviors and on-off ratio of 106. The GaSe nanobelts not only show good responsivity of 164.4 A W−1, but also exhibit excellent stability and reliability, which are superior to their bulk counterparts. These results make GaSe nanobelt a promising optoelectronic material in integrated electronic/optoelectronic devices.

Chloride ions are known as one of the most crucial factors for rebar corrosion in reinforced concrete (RC) structures exposed to marine environments under drying-wetting cycles. In this condition, the chloride ion content in unsaturated concrete will change under the coupled effect of diffusion and capillary suction. This study simulates the atmosphere zone of the marine environment to explore the law of the chloride transmission behavior under the context of constant temperature and humidity. To analyze the effect of different drying-wetting ratios on the chloride ion profile in the concrete by conducting the dry-wet cycle tests. It is found that the most unfavorable drying-wetting ratios for RC structures in this study is 1:5.5. A finite element numerical model of chloride ion transmission based on Fick's Ⅱ law was established by COMSOL Multiphysics. It can be used to predict the range of concrete surface chloride ion concentration, and dynamic change of the distribution of chloride ion concentration inside the RC structures under different drying-wetting cycles over time. The comparison of experiment data and simulation results verify that the chloride diffusion prediction model has a good correlation.

Reinforced concrete (RC) structures, serving in marine and cold environments, are attacked by freeze–thaw cycles (FTCs) and chloride penetration, both of which can cause serious deterioration of RC structures. Existing studies lack of models considering the development of pore structure, as well as crack propagation caused by freeze and thaw. In this study, a multi-phase numerical model is proposed for studying chloride transport in concrete under FTCs. Unlike the existing models, the diffusion coefficient in the presented work is associated with the evolution of pore structure, and the induced crack is considered to be time-dependent and propagates with cycles of freeze–thaw action. The validity of the presented model is verified against a set of third-party experiments. Some important factors, such as FTCs, crack width, porosity, connectivity and most probable pore diameter factor are elaborated to illustrate how these factors affect chloride transport. The findings can bring insights to the durability design of RC structures serving in cold or marine regions.

The low temperature of ice and snow all year round in Sweden leads to the common use of deicing salt to melt the roads, but the splash of the deicing salt on the reinforced concrete (RC) on both sides of the roads brings about the deterioration of the durability of RC components. The chloride ions diffusion coefficient is an important parameter to evaluate the durability of RC. By adopting the rapid chloride migration method (RCM) and replacing chloride ions with iodide ions, the samples of concrete blocks exposed on the side of the highway for 20 years were taken. This is directly beneficial to study the influence of the type, content, and water-cement ratio of mineral additions on the diffusion and distribution of iodide ions in concrete and analyze the surface environmental effect depth of concrete. The influence of chloride ions on the pore structure and microscopic morphology of concrete also were studied by scanning electron microscope-energy dispersive spectrum and X-ray diffractometer. The results show that as the water-cement ratio increases, the surface environmental effect depth of concrete and the diffusion area of iodide ions gradually increase. Silica fume and ground granulated blast furnace slag (GGBF slag) have an impediment to the diffusion of iodide ions, especially with the high volume of the GGBF slag (about 50%), the diffusion of iodide ions is very low. In general, this research is helpful to provide some empirical ideas and suggestions for the manufacturing and durability design of concrete structures in marine environments or deicing salt road environments.

This paper presents an analytical model for calculation of corrosion induced stress field and cracking time of concrete cover with initial defects in a reinforced concrete. In the proposed model, two types of initial defects in concrete cover (surface and middle defect) were considered. Experiments were also performed to validate the effectiveness and accuracy of the proposed model. Based on the model analysis, it was found out that initial defects have significant influence on the stress distribution, the corrosion induced expansion pressure in concrete cover, the critical mass of corrosion products, and the cracking time of concrete cover.

