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• A deep learning model was proposed to estimate the temperature exposure of mortar and concrete samples based on their SEM images. • A large dataset of 16,484 SEM images with temperature labels ranging from 20 to 800 °C was collected. • The generalizability of the model was evaluated by testing it on different mix proportions of mortar and concrete. • Visualization was applied to analyze the features learned by the model and to identify the regions of interest for different temperature levels. This study presents a framework for identifying the temperature experienced by fire-damaged mortar and concrete using scanning electron microscopy (SEM) images and deep learning. A dataset of 16,484 SEM images of cement paste mixes with varying water-to-binder ratios and pozzolanic materials, exposed to temperatures ranging from 200 to 800 °C was established. Then a deep-learning model based on a convolutional neural network (CNN) for SEM image classification was trained, achieving a high accuracy above 98 %. To test the method's generalizability, cement paste mixture with a different water-to-binder ratio, mortar mixture with sand inclusion, and concrete mixture with coarse aggregates were prepared and exposed to different temperatures. The predicted temperatures deviated from the target temperatures within 8.6 %. Finally, visualization of the deep learning model was used to identify the critical features that influenced the prediction. The outer hydration products with smaller pores had a higher influence on samples before heating, whereas porous dehydrated products were more influential in samples exposed to high temperatures. [ABSTRACT FROM AUTHOR]

Due to the dilution-induced early-age strength reduction, the glass powder (GP) dosage used in concrete to replace ordinary Portland cement (OPC) is restricted. This study used carbonation curing on GP blended cement pastes to overcome this obstacle. The experimental investigations concluded that mutual improvements could be achieved, where, in comparison to the carbonated OPC batch, not only the compressive strength of 20% GP-incorporated batches was higher for both early-age (increment of 13.4%, 1-day strength of 55.4 MPa) and late-age (increment of 11.2%, 28 days strength of 62.4 MPa), but the carbon sequestration degree was also promoted. According to the characterizations of mineralogy, microstructure, and phase evolution of the blended cement paste subjecting to carbonation curing, the addition of 20% GP induced a higher carbonation degree, smaller calcite crystal size, refined pore structure, and reduced porosity than that of pure OPC control references. The sustainability assessments confirmed that carbonated GP blended cement is a cleaner alternative to OPC. • Paste properties were improved by synergizing glass powder and carbonation curing. • The optimal glass powder substitution ratio in OPC pastes was 20%. • Carbonated glass powder blended cement was sustainable as an alternative to OPC. [ABSTRACT FROM AUTHOR]

Improving the adhesion between metal sheet and resin is an important issue for the development of high-performance fiber metal laminates (FMLs). In this study, a novel rare-earth surface modification is applied for the first time to enhance the interfacial bonding strength of titanium sheets and polyetheretherketone (PEEK). Density functional theory (DFT) calculations show that cerium element could form coordination bonds at the interfaces between metallic titanium and resin. The surface wettability of titanium sheet is boosted, which is beneficial to PEEK infiltration and physical adhesion improvement. Meanwhile, with the existence of coordination bonds at the interface, the interfacial shear strength between titanium and PEEK, and the flexural strength and interlaminar shear strength of CF/PEEK-Ti laminates are enhanced significantly. Therefore, the cerium surface modification method proposed in this study has great potentials for FMLs, which provides a new strategy for generating chemical bond at interfaces between metal and resin. [Display omitted] • Proposed a novel and facile rare-earth surface modification method. • The interface between titanium and PEEK was bonded by rare-earth coordination. • The single lap shear strength of rare-earth modified interface between titanium and PEEK had an increment of 178.0%. • The flexural strength (180.0%), and ILSS (40.0%) of rare-earth modified CF/PEEK-Ti composites were significantly enhanced. [ABSTRACT FROM AUTHOR]

