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• A systematic framework is proposed for epistemic uncertainty quantification. • Uncertainty quantification of environmental, material and geometric properties. • MCMC predicts a wider range of corrosion responses with strong correlation. Due to ambiguous correlations between input random variables and multi-source uncertainties from the electrochemical model, significant differences between deterministic corrosion prediction models and actual measurements are often observed. A systematic framework of quantification of uncertainties is developed for structures with correlated random variables originated from multiple sources, which allows efficiently estimating the failure probability distribution of the steel corrosion over time considering the randomness of the cover depth, the surface chloride concentration, and the chloride diffusion coefficient. After partitioning correlated random variables into different groups based on their uncertain sources, the Morris one-step-at-a-time and Sobol model is established to rank with respect to the importance of each correlated random variable. Based on polynomial chaos expansions and genetic programming methods, a more condensed set of random variables is created to propagate parametric problems. The unknown probability distribution of the input random variables is formulated by the Markov chain Monte Carlo to realize rigorous uncertainty quantification of the structural reliability. The application of the systematic framework to a set of numerical examples of steel corrosion includes experimental validation and uncertainty quantification and propagation of environmental, material and geometric properties. The results show that the framework can be integrated with parametric electrochemical models to allow robustness and reliability of corrosion prediction. [ABSTRACT FROM AUTHOR]

• The scale of fluctuation for surface chloride content under varying exposure zone on marine structure. • The modified spatiotemporal kriging interpolation method to re-establish the non-uniform spatiotemporal correlation distance. • The optimal strategy to improve the cost benefit ratio of surface chloride content detection on RC structures. Chloride-induced corrosion of marine reinforced concrete structures involves numerous uncertainties related to environmental exposure zone. The exposure zone is strongly correlated with surface chloride content, which exhibits significant spatiotemporal variability. In this study, the scale of fluctuation of the chloride content in different exposure zones was estimated to explore the effect of the exposure zone on the spatial variability of the marine chloride environment. Based on the detection data of surface chloride content over a time span of 18 years at Zhapu Port, we present a modified spatiotemporal Kriging interpolation method that extends interpolation from 2D plane to 3D space by replacing surface distance with the Euclidean distance. The chloride environmental spatiotemporal distance field model was constructed using the particle swarm optimization algorithm. The results show that the prediction of surface chloride content is physically more realistic when modified spatiotemporal Kriging is used with the spatiotemporal distance amplified by 2–3 times. Additionally, a method to optimise the location of the detection point is proposed, which can improve the cost–benefit ratio of surface chloride content detection on reinforced concrete structures by 37.5%. [ABSTRACT FROM AUTHOR]

• A multi-class Boosting method is proposed for the multi-class imbalanced problem. • Parametrized division of exposure zone is achieved using RMS, C r , C s , and D cl , etc. • Field chloride profile data with time span of 18 years validates proposed method. • The distribution of exposure zone satisfies the Weibull distribution. The analysis of marine reinforced concrete structures using chloride profile data is a commonly used exposure zone classification method. However, chloride profile data is multi-class, unbalanced and non-parametric, which makes it difficult for the commonly used machine-learning methods to construct an appropriate classification model. To solve this problem, chloride profile is parametrized by the minimum redundancy maximum relevance algorithm and a multi-class Boosting method using F-measure as inductive bias indicator to evaluate the weight of base classifiers is put forward. The method is based on field test data of the chloride profile over a period of 18 years in Hangzhou Bay, China. The method outperforms the original Boosting method with an average F-measure improvement of 6.2 %. The results show that parametric partitioning of the exposure zone is achieved and the distribution of the exposure zone satisfies the Weibull distribution. [ABSTRACT FROM AUTHOR]

