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Owing to of its freedom from energy inputs, radiative cooling is emerging as a frontier in renewable energy research. Recent advances in nanophotonic structures have enabled scalable passive daytime radiative cooling (PDRC), such as porous polymer films, which can spontaneously reflect solar irradiance and emit heat to the ultra-cold outer space. However, there is still limited fundamental understanding of these nanophotonic structures underlying the cooling effects of these porous polymer-based PDRC films. Hence, we performed optical simulations validated by experiments to quantify how the spatial distribution of nanopores in the polymer film affect its PDRC performance. Our simulation results showed that the influence of spatial distribution of pores on the PDRC performance replies significantly on solar reflectance. A gradient distribution of pores with random pattern can remarkably enhance solar reflectance under direct sunlight up to 153.4 %, while maintaining a slight variation of thermal emittance

The spraying method offers the advantages of environmental protection, convenient construction, and cost-effectiveness, making it widely used in pipeline structure repair. Given the complex service environment of pipelines, there is an urgent demand for high-strength and durable spraying materials. To achieve this goal, a PVA fiber reinforced cement mortar material (PFCM) with high early strength, excellent impermeability and stable acid corrosion resistance was developed through orthogonal test design. The optimal material was obtained through factors such as setting time, fluidity, compressive strength and flexural strength. The effects of the contents of fly ash, redispersible polymer powder and PVA fiber on the working and mechanical properties of the material were investigated, and further research was conducted on its tensile strength, impermeability, acid corrosion resistance. In addition, Thermogravimetric-differential Thermal Analysis (TG-DTA) was utilized to analyze the thermal stability of PFCM. X-ray diffraction (XRD) was utilized to analyze the composition of PFCM. Mercury intrusion porosimetry (MIP) was utilized to analyze the pore structure of PFCM, and the feasibility of the PFCM was verified. The results indicate that the contents of fly ash, redispersible polymer powder and PVA fiber have significant effects on the working and mechanical properties. The optimum initial setting time is 60–80 min, and the optimum fluidity is between 170 and 180 mm. The compressive strength and flexural strength of the mortar prepared with the optimum parameters are 102.5 MPa and 20 MPa, respectively. The material has an excellent spraying effect with no sagging, and exhibits high early strength, outstanding corrosion resistance, low porosity, and exceptional impermeability. This study lays the foundation for achieving high-quality spray repairs of underground drainage pipelines.

The increasing concern over electromagnetic wave (EMW) contamination has led to the emergence of the EMW-absorbing superstructure element. Cementitious composites typically possess poor electromagnetic wave reflectivity, but this was improved through 3D printing technology, which offers greater productivity and design flexibility. In this study, a new wave-shaped EMW absorbing superstructure was manufactured using 3D cement printing, and mechanical testing showed a significant improvement in flexural and shearing strength. Molecular dynamic simulation was utilized to investigate the mechanism of the enhanced mechanical properties at the molecular scale. The EMW absorption performance of the printed specimens was analyzed from 1 GHz to 18 GHz through the Naval Research Laboratory (NRL) equipment, exhibiting a significant improvement in reflectance, especially in the low-frequency domain. Based on experimental results, the optimized design of the superstructure was proposed, which possesses an average reflection loss of −25 dB, a peak reflectivity of −37.4 dB, and an absorbing bandwidth of 17 GHz. These findings suggest that the 3D-printed EMW absorber element has great potential for use in minimizing electromagnetic contamination in various applications.

Conductive fillers, such as graphite particles (GP), steel slags (SS), and ground granulated blast furnace slag (GGBS) have been widely utilized in designing electrically conductive cementitious composites (ECCC) for various applications, including traffic detection, structural health monitoring (SHM), and pavement deicing. Owing to the complex working field, a comprehensive understanding of the role that the conductive fillers played in ECCC is essential for designing high-performance ECCC. In the present study, mechanical and conductivity experiments were conducted to explore the influences of these fillers on ECCC performances in strengths and electrical resistance. In addition, the reactive molecular dynamic (MD) simulation was firstly performed to quantify the interfacial properties of GP, SS, and GGBS in ECCC at the molecular level. Simulation results indicated that the chemical components of these conductive fillers dominate the atomic interfacial properties. Mineral components in SS or GGBS, especially Al2O3 and SiO2, led to a stronger interfacial bonding with cement in comparison to graphite in GP. At last, a hybrid mixing design of GP and SS was proposed in this study, balancing the mechanical and conductive performance of ECCC.

