Study of potential advantages of pre-soaking on the properties of pre-cast concrete made with recycled coarse aggregate

Abstract

Recycled aggregate (RA) from construction and demolition waste is traditionally used for the manufacture of concrete for different applications. Due primarily to high water content required by RA, the quality of the concrete is determined by the amount of replacement RA. The aim of this study is to determine if RA pre-soaking enhances the properties of pre-cast concrete for street furniture, with low mechanical and structural requirements, in which 100% of the coarse fraction is replaced. The results of physical and mechanical tests performed on concrete specimens in which the RA was pre-soaked using five different methods applied are compared with a reference concrete sample and a concrete sample made with non-pre-soaked RA. The results show that non-pre-soaked RA offers improved physical-mechanical properties for pre-cast concrete, except for the workability; problems arising from poorer workability could be improved with the use of plasticizers, which can be easily included in the production process. RESUMEN: Estudio de las ventajas potenciales del premojado en las propiedades del hormigón prefabricado con árido reciclado grueso.El árido reciclado (AR) procedente de residuos de construcción y demolición se utiliza tradicionalmente en la elaboración de hormigón para diferentes aplicaciones. Debido principalmente al mayor contenido en agua requerido por el AR, la calidad del hormigón está determinada por la cantidad de AR reemplazado. El objetivo de este estudio es determinar si el AR premojado mejora las propiedades del hormigón prefabricado para mobiliario urbano, con bajas exigencias mecánicas y estructurales, en el que se sustituye el 100% de la fracción gruesa. Los resultados de los ensayos físicos y mecánicos realizados sobre muestras de hormigón en las cuales el AR se ha premojado usando cinco métodos diferentes se han comparado con una muestra de hormigón de referencia y una muestra de hormigón fabricada con AR no premojado. Los resultados muestran que el AR no premojado proporciona propiedades físico-mecánicas mejoradas en el hormigón prefabricado, a excepción de la trabajabilidad; los problemas derivados de una deficiente trabajabilidad pueden ser fácilmente corregidos con la incorporación de plastificantes en el proceso de fabricación.

Study of recycled concrete aggregate quality and its relationship with recycled concrete compressive strength using database analysis

“…Aggregate from concrete demolition and debris generally presents a low quantity of impurities (160,161), however, the results for the compositions of recycled concrete aggregates obtained from literature are not significant enough to encounter any kind of relationship. Figure 2 shows an example of the composition of these aggregates measured according to EN 933-11 "Test for the classification of recycled aggregates according to their composition".…”

“…The grain size distribution of recycled coarse aggregate does not differ appreciably from natural coarse aggregates. Hence, the recycled aggregate fineness modulus undergoes small variations for the same maximum aggregate size, depending mainly on the crushing process used and the original concrete quality (160).…”

Mechanical Behavior of Masonry Mortars Made with Recycled Mortar Aggregate

“…The rest of the aggregates were used with their natural humidity (2.3 ± 0.2). Pre-wetting was performed to reach 80% of the total absorption capacity of the RA, guaranteeing the presence of water in the aggregate and decreasing the migration of water from the mixture to the RA [5,41]. The procedure used to achieve the aforementioned wetting was based on that described by Fonseca et al [53]: the aggregate was immersed in water for five minutes and then allowed to drain before its use.…”

Influence of bagasse ash and recycled concrete aggregate on hardened properties of high-strength concrete

“…As reported in the literature, the weakness and high porosity of recycled aggregate, which is poorer than crushed limestone (10)(11)(12), results in a lower quality concrete. However, recycled concrete can also be used as the aggregate for new concrete if its quality is been improved (12,13). Similarly, the concrete mixing method and the use of a pozzolanic material leads to an increase in the quality of concrete containing RCA (14,15).…”