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Title: Recycled Additive to Improve Freeze-Thaw Durability of High Fly Ash Content Mortar

Author(s): Ahmed A. Gheni and Mohamed A. ElGawady

Publication: Symposium Paper

Volume: 334


Appears on pages(s): 166-184

Keywords: recycled rubber, freeze-thaw, fly ash concrete, durability, eco-friendly, sustainable construction admixture

DOI: 10.14359/51720259

Date: 9/30/2019

Statistics show an increase in the use of fly ash in concrete to improve both sustainability and performance. However, concrete incorporating high volume fly ash has encountered an issue with incompatibility between fly ash and air entraