Influence of recycled concrete aggregate on the foam stability of aerated geopolymer concrete. (15th February 2021)

• Record Type: Journal Article
• Authors: Pasupathy, Kirubajiny; Ramakrishnan, Sayanthan; Sanjayan, Jay
• Is Part Of: Construction & building materials. Volume 271(2021)
• Publication Date: 2021-02-15
• Subjects: Aerated geopolymer concrete -- Foam stability -- Recycled concrete aggregate -- Rheology -- Thermal properties; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2020.121850
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Effect of RCA on the foam stability of GFC is studied. The settlement of fresh GFC is significantly reduced with RCA. The initial yield stress and yield stress growth rate increased with the replacement of RCA. The fresh foam stability influenced the air void distribution in the GFC. Abstract: The effect of recycled concrete aggregates (RCA) in enhancing the foam stability and hardened properties of aerated geopolymer concrete (GFC) produced by a mechanical foaming method is investigated. The RCA was used as a partial or full replacement to fine aggregates, and approximately the same amounts of foam were used in all mixes to achieve a targeted density of 800 kg/m 3 . Despite the same water/binder and activator/binder ratios in all mixes, the fresh and hardened properties of GFC significantly varied between mixes. The instability of fresh geopolymer mix, caused by the collapse of air bubbles and the settlement was identified as a major issue in the control GFC mix. The use of RCA in GFC has significantly improved the foam stability with a significant reduction in settlement. The foam stability criterion was correlated to the yield stress development of base mixes, where the addition of RCA increases the initial yield stress and yield stress development over time. This has significantly influenced the stability of bubbles in GFC. On the other hand, the setting time of the geopolymer has reduced with the increasing RCA content. Nevertheless, the foam instability and corresponding settlement were stabilized well ahead of the initial setting time, indicating the setting of geopolymer has less impact on the foam instability in GFCs. The XRD and TGA analyses detect the presence of Ca(OH)2 in RCA, which increases the yield stresses of fresh geopolymer pastes. The variation in foam stability was well reflected on the hardened properties of GFC, such as porosity, pore size distribution, and thermal properties.