Durability and shrinkage performance of concrete made with coarse multi-recycled concrete aggregates

Since construction is one of the most environmental impacting activities in existence, it is important to study and develop solutions to make its processes more efficient. Thus, multiple-recycling of concrete presents itself as a possible alternative for the reutilization of construction and demolition waste (CDW) over a large period of time. This paper presents the results and conclusions obtained from an extensive experimental campaign intended to study the durability performance of concrete made with aggregates resulting from multiple recycling cycles. Concrete mixes with 25% and 100% of substitution of natural coarse aggregates with recycled coarse concrete aggregates obtained from one, two and three recycling cycles were produced. Tests such as sieve analysis, water absorption, particle density, shape index, particle bulk density and Los Angeles abrasion were made to study the recycled coarse aggregates properties. Additionally, the workability and bulk density of fresh concrete were measured, and water absorption by immersion and capillarity, carbonation and chloride penetration were assessed to evaluate the durability performance of hardened concrete, as well as shrinkage. The results obtained in the various tests show that, with the increase of recycling cycles, the recycled coarse aggregates demonstrate a quality decrease in their properties, resulting in a worse durability and shrinkage performance of the resulting concrete. Furthermore, it is shown that the decrease in performance tends to slow down with the increase of the recycling cycles, thus presenting an asymptotic behaviour. However, in most cases, it was not possible to establish that three recycling cycles were enough to stabilize the properties. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

An extensive experimental study was conducted to investigate the durability performance of concrete made with recycled coarse aggregates from multiple recycling cycles. The results show that as the number of recycling cycles increases, the properties of the recycled coarse aggregates decrease, leading to poorer durability and shrinkage performance of the resulting concrete. Moreover, the decrease in performance tends to slow down with the increase of recycling cycles, showing an asymptotic behavior.