Contact-hardening is a new type of binding property for amorphous calcium silicate hydrate (C-S-H) with which a hardened specimen can be prepared in a few minutes by compressing C-S-H powders directly. However, the relation between contact-hardening behaviours and the drying conditions of powders is still poorly understood. In this study, the influence of air-drying and oven-drying on the physical properties and microstructure of hydrothermally synthesised C-S-H powders were investigated. The results provide further insight into the contact-hardening behaviours of these powders by measuring the bulk density, mechanical strength and water-resistant properties of the compacts. Factors affecting particleparticle contact and hardening of C-S-H powders are discussed in parallel with the mechanical properties and microstructure of the compacts. The result highlights that the moisture content, which is highly related to the drying conditions, is essential to contact hardening of C-S-H.

This paper presents a discussion of the paper published by Lv et al. in Cement and Concrete Composites, 2016, 66: 1–9. The discussion is mainly focused on whether or not graphene oxide (GO) nanosheets can regulate formation of flower-like cement hydration crystals. Lv et al. in their paper proposed a regulation mechanism stating that GO nanosheets can control ettringite (AFt), monosulfate (AFm) and calcium hydroxide (CH) to form the flower-like and polyhedron crystals, whilst our experimental results show that there might be a possible pitfall in sample preparation for SEM analysis. It is here suggested that the main chemical components of flower-like and polyhedron crystals are calcium carbonates, which are not the products from cement hydration but from carbonation of cementitious hydrates. It is therefore suggested that further study is needed to verify the regulation mechanism of GO on cement hydration crystals proposed by Lv et al. in the discussed paper.

Red mud, an industrial waste obtained from alumina plants, is usually discharged into marine or disposed into a landfill polluting the surrounding water, atmosphere, and soil. Thus, disposal of red mud is an environmental concern and it should be recycled in an effective way. Since red mud consists of iron- and aluminum-rich phases, it can potentially be processed into cementitious material and can be used for a construction purpose. This research investigated the synthesis of nanoferrite (NF) clinker by using red mud as a raw material through chemical combustion technology for potential use in cement-based composite. Before the synthesis of NF, red mud was characterized by using XRF, XRD, and SEM techniques. From characterization results, the stoichiometric ratio of raw materials was calculated and experimentally optimized. The sample was then tested at various temperatures (815, 900, 1000, and 1100°C) to find the optimum synthesis temperature. Finally, the hydraulic activity of NF was verified and the contribution to mechanical properties was determined by replacing cement with NF at various substitution levels (0, 5, 10, and 20 wt%). Test results showed that the optimum condition for the synthesis of NF was found when the ratio of CaCO3/red mud was 1.5 and the sintering temperature was 815°C. The synthesized NF had an average diameter of 300 nm, and the main composition was brownmillerite (C4AF) with distinct hydraulic reaction. When NF was used as a substitute of Portland cement in mortar, the flexural strength with a 5% replacement level improved by 15%. Therefore, it can be concluded that the synthesis of NF provides an alternative approach to recycle red mud and could significantly help in reducing environmental pollution.

The purpose of this study is to investigate the influence of moisture content on the contact-hardening properties of calcium silicate hydrate. The materials with moisture content ranging from 0 to 76% were directly compressed at the pressure of 40 MPa for three minutes to produce solid compacts. Bulk density, mechanical strength and water-resistant property of the compacts were measured, and temperature evolution of the powders during compaction was evaluated. An obvious increase in bulk density of compacts but a slight decrease in compressive strength was found with moisture content increased up to approximately 25%, ascribed to the lubricant effect of water films on the surface of particles that facilitates the rearrangement and spillage of particles. Moisture could reduce the temperature evolution by reducing surface energy of the particles, and separate the interparticulate bonding. Consequently, for the material with moisture content higher than 25%, the bulk density of the compacts was almost constant, but the compressive strength decreased dramatically. Different tendency was observed in the flexural strength that the value increased with moisture content increased up to 11%, attributed to the consolidation of particles and formation of hydrogen bonding, and the water- resistant property of the compacts was also improved. Subsequent decrease in flexural strength was due to the disruption of hydrogen bonding.