• Compressive strength of both UHPC and mortar increases at 300 ℃ but decreases at higher temperature. • Post-fire water curing is more effective on recover the compressive strength of the UHPC mix and Mortar than the post-fire air curing. • Strength recovery of the Mortar is greater than that of the UHPC. • Precipitation of portlandite heals the coarsened microstructure and recovers compressive strength. This paper investigates effects of post-fire curing on strength recovery and changes in microstructure of ultra-high performance concrete (UHPC) and mortar. Specimens were heated to elevated temperatures 300, 600, and 900 °C with a heating rate of 1 °C/min. After cooling, the specimens were subjected to post-fire curing in either air or in water for 56 days. Compressive strength, X-ray diffraction (XRD), mercury intrusion porosimeter (MIP), and field emission scanning electron microscope (FESEM) tests were conducted to examine the changes at both macro and micro scale and to reveal deterioration mechanisms due to fire effect and healing mechanisms due to post-fire curing. The test results showed that compressive strength of both UHPC and mortar increased slightly after 300 °C exposure but decreased significantly at higher temperature due to the coarsening of microstructure. Post-fire curing in air showed very limited strength recovery since new curing products did not heal thermal cracks larger than 1 μm. On the other hand, curing in water led to substantial strength recovery of the mortar mix due to formation of portlandite which compactly filled the microcracks in fire-damaged samples. However, the loose ettringite phase formed in the UHPC mix did not contribute to regaining the initial compressive strength. [ABSTRACT FROM AUTHOR]

The weak interfacial bonding between fiber and matrix needs to be improved for obtaining good mechanical properties of carbon fiber/polyetheretherketone (CF/PEEK) composites due to the inert nature of both components. Organic sizing is a typical interface improvement method, but it is harmful to both the human and local environment. Here, a two-step process is proposed to modify PEEK for preparing an environmentally friendly water-based sizing agent, involving taking the ketone reduction via NaBH 4 and then an esterification reaction with phosphoric acid. This PEEK derivative has good thermal stability, and its dispersion in water is stable for one month. It improves the interface between CF and PEEK by increasing the wettability and surface roughness of CFs, ultimately enhancing the mechanical properties of composites. The two-step process of fabricating the PEEK derivative may have potentials in the industrial application of the polyaryletherketone family. [Display omitted] • Proposing a novel and facile two-step modification route on PEEK. • Preparing eco-friendly water-based phosphorylated PEEK sizing agent. • Excellent dispersion stability of phosphorylated PEEK in water over one month. • Enhancing interface between CF and PEEK by phosphorylated PEEK sizing. [ABSTRACT FROM AUTHOR]

The weak interfacial adhesion caused by the low wettability of carbon fiber (CF) and inert polyetheretherketone (PEEK) hinders the great application potential of CF/PEEK composites. In this study, the interface between CF and PEEK was modified by coating hydroxylated PEEK grafted onto multi-walled carbon nanotubes (M-HPEEK). Modified CFs by M-HPEEK sizing had rougher surfaces with more polar groups, showing decreased contact angle and increased surface energy. The wettability of these CFs was enhanced, beneficial to PEEK infiltration and physical adhesion improvement. As a result, the interlaminar shear strength, flexural strength, and flexural modulus of modified CF/PEEK composites were increased by 73.0% (84.7 MPa), 163.2% (906.2 MPa), and 84.8% (58.4 GPa), respectively. An improved interface with stress transferring was proved by the interface debonding failure changed to fiber crack and resin yield. M-HPEEK sizing is considered as a promising modification method to optimize the interface performance of composites. [Display omitted] [ABSTRACT FROM AUTHOR]

