Key Engineering Materials Vol. 1015

Abstract: Tall buildings with different structural systems can be exposed to explosive loading, and a proper understanding of their structural response under blast loads is crucial for robust structural design. This study investigates the structural performance of selected tall structural systems - shear wall frame, outrigger, and tube-in-tube systems - under different blast load effects. Nonlinear finite element analysis was performed using commercial package ETABS with blast loads applied as time-history functions for various charge weights and standoff distances. Structural responses were compared in terms of displacement and inter-story drift. Results showed that the tube-in-tube system performed relatively better in terms of displacement and inter-story drift as standoff distance increased and charge weight was constant. When explosive charge weights increased, and standoff distance was constant, the tube-in-tube system displayed better performance with respect to displacement, whereas the outrigger system was the optimum with reference to inter-story drift. The overall study indicates that selecting a tall structural system for better resilience against blast loading depends on specific aspects of structural behavior, identified as the required criteria.

Abstract: Serious efforts are currently undertaken to produce sustainable composite building materials by exploiting industrial by-products. This study examines the use of industrial by-products, specifically limestone filler and silica fume, as alternatives to cement and fine aggregates (washed or non-washed sand), for the production of a novel sustainable cementitious masonry block. The research involved the design of various mixtures with different proportions of the aforementioned raw materials and the evaluation of their mechanical, durability and thermal performance. The findings reveal that, depending on the type of sand used (washed or non-washed), high volumes of limestone filler can be incorporated into the mixtures, without compromising the overall performance of the end-product. This approach not only promotes the use of waste by-product materials in the design and production of composite building materials, but also contributes to more eco-friendly and sustainable construction practices.

Abstract: The cement production process significantly contributes to greenhouse gas emissions, accounting for 25% of total industrial emissions. This study systematically examined new, underutilized materials—sewage sludge ash (SSA), marble waste (MW), and calcined clay (CC)—to evaluate their effects when partially replacing white Portland cement (WPC) in cement paste formulations. Various replacement proportions (10%, 20%, and 30%) were tested, along with different treatment temperatures (600°C, 630°C, 730°C, and 850°C) for SSA and CC. To gain a deeper understanding of the resulting materials, analyses such as XRF, XRD, and SEM were conducted. The highest compressive strength recorded for the 28-day cured cement paste was 91 MPa when 20% SSA (treated at 600°C) was used, compared to just 53 MPa for the control sample. Conversely, CC exhibited minimal enhancement in compressive strength, while MW had detrimental effects. Additionally, replacing WPC with SSA and CC at 9% and 21% resulted in slight improvements in compressive strength. This research highlights the potential of utilizing underexploited materials like SSA to improve the mechanical and chemical properties of cement paste, indicating that further investigation is necessary to enhance environmental sustainability.

Abstract: Limestone fillers are increasingly recognized as a sustainable alternative to cement and sand in mortar and concrete mixtures, driven by environmental concerns over the excessive use of natural resources and raw materials. This study investigates the potential exploitation of different limestone fillers, waste products of the quarrying industry, in the production of cementitious composites. The investigation includes the physico-mechanical characterization of a number of mixtures with different percentages of limestone fillers used as partial replacement to sand. The results show that increasing the limestone filler content negatively influences the mechanical performance of the hardened end-products, decreases their density and increases their open porosity. At the same time, increased clay particle content in the limestone filler decreases the workability of the fresh mixtures.

Abstract: The exponential increase in global plastic wastes dangerously impacts the environment and human health. In this study, Polyethylene Terephthalate (PET), High-density Polyethylene (HDPE), Polypropylene (PP), and Polymethyl methacrylate (PMMA) were recycled into sandwich panels and polymer blends. Recycled PET (rPET) fibers, with 25 and 50 fibers, were used as the middle layer for the sandwich panels. The face layers were made from the recycled HDPE (rHDPE), recycled PP (rPP), and recycled PMMA (rPMMA). The weak interaction between rPET fibers and the face panels resulted in low mechanical performance. The sandwich panel with rPMMA as the face layers and 25 rPET fibers as the core exhibited good overall mechanical performance. The stiffness of sandwich panels was improved. The polymer blends were prepared using rPET at 70 wt% and other plastic wastes at 30 wt%. The addition of a compatibilizer can enhance the mechanical properties of polymer blends. The rPET/ rPP blend and rPET/ rHDPE blend showed slightly higher mechanical performance compared to the rPET/ rPMMA blend. All polymer blends exhibited higher flexural strength, impact strength, and hardness compared to neat rPET.