The self-healing capacity of cementitious materials is opening a new branch in the field of smart materials which are able to heal themselves and thus increase their durability and improving the service life of the various structures, there are currently two primary factors that are given priority when it comes to concrete constructions. The first is the economic perspective, which shows how much of the yearly budget will be allocated to construction and maintenance. and secondly, the environmental problems related to the CO2 emissions from cement manufacture. The investigation was based on examining the usefulness of ultra-high-performance steel fibre reinforced concrete autogenous self-healing capacity in the fatigue life under cyclic loading in repairing cracks in concrete structures. Through an experimental program, three stages had been established to evaluating the ability for healing: We were able to determine the mechanical characteristics of the specimens in the first stage of cracking them using a limit of crack opening of (250 m) using the 4 points bending test (4PBT). A second stage of healing through submersion in water was applied to numerous specimens with variable healing periods of 1 month, 2 months, 3 months, and 6 months, depending on the cycling load introduced based on definition of the strength of the various specimens in the pre-cracking stage. The third stage—considered as the post-fatigue stage—was presented through the application of cyclic loads. Comparisons between the pre- and post-healing periods included the critical crack opening displacement (COD) and the rate of (COD) for each specimen, in order to understand whether the mechanical properties had improved. Finally, the indices of healing, representative of crack closure and, in case, performance recovery, were presented including the Ultrasonic pulse velocity as well as the microscopic imaging tests. The results for the different specimens in various durations of healing showed percentages of healing increased with an increase in the time duration.
La capacità di autoguarigione dei materiali cementizi sta aprendo un nuovo ramo nel campo dei materiali intelligenti che sono in grado di guarire se stessi e quindi di aumentare la loro durata ed estendere la vita di servizio delle strutture, Attualmente sono due i fattori primari ai quali viene data priorità quando si tratta di costruzioni in calcestruzzo. Il primo è la prospettiva economica, che mostra quanto del bilancio annuale sarà destinato alla costruzione e alla manutenzione. In secondo luogo, i problemi ambientali legati alle emissioni di CO2 prodotte dalla produzione di cemento. L'indagine si è basata sul l'esame del l'utilità del calcestruzzo ad elevate prestazioni con la capacità autorigenerante autogena nella vita a fatica sotto carico ciclico per riparare le crepe nelle strutture in calcestruzzo. Attraverso un programma sperimentale, sono state stabilite tre fasi per valutare la capacità di guarigione: siamo stati in grado di determinare le caratteristiche meccaniche dei campioni nella prima fase di cracking utilizzando un limite di apertura di fessura di (250 m) utilizzando la prova di flessione a 4 punti (4PBT). Una seconda fase di guarigione attraverso l'immersione in acqua è stata studiata per una serie di provini con periodi di guarigione variabili di 1 mese, 2 mesi, 3 mesi e 6 mesi, a seconda del carico ciclistico introdotto in base alla definizione della forza dei vari esemplari nel prefase di cracking. La terza fase, considerata la fase post-fatica, è stata presentata mediante l'applicazione di carichi ciclici. Il confronto tra i periodi di pre e post-guarigione ha compreso la valutazione delllo spostamento critico di apertura della fessura (COD) e la velocità di (COD) per ogni campione, al fine di comprendere se le proprietà meccaniche erano migliorate. Infine, gli Indici di guarigione sono stati presentati, basati ad esempio sulla velocità di impulso ultrasonico ovvero su visualizzazione microscopica delle fessure; i risultati per i diversi esemplari in varie durate di guarigione hanno mostrato percentuali di guarigione aumentate con un aumento della durata.
Stimulated Autogenous Self-Healing Capacity Of High Performance Concrete Under Cyclic Loads
Azhari Ahmed Zakria, Mohammed
2021/2022
Abstract
The self-healing capacity of cementitious materials is opening a new branch in the field of smart materials which are able to heal themselves and thus increase their durability and improving the service life of the various structures, there are currently two primary factors that are given priority when it comes to concrete constructions. The first is the economic perspective, which shows how much of the yearly budget will be allocated to construction and maintenance. and secondly, the environmental problems related to the CO2 emissions from cement manufacture. The investigation was based on examining the usefulness of ultra-high-performance steel fibre reinforced concrete autogenous self-healing capacity in the fatigue life under cyclic loading in repairing cracks in concrete structures. Through an experimental program, three stages had been established to evaluating the ability for healing: We were able to determine the mechanical characteristics of the specimens in the first stage of cracking them using a limit of crack opening of (250 m) using the 4 points bending test (4PBT). A second stage of healing through submersion in water was applied to numerous specimens with variable healing periods of 1 month, 2 months, 3 months, and 6 months, depending on the cycling load introduced based on definition of the strength of the various specimens in the pre-cracking stage. The third stage—considered as the post-fatigue stage—was presented through the application of cyclic loads. Comparisons between the pre- and post-healing periods included the critical crack opening displacement (COD) and the rate of (COD) for each specimen, in order to understand whether the mechanical properties had improved. Finally, the indices of healing, representative of crack closure and, in case, performance recovery, were presented including the Ultrasonic pulse velocity as well as the microscopic imaging tests. The results for the different specimens in various durations of healing showed percentages of healing increased with an increase in the time duration.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/197463