The construction industry must meet current environmental requirements, mostly those pertaining to the reduction in construction and demolition waste and the consumption of raw materials. The use of recycled concrete aggregates can be part of the solution, but one question that arises is how many times recyclables can be recycled. This unknown involves other related queries regarding the properties and possible uses of repeated recycled concrete aggregates. This research is derived from the precast concrete industry, where multi-recycling is a pressing need. From good-quality parent concretes, three cycles of recycled concrete aggregates were produced and analysed. The final results are promising due to the good quality of the recycled and multi-recycled concrete aggregates obtained. Not only can they be used in low-level applications (backfilling) as usual, but they can also be used for more demanding purposes, such as graded aggregates, cement-treated road bases and concrete pavements. Their use in structural concrete is feasible, but it will be dependent on the water absorption level and the amount of recycled aggregate substitution. This research proves the viability of multi-recycled concrete aggregates with all of the associated environmental benefits.

A regulatory framework is required to ensure the correct design of Fibre-Reinforced Polymers (FRPs) increasingly being used as an externally-bonded strengthening system on concrete columns. Several design guidelines on the confinement of FRP concrete have been developed over the past few years worldwide, each proposing a different approach, resulting in different predictions. This study aims to evaluate and compare nine international design guidelines used to predict the compressive strength of confined concrete in FRP-strengthened concrete columns and weigh them against experimental results. The results of this investigation reveal that the predictions from the guidelines on the compressive strengthening of FRP-confined concrete are generally suitable for circular columns, with the ACI-440 and CNR-DT 200 guideline predictions being two of the most accurate. Nevertheless, the guidelines generally tend to overestimate the load-carrying capacity for the compressive strength of FRP-confined concrete in non-circular columns, for which further experimental work using large-scale specimens is required.

In the present study, the recycling of modified bitumen soundproofing membranes, known as automotive type membranes (ATR), was carried out. The ATR sheet waste was incorporated in the mixing stage of the asphalt mastic, which is part of the manufacturing process of new sheets. The selection of the best asphalt mastic formulation was carried out at laboratory scale, where the ATR sheet cutting waste was added to the original asphalt mastic in percentages of 2.5, 5.0, 5.0, 7.5, 10.0 and 15.0 % w/w. The formulations were evaluated for six parameters of interest associated with softening point, rotational viscosity, density, weight per area, thickness and creep. It was determined that the properties of all the formulations studied met the minimum requirements stipulated for the commercialization of the product. The recycling process was carried out on an industrial scale using the formulation with 5% w/w of ATR residues, which presented a viscosity close to that of the original mastic. The results at industrial scale were favorable, since the six parameters of interest were within the ranges established in the regulations. Translated with www.DeepL.com/Translator (free version) En el presente estudio se realizó el reciclaje de residuos de corte de láminas insonorizantes de asfalto modificado, denominadas como láminas tipo automotriz (ATR). Los residuos de láminas ATR se incorporaron en la etapa de mezclado del mástico asfáltico, el cual es parte del proceso de fabricación de nuevas láminas. La selección de la mejor formulación del mástico asfáltico se realizó a escala de laboratorio, donde se añadieron los residuos de corte de láminas ATR al mástico asfáltico original en porcentajes de 2.5, 5.0, 7.5, 10.0 y 15.0 % p/p. Las formulaciones se evaluaron en función de seis parámetros de interés asociados con punto de reblandecimiento, viscosidad rotacional, densidad, peso por área, espesor y fluencia. Se determinó que las propiedades de todas las formulaciones estudiadas cumplen con los requerimientos mínimos estipulados para la comercialización del producto. El proceso de reciclaje se llevó a escala industrial utilizando la formulación con 5% p/p de residuos de ATR, la cual presentó una viscosidad cercana a la del mástico original. Los resultados a escala industrial fueron favorables, ya que los seis parámetros de interés estuvieron dentro de los rangos establecidos en normativa.