Effect of Modified Cow Dung Fibers on Strength and Autogenous Shrinkage of Alkali-Activated Slag Mortar.

Alkali-activated slag (AAS) presents a promising alternative to ordinary Portland cement due to its cost effectiveness, environmental friendliness, and satisfactory durability characteristics. In this paper, cow dung waste was recycled as a renewable natural cellulose fiber, modified with alkali, and then added to AAS mortar. The physico-chemical characteristics of raw and modified cow dung fibers were determined through Fourier transform infrared (FTIR), X-ray diffraction (XRD), and Scanning electron microscope (SEM). Investigations were conducted on the dispersion of cow dung fibers in the AAS matrix, as well as the flowability, strength, and autogenous shrinkage of AAS mortar with varying cow dung fiber contents. The results indicated that modified fiber has higher crystallinity and surface roughness. The ultrasonic method showed superior effectiveness compared to pre-mixing and after-mixing methods. Compared with raw cow dung fibers, modified fibers led to an increase of 11.3% and 36.3% of the 28 d flexural strength and compressive strength of the AAS mortar, respectively. The modified cow dung fibers had a more significant inhibition on autogenous shrinkage, and the addition of 2 wt% cow dung fibers reduced the 7 d autogenous shrinkage of the AAS paste by 52.8% due to the "internal curing effect." This study provides an alternative value-added recycling option for cow dung fibers as a potential environmentally friendly and sustainable reinforcing raw material for cementitious materials, which can be used to develop low autogenous shrinkage green composites.

NOx degradation ability of S-g-C3N4/MgAl-CLDH nanocomposite and its potential application in cement-based materials.

In this study a new photocatalytic nanocomposite, S-g-C3N4/MgAl-CLDH, was synthesized and implemented into cement mortar by internal mixing or coating. The photocatalytic NOx degradation efficiency of the S-g-C3N4/MgAl-CLDH and photocatalytic mortar was investigated. The NOx degradation efficiency and photoluminescence spectra of S-g-C3N4/MgAl-CLDH after being immersed in the simulated concrete pore solution were evaluated to assess its chemical stability. The results show that compared with S-g-C3N4, the S-g-C3N4/MgAl-CLDH exhibits a narrower bandgap (2.45 eV), a lower photogenerated electron-hole pair recombination rate and a higher specific surface area (36.86 m2 g-1). After 21 min of visible light irradiation, the NOx degradation rate of S-g-C3N4/MgAl-CLDH achieves 100% as compared to merely 81.5% of S-g-C3N4. After being submerged in simulated concrete pore solution, the S-g-C3N4/MgAl-CLDH exhibits only a slight decrease of 5% in degradation rate after 12 min of irradiation, confirming a good compatibility and stability in cement-based materials. The NOx degradation ability of the internally mixed mortar is enhanced with an increase in the dosage of S-g-C3N4/MgAl-CLDH. For coated mortar, in contrast, a decline in NOx degradation rate is observed after 5 layers of coating owing to the lower porosity of mortar after excessive coating.

Deep Learning Methodology for Obtaining Ultraclean Pure Shift Proton Nuclear Magnetic Resonance Spectra.

Nuclear magnetic resonance (NMR) is one of the most powerful analytical techniques. In order to obtain high-quality NMR spectra, a real-time Zangger-Sterk (ZS) pulse sequence is employed to collect low-quality pure shift NMR data with high efficiency. Then, a neural network named AC-ResNet and a loss function named SM-CDMANE are developed to train a network model. The model with excellent abilities of suppressing noise, reducing line widths, discerning peaks, and removing artifacts is utilized to process the acquired NMR data. The processed spectra with noise and artifact suppression and small line widths are ultraclean and high-resolution. Peaks overlapped heavily can be resolved. Weak peaks, even hidden in the noise, can be discerned from noise. Artifacts, even as high as spectral peaks, can be removed completely while not suppressing peaks. Eliminating perfectly noise and artifacts and smoothing baseline make spectra ultraclean. The proposed methodology would greatly promote various NMR applications.

Visible light antibacterial potential of cement mortar incorporating Cu-ZnO/g-C3N4 nanocomposites.

In this work, a hybrid Cu-ZnO/g-C3N4 nanocomposite was synthesized and introduced to fabricate photocatalytic cement mortars by internal mixing. The bactericidal properties of the photocatalytic mortars were explored by using E. coli, S. aureus and P. aeruginosa as a bacteria test strain. The results showed that the Cu-ZnO/g-C3N4 nanocomposite had an enhanced harvesting of visible light energy and exhibited excellent stability during the photocatalytic process, which favored a long-term usage performance. The sterilizing efficiency of the photocatalytic cement mortars improved with an increasing content of Cu-ZnO/g-C3N4 nanocomposites. A possible bactericidal mechanism was proposed based on the active species trapping experiments, verifying that the photogenerated holes (h+) and ˙O2 - radicals were the main active species.

