Mehdi Zadshir

The increasing global population has intensified the demand for energy and food, leading to significant greenhouse gas (GHG) emissions from both sectors. To mitigate these impacts and achieve Sustainable Development Goals (SDGs), passive thermal storage methods, particularly using phase change materials (PCMs), have become crucial for enhancing energy efficiency and reducing GHG emissions across various industries. This paper discusses the state of the art of bio-based phase change materials (bio-PCMs), derived from animal fats and plant oils as sustainable alternatives to traditional paraffin-based PCMs, while addressing the challenges of developing bio-PCMs with suitable phase change properties for practical applications. A comprehensive process is proposed to convert bacon fats to bio-PCMs, which offer advantages such as non-toxicity, availability, cost-effectiveness, and stability, aligning with multiple SDGs. The synthesis process involves hydrolysis to break down fat molecules obtained from the extracted lipid, followed by three additional independent processes to further tune the phase change properties of PCMs. The esterification significantly decreases the phase transition temperatures while slightly improving latent heat; the UV-crosslinking moderately raises both the phase transition temperature and latent heat; the crystallization remarkably increases the both. The future research and guidelines are discussed to develop the large scale manufacturing with cost effectiveness, to optimize synthesis process by multiscale modeling, and to improve thermal conductivity and latent heat capacities at the same time.

When cylinders are packed and wrapped by the bands around the surface, the effective elastic behavior in the cross section of the assembly, which is of significance to its stability and integrity, can be controlled by the wrapping force in the band. The wrapping force is transferred to the cylinders through the Hertz contact between each pair of neighboring cylinders, which is validated by the experiments. The Singum model is introduced to study the mechanical behaviors of the packed cylinders with two-dimensional (2D) packing lattices, in which an inner cylinder is simulated by a continuum particle of Singum and the inter-cylinder force is governed by the Hertz contact model so as to derive the effective stress-strain relationship. The wrapping force will produce configurational forces given a displacement variation, which significantly changes the effective stiffness of the packed cylinders. The hexagonal packing exhibits isotropic elasticity whereas the square packing is anisotropic. The efficacy of our model is demonstrated by comparing the closed form elasticity against the numerical simulation and the previous models. The explicit form of elasticity can be used for packing design and quality control of cable construction and installation.

In this work, the effect of ultraviolet (UV) radiation on samples of asphalt binder mixed with crumb rubber is studied. Two sets of samples are characterised using a PG 64-22 neat binder with different percentages of rubber particles being 0, 16.6, and 20.0 wt.%. One set of the samples was stored at ambient temperature (called the unaged set) and the other was inserted inside an accelerated weathering tester for 100 h (called the UV-aged set). Thermal conductivity, chemical indices, rheology, and morphology of both sets of samples are tested using the flash method, differential scanning calorimeter (DSC), Fourier-Transform Infrared Spectroscopy (FTIR), dynamic shear rheometer (DSR), and Scanning Electron Microscope (SEM), respectively. Results show that the addition of rubber leads to a reduction of specific heat for the rubber-modified binders. Specific heat capacities of the three UV aged samples are larger than those of their unaged counterparts, and the 16.6%-aged has the highest value. FTIR spectra of the three unaged samples are very similar, whereas distinct changes occur after UV exposure. The normalised absorbance of the peak associated with S = O group increases and the peak for the aliphatic group decreases after UV aging, showing some evidence of oxidation due to UV aging. Use of crumb rubber in the binder decreases the thermal conductivity and 20.0 wt.% sample is even less conductive compared to the 16.6 wt.%. At all temperatures above 25°C, aged samples have lower thermal conductivity than the unaged ones, except neat binder which is opposite. Rheological measurements show that the complex modulus of the samples increases with the addition of rubber particles and also after aging. However, 16.6% rubber-modified sample shows the least increase in modulus after aging. Microscopic morphology shows that UV radiation causes cracks in both neat and rubber modified binder. Smaller cracks are seen to form, and the cracked pieces are stuck together in the rubber modified binders, whereas less cohesion between the cracks is observed in the neat binder.

This study examines the merits of applying a biomodifier (Bio-binder, Sustainable Infrastructure Material Lab, NC A&T State University, Greensboro, North Carolina) as a fog sealant on the surface of bituminous materials to delay aging specifically caused by ultraviolet (UV) radiation during pavement service life. This study uses four types of bituminous-based materials: an asphalt binder [Performance Grade (PG 64-22) and three types of crack sealants with varying polymer content and different viscosities. Materials were prepared in small samples on aluminum plates and aged under continuous UV and UV/moisture/condensation conditioning. Changes in the chemical characteristics of the materials were then analyzed using Fourier-transform infrared spectroscopy and energy-dispersive X-ray spectroscopy. The results show that the oxygen uptake of bituminous materials after exposure to UV aging are significantly lower in specimens covered with Bio-binder compared with uncoated ones. The complex modulus and creep compliance were measured using a dynamic shear rheometer. The complex modulus for asphalt binder samples showed an increase that could be due to partial diffusion of the biomodifier in the specimens. However, in sealant samples in which the Bio-binder was removed prior to performing the experiments, the shear modulus showed a significant decrease, indicating that the sealants covered with Bio-binder remained softer compared with the uncovered samples. The results also showed a higher nonrecoverable creep compliance and a lower percent recovery at 3.2 kPa strain rate for specimens coated by Bio-binder compared with the samples with no coating, showing that the fog sealant can effectively improve properties of the sealant samples. Overall, the findings demonstrate that Bio-binder can be a promising candidate to be used as a fog sealant for bituminous binder and crack sealants to delay UV aging.

This paper reports an experimental study carried out to investigate the effects of using metakaolin (MK) and rice husk ash (RHA) as a partial replacement material for cement, and polypropylene (PP) as an additive, on the mechanical and water absorption properties of mortar. Cement mortar was produced using various replacement ratios of metakaolin ranging from 5 to 15%, and of rice husk ash ranging from 10 to 30%, by weight of cement. The PP fiber content considered was constant at 0.3%. Compressive strength, flexural strength, water absorption, ultrasonic pulse velocity (UPV) and scanning electron microscopy (SEM) analysis are reported in this paper. Results revealed that the combination of metakaolin, rice husk ash, and PP provided a positive influence on the mechanical properties of mortar. The samples incorporating the replacement of cement with a combination of 10% MK, 10% RHA, and 0.3% PP fiber showed better mechanical characteristics than the other mortar samples. In terms of water absorption, the addition of PP fiber reduced the permeability when compared with the mixtures with 15% MK and 10–30% RHA, and results indicated a higher absorption in comparison with the mortar containing 5–10% MK.