A Green Way of Producing High Strength Concrete Utilizing Recycled Concrete

Multiple studies have investigated the influence of recycled aggregates derived from concrete waste on the efficacy of structural concrete manufactured in recent times. By utilizing recycled aggregates obtained from construction and demolition debris, it is possible to safeguard natural aggregate resources, reduce the demand for landfill space, and promote the utilization of sustainable building materials. However, compared to natural aggregate, bonded cement mortar on recycled concrete aggregate exhibits higher porosity, greater water absorption capacity, and lower strength. The mechanical and durability characteristics of freshly poured and hardened concrete made from recycled concrete aggregate are adversely affected as a result. This study presents comprehensive experimental research aimed at examining the residual mechanical properties and resistance to acid attack of normal and high-strength mixes of recycled aggregate concrete (RAC) using the compressible packing model. Recycled aggregate was employed as both coarse and fine aggregate. The recycled concrete samples were prepared in a manner that corresponded to the proportions of both the coarse and fine aggregates. Twelve mixtures were designed and cast, and their performance was evaluated based on various strength parameters (compressive strength, splitting tensile strength, and flexural strength) as well as acid attack resistance properties (porosity and ultrasonic pulse velocity). The findings indicate that recycled concrete aggregate can be utilized in the production of high-strength concrete, with mechanical property values that are significantly acceptable compared to concrete containing natural aggregates. Moreover, the addition of Silica Fume as a cement replacement in concrete plays a crucial role in enhancing sulphate resistance. In terms of concrete product utilization, recycled concrete and its significance in this study played a crucial role in environmental preservation. Doi: 10.28991/CEJ-2023-09-10-08 Full Text: PD

Gender considerations in optimizing usability design of hand-tool by testing hand stress using sEMG signal analysis

To design comfortable and efficient hand tools, an objective measurement such as using surface electromyography (sEMG) is required, where the ergonomic design tries to find the most optimal and most fit design of hand-tool that doesn't cause stress on the hand muscles. The hand tool design optimization will be demonstrated in this study on designing shampoo bottles, where the design of bottle and its compatibility with the slippery watery area, in addition to the aesthetic considerations are important issues that must be taking by the manufacturers concerned with such industries. Six different designs of shampoo bottles, as outcomes of industrial design graduation project in the department of Industrial design at our university, were used in this study. The new designs, together with other traditionally bottle designs, were evaluated in simulated shampoo pouring task in the laboratory. Several important parameters extracted from the sEMG signal in both temporal domain and frequency domain provide useful information about the tested designs. Twenty healthy university students (10 males and 10 females; mean age of 21 ± 2 years) were included in this study. Each subject was asked to handle the bottle and simulate the shampoo pouring activity in gentle and delicate manner using the grasp pattern that is found most comfort for him/her. Muscular behavior during bottle holding and shampoo pouring tasks show that male and female have different preferences in dealing with different bottle design, where male have less hand stress with designs that achieve the best fit of their full hand, while female have less hand stress with designs that achieve the best fit of their fingertips, and therefore, the end-user gender must be considered in designs of such industries. Keywords: Surface electromyography, Ergonomic design, Hand-tools, Hand stress, Mean frequency, Euclidean distance, Root mean square, Gender consideration