[en] This doctoral thesis aims at taking a step forward in concrete recycling, since it is proposed to replace simultaneously the fine and coarse fraction of the aggregate without having to previously sieve the raw recycled aggregate. The structural behaviour of both precast reinforced and prestressed concrete elements was assessed, compared to conventional concretes with similar compressive strength. A first experimental campaign was performed with self‐compacting recycled concrete. Different percentages of the total amount of natural aggregates (0, 20, 35 and 50%, including fine and coarse fraction) were replaced with recycled aggregates from rejected members of a precast plant. Fresh and hardened concrete properties were compared in laboratory for the different replacement levels. The mechanical properties were not significantly affected. So, the resulting recycled concrete was utilised for the fabrication of reinforced concrete beams in a precast plant with replacement levels of 0, 10, 20, 35 and 50%. Reinforced beams were subjected to quality control shear and flexural failure tests in the precast plant showing a similar ultimate bending moment and shear strength regardless of the replacement ratio. However, the ductility factor of flexural beams and cracking moment decreased for higher replacement levels. Flexural tests were repeated with displacement control and accurate monitoring in the CITEEC at the University of A Coruña, including strain gauges on concrete surface to obtain the flexural behaviour up to failure, the ductility factors, and moment vs. curvature relationships. The results obtained showed a lower cracking moment and ductility for the higher replacement levels but similar ultimate moments. A second experimental campaign was performed with vibrated concrete and prestressed precast concrete beams. In this case, the source of the recycled aggregate was old concrete sleepers. Different percentages of the total amount of natural aggregates (0, 8, 20 and 31%, including fine and coarse fraction) were replaced by recycled aggregates and fresh and hardened properties were compared in laboratory for the different replacement levels. The mechanical properties did not experience considerable decrease depending on the replacement percentage. So, the resulting recycled concrete was utilised for the fabrication of prestressed concrete beams, as well as Pull‐Out test samples with replacement levels of 0 and 8%. The aim was to evaluate the loss of bond performance between prestressed strands and surrounding concrete when recycled aggregates are introduced in the mix. Pull‐Out tests showed that the bond stress at which the first slip occurs is approximately 24% lower when 8% of the total aggregate is replaced with recycled aggregate. Prestressed beams were monitored to evaluate transfer and development length. Transfer length was evaluated measuring the strain values with DEMEC points at different ages. It was determined to be 717 mm in natural concrete beams and 957 mm in recycled beams. That is, there is an increase of 33% in transfer length when 8% recycled aggregate is incorporated in the concrete mix. Development length was evaluated performing flexural tests at different embedment lengths and measuring the strand end slips during the tests. It was determined to be 1475 mm in natural concrete beams and 1850 mm in recycled concrete beams. That is, there is an increase of 25% in development length when 8% recycled aggregate is incorporated in the concrete mix. From this research it may be concluded that it is feasible to replace up to 50% of the total aggregate (fine and coarse) in reinforced concrete beams. However, the incorporation of recycled aggregate in prestressed concrete significantly reduces the bond between prestressed strands and surrounding concrete in beams fabricated with 8% replacement of the total aggregate. Consequently, further research is recommended in this subject.

[gl] Resumo Esta tese doutoral busca levar un paso adiante o reciclado do formigón xa que propón substituír simultaneamente a fracción fina e grosa do árido, sen ter que cribar previamente o árido reciclado bruto. O comportamento estrutural tanto de vigas prefabricadas armadas como pretensadas foi avaliado, comparándoo co dun formigón convencional cunha resistencia a compresión similar. Realizouse una primeira campaña experimental con formigón autocompactante reciclado. Diferentes porcentaxes da cantidade total do árido natural (0, 20, 35 e 50%, incluíndo a fracción fina e grosa) foron substituídos por árido reciclado de elementos rechazados dunha planta de prefabricados. As propiedades do formigón fresco e endurecido foron comparadas no laboratorio para os diferentes porcentaxes de substitución. As propiedades mecánicas non foron significativamente afectadas. Polo tanto, o formigón reciclado resultante foi utilizado para a fabricación das figas de formigón armado nunha planta de prefabricados con porcentaxes de substitución do 0, 10, 20, 35 e 50%. As vigas armadas foron sometidas a ensaios de control de calidade a flexión e cortante na planta, amosando un momento último e resistencia a cortante similares, independentemente do porcentaxe de substitución. Sen embargo, o factor de ductilidade e o momento de fisuración diminuíron para os porcentaxes máis altos. Os ensaios a flexión foron repetidos mediante control de desprazamento e cunha instrumentación máis precisa no CITEEC da Universidade da Coruña, incluíndo galgas de deformación na superficie do formigón para obter o comportamento a flexión ata rotura, os factores de ductilidade e a relación Momento‐Curvatura. Os resultados obtidos amosan un momento de fisuración e ductilidade más baixo para os porcentaxes de substitución máis altos, pero igual momento último. Unha segunda campaña experimental foi realizada con formigón convencional e vigas prefabricadas pretensadas de formigón. Neste caso, a orixe do árido reciclado foi travesas vellas de formigón. Diferentes porcentaxes da cantidade total do árido natural (0, 8, 20 e 31%, incluíndo a fracción fina e grosa) foron substituídos por árido reciclado, comparando as propiedades en estado fresco e endurecido para os diferentes porcentaxes. As propiedades mecánicas non se viron excesivamente afectadas. Polo tanto, o formigón resultante foi utilizado para a fabricación das vigas pretensadas e probetas para ensaios Pull‐Out, con substitucións do 0 e 8%. A finalidade foi avaliar a pérdida do comportamento adherente entre os cordóns pretensados e o formigón que os envolve cando o árido reciclado é introducido no formigón. Os ensaios Pull‐Out reflexaron que a tensión adherente á que se produce o primeiro deslizamento é aproximadamente un 24% inferior cando se introduce un 8% de árido reciclado no formigón. As vigas pretensadas foron instrumentadas interna e externamente para avaliar a lonxitude de transmisión e de ancoraxe. A lonxitude de transmisión avaliouse medindo as deformación con puntos DEMEC a diferentes idades. Determinouse un valor de 717 mm nas vigas de formigón natural e 957 mm nas de reciclado. Polo tanto hai un incremento do 33% na lonxitude de transmisión cando o 8% do árido reciclado se incorpora no formigón. A lonxitude de ancoraxe avaliouse realizando ensaios a flexión con diferentes puntos de aplicación das cargas e medindo a penetración dos cordóns durante o ensaio. Determinouse un valor de 1475 mm nas vigas de formigón natural e 1850 mm nas vigas de formigón armado. É dicir, hai un incremento do 25% na lonxitude de ancoraxe cando o 8% do árido reciclado se incorpora no formigón. Desta investigación pódese concluír que é viable substituír ata un 50% do árido total (fino e groso) en vigas armadas. Sen embargo, non é aconsellable incluír árido reciclado en formigón pretensado debido á gran pérdida de adherencia observada cun 8% de substitución do árido total. Por conseguinte, é recomendable realizar unha investigación mais profunda neste tema.