Browsing by Keyword "Recycled concrete aggregate"
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Item Self-Compacting Concrete with Recycled Concrete Aggregate: Resistance against Aggressive External Agents(International Center for Numerical Methods in Engineering, 2020) Revilla-Cuest, Víctor; Skaf, Marta; García-Llon, Aratz; Piñero, Ignacio; Manso, Juan M.; Ortega-Lópe, Vanesa; Serrat, Carles; Casas, Joan Ramon; Gibert i Armengol, Vicente; Tecnalia Research & Innovation; E&I SEGURAS Y RESILIENTESThe use of waste in civil-engineering products, such as concrete and asphalt mixes, is a very effective strategy for reducing high consumption levels of Natural Aggregates (NA) in the construction sector. In this research, rejected precast concrete elements of high compressive strength are studied, following their crushing for use as a high quality Recycled Concrete Aggregate (RCA) in the manufacture of Self-Compacting Concrete (SCC). High volumes of this waste stream are employed in the mixture, completely replacing the coarse fraction of the natural aggregate (100% replacement rate) and half of the fine fraction (50% replacement rate). Once hardened, samples of the recycled SCC are exposed to several aggressive external agents, in order to evaluate their performance and durability in aggressive environments. Behavioral tests on the concrete in the presence of the most frequent aggressive agents in the surrounding environment demonstrated that the SCC containing RCA was resistant to freeze/thaw and moist/dry cycles, and sulphate attack, according to the results obtained in 4, 3 and 2 samples respectively, and of sufficient durability for use in structural concrete components.Item VALIDATION OF ULTRASONIC PULSE TO QUALITY CONTROL OF RECYCLED AGGREGATE SELF-COMPACTING CONCRETE(University of Cantabria - Building Technology R&D Group, 2022) Revilla-Cuesta, Víctor; Santamaría, Amaia; Espinosa, Ana B.; Chica, José A.; Manso, Juan M.; Ortega-López, Vanesa; Blanco, Haydee; Boffill, Yosbel; Lombillo, Ignacio; SGOne of the main operations in any civil work is to verify that the concrete supplied and placed on site reaches the required minimum compressive strength. This verification is usually performed statistically through the preparation and testing of a large number of specimens. However, its indirect control is also useful due to its simplicity, ease of execution, and low cost. One of the most common methods to perform this operation is the measurement of the Ultrasonic Pulse Velocity (UPV) of the cast concrete, checking that its value corresponds to the necessary concrete’s strength class. This study aims to analyze whether this indirect measurement, widely used in vibrated concrete produced with natural aggregate, is also valid when large quantities of Recycled Concrete Aggregate (RCA) are added to Self-Compacting Concrete (SCC). For this purpose, six SCC mixes were produced with 100% coarse RCA and variable fine RCA contents (0%, 50%, and 100%). In addition, two different types of powder were used: Limestone filler <0.063 mm and limestone fines 0/0.5 mm. The determination of the compressive strength and the UPV at 7 and 28 days in all mixes allowed demonstrating the existence of a close relationship between these two magnitudes in this type of concrete. It was even possible to develop highly accurate simple-regression models to interrelate both variables. These findings show that the use of SCC with RCA in engineering works would still allow the control of compressive strength using one of the most common traditional techniques, the ultrasonic pulse.