Evaluation of the influence of polycarboxylic superplasticizing admixture and silica fume on high-strength concrete with recycled aggregates

Abstract

The construction sector exerts considerable environmental pressure, primarily due to pollution and the intensive extraction and use of raw materials. In response to these environmental challenges, a sustainable alternative in the production of concrete is to replace natural aggregate with recycled aggregate (RA); however, this type of aggregate affects the mechanical and physical properties of concrete. Therefore, it is recommended to use polycarboxylate superplasticizing (SP) admixture to improve workability and silica fume (SF) to increase the strength of concrete. The experimental plan was performed at the Structures Laboratory of Universidad de Lima. The main objective of this study is to determine the influence of the incorporation of polycarboxylate superplasticizer and SF on the strength of high-strength concrete with recycled aggregates. The properties of the concrete in the fresh state (temperature, slump and unit weight) and the properties in the hardened state were evaluated through physical tests (compression, tensile, elasticity and ultrasonic pulse velocity). The experimental plan was developed using four dosages of RA (0%, 33%, 66% and 100%), two dosages of SF (0% and 10%) and three dosages of SP (0.5%, 1.0% and 1.5%). A total of 12 mixes were designed, with 9 cylindrical specimens and 3 beams were produced per mix. In addition, a statistical analysis was carried out to analyze the correlation between the independent variables and the mechanical properties of the recycled concrete, and an analysis of environmental impact and costs. Finally, it is concluded that the addition of SF and SP contributes to improve the characteristics of recycled concrete, although it is necessary to balance these benefits with the environmental impact and associated costs.