STRUCTURAL MONITORING OF HYBRID SPECIMENS AT EARLY AGE USING FIBRE OPTIC SENSORS
Hybrid structures, notably bridges, consisting of steel girders and concrete decks, are designed to explo it in the best way the mechanical properties of both materials. In order to guarantee safe, durable and low-cost service of such structures, a long-term quality and a robust connection between steel and concrete must be guaranteed. Even if experience in construction, maintenance and exploitation of these structures is large, a good and long-lived connection remains a challenging point in their realisation. This is mainly due to the initial incompatibility in the dimensional behaviour of two materials: early and very early age deformations of concrete (thermal expansion and total shrinkage) generate stresses in both materials even before service and imperils their good interaction. With the intention of a better understanding and an accurate numerical modelling of the steelconcrete connection in hybrid structures, measurements are indispensable and, in particular the deformation evolution in both materials during the early and very early age of concrete. In this paper we present examples of this type of measurements, the monitoring of the total dimensional evolution of hybrid elements, the determination of hardening time of concrete and structural monolithisation and, indirectly, the determination of concrete’s Young modulus evolution. An approach to concrete delamination detection is also assessed. All these parameters are evaluated using fibre optic sensors directly embedded in the fresh concrete or attached to steel elements. Their high accuracy, longterm stability and especially their ability to measure early and very early deformation of concrete are essential for monitoring of mentioned parameters.
Characterization of Early Age Curing and Shrinkage of Metakaolin-Based Inorganic Binders with Different Rheological Behavior by Fiber Bragg Grating Sensors
This paper reports results related to early age temperature and shrinkage measurements by means fiber Bragg gratings (FBGs), which were embedded in geopolymer matrices. The sensors were properly packaged in order to discriminate between different shrinkage behavior and temperature development. Geopolymer systems based on metakaolin were investigated, which dealt with different commercial aluminosilicate precursors and siliceous filler contents. The proposed measuring system will allow us to control, in a very accurate way, the early age phases of the binding systems made by metakaolin geopolymer. A series of experiments were conducted on different compositions; moreover, rheological issues related to the proposed experimental method were also assessed.
Endodontic regeneration: hard shell, soft core
A loss of organs or the destruction of tissue leaves wounds to which organisms and living things react differently. Their response depends on the extent of damage, the functional impairment and the biological potential of the organism. Some can completely regenerate lost body parts or tissues, whereas others react by forming scars in the sense of a tissue repair. Overall, the regenerative capacities of the human body are limited and only a few tissues are fully restored when injured. Dental tissues may suffer severe damage due to various influences such as caries or trauma; however, dental care aims at preserving unharmed structures and, thus, the functionality of the teeth. The dentin–pulp complex, a vital compound tissue that is enclosed by enamel, holds many important functions and is particularly worth protecting. It reacts physiologically to deleterious impacts with an interplay of regenerative and reparative processes to ensure its functionality and facilitate healing. While there were initially no biological treatment options available for the irreversible destruction of dentin or pulp, many promising approaches for endodontic regeneration based on the principles of tissue engineering have been developed in recent years. This review describes the regenerative and reparative processes of the dentin–pulp complex as well as the morphological criteria of possible healing results. Furthermore, it summarizes the current knowledge on tissue engineering of dentin and pulp, and potential future developments in this thriving field.