Early-age evolution of recycled concrete strength: insights from micromechanics modeling and experimental testing

Author(s): Markus Königsberger, Brice Delsaute and Stéphanie Staquet
Paper category: Proceedings
Book title: Proceedings of the International Conference on Sustainable Materials, Systems and Structures (SMSS2019) New Generation of Construction Materials
Editor(s): Marijana Serdar, Nina Štirmer, John Provis
ISBN: 978-2-35158-217-6,
Vol 1. ISBN: 978-2-35158-223-7
e-ISBN: 978-2-35158-218-3
Publisher: RILEM Publications SARL
Publication year: 2019
Pages: 272-278
Total Pages: 7
Language : English

Abstract: Recycled concrete, i.e. concrete which contains aggregates that are obtained from crushing waste concrete, exhibits reduced stiffness and strength as compared to virgin concrete. Micromechanics-based multiscale modeling techniques are used to study the origin and quantify the extend of the reduction of mechanical properties. Therefore, recycled aggregates are divided into three morphology classes: plain aggregates (without old cement paste), mortar aggregates (mixture of old sand and old cement paste), and aggregates entirely covered by old cement paste. Stress concentrations in interfacial transition zones (ITZs), which occur mutually between aggregates, old paste, and new paste, are quantified and allow for bottom-up strength predictions. Modeled strength evolutions are compared to novel data from an ongoing testing campaign performed at ULB as well as to experimental data available in the literature. The
study shows that critical ITZs in recycled concrete are much weaker than their counterparts in ordinary concrete and that the ratio of ITZ porosity to bulk porosity of the new cement paste decreases with increasing water-to-cement ratio. This suggests that the amount of water transferred trough the ITZ is responsible for the ITZ weakening.

Online publication : 2019
Publication type : full_text
Public price (Euros) : 0.00