• The influences of moisture variations on ion transport and physical crystallization were discussed. • The respective contributions of chemical and physical attack to crystallization pressure were distinguished. • The deterioration in concrete performance was considered under the combined impacts of external sulfate attack and drying–wetting cycles. • A transport-chemical-physical–mechanical model was developed to evaluate and predict damage progression to concrete. When coupled with drying–wetting cycles, the deterioration process of concrete subjected to external sulfate attack (ESA) is significantly accelerated. The impact of moisture variations on ion transport was considered to establish a mass conservation equation with pore solution concentration as the variable. The contributions of chemical and physical attack to crystallization pressure were distinguished, and a bulk modulus reduction function was introduced to ascertain the stiffness deterioration. An ESA model was proposed and verified by comparing it to published experimental data, which could accurately predict the deterioration process of concrete under ESA and drying–wetting cycles. [ABSTRACT FROM AUTHOR]

The weak interfacial adhesion between carbon fiber (CF) and polyetheretherketone (PEEK) is a longstanding problem that hinders the applications of CF/PEEK composites. To solve this problem, a mixture sizing agent containing hydroxylated boron nitride (BNO) and polyetherimide (PEI) is synthesized to coat CF. In this study, BNO is synthesized via the liquid exfoliation method. The interfacial adhesion between CF and PEEK is improved using a mixture sizing layer of BNO and PEI on CF. The synergistic effects of hydrogen bonding, π-π interaction and good compatibility are evaluated to remarkably increase the miscibility and mechanical interlocking, ultimately enhancing the thermal conductivity, mechanical and tribological properties. Therefore, the PEI-BNO sizing layer on CF has proven to have great potential for high-performance CF/PEEK composites. [Display omitted] [ABSTRACT FROM AUTHOR]

The development of underground space is an important trend for urban infrastructure in cities supporting socio-economic activities, while it also results in an enormous accumulation of sediment waste, which consumes vast land resources, causes serious environmental problems and endangers public safety. It is urgent to explore pathways of recycling sediment waste with low carbon impact for sustainable infrastructure. This study employed calcination and alkali activators to recycle sediment waste into geopolymer paste. The mechanical properties and working performance of recycled geopolymer paste were investigated and the underlying mechanism of this recycling scheme was revealed with microscale characterizations. Results showed that the compressive strength of recycled geopolymer paste could reach 50 MPa. The environmental impact of geopolymer paste and cement-based paste has been analyzed via life cycle assessment (LCA). Recycled geopolymer paste can save 310 kg CO 2 eq/t of carbon emissions, which is 39% lower than that of cement-based material. Moreover, the multi-criteria approach was adopted to evaluate geopolymer paste and cement paste considering mechanical properties, working performance, carbon emissions, energy consumption and cost, and geopolymer paste exhibits better overall performance. The findings inspire a construction waste management strategy and contribute to low-carbon construction materials for sustainable urban infrastructure. • Sediment waste is recycled into geopolymer paste via calcination and alkali activator. • The optimum mix ratio range of geopolymer paste with sediment waste is determined. • Mechanical and environmental performance of geopolymer paste has been studied. • A sustainable sediment waste management strategy and a low-carbon construction material is inspired. [ABSTRACT FROM AUTHOR]

Low-carbon emission mortar samples were prepared using reactivated cementitious materials (RCMs) produced by calcinating hydrated cement paste with adjusted Ca/Si ratios. Carbonation curing was employed to enhance the cementing capacity of the RCMs and to sequestrate CO 2. The compressive strength, phase assemblage, microstructure, and environmental impacts of the mortars were analyzed. According to the results, the mortar sample produced with the RCM with a 10% addition of silica fume during calcination attained the highest compressive strength (35.3 MPa) after water curing, while higher silica contents were unfavorable because the low-lime calcium silicates that formed have limited water reactivity. Carbonation curing significantly promoted reactions of the RCMs and, thus, the compressive strength of the mortars compared to water curing. The amorphous and metastable calcium carbonates contributed more to the densification of the microstructure than the calcite. From the life cycle assessment, the RCM mortars had a significantly lower impact on global warming potential compared to Portland cement mortars. [Display omitted] [ABSTRACT FROM AUTHOR]