Influence of recycled aggregates on properties of self-consolidating concretes

Abstract

h i g h l i g h t sIt is feasible to incorporate crushed concrete powder in order to achieve maximum use of the recycled concrete. The influence of admixtures must be studied not only in fresh mixtures but also in hardened concrete. Petrographic studies revealed that the incorporation of crushed concrete powder makes the mortar matrix denser. a b s t r a c tRecycled aggregates are made from crushed waste concretes and can be used as a replacement of natural aggregates in concrete production. Despite having lower density and higher absorption than natural aggregates, they can be used to manufacture conventional concretes with good performance if they are added in the proper amounts. To make self-consolidating concretes, the same aggregates used to manufacture conventional concretes can be used, but in order to increase segregation resistance and keep mix cohesion, a large amount of fine aggregates and a suitable admixture are required. The main goal of this work is to study the influence of recycled aggregates on self-consolidating concrete. Concretes were mixed with 50% of the coarse aggregate replaced by recycled aggregates (Patagonia gravel) and with 20% of the fine aggregate (natural sand) replaced by crushed concrete powders. Fresh concrete properties were tested, and physical and mechanical properties were determined in the hardened state. The petrographic composition of the concrete was examined to assess the interfacial transition zone and the contribution of the powders to the mortar microtexture. The results vary depending on the type of admixture and aggregate. However, it is shown that the inclusion of these crushed aggregates to make good selfconsolidating concrete is feasible.

Effect of Supplementary Cementitious Materials on Rheology of Different Grades of Self-Compacting Concrete Made with Recycled Aggregates

“…In both these concrete grades, compressive strength decreased by not more than 5% for complete replacement of the NCAs with the RCAs. Various authors (Senas et al 2016;Guneyisi et al 2016b;Revathi et al 2013;Kou and Poon 2009) have stated that behaviour of fresh self-compacting concrete is significantly affected by the use of recycled aggregates. According to Guneyisi et al (2016b), "the selfcompactability characteristics of the concrete are remarkably improved by the replacement levels of CRCA and FRCA used in the SCC mixtures".…”

Influência dos agregados reciclados nas propriedades reológicas e mecânicas do concreto autoadensável

“…De modo geral, a resistência à tração por compressão diametral dos concretos parece ter sido menos influenciada pela incorporação dos agregrados reciclados às misturas, dada a menor redução constatada dessa propriedade. Resultados semelhantes foram observados por SEÑAS et al [50], que relataram queda de apenas 2,27% na resistência à tração de um concreto autoadensável com substituição de 50% da brita natural por agregado graúdo reciclado. Em outra composição, que empregou 50% de agregado graúdo reciclado e 20% de areia reciclada, os mesmos autores verificaram redução de 11,36% na resistência à tração.…”

Propiedades Físico-Mecánicas De Concretos Autocompactantes Producidos Con Polvo De Residuo De Concreto

“…El Concreto Autocompactante (CAC) es un concreto especial que fluye por su propio peso, toma la forma del encofrado y llena todos los espacios vacíos, manteniendo su homogeneidad, incluso, en presencia de refuerzos (Señas;Priano;Marfil, 2016;Matos;Prudêncio-Jr.;Oliveira;Pelisser;Gleize, 2018), esto hace que el CAC sea particularmente útil donde el vaciado es difícil, tal como ocurre en estructuras de concreto altamente reforzadas o con cimbras complicadas Robayo;Mattey;Delvasto, 2016). La aparición del concreto autocompactante ha impactado positivamente al sector de la construcción por la innovación que conlleva.…”