Ciências Exatas e Tecnológicas
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/4
Navegar
2 resultados
Resultados da Pesquisa
Item Self-sensing concrete blocks and mortar joints for health monitoring of structural masonry before and after exposure to high temperatures(Universidade Federal de Viçosa, 2024-02-23) Nalon, Gustavo Henrique; Ribeiro, José Carlos Lopes; http://lattes.cnpq.br/3130030223972786Self-sensing cementitious materials are emerging technologies for stress/strain monitoring and damage detection in structural members. This research presents the development and validation of innovative technology for Structural Health Monitoring (SHM) of concrete masonry: self-sensing concrete blocks and mortar joints containing carbon-black nanoparticles (CBN). A factorial experiment was carried out to evaluate the effects of lime/cement ratio and CBN dosage on the self-sensing, mechanical and microstructural behavior of masonry mortars. Different approaches for producing self-sensing concrete units were also investigated. The results indicated that epoxy-based structural adhesives provided the best bonding performance between cementitious sensors and concrete substrates. In addition, concrete units could be successfully cast around hardened cement-based sensors. When an expansive agent was added to the self-sensing matrix, the fresh cementitious sensor was successfully embedded into hardened concrete units. The effects of different types of shrinkage-reducing admixtures and expansive agents on the drying shrinkage, self-sensing properties, microstructure and strength of cementitious materials were also reported. Finally, a validation study was carried out to investigate the mechanical and piezoresistive behavior of self-sensing masonry units and joints applied to masonry prisms under uniaxial compression. This study covered the use of different types of concrete units, mortar bedding approaches, bonding arrangements, relative strengths of mortar and units, joint thicknesses, and locations of self-sensing regions. The self-sensing units and joints were found to be promising alternatives for stress and strain monitoring of structural masonry elements, before and after high temperatures. The self-sensing masonry also demonstrated the ability for real- time detection and quantification of damage due to exposure to elevated temperatures. The electrical response of the self-sensing masonry also provided valuable insights into the recovery of damage due to rehydration procedures. This research enabled the effective design and application of smart units and joints in SHM systems of concrete masonry. Keywords: Structural masonry; Structural Health Monitoring; self-sensing concrete unit; self-sensing masonry joint; high temperatures.Item Experimental evaluation of self-sensing cement-based composites with carbon nanofillers for Structural Health Monitoring of fire-damaged structures(Universidade Federal de Viçosa, 2020-02-27) Nalon, Gustavo Henrique; Ribeiro, José Carlos Lopes; http://lattes.cnpq.br/3130030223972786The deeper understanding of the electrical properties of cement-based materials and the recent knowledge on Nanoscience and Nanotechnology allowed the development of smart pastes, mortars and concretes with intrinsic strain sensing and damage detection properties. Since fire is one of the most severe threats to the structural integrity of concrete elements, the reuse of fire-damaged structures requires an accurate diagnosis of their damage level and residual structural performance. In this work, an experimental evaluation of innovative technologies for Structural Health Monitoring of fire-damaged concrete elements was developed: self-sensing cement-based composites containing multi-walled carbon nanotubes (MWCNT) or carbon-black nanoparticles (CBN). Microstructure, residual mechanical properties and sensing ability of different composites exposed to temperatures of 200 ºC, 400 ºC and 600 ºC were investigated. The effects of rehydration after fire exposure on these parameters were also studied. Composites with an intrinsic ability to measure strain and detect damage after exposure to temperatures up to 600 ºC were developed. They also exhibited an interesting ability of detection of damage recovery due to the post-fire rehydration. Keywords: Structural Health Monitoring. Nanomodified cementitious materials. Post-fire structural behavior. Self-sensing composites.