In this research, combined solution of chloride and sulfate was investigated for three different mixtures, including fly ash and slag. Mass change, dynamic modulus of elasticity, chloride penetration depths were tested in the different solution. Results indicated that OPC specimens showed bigger deterioration compared specimens with fly ash and slag exposed to combined solution attack under drying-wetting cycles. Additional, higher sulfate contend in combined solution retarded damage for OPC under drying-wetting cycle. Concerning the microstructure and deformation of samples, XRD-analyses is in accordance with TG/DSC-analyses, moreover, DSC/TG could quantified the results from XRD-analyses. (C) 2015 Published by Elsevier Ltd.

The effects of CO2 concentration on changes in chemical phases and microscopic characteristics for fly ash (FA) blended cement pastes were investigated in this study. Several microscopic test methods, including X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), 29Si nuclear magnetic resonance (29Si NMR) and scanning electron microscope (SEM), were used to characterize the chemical compositions and microscopic features. The XRD results showed that the precipitation of allotropic calcium carbonate (CC) includes calcite (c), aragonite (a) and vaterite (v). The ratio of c/(a + v) was around 0.6 under 3% and 20% CO2, while more percentage of calcite was generated under 100% CO2 (c/(a + v) = 0.79). The precipitation of more calcite than vaterite and aragonite happened with the CO2 concentration elevated to 100%. TGA analysis indicated that the total content of CC was similar under all accelerated conditions and higher than that under natural carbonation. Additionally, in the 29Si NMR spectra, more C-S-H (about 70%) was decalcified after accelerated carbonation compared with natural carbonation (54.1%). The decalcification degree was the same for 3% and 20% CO2 and showed the highest value under 100% CO2. The microstructure changes characterized by SEM observation exhibited denser microstructure after carbonation with the formation of CC but no apparent difference was observed with different CO2 concentrations based on the SEM pictures. Compared with the carbonation of ordinary Portland cement (OPC) paste, the carbonation of FA blended cement paste was more inclined to precipitate as calcite than vaterite and aragonite and caused a lower decalcification degree of C-S-H. Overall, similar to OPC paste, the carbonation results obtained in natural and accelerated conditions for FA blended cement pastes were different and the conditions between 3% and 20% CO2 were similar while 100% CO2 showed different results.

As a novel low carbon cementitious material, alkali-activated slag (AAS) attracted many researchers’ interests, not only because of its environmental benefits, but also some superior properties than Portland cement (PC). Due to different chemical reactions of AAS, gypsum, a commonly used expansive agent in PC, exhibits a different behaviour in AAS. This paper reports the investigation on the shrinkage behaviour of sodium silicate activated slag (SSAS) incorporated with gypsum and PC. In addition, the early properties, including setting time and early hydration products, were determined by Vicat apparatus, XRD and TG. The hardened properties, namely flexural and compressive strength, were investigated as well. The results showed that, by incorporating gypsum and PC, the drying shrinkage of SSAS could be significantly reduced because of the formation of expansive sulfate-rich and calcium-rich hydration products in terms of ettringite and Portlandite. The initial setting was delayed by blending PC, although adding gypsum accelerated the hydration of SSAS. The addition of gypsum and blend with 20% PC slightly increased flexural and compressive strengths of SSAS at 7 days and 28 days.

The impressing current technique with different current densities is widely adopted for investigating the deterioration problems caused by the reinforcement corrosion. Additionally, the theoretical mass loss of reinforcement is obtained using Faraday’s Law with the assumption that all of the impressed charge participates in the corrosion reaction. In this study, the accelerated corrosion of the reinforcements with different current densities was non-destructively traced by the X-ray micro-computed tomography (XCT). The results indicated that the current efficiency was not constant during the corrosion process. The evolution of the current efficiency was influenced by the current density.

Impressed current technique is a widely adopted method for accelerating corrosion of steel reinforcement. The mass loss of steel can be theoretically estimated by Faraday's law with the assumption that all of the impressed current participated in the corrosion reaction. In the present study, accelerated corrosion process of reinforcing steel with impressed current was non-destructively traced by X-ray micro-computed tomography (μCT) with high accuracy. The mass loss of steel at different accelerated corrosion periods was analyzed and the efficiency of impressed current was calculated. It was found that the mass loss of steel did not always follow Faraday's law, and impressed current efficiencies varied with different corrosion periods. In the early corrosion periods, the water electrolysis occurred and lowered the current efficiency due to the high anode potential. While in the late corrosion periods, the natural corrosion caused the current efficiency to exceed 100%.