Low-dimensional organic-inorganic hybrid perovskites possess unique microstructural, optical, and electrical properties and offer great application prospects in other fields in addition to optoelectronics. In this study, one-dimensional methylammonium lead iodide (MAPbI 3) nanowires (NWs) were fabricated using an antisolvent-assisted solution method with the addition of phenethylammonium iodide (PEAI). The effects of PEAI on the crystal growth, morphology and microstructure, photoluminescence (PL), and photoresponse performance of the NWs were investigated. The results showed that the addition of the appropriate amount of PEAI transformed the morphology of MAPbI 3 from micron-scale wires to elongated NWs with a high-aspect ratio. Scanning electron microscopy, X-ray diffraction, atomic force microscopy, scanning Kelvin probe microscopy, PL, and time-resolved PL spectroscopic characterizations were conducted, and the results confirmed that PEAI improved the microstructural properties of the as-prepared NWs and manifested surface passivation. The PEAI-treated MAPbI 3 NWs devices also exhibited a superior photoresponsivity as photodetectors compared with the untreated MAPbI 3 microwires devices. This study proposed a simple and effective method that can improve the microstructural and photoelectrical properties of low-dimensional MAPbI 3 crystals, which have a broad application potential for next-generation optoelectronic devices or detectors. • Nanowire-shaped MAPbI 3 with superior microstructural features were fabricated. • A novel approach of adding PEAI was presented to improve MAPbI 3 crystal properties. • PEAI-modified nanowires with larger crystallite size and smaller microstrain were obtained. • Emission and photoresponse properties were improved after PEAI treatment. • PEAI has a remarkable effect on the growth of low-dimensional MAPbI 3 crystals. [ABSTRACT FROM AUTHOR]

• Numerical analysis on geometric characteristics and distribution region of steel corrosion morphology. • The effects of aggregate proportion and spatial arrangement on corrosion morphology. • Statistical analysis based on the 600 sets of models with random aggregate distribution. • The variability of corrosion morphology varies with the increase of aggregate proportion. The random distribution of aggregates plays a key role in the variation of steel corrosion morphology in chloride-contaminated RC structures. The purpose of this study is to investigate the influence of random aggregate distribution on the regularity and variability of steel corrosion morphology through probabilistic analysis based on numerical simulation results. The statistical corrosion parameters of steel (corrosion current density, chloride ion concentration, corrosion morphology, and corrosion mass loss) were obtained from 600 numerical sample simulations to analyse the influence of the proportion and spatial arrangement of aggregates. The simulated results showed that random aggregate distribution causes a non-uniform distribution of corrosion parameters temporally and spatially. The position of the steel surface where the maximum corrosion depth occurs exhibits randomness. The corrosion degree decreases by 24.4% as the aggregate proportion increases from 0.30 to 0.55. However, the variability of the corrosion morphology first increases and then decreases with the aggregate proportion; the inflection point is between 0.30 and 0.45. The distribution of corrosion parameters satisfies the normal distribution according to the chi-square test. [ABSTRACT FROM AUTHOR]

The cement manufacturing industry, a resource- and energy-intensive sector, took up more than 15% of total greenhouse gas emissions in China, thus finding a clean technology option for sustainable development is essential. CO 2 curing has emerged as a promising novel method for large-scale carbon sequestration and mechanical properties improvement of cement-based composites. Currently, a body of related works is mainly investigated in the laboratory, and understandings of the behaviors of CO 2 -cured cement-based composites are still less than complete, including, 1) the CO 2 storage potential has plenty of room for improvement due to the influence mechanism of variables factors remains unclear; 2) previous evaluations were mostly based on the subsets of individual result rather than an integrated dataset; 3) whether CO 2 curing is suitable for the manufacturing process of reinforced concrete. Therefore, this paper presents a comprehensive overview covering a wide range of parameters as well as fabrication, mechanical (compressive strength), and environmental (CO 2 uptake value) performances on the basis of a correct understanding of the differences between active and passive carbonation reactions. Notably, the influences of critical factors, including those less understood, e.g., types of curing setup (flow-able, enclosed, and others), components of binder, and aggregate/binder ratio, are also analyzed and the corresponding mechanisms discussed to achieve satisfied curing efficiency. Besides, corrosion-related challenges are also be pointed out to convince the widespread acceptance of this technology. Finally, based on this paper, limitations of existing research are identified and future scope on CO 2 curing regime is proposed. • 170 studies related to CO 2 /carbonation-cured cement-based composites are analyzed. • The differences between active/passive-carbonation together with reaction mechanisms are expounded. • Fabrication and influence factors on engineering and environmental properties are systematically reviewed. • CO 2 -cured cement-based composites exhibit excellent resistance to aggressive conditions. • The challenges and opportunities in the CO 2 curing method are innovatively discussed. [ABSTRACT FROM AUTHOR]

The development of one-part geopolymer mortars has greater potential than the traditional two-part mortars, especially in repair applications, to convert waste into useful beneficial products while simultaneously eliminating the hazards associated with the alkaline solutions. Nevertheless, the inherent brittleness exhibited by the one-part geopolymers displays drawbacks like OPC when subjected to flexural loading. The fibers selection as well as their strengthening effects from literature is considerably scarce, especially for the repairing geopolymer system. This work aims to investigate the influences of fiber types and volume fractions on the workability, physical behavior, and cracking/fatigue resistance of ambient air-cured one-part geopolymer mortar. Reaction kinetics, mineralogical phases, and elemental components were explored by means of the TAM, quantitative XRD, and EDS mapping analysis. The FESEM and X-CT were employed to compare the microstructures and pore characteristics of the fibers-reinforced products. The results show that the copper-plated steel fiber produced the least change in workability, while the basalt fiber produced the lowest flow values. Setting time was the shortest for the basalt fiber reinforced, followed by polyvinyl-alcohol fiber. The steel fiber and carbon fiber would improve the mechanical properties of mortar significantly, especially in the early stage. The fatigue strength of 1 vol% carbon fiber reinforced mortar under 2 million cycles loading was the highest (3.72 MPa). The fibers addition a substantial decrease in sphericity and compactness of the pores (high anisotropy) as evidenced by X-CT data. Moreover, three hydration heat processes occurred after water was added to the one-part geopolymer mortar, which included dissolution of Na 2 SiO 3 particles, network degradation, and a second pozzolanic reaction. More crystalline formation occurred over curing time to form gel networks with high stability and generated different bonding modes with various fibers. • Geopolymer powder could produce ambient-cured one-part GPMs by mixing with water. • Effects of micro-fiber type and volume fraction on the one-partGPMs were investigated. • Workability, strength properties, cracking/fatigue resistance were measured. • Geopolymerization and fiber bonding of GPMs were analyzed using TAM, FESEM, EDS, QXRD and X-CT. [ABSTRACT FROM AUTHOR]

The destabilization together with boundary chloride ions releasing leads to the corrosion of steel bars, posing nonnegligible risks to the durability of structures. This work attempted to design the typical pore solution of underground constructions via methods of combining NaCl with Na 2 SO 4 along with conducting a stray current continuously. The bound chloride stability of mortar under the action of electric current was systematically determined. The reaction mechanisms were tested by quantitative XRD, TG-DTG, FTIR, FESEM, and X-CT. Molecular dynamics was utilized to simulate the physical binding processes of C–S–H of Cl−/SO 4 2- and their interaction under the actions of electric field by comparing the ions displacement trajectory, radial distribution function, and moving ability. The experimental results showed that the SO 4 2- weakened the chemical chloride binding capacity with the Friedel's salt, portlandite, and calcium silicate decomposed to produce gypsum or ettringite. The electric field demonstrated less impact on the stabilities of chemical-bound Cl−, but promoted SO 4 2- redistributions, causing substantial pore coarsening. The simulation revealed that the physical binding contained short-range ion Coulomb-interactions and long-range van der Waals interactions. The SO 4 2- inhibited the binding of the C–S–H on Cl− by fact that the deposition large cluster of Na–SO 4 blocked the nano-meter channels and competitive adsorption occurred at the SiOCa+ sites, while the introduction of electric field weakened the dominating effects of Coulomb-interactions and improved the ions desorption gradually. Hopefully, the transport and adsorption mechanisms of the Cl− in the cement-based materials can help guide the underground concrete with durability. [ABSTRACT FROM AUTHOR]