Fast Acquisition of High-Quality Nuclear Magnetic Resonance Pure Shift Spectroscopy via a Deep Neural Network.

Pure shift methods improve the resolution of proton nuclear magnetic resonance spectra at the cost of time. The pure shift yielded by chirp excitation (PSYCHE) method is a promising pure shift method. We propose a method of reconstructing the undersampled PSYCHE spectra based on deep learning to accelerate the spectra acquisition. It only takes 17 s to obtain a high-quality pure shift spectrum. The network can completely remove undersampling artifacts and chunking sidebands and improve the signal-to-noise ratio, obtaining completely clean pure shift spectra. The reconstruction quality is better than the iterative soft thresholding method. In addition, the network can differentiate low-level signals and chunking sidebands with similar intensities in the mixture, remove sidebands, and retain signals, promoting correct mixture analysis.

Investigation of PEG/mixed metal oxides as a new form-stable phase change material for thermoregulation and improved UV ageing resistance of bitumen.

The form-stable phase change material (PCM), polyethylene glycol (PEG)/ZnMgAl-mixed metal oxides (MMO), is prepared as a performance-enhancing additive of bitumen. In PEG/MMO PCM, PEG exhibits the phase-change function while ZnMgAl-MMO acts as the support carrier to prevent leakage of liquid PEG during phase transition. The properties of PEG/MMO PCM were analysed by XRD, SEM, FTIR, DSC, TG and UV-vis spectrophotometry. The results showed that the maximum PEG confined by MMO could be 65% and 65PEG/MMO PCM exhibited good thermal and chemical stability, sufficient phase change enthalpy and excellent UV absorption properties. Furthermore, the temperature regulation and UV ageing resistance of PEG/MMO PCM modified bitumen was evaluated by the thermal storage and release test and accelerated UV aging test. As a new type of performance-enhancing additive, PEG/MMO PCM is expected to be effective in regulating extreme temperature and resisting UV aging of bitumen and thus significantly extending the service life of bitumen pavement.

Ink-bottle Effect and Pore Size Distribution of Cementitious Materials Identified by Pressurization⁻Depressurization Cycling Mercury Intrusion Porosimetry.

Capturing the long-term performance of concrete must be underpinned by a detailed understanding of the pore structure. Mercury intrusion porosimetry (MIP) is a widely used technique for pore structure characterization. However, it has been proven inappropriate to measure the pore size distribution of cementitious materials due to the ink-bottle effect. MIP with cyclic pressurization-depressurization can overcome the ink-bottle effect and enables a distinction between large (ink-bottle) pores and small (throat) pores. In this paper, pressurization-depressurization cycling mercury intrusion porosimetry (PDC-MIP) is adopted to characterize the pore structure in a range of cementitious pastes cured from 28 to 370 days. The results indicate that PDC-MIP provides a more accurate estimation of the pore size distribution in cementitious pastes than the standard MIP. Bimodal pore size distributions can be obtained by performing PDC-MIP measurements on cementitious pastes, regardless of the age. Water-binder ratio, fly ash and limestone powder have considerable influences on the formation of capillary pores ranging from 0.01 to 0.5 µm.

Microstructure-Based Relative Humidity in Cementitious System Due to Self-Desiccation.

The internal relative humidity (RH) plays a crucial role in most of the concrete properties. Self-desiccation caused by continuous cement hydration is a major factor affecting the RH of concrete. This paper investigates the relationship between RH and microstructure for cementitious systems in the case of self-desiccation. A series of paste specimens prepared with different binder and water-binder-ratio (w/b) were cured under sealed conditions from 1 day to 1.5 years. The RH and microstructure of the paste specimens were measured. The microstructure characteristics under study include porosity, pore size, evaporable and non-evaporable water content. The results reveal that the RH of cementitious system drops to a great extent in the first 105 days' hydration and decreases slowly afterwards. The blended materials such as fly ash, slag or limestone powder have different influences on the RH. A mathematical model between RH and the average pore diameter is proposed for cementitious systems under self-desiccation, regardless of age, w/b or cement type.

Preparation and characterization of PEG/surface-modified layered double hydroxides as a new shape-stabilized phase change material.