Chloride ingress is one of the main causes for the degradation of reinforced concrete structures. Increasing the chloride binding capacity of concrete is generally thought as a feasible way to restrain the chloride ingress. In our previous study, the γ-phase nano-Al2O3 (NA) was found to be beneficial for improving the chloride binding of plain Portland cement paste as a result of the formation of additional Friedel’s salt. Herewith, the cases of blended cement pastes were further investigated, into which supplementary cementitious materials (SCMs) were incorporated, including fly ash (FA), blast furnace slag (SL) and silica fume (SF). NA with a dosage of 1% and 2% was introduced to blended cement paste, and the chloride binding capacity of which were determined with the conventional equilibrium method. The results showed that the use of NA was even viable to improve the chloride binding capacity of blended cement pastes. X-ray diffraction (XRD)/Rietveld refinement method and thermogravimetric analysis (TGA) were performed to unravel the phase assemblages change upon exposure. It was revealed that besides the formation of more Friedel’s salt, the addition of NA could allow the enhanced physical binding of chloride as a result of the formation of C-A-S-H, i.e., the substitution of Si by Al in C-S-H gel.

X-ray computed tomography (XCT) can non-destructively detect microstructure of cement-based material. However, its raw results involve errors induced by the equipment and external factors. Once studying changes taken place in a sample, such as durability related studies, which need testing on a same sample at intervals, these errors will result in misleading conclusions. At the moment, in literature, no method focusing on effectively and reasonably eliminating or minimising these errors has not been observed. After testing and analysing ten series of XCT results for samples experiencing various types of exposures, authors established a rational data-processing method to minimise the influence of these errors on test results, and is introduced in this paper. To assist readers’ understanding, the method and relevant information are illustrated with a case of immersion of hardened cement pastes in NaCl solution. Obtained results prove that diffusion of substances in the hardened cement paste can be properly revealed with the data processing method introduced; trend and depth of microstructure change caused by the exposure can be determined; the immersion of samples in NaCl solution led to a gradual decrease in density and a further hydration of cement particles, which should be related to leaching of Calcium from the sample into immersion solution; once immersed in same NaCl solution, the change of microstructure in the 0.35 w/c was slower than that in the 0.5 w/c sample and the influence depth had an approximate linear relationship with square root of immersion duration.

Poly (vinyl alcohol) (PVA) emulsion is commonly used in cement-based materials to obtain higher performance. The present work investigates the interaction mechanisms between PVA and calcium silicate hydrates (C-S-H) using ambient and high pressure X-ray diffraction (XRD), 29Si magic angle spinning nuclear magnetic resonance (MAS NMR), nano-indentation, and molecular dynamics simulation. In a C-S-H nano-particle, small-size PVA molecules can be intercalated into the interlayer region of the calcium silicate sheets, lowering the interlayer incompressibility and the overall bulk modulus of C-S-H at the crystal length scale. At a larger length scale, the large-size PVA chains can be in the midst among the C-S-H nano-particles, decreasing the porosity, thus the indentation modulus of the meso-composite is improved.

The manipulation and tailoring of the structure and properties of semiconductor nanocrystals (NCs) is significant particularly for the design and fabrication of future nanodevices. Here, a novel domain‐confined growth strategy is reported for controllable fabrication of individual monocrystal hollow NCs (h‐NCs) in situ inside a transmission electron microscope, which enables the atomic scale monitoring of the entire reaction. During the process, the preformed carbon shells serve as nanoreaction cells for the formation of CdSeS h‐NCs. Electron beam (e‐beam) irradiation is demonstrated to be the key activation factor for the solid‐to‐hollow shape transformation. The formation of CdSeS hollow NCs is also found to be sensitive to the volume ratio of the CdSe/CdS NCs to the carbon shell and only those CdSe/CdS NCs with a volume ratio in the range 0.2–0.8 are successfully converted into hollow NCs. The method paves the way to potentially use an e‐beam for the in situ tailoring of individual semiconductor NCs targeted toward future nanodevice applications.