Concreto submetido a vibrações nas primeiras idades

Abstract

This study describes the early-age behavior of high-strength concrete made with high initial strength cement and exposed to an environment with vibrations. A sequence of tests is presented which includes the molding of concrete specimens subjected to traffic vibrations, as well as a mechanical characterization and steel-concrete bonding tests. Results indicated that early age concrete specimens subjected to vibrations undergo losses in tensile strength and in their modulus of elasticity. Such reduction in stiffness may have a negative impact on structural serviceability and result in higher deflections. Thus, a reduction in tensile strength should be taken into account when designing rigid floors, given that tensile strength is a key factor which guarantees the system's durability. The effect of vibration on early-age concrete and its effects on properties which influence the structural behavior of the system are discussed.Keywords: high-strength concrete, traffic-induced vibration effects, mechanical properties characterization tests, steel-concrete bond; pull-out test.Este artigo traz informações sobre o comportamento nas primeiras idades de um concreto de alta resistência, produzido com cimento de alta resistência inicial, lançado e adensado em ambientes submetidos a vibrações, como em obras de pontes de rodovias. Apresenta-se o programa experimental desenvolvido, descrevendo desde a moldagem dos corpos-de-prova, sob ação de vibrações similares às induzidas pelo tráfego, até os ensaios de caracterização mecânica e de aderência aço-concreto. Os resultados experimentais indicam que o concreto submetido à vibração nas primeiras idades pode sofrer perdas na resistência à tração e no módulo de elasticidade. A redução dessas propriedades pode comprometer a utilização da estrutura devido ao aparecimento de flechas e fissuras acima dos limites de norma. A redução da resistência à tração do concreto deve ser considerada, também, na aplicação de pavimentos rígidos, onde essa propriedade é fundamental para garantir a durabilidade do sistema. Não foi observada nenhuma redução na resistência à compressão ou na capacidade de aderência devido à introdução de vibrações nas primeiras idades do concreto.Palavras-chave: concreto de alta resistência, efeito de vibração induzida pelo tráfego, ensaios de caracterização mecânica, aderência aço-concreto; teste de arrancamento. Concrete subjected to vibrations in early-ages Concreto submetido a vibrações nas primeiras idades

Effects of Vehicle-Induced Vibrations on the Tensile Performance of Early-Age PVA-ECC

“…Additionally, Figure 5 also shows that the cracking strength was the most sensitive to the variables in this section, and then it followed the ultimate tensile strength and strain. These results were similar to the studies on compressive strength [34], bond strength [35], splitting strength [36] of early-age concrete that was subjected to vibrations during this period.…”

“…Their results showed that if the vibration occurred before the final set, there would be a considerable reduction in the compressive and bond strengths of early-age bridge deck repairs [34]. In particular, studies have shown that, when subjected to vehicle-induced vibrations during the period between the initial set and the final set, concrete bridge deck repairs experienced tensile strength and elastic coefficient losses [35]. Fernandes pointed out that special care must be taken with regard to the tensile strength of concrete repairs, because its reduction can have a negative effect on the usability of a bridge deck, and it can result in a greater deflection [35].…”

“…In particular, studies have shown that, when subjected to vehicle-induced vibrations during the period between the initial set and the final set, concrete bridge deck repairs experienced tensile strength and elastic coefficient losses [35]. Fernandes pointed out that special care must be taken with regard to the tensile strength of concrete repairs, because its reduction can have a negative effect on the usability of a bridge deck, and it can result in a greater deflection [35]. The results of Zhang [36] further confirmed that both visible cracks and serious internal damage of concrete repairs occurred when the concrete was vibrated during the period between the initial set and the final set.…”

Towards a robust and versatile method for monitoring E‐modulus of concrete since casting: Enhancements and extensions of EMM‐ARM

“…Even though forced vibration techniques can increase the accuracy of the modal identification of the composite beam, it has to be taken into account that the application of an external vibration during the curing period of the cementitious materials may potentially affect the development of the mechanical properties, particularly during the setting time when bonds are being formed in the cement matrix that can be damaged due to the vibrations. This issue was studied by several authors, and it was found that excessive vibration during the curing process can affect the elastic modulus by almost 10%. Also in the work of Hong and Park, it was found that even small vibrations (with maximum accelerations of 14.4 mg at 5 Hz) can have a relevant impact in the concrete curing process and affect its mechanical properties.…”

Effect of Vibration Procedure on Particle Distribution of Cement Paste

“…The impact of mechanical vibration on the performance of cement-based materials has been extensively studied, as it is the most commonly encountered type of vibration during construction and directly affects the quality and service life of concrete structures [ 5 , 6 ]. Vibration is a macroscopic physical process, and the microstructure of cement-based materials is altered during this process [ 7 ].…”