The Alkali-Aggregate reaction (AAR) is a chemical reaction that occurs in concrete. It depends on the presence of mineral components, which are chemically unstable in high pH environment. The phenomenon is influenced by the water content and the moisture. This kind of reaction may affect any kind of concrete structure but is particularly relevant for hydraulic structures. Therefore, this thesis conducts a wide investigation of AAR effects on dams, including the Benchmark Workshops proposed by the International Commission on Large Dams (ICOLD). However, this work also contains a summary of the AAR effects on reinforced structures, with a specific reference to the concrete-reinforcement bond. Nowadays, it is possible to understand the AAR induced phenomena with the aid of different modeling methods capable of reproducing the kinetics of the reaction, the effect of the stresses, and their combination. The reliability and effectiveness of the existing models have been evaluated. Then, the most promising kinetic law has been subjected to sensitivity analysis in order to have a robust basis for the development of a parameter identification procedure.
La reazione alcali-aggregati (AAR) è un fenomeno chimico che ha luogo nel calcestruzzo. Essa dipende dalla presenza di determinati componenti minerali, chimicamente instabili in ambienti fortemente basici. Il fenomeno è influenzato dal contenuto d’acqua e dall’umidità. Questo tipo di reazione è particolarmente rilevante per le strutture idrauliche. Questo elaborato presenta quindi un’ampia sintesi degli effetti dell’AAR nelle dighe, ed include i risultati dei Workshops di riferimento, proposti dalla Commissione Internazionale sulle Grandi Dighe (ICOLD). Questo lavoro contiene inoltre un riassunto degli effetti della reazione sulle strutture/elementi in c.a., mettendo in evidenza l’effetto sull’aderenza tra calcestruzzo ed armatura. Gli effetti dell’AAR possono essere compresi mediante la modellazione del fenomeno che può essere descritto tramite la cinetica della reazione, l’effetto degli sforzi e la loro interazione. Questa tesi valuta l’affidabilità e l’efficacia dei modelli esistenti tramite un attento confronto. La descrizione cinetica più promettente è stata sottoposta ad analisi di sensitività, in modo da poter sviluppare una solida procedura di identificazione dei parametri.
The alkali-aggregate reaction (AAR) in structural engineering : effects and models
VALSECCHI, RUBEN
2017/2018
Abstract
The Alkali-Aggregate reaction (AAR) is a chemical reaction that occurs in concrete. It depends on the presence of mineral components, which are chemically unstable in high pH environment. The phenomenon is influenced by the water content and the moisture. This kind of reaction may affect any kind of concrete structure but is particularly relevant for hydraulic structures. Therefore, this thesis conducts a wide investigation of AAR effects on dams, including the Benchmark Workshops proposed by the International Commission on Large Dams (ICOLD). However, this work also contains a summary of the AAR effects on reinforced structures, with a specific reference to the concrete-reinforcement bond. Nowadays, it is possible to understand the AAR induced phenomena with the aid of different modeling methods capable of reproducing the kinetics of the reaction, the effect of the stresses, and their combination. The reliability and effectiveness of the existing models have been evaluated. Then, the most promising kinetic law has been subjected to sensitivity analysis in order to have a robust basis for the development of a parameter identification procedure.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/143803