Browsing by Author "Monteiro, Carlos"
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- Eggshell waste to produce building lime: calcium oxide reactivity, industrial, environmental and economic implicationsPublication . Ferraz, Eduardo; Gamelas, José A. F.; Coroado, João; Monteiro, Carlos; Rocha, FernandoEggshells wastes are produced in huge amounts worldwide. The recycling or valorization of this waste, which otherwise is usually disposed in landfills, represents an opportunity within a circular economy perspective. In the present work, the potential of chicken eggshell waste to produce calcitic lime was explored. After collection from an industry supplier, the waste was thoroughly characterized for its mineralogical, chemical, and thermal properties. The material was calcined at 1000 °C, and the obtained calcium oxide was evaluated for its reactivity in wet slaking tests. Comparison was made with commercial limestone used as reference. It was found that the calcium oxide from eggshell waste belonged to the most reactive class (R5—60 °C within 10 min), the same of the calcium oxide from limestone. However, different times were obtained to reach 60 °C (25 s and 4:37 min:s) and for 80% of the reaction (28 s and 5 min) for calcium oxide from limestone and eggshell waste, respectively. The lower reactivity of calcium oxide from eggshell waste was related to its larger size particles with smoother surfaces and lower specific surface area in comparison to limestone calcium oxide. Industrial, environmental and economic implications concerning the use of this waste to produce lime were also evaluated. The eggshell waste could be all consumed at an industrial scale in Portugal allowing for approximately 2.6% partial substitution of limestone in a lime factory.
- Perception of the special troops (comandos) soldiers regarding physical fitness, motor control and psychological skillsPublication . Monteiro, Carlos; Dias, Gonçalo; Ramos, Susana; Gomes, Ricardo; Gama, José; M. L. Martins, Fernando; Mendes, Rui; Castro, Maria AntónioPhysical fitness and motor skills are considered important attributes for the military, affecting their professional performance. The high physical and psychological demand that the special forces are subjected to requires the acquisition of a set of volitional skills such as resilience, effort, perseverance, or resistance to frustration, which are worthy of further research. This study aimed to analyse the perception of the special troops (commandos) in physical fitness, motor control and psychological skills. A total of 35 male soldiers that ended the commando recruit training program (21.69 ± 2.36 years old) were investigated. A questionnaire was applied to verify differences in perception of physical fitness, motor capacity, physical effort and military training during recruit training according to age, education, work experience and sports background. Descriptive statistics were used to characterize the participants. All data collected were analysed using IBM-SPSS Statistics, version 24. Our results revealed differences in the importance given to the training of motor skills within military training (χ2 = 19.284; p = 0.023), conditional motor skills – speed (χ2 = 17.378; p = 0.043), coordinative motor skills—motor control (χ2 = 20.616; p = 0.014), psychological skills in a military context (χ2 = 13.730; p = 0.008), volitional skills—resistance to frustration (χ2 = 21.568; p = 0.043) and volitional skills—psychological resistance (χ2 = 29.144; p = 0.004). The participants highlighted the importance of instructors having scientific knowledge in physical education to provide military physical training to be better prepared for this purpose. We concluded that motor skills and psychological abilities tend to be equally important in the context of military training. Physical fitness and motor skill development can be considered essential in military training for most of the inquired participants.
- Recycling Waste Seashells to Produce Calcitic Lime: Characterization and Wet Slaking ReactivityPublication . Ferraz, Eduardo; Gamelas, José A. F.; Coroado, João; Monteiro, Carlos; Rocha, FernandoThe present work aimed at valorizing marine bivalve shells. First, clam, mussel, edible cockle, wedge, razor, oyster, dog cockle and scallop shells wastes were thoroughly characterised for their mineralogical, chemical and thermal properties. Then, the materials were calcined at 1000 °C, milled and sieved to lower than 0.250 mm. The obtained calcium oxide was subjected to wet slaking test to evaluate its reactivity in the production of hydrated lime. The reactivity results of the calcined materials showed that, dog cockle (60 °C in 7:54 min:s) and edible cockle (60 °C in 9:20 min:s) can be classified in the most reactive class (R5) in which 60 °C is reached in less than 10 min. The remaining species were classified in the R4 class, reaching 60 °C between 10 and 25 min, with the lowest reactivity being found for oyster shell (60 °C in 19:09 min:s). Interestingly, the hydrated limes from seashells typically presented a white tonality superior that of the lime from commercial limestone used as reference. Overall, seashell wastes can be used in the production of lime, with several benefits, including, the inexistence of environmental impacts related to the exploitation of limestone on quarry, lesser energy spent in the comminution process, or, inexistence of disposal costs related with landfill tariff. These wastes could thus be used as raw materials in other industrial sector.