•Sand 5% and proper compaction significantly improved durability performance.•SCMs have a positive influence on the mechanical and durability of pervious concrete.•The optimum content of SCMs was 10% ...based on mechanical and durability performance.•Latex improved the mechanical property, but did not noticeably improve the durability.•The combined attack induced more severe surface deterioration and damages.
This study evaluates the performance of pervious concrete subjected to rapid freeze–thaw (F-T) cycling, calcium leaching and the combined attack of calcium leaching and F-T cycling. Silica fume, metakaolin and SBR polymer emulsion were incorporated at different levels into pervious concrete mixes to improve strength and durability performances. The results indicated that the addition of 5% fine sand and proper compaction had a positive influence on improving the resistance of pervious concrete to F-T cycling. The increase of supplementary cementitious materials (SCMs) from 5% to 10% significantly improved the resistance to rapid F-T cycling and to the combined attack of calcium leaching and F-T cycling. The optimum content of SCMs was 10% based on the mechanical and durability performance of pervious concrete with acceptable permeability. Calcium leaching in 6 M NH4NO3 solution combined with F-T cycling induced severe surface deterioration and internal damage compared to individual attacks of F-T cycling or leaching. Compared with control and polymer-modified mixes, pervious concrete incorporated SCMs possessed better resistance of calcium leaching and frost. The morphological changes caused by calcium leaching exhibits the decreased volume fraction of solid phases in a cement matrix and consequently increased the porosity, which ultimately degraded strength and durability performance of pervious concrete.
•Progress on graphene-cement composites have been comprehensively reviewed.•Graphene-based NanoSheets (GNS) significantly enhance cement composites properties.•Three main challenges to implement GNS ...in the construction field were identified.
Graphene and graphene-based nanosheets (GNS) possess extraordinary mechanical, chemical, thermal and electrical properties, enabling attractive applications, ranging from structural strength/durability improvement, anti-corrosion, to self-cleaning surfaces and energy saving. Recent extensive research demonstrates that GNS also have the ability to transform conventional construction materials into smarter, stronger and more durable advanced composites. This review provides a comprehensive overview on developments and novelties in the fabrication, properties and applications of GNS in enhancing the strength and durability of concrete composites, pointing out the main challenges and future perspectives for GNS in the construction field.
Designing organic components that can be used to construct porous materials enables the preparation of tailored functionalized materials. Research into porous materials has seen a resurgence in the ...past decade as a result of finding of self‐standing porous molecular crystals (PMCs). Particularly, a number of crystalline systems with permanent porosity that are formed by self‐assembly through hydrogen bonding (H‐bonding) have been developed. Such systems are called hydrogen‐bonded organic frameworks (HOFs). Herein we systematically describe H‐bonding patterns (supramolecular synthons) and molecular structures (tectons) that have been used to achieve thermal and chemical durability, a large surface area, and functions, such as selective gas sorption and separation, which can provide design principles for constructing HOFs with permanent porosity.
HOF the shelf: Hydrogen‐bonded organic frameworks (HOFs) are described systematically based on hydrogen‐bonding patterns (supramolecular synthons) and molecular structures (tectons). HOFs can show thermal and chemical durability, a large surface area, and permanent porosity.
Abstract
Generating sustainable electricity from ambient humidity and natural evaporation has attracted tremendous interest recently as it requires no extra mechanical energy input and is deployable ...across all weather and geography conditions. Here, we present a device prototype for enhanced power generation from ambient humidity. This prototype uses both heterogenous materials assembled from a LiCl-loaded cellulon paper to facilitate moisture adsorption and a carbon-black-loaded cellulon paper to promote water evaporation. Exposing such a centimeter-sized device to ambient humidity can produce voltages of around 0.78 V and a current of around 7.5 μA, both of which can be sustained for more than 10 days. The enhanced electric output and durability are due to the continuous water flow that is directed by evaporation through numerous, negatively charged channels within the cellulon papers. The voltage and current exhibit an excellent scaling behavior upon device integration to sufficiently power commercial devices including even cell phones. The results open a promising prospect of sustainable electricity generation based on a synergy between spontaneous moisture adsorption and water evaporation.
•The impact of MWCNT on properties of regular and high-performance concrete was tested.•Self-sensing as stress detection in regular and HP concrete was compared using cyclic compression.•Crack ...detection was evaluated by combining wedge splitting test with digital image correlation.•The MWCNT addition enhanced stress detection and enabled microcracking detection.
