Multifunctional Lightweight Aggregate Containing Phase Change Material and Water for Damage Mitigation of Concrete

This paper presents an innovative concept of multifunctional lightweight aggregate, which is produced by loading phase change material (PCM) into the interior of lightweight sand (LWS) and sealing the surface pores using water. The PCM loaded in the LWS functionalizes it as a temperature management agent in concrete, and the water in surface pores enables internal curing. It has been found that the particle shape and pore structure of crushed expanded shale LWS makes it an ideal carrier for PCM, loading sufficient PCM and maintaining better (compared to natural sand) mechanical interlocking. When coupled with the internal curing effect, the LWS yields an interpenetrated interfacial transition zone with the cement paste, leading to a compressive strength comparable to natural sand mortar. The hydration products penetrated into the surface pores also helps stabilizing PCM in the LWS. However, any PCM residuum non-stabilized in LWS tends to compromise the strength. Under an optimized scenario, the LWS-PCM composite aggregate is produced by grading, PCM impregnation, rinsing, and water saturation. A mortar proportioned with this aggregate yields comparable 28-day strength to the reference mortar and a 63% lower autogenous shrinkage (because of internal curing). Furthermore, it shows a 7 ⁰C lower semi-adiabatic temperature rise, delayed appearance of peak temperature and gentled cooling curve. These results indicate that the functional aggregate can effectively mitigate the risk of thermal cracking in early-age mass concrete. In addition, PCM remained in aged concrete has a potential to improve its adaptivity to temperature fluctuations in the service environment

Development And Characterization Of Coal-Based Thermoplastic Composite Material For Sustainable Construction

The exploitation of coal and the disposal of waste plastic present significant environmental and economic challenges that require sustainable and profitable solutions. In response, we propose a renewable construction composite material of coal-based thermoplastic composite (CTC) that can be made from low-grade coal and plastic waste. We developed and tested the hot-press fabrication method for this CTC, using coal with a maximum particle size of 4.75 mm and recycled high-density polyethylene (HDPE). The effects of the coal fraction (50–80 wt.%) on compressive properties, thermal properties, microstructure, and ecological and economic efficiencies of the CTC were investigated. Test results revealed that the compressive strength and modulus decrease as the coal fraction increases. However, the thermal properties, including thermal conductivity and specific heat, increase with higher coal contents. Compared to concrete, the CTC has about half the thermal conductivity and twice the specific heat, making it a more energy-efficient construction material. Microstructure testing helped to reveal the mechanisms behind the above behaviors of CTC from the observation of binder volume, bonding quality between coal and HDPE, and porosity variation. The life cycle analysis indicated that the CTC production reduced embodied energy, carbon footprint, and cost by up to 84%, 73%, and 14%, respectively. Therefore, we recommend the CTC with 50–70% coal fraction as an innovative construction material with satisfied mechanical and thermal properties, better cost efficiency, and a reduced ecological impact

Yelp Reviews and Food Types: A Comparative Analysis of Ratings, Sentiments, and Topics

This study examines the relationship between Yelp reviews and food types, investigating how ratings, sentiments, and topics vary across different types of food. Specifically, we analyze how ratings and sentiments of reviews vary across food types, cluster food types based on ratings and sentiments, infer review topics using machine learning models, and compare topic distributions among different food types. Our analyses reveal that some food types have similar ratings, sentiments, and topics distributions, while others have distinct patterns. We identify four clusters of food types based on ratings and sentiments and find that reviewers tend to focus on different topics when reviewing certain food types. These findings have important implications for understanding user behavior and cultural influence on digital media platforms and promoting cross-cultural understanding and appreciation

In Situ Monitoring Of The Hydration Of Calcium Silicate Minerals In Cement With A Remote Fiber-optic Raman Probe

This study utilized a novel in situ fiber-optic Raman probe to continuously monitor the hydration progress of tricalcium silicate (C3S) and dicalcium silicate (C2S) without the need for sampling, from early hydration stage to later stages, and from fresh to hardened states of paste samples. By virtue of the remarkable ability of this technique in characterizing either dry or wet and crystalline or amorphous samples, the hydration processes of C3S and C2S pastes with different water-to-solid (w/s) ratios could be monitored from the start of the hydration reaction. The main hydration products, calcium silicate hydrate (C–S–H) and portlandite/calcium hydroxide (CH), have been successfully identified and continuously monitored for variations in their respective amounts in situ. The effect of w/s ratio on the hydration processes of C3S and C2S pastes was also considered. Meanwhile, the x-ray diffraction (XRD) and thermogravimetric analysis (TGA) results showed a great correlation with the in situ Raman test results about hydration products, which demonstrated the reliability of this technology. Moreover, the signal-to-noise ratio (SNR) of this Raman probe is significantly superior to existing technologies for in situ fiber-optic Raman spectroscopy. This remote fiber-optic Raman probe enables the use of Raman spectroscopy in future construction projects for on-site monitoring and evaluation of health conditions and performance of concrete structures

