Recycling of Waste Facial Masks as a Construction Material, a Step towards Sustainability.

Amid the COVID-19 pandemic, a sudden surge in the production and utilization of disposable, single-use facial masks has been observed. Delinquency in proper disposal of used facial masks endangers the environment with a new form of non-biodegradable plastic waste that will take hundreds of years to break down. Therefore, there is an urgent need for the resourceful recycling of such waste in an environmentally friendly way. This study presents an efficient solution by using waste masks in fibered or crushed form to produce environmentally friendly and affordable green concrete. This investigation assessed the mechanical and durability properties of waste masks-incorporated concrete. A total of six mixes were prepared for standardized tests to determine compressive strength, split cylinder tensile strength and rapid chloride penetration test (RCPT), and freeze-thaw resistance. The percentage of mask fibers used were 0.5, 1, 1.5, and 2% of concrete by volume, while crushed masks were used at 0.5% only. The mask waste in both forms was found suitable to be used in concrete. One percent of waste mask fibers was found as an optimum value to increase compressive and tensile strength, reduce chloride permeability, and increase freeze-thaw resistance. Besides this, 0.5% crushed mask fiber also performed well, especially for producing less permeable and highly durable concrete. It is thus corroborated that waste masks that increase pollution worldwide can be utilized sustainably to help build green buildings. By reutilizing waste masks to produce improved concrete with better strengths and higher durability, circular economy and sustainability are achieved, along with efficient waste management.

Effect of Silicon Carbide and Tungsten Carbide on Concrete Composite.

Flexural strength of concrete is an important property, especially for pavements. Concrete with higher flexural strength has fewer cracking and durability issues. Researchers use different materials, including fibers, polymers, and admixtures, to increase the flexural strength of concrete. Silicon carbide and tungsten carbide are some of the hardest materials on earth. In this research, the mechanical properties of carbide concrete composites were investigated. The silicon carbide and tungsten carbide at different percentages (1%, 2%, 3%, and 4%) by weight of cement along with hybrid silicon carbide and tungsten carbide (2% and 4%) were used to produce eleven mixes of concrete composites. The mechanical tests, including a compressive strength test and flexural strength test, along with the rapid chloride permeability test (RCPT), were conducted. It was concluded that mechanical properties were enhanced by increasing the percentages of both individual and hybrid carbides. The compressive strength was increased by 17% using 4% tungsten carbide, while flexural strength was increased by 39% at 4% tungsten carbide. The significant effect of carbides on flexural strength was also corroborated by ANOVA analysis. The improvement in flexural strength makes both carbides desirable for use in concrete pavement. Additionally, the permeability, the leading cause of durability issues, was reduced considerably by using tungsten carbide. It was concluded that both carbides provide promising results by enhancing the mechanical properties of concrete and are compatible with concrete to produce composites.

Compaction Characteristics and Permeability of Expansive Shale Stabilized with Locally Produced Waste Materials.

Waste is available in an abundant form and goes to landfill without any use, creating threats to the environment. Recent and past studies have used different types of waste to stabilize soil and reduce environmental impacts. However, there is a lack of studies on the combined use of marble dust, rice-husk ash, and saw dust in expansive shale soil. The current study tries to overcome such a gap in the literature, studying the effect of marble dust, rice-husk ash, and saw dust on expansive shale's compaction characteristics and permeability properties. According to unified soil classification and the AAHTO classification system, the geotechnical properties of natural soil are classified as clay of high plasticity (CH) and A-7-5. Several tests are performed in the laboratory to investigate the compaction characteristics and permeability properties of expansive shale. Moreover, permeability apparatus is used to investigate the permeability properties of soil. In addition, due to the accuracy of the apparatus, the conventional apparatus has been partly modified. The experimental results show that the addition of waste to the soil has significantly improved soil stabilization, increasing permeability and decreasing plasticity indexes. In addition, there is a gradual decrease in the dry density of soil and an increase in the permeability of stabilized soil. Based on the outcomes of the current study, it claims and concludes that these waste materials can be used as soil stabilizers or modifiers, instead of being dumped in landfill, which will provide a green, friendly, and sustainable environment. The current study recommends that future researchers use various wastes in the concrete and soil to improve their compaction and mechanical properties.

Effects of aging on the human motor cortical plasticity studied by paired associative stimulation.

OBJECTIVE: To test whether the normal aging itself may change the cortical plasticity in human. METHODS: Motor-evoked potentials (MEPs) were measured from 48 right-handed healthy volunteers (age 21-79) before and after the paired associative stimulation (PAS), comprising a single electric stimulus to the right median nerve at wrist and subsequent transcranial magnetic stimulation (TMS) of the left primary motor cortex. RESULTS: The magnitude of MEP increased by PAS in the young and middle but not in the elderly and its change was negatively correlated with the age. CONCLUSIONS: These results suggest that the human M1 shows age-dependent reduction of cortical plasticity. SIGNIFICANCE: The reduction of the M1 plasticity may be caused by the attenuated responsiveness of intracortical circuits in the M1 and/or disrupted sensorimotor integration within basal ganglia-thalamocortical loop.

Suppression of human cortico-motoneuronal excitability during the Stop-signal task.

OBJECTIVE: To investigate whether motor suppression is an active process, and to clarify its somatotopic organization, we investigated cortico-motoneuronal excitability using transcranial magnetic stimulation (TMS) during the Stop-signal task. METHODS: Subjects were asked to press a button following a Go cue; a Stop-signal followed the Go cue by a certain time delay in 25% of trials, indicating to subjects that they were not to press the button. TMS was given to the primary motor area of the left or right-hand or leg at variable time delays. Motor evoked potentials (MEPs) were recorded from the hand and leg muscles bilaterally. RESULTS: When TMS was delivered 400 ms after the Go cue, there was significant suppression of the MEPs of the bilateral hand and leg muscles during successful Stop trials, but not during failed Stop trials. CONCLUSIONS: The voluntary stopping of movement in the Stop-signal task is an active process, which likely suppresses not only the cortico-motoneuronal excitability of the task-performing hand, but also causes the widespread suppression of the motor system. SIGNIFICANCE: Studies in the normal physiology of response inhibition would be of help in understanding the pathophysiology of neuro-psychiatric disorders associated with deficits in motor suppression.