Abstract To overcome the drawbacks caused by the intrinsic brittleness of cementitious materials, various types of fibres were incorporated as reinforcements. Extensive research on Ordinary Portland cement indicated that compared with the use of a single type of fibres, the mixed-use of multiple fibres can significantly improve both strength and toughness of the cementitious composites, which is referred to as the hybrid effect. However, such hybrid effect in multiple fibre-reinforced magnesium phosphate cement-based composite (HFRMC) still lack quantitative understanding. Therefore, this study conducted a series of experiments, including slump flow tests, compression tests, four-point bending tests and microstructure analysis, to investigate the hybrid effect of micro-steel fibres (MSF) and polypropylene (PP) fibres in HFRMC. Two types of mixed designs of HFRMC were conducted: 1. total fibres fraction (including both PP fibres and MSF) was fixed to be 1.6%; 2. PP fibres fraction was fixed to be 1.6% with different addition of MSF. Our results indicated that the slump flow of magnesium phosphate cement mortar varied around 7.6–8.8% with the hybrid use of MSF and PP fibres, while the flexural strength and toughness increased around 13.7–23.1% and 1.6–45.9%, respectively.

Waste glass is inert and non-degradable which leads to enormous environmental and sustainability troubles, but it can be reused in concrete due to the potential of the pozzolanic activity. This study proposes methods on activity excitation of waste glass powder (WGP) including mechanical, chemical, and mechanical-chemical activation. The results showed that the mortar containing 30% 75 μm WGP activated by the mechanical-chemical method was optimal to increase the mechanical property and reduce the detrimental expansion. In addition, the microstructural analysis was conducted to explore the activation effect on WGP and WGP-cement system. An artificial intelligence (AI) based multi-objective optimisation (MOO) model was proposed to seek the optimal mix proportions for the unconfined compression strength (UCS), alkali-silica reaction (ASR), and cost. A comprehensive dataset was investigated including 549 specimens for the UCS test and 366 test results for the expansion test. Random Forest (RF) model was utilized for the prediction of UCS and ASR values with hyperparameters tuned by a firefly algorithm (FA). The high correlation coefficients (0.93 for UCS and 0.91 for ASR) verified the feasibility of FA-RF. Subsequently, the FA-RF model was extended as the objective function for the mi-objective firefly algorithm (MOFA-RF) to obtain the consequent Pareto fronts. This paper combined the results of experiments, machine learning prediction, and multi-objective optimisation design for activated WGP mortar, which provided a comprehensive basis for the practical application.

The anti-collision pier plays an irreplaceable role in road traffic protection due to its significance. In this research, the biomimetic honeycomb structure was applied to internal anti-collision pier interior structures. The enhancement of mechanical strength and energy absorption characteristics was explored and optimized by five anti-collision pier honeycomb structures. Finite elements of the piers are designated as 650 mm in diameter and 850 mm in height. Polypropylene Acetate (PLA) material is utilized in this research due to its environment-friendly characteristics. Displacement loading in finite element simulation is 50 mm to the middle region of the model at YOZ direction. The energy-absorbing properties of five optimized honeycomb anti-collision piers at the same force position will be carefully compared. Moreover, the influence of internal hexagon direction-quantity configuration upon loading resistance under displacement loading is outlined. The results determined the best biomimetic structure to be three honeycomb shapes with a central triangle area, with maximum stress of 503.8 MPa and fracture displacement of 58.02 mm. Furthermore, the numerical simulation shows that the number of nest increases has a negative relationship with the effect upon force and deformation of the model. Moreover, the triangular central area is superior to the Y-shape central area in both mechanical strength and energy absorption performance.