NO Reduction By Propane Over Monolithic Cordierite-based Fe/Al2O3 Catalyst: Reaction Mechanism And Effect Of H2O/SO2

The selective reduction of NO by C3H8and the sensitivity to H2O and SO2have been studied over monolithic cordierite-based Fe/Al2O3catalysts, which were prepared by the sol–gel and impregnation method. The catalysts were investigated by N2 adsorption, X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) techniques. Results showed that NO reduction was more than 90% in the absence of oxygen at 500 °C and in the presence of oxygen at 600 °C respectively. In a continues test of 12 h at 600 °C, 0.02% of SO2caused an irrecoverable decrease of NO conversion from 94% to 85% and 2.5% of H2O caused a drop of NO conversion from 86% to 56%, while NO conversion totally recovered when H2O was removed. The catalysts lost 15% of the initial activity after a hydrothermal treatment due to the agglomeration of iron oxide nanorods. Sulphidation treatment caused about a loss of 30% of the initial activity because of the deposited SO42−species. In situ study by DRIFTS indicated that coexisting H2O influenced the formation NO2 ad species and unidentate nitrate, while SO2 slightly inhibited the formation of NO2/NO3−species but promoted the formation of acetate/formate species during NO reduction by C3H8. Based on the results, a preliminary mechanism was proposed and discussed. The results may help understand the fundamental performance of monolithic cordierite-based Fe/Al2O3catalysts and provide some reference for SCR-HC catalyst design

MIM4D: Masked Modeling with Multi-View Video for Autonomous Driving Representation Learning

Learning robust and scalable visual representations from massive multi-view video data remains a challenge in computer vision and autonomous driving. Existing pre-training methods either rely on expensive supervised learning with 3D annotations, limiting the scalability, or focus on single-frame or monocular inputs, neglecting the temporal information. We propose MIM4D, a novel pre-training paradigm based on dual masked image modeling (MIM). MIM4D leverages both spatial and temporal relations by training on masked multi-view video inputs. It constructs pseudo-3D features using continuous scene flow and projects them onto 2D plane for supervision. To address the lack of dense 3D supervision, MIM4D reconstruct pixels by employing 3D volumetric differentiable rendering to learn geometric representations. We demonstrate that MIM4D achieves state-of-the-art performance on the nuScenes dataset for visual representation learning in autonomous driving. It significantly improves existing methods on multiple downstream tasks, including BEV segmentation (8.7% IoU), 3D object detection (3.5% mAP), and HD map construction (1.4% mAP). Our work offers a new choice for learning representation at scale in autonomous driving. Code and models are released at https://github.com/hustvl/MIM4

Evaluation Of Carbonation Resistance Of Paint Coated Concrete For Buildings

When evaluating the carbonation resistance of paint coated concrete, the effects of both the strength grade and the curing conditions (standard curing and accelerated curing) of concrete substrate on carbonation resistance of paint coated concrete were investigated. The concept of the carbonation suppression ratio of paint was presented for evaluation of the anti-carbonation performance of the two types of paints (exterior and interior paints) when applied to a reference concrete substrate. The test results showed a good linear relationship between the carbonation depths of the paint coated concrete and the square root of exposure times. Concrete with higher strength grade exhibited greater carbonation resistance. The carbonation depth of the C35 standard cured concrete was reduced by 56% in comparison with that of the C25 standard cured concrete. It was found that concrete substrate prepared by accelerated curing method displayed lower carbonation resistance than standard cured concrete. Compared with the standard cured specimen, the carbonation depth of the accelerated cured specimen increased by 61% for the control C25 concrete and by 56% for the control C35 concrete. This phenomenon was attributed to the formation of a higher volume of capillary pores in concrete prepared by accelerated curing. Additionally, the exterior paint had a higher carbonation suppression ratio than the interior paint. The suppression ratios of the exterior and interior paint coatings applied on C25 standard cured concrete were 71% and 56%, respectively. The exterior paint coated concrete had a better carbonation resistance with longer effective blockage time and smaller carbonation rate

Investigation of Corrosion Mechanism of Ribbed Mild Steel Bars Coated with Magnesium Potassium Phosphate Cement Paste