Concrete is the worldwide most utilized construction material because of its very good performance, forming ability, long-term durability, and low costs. Concrete is a brittle material prone to cracking. Extensive cracking may impact durability and performance over time considerably. The addition of a small amount of carbon nanotubes (CNT) increases the concrete’s overall electrical conductivity, enabling internal structure condition monitoring (self-sensing). This article presents the mechanical and self-sensing properties of regular and high-performance concrete (HPC) with multi-wall carbon nanotubes (MWCNT). The stress detection was investigated in cyclic compression, while damage detection was assessed by means of wedge splitting tests combined with the digital image correlation (DIC) method. The results proved that a small addition of MWCNT (0.05% and 0.10%) enhances the stress detection capabilities and enables the monitoring of microcracking.
•The research adopted scientometric review in graphene oxide (GO).•Science mapping and in-depth review were adopted as research methods.•GO-reinforced cement composites remain a new research ...area.•Durability in GO-reinforced cement composites has not been widely investigated.•Main research themes and research directions in GO-reinforced cement composites are provided.
Adopting a holistic review approach, this study started from the scientometric analysis by analyzing the mainstream journals, keywords, scholars, publications, and institutions active in the research of cement composites reinforced with graphene oxide (GO). Further statistical summary of research themes and in-depth discussion addressed the current research findings and gaps in terms of workability, mechanical properties, durability, and other issues when adding GO into cementitious materials. Recommendations for future research were provided, including but not limited to the necessity to study the long-term mechanical properties of cement composites reinforced with GO, and the application of GO in concrete.
One of the most promising strategies to manage the large volume of construction and demolition (C&D) waste is recycling and utilizing it for the production of new concrete. However, recycled concrete ...aggregate (RCA) derived from C&D waste possesses relatively higher porosity and water absorption capability, which often limits its wild utilization. In this study, pozzolan slurry (includes silica fume, nano-SiO2, and fly ash slurries) and CO2 treatments as enhancement methods for RCA were investigated. Test results showed that CO2 treatment was more effective in reducing water absorption and enhancing fluidity, whereas pozzolan slurry treatment could decrease fluidity. Mortars prepared with treated RCA exhibited better mechanical strength and higher resistance towards carbonation and chloride-ion diffusion than those with untreated RCA. Both pozzolan slurry and CO2 treatments enhanced not only the properties of RCA, but also the old and new interfacial transition zones (ITZs) as demonstrated in the measured micro-hardness and SEM observation.
Recently, the development of high-performance non-platinum electrocatalysts for fuel cell applications has been gaining attention. Palladium-based nanoalloys are considered as promising candidates to ...substitute platinum catalysts for cathodic and anodic reactions in fuel cells. Here, we develop a facile route to synthesize dendritic palladium-copper-cobalt trimetallic nanoalloys as robust multifunctional electrocatalysts for oxygen reduction and formic acid oxidation. To the best of our knowledge, the mass activities of the dendritic Pd
Cu
Co
nanoalloy toward oxygen reduction and formic acid oxidation are higher than those previously reported for non-platinum metal nanocatalysts. The Pd
Cu
Co
nanoalloys also exhibit superior durability for oxygen reduction and formic acid oxidation as well as good antimethanol/ethanol interference ability compared to a commercial platinum/carbon catalyst. The high performance of the dendritic Pd
Cu
Co
nanoalloys is attributed to a combination of effects, including defects, a synergistic effect, change of d-band center of palladium, and surface strain.
Perovskite‐based electrocatalysts are one of the most promising materials for oxygen evolution reaction (OER), but their activity and durability are still far from desirable. Herein, we demonstrate ...that the double perovskite LaFexNi1−xO3 (LFNO) nanorods (NRs) can be adopted as highly active and stable OER electrocatalysts. The optimized LFNO‐II NRs with Ni/Fe ratio of 8:2 achieve a low overpotential of 302 mV at 10 mA cm−2 and a small Tafel slope of 50 mV dec−1, outperforming those of the commercial Ir/C. The LFNO‐II NRs also show high OER stability with slight current decrease after 20 h. The enhanced activity is explained by the improved surface area, tailored electronic structure as well as strong hybridization between O and Ni.
Double perovskite nanorods LaFexNi1−xO3 (LFNO NRs) with reduced diameter have been successfully created and adopted as efficient OER catalysts. The optimized LFNO NRs have proper d‐band electronic structure, enabling strong binding between adsorbates and NRs, which boosts their intrinsic OER activity.
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