A new shape-stabilized phase change material based on polyethylene glycol (PEG) and surface-modified layered double hydroxides (LDHs) was prepared by a solution impregnation method. PEG enabled thermal energy storage and release as a phase change material; 3-aminopropyl triethoxysilane (KH550) was used to modify the surface of LDHs (KH-LDHs) which then acted as a carrier to keep the solid form of the molten PEG at high temperature. The maximum weight percentage of PEG confined in the PEG/KH-LDHs composite was 55%. The detailed structures, thermal properties and UV absorption of the composite were characterized systematically by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermal gravimetric (TG) analysis and UV-vis absorption spectra. Results show that the PEG/KH-LDH composite has a suitable phase change temperature, considerable enthalpy, and good thermal stability as well as remarkable ultraviolet absorption ability. As a new shape-stabilized phase change material, the PEG/KH-LDH composite is expected to contribute to the effort of searching effective measures for thermal management of building and pavement materials.

Characteristics and Applications of Sugar Cane Bagasse Ash Waste in Cementitious Materials.

Sugar cane bagasse ash (SCBA) is an abundant byproduct of the sugar and ethanol industry. SCBA is generally used as a fertilizer or is disposed of in landfills, which has led to intensified environmental concerns. In recent years, SCBA research has mainly been focused on utilization in construction materials due to the abundance and pozzolanic characteristics of SCBA. In this paper, a comprehensive review of the state-of-the-art morphology, physical properties, chemical composition, and mineralogical composition of SCBA is presented. Studies indicate that SCBA is a potentially promising construction material. The applications of SCBA as a pozzolanic material, a new source for preparing alkali-activated binders, aggregates, and fillers in construction materials, are summarized. The impacts of SCBA on fresh and hardened concrete properties are highlighted, including the physical properties, mechanical strength, microstructure, and durability. Key factors that govern pozzolanic activity are discussed in detail, including calcination and recalcination temperatures, and durations, fineness, loss on ignition (LOI), and crystal silicon dioxide. Finally, further research on the optimal and broad utilization of SCBA in construction materials is recommended.

Recent Advances in Intrinsic Self-Healing Cementitious Materials.

Self-healing is a natural phenomenon whereby living organisms respond to damage. Recently, considerable research efforts have been invested in self-healing cementitious materials that are capable of restoring structural integrity and mechanical properties after being damaged. Inspired by nature, a variety of creative approaches are explored here based on the intrinsic or extrinsic healing mechanism. Research on new intrinsic self-healing cementitious materials with biomimetic features is on the forefront of material science, which provides a promising way to construct resilient and sustainable concrete infrastructures. Here, the current advances in the development of the intrinsic healing cementitious materials are described, and a new definition of intrinsic self-healing discussed. The methods to assess the efficiency of different healing mechanisms are briefly summarized. The critical insights are emphasized to guide the future research on the development of new self-healing cementitious materials.

Spatial and temporal variations of heavy metals in marine sediments from Liaodong Bay, Bohai Sea in China.

An integrated analysis has been carried out using surface sediment monitoring data in order to characterize the spatial distributions and temporal trends of heavy metals within ten years from 2004 to 2013 in the entire Liaodong Bay. Hg, Cd and As were predominant contaminants with their median concentrations of 0.04-0.15, 0.01-0.65, and 1.80-30.3mg/kg respectively. Both areas and levels of Cu and Pb contamination were low. Cd contents exhibited an obvious decreasing trend and As presented a similar law during these 10years. Further, emissions from different sources were analyzed to identify the possible reasons contributing to the metal pollution. Dramatic descending of waste water might be the top reason for Cd and As variations. Local flue gases and smoke emissions might not be the main sources contributing to Hg pollution, whereas atmospheric deposition at a larger scale was supposed to be the leading factor.

Micromechanical Properties of a New Polymeric Microcapsule for Self-Healing Cementitious Materials.

Self-healing cementitious materials containing a microencapsulated healing agent are appealing due to their great application potential in improving the serviceability and durability of concrete structures. In this study, poly(phenol-formaldehyde) (PF) microcapsules that aim to provide a self-healing function for cementitious materials were prepared by an in situ polymerization reaction. Size gradation of the synthesized microcapsules was achieved through a series of sieving processes. The shell thickness and the diameter of single microcapsules was accurately measured under environmental scanning electron microscopy (ESEM). The relationship between the physical properties of the synthesized microcapsules and their micromechanical properties were investigated using nanoindentation. The results of the mechanical tests show that, with the increase of the mean size of microcapsules and the decrease of shell thickness, the mechanical force required to trigger the self-healing function of microcapsules increased correspondingly from 68.5 ± 41.6 mN to 198.5 ± 31.6 mN, featuring a multi-sensitive trigger function. Finally, the rupture behavior and crack surface of cement paste with embedded microcapsules were observed and analyzed using X-ray computed tomography (XCT). The synthesized PF microcapsules may find potential application in self-healing cementitious materials.