This Study Investigated the Anti-Corrosion Performance of Magnesium Potassium Phosphate Cement (MKPC) Paste Applied to the Surface of Ribbed Mild Steel Bars – Which Was Exposed to Simulated Accelerated Corrosive Environment. Four Electrochemical Approaches Were Used Including Open-Circuit Potential (OCP), Electrochemical Impedance Spectroscope (EIS), Polarization Resistance (PR) and Potentiodynamic Polarization (PDP) over a Period of 5376 H (224 Days). Moreover, Visual Inspection, Optical Microscope, and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) Were Used to Assess the Extent of Corrosion on the Samples. to Understand the Mechanism of Corrosion Protection of the Coating System, X-Ray Photoelectron Spectroscopy (XPS) Was Employed to Characterize the Chemical Groups on the Surface of Mild Steel, and the Chemical Changes in the Coating Layer Were Characterized using Thermogravimetric/differential Thermal Analysis (TG/DTA) and X-Ray Diffraction (XRD). the MKPC Paste Coated Bars Were Compared with Not Only Uncoated Bars, But Also Bars Coated with Ordinary Portland Cement (OPC) that is Known to Passivate Steel Due to its High Alkalinity. Results Indicated that MKPC Paste Coating Layer Could Effectively Protect the Ribbed Mild Steel Bars, and its Protectiveness Significantly Surpassed that of OPC. Both the De-Passivation Effects of Chloride Ions and Carbonation of the OPC Resulted in Relatively Severe Corrosion of the OPC Coated Bars during the Long Exposure Duration; While the Anti-Corrosion Merit of the MKPC Paste Coating Layer Could Be Attribute to a Double-Protection System– the Dense Microstructure of MKPC and the Formation of an Iron (III) Phosphate Passivation Layer between the Substrate Steel and the MKPC Paste Coating Layer

Characterization Of Alkali-Silica Reaction (ASR) Products And C-S-H Using SWIR Spectroscopy For Nondestructive Detection Of ASR

This study explores the feasibility of characterizing alkali-silica reaction (ASR) products and calcium silicate hydrates (C-S-H) from short-wave infrared (SWIR) spectroscopy. ASR products and C-S-H samples with different Ca/Si ratios were synthesized and analyzed through XRD, 29Si nuclei magnetic resonance (NMR) and SWIR spectroscopy. Fourier-transform infrared spectroscopy (FTIR) was collected to help interpret the results from the SWIR spectroscopy. The obtained spectroscopic features were applied to quantify the ASR product abundance denoted by the length expansion of mortar bars after an accelerated ASR test. The results show that the SWIR spectra of the synthetic ASR gels are similar regardless of the crystallization status but differ from C-S-H samples. ASR products show only one major absorption at 5210 cm-1 in SWIR while C-S-H samples yield two significant bands at 5820 cm-1 and 4370 cm-1. Shoulders around 6865 cm-1 and 5102 cm-1 are two unique features for ASR products. The length change of mortar bars after the accelerated ASR test logarithmically increases the shoulder absorptance around 6865 cm-1 irrespective of the alkali environment. The disappearance of the shoulder 5102 cm-1 is exclusively observed in the K dominated ASR environment. However, this shoulder absorptance is approximately linear to the ASR expansion of the mortar bars cultivated in Na thriving environment

Development Of Structural-functional Integrated Energy Storage Concrete With Innovative Macro-encapsulated PCM By Hollow Steel Ball

Phase change materials (PCMs) have great potential for applications in energy efficient buildings. In this study, an innovative method of macro-encapsulation of PCM using hollow steel balls (HSB) was developed and the thermal and mechanical performance of PCM-HSB concrete was examined. The macro-encapsulation system (PCM-HSB) was attached with a metal clamp (c) for better mechanical interlocking with the mortar matrix. The latent heat of PCM-HSB-c that can be acquired is approximately 153.1 J/g, which can be considered to rank highly among PCM composites. According to the self-designed thermal performance evaluation, the PCM–HSB-c concrete panel is capable of reducing and deferring the peak indoor temperature. The indoor temperature of the room model using PCM-HSB-c panels was significantly lower than the ones with normal concrete panels by a range of 3–6%. Furthermore, the test room using a higher PCM-HSB-c content demonstrated a greater ability to maintain a lower indoor room temperature for a longer period of time during heating cycles. In consideration of the mechanical properties, thermal performance and other aspects of cost factors, 50% and 75% PCM-HSB-c replacement levels are recommended in producing concrete