Abstract The improper disposal of this waste poses environmental challenges, which can be addressed through effective reuse strategies. This study aims to explore the potential of utilizing marine shell waste as partial substitutes for aggregates in concrete. The research involves investigating the physical characteristics of the recycled aggregate using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) techniques to elucidate the contact surface with the paste. Additionally, chemical and mineralogical characteristics are analyzed through X-ray fluorescence and X-ray diffraction tests. The compressive strength test is conducted on concrete samples to assess the performance of these materials as both aggregate (shell type A) and filler (shell type B). The findings indicate that replacing up to 20% of marine shells as coarse aggregate and 10% as filler demonstrates feasibility for applications in structural concrete. Furthermore, up to 30% replacement can be directed towards non-structural concrete, providing a comprehensive understanding of the potential applications of marine shell residues in concrete production.

Resumo As atividades de mariscagem e malacocultura produzem uma grande quantidade de resíduos sólidos compostos por conchas marinhas. O impacto ambiental do descarte inadequado pode ser atenuado com estratégias de reaproveitamento. O objetivo deste trabalho é investigar a viabilidade do uso de resíduo de conchas marinhas com substituintes parciais de agregados no concreto. As características físicas do agregado reciclado foram investigadas através das técnicas de Microscopia de Força Atômica (MFA) e Microscopia Eletrônica de Varredura (MEV) a fim de esclarecer aspectos da superfície de contato com a pasta; as características químicas e mineralógicas foram investigadas por meio dos ensaios de fluorescência de raios-X e difração de raios-X; e o ensaio de resistência à compressão foi conduzido em amostras de concreto foram moldadas para avaliação do comportamento destes materiais do comportamento destes materiais como agregado (concha tipo A) e fíler (concha tipo B). Concluiu-se que o uso de até 20% de substituição de concha marinha como agregado graúdo e 10% como filer mostrou viabilidade para aplicações em concretos estruturais e, de forma complementar, teores de até 30% podem ser direcionados à concretos não estruturais.

ABSTRACT The cement mass is the part of the cementitious composite that has low resistance to friction and its mechanical and microstructural properties are decisive for the durability of the material. Microscopy techniques are commonly used to elucidate these mechanical, physical and chemical behaviors of cementitious compounds. The objective of this work was to elucidate the importance of microscopy techniques for the direct evaluation of the abrasive behavior of cement pastes with silicon carbide (SiC) microparticles. The methodology of the work consists of the manufacture of Exceptions of reference cementitious masses and with 10% SiC addition, analysis of the compressive and abrasive mechanical properties, in addition to Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) tests. The results that the intensification of the mechanical properties with the addition of SiC microparticles can be related to the external micrographs in the SEM, through the accentuated filling of the pores, and through the attenuated surface roughness identified in the AFM. It was concluded that the roughness and porosity results, acquired by the SEM and AFM techniques, can provide relevant information for the analysis of the durability of cementitious materials.

RESUMO A pasta de cimento é a parte do compósito cimentício que possui baixa resistência ao atrito e suas propriedades mecânicas e microestruturais são determinantes para a durabilidade do material. As técnicas de microscopia são comumente utilizadas para elucidar esses comportamentos mecânicos, físicos e químicos de compósitos cimentícios. O objetivo deste trabalho foi elucidar a importância de técnicas de microscopia para avaliação direta do comportamento abrasivo de pastas de cimento com micropartículas de carbeto de silício (SiC). A metodologia do trabalho consistiu na fabricação das amostras de pastas cimentícias de referência e com 10% de adição de SiC, análise das propriedades mecânicas compressivas e abrasivas, além de ensaios de Microscopia Eletrônica de Varredura (MEV) e Microscopia de Força Atômica (MFA). Os resultados mostraram que a intensificação das propriedades mecânicas com adição de micropartículas de SiC podem ser relacionados com as micrografias obtidas no MEV, através do acentuado preenchimento dos poros, e por meio da atenuada rugosidade superficial identificada no MFA. Concluiu-se que os resultados de rugosidade e porosidade, adquiridos pelas técnicas de MEV e MFA, podem fornecer informações relevantes para análise da durabilidade de materiais cimentícios.

Abstract Paper aims Conduct a set of case studies on risk management in telecommunication companies, in order to reduce the risks of accidents. Originality The present study furthers the discussion of risk management during the maintenance of telecommunication towers. Research method Three teams were assessed during their maintenance work. The risks of accidents were identified through self-made questionnaires and the checklist structured from 95 items from Brazilian regulatory and technical norms. The analysis was conducted by using the Hazard Rating Number and the OHSAS hierarchy of risk control, finally comparing the results with the OSHA´s potential draft of the standard addressing telecommunication tower safety. Main findings The main risks of accidents were: falling objects; falls from height; electrocution; and attacks from animals. Only 20% of occupational safety items were in conformity. Implications for theory and practice Suggestions on control measures were given and discussed for all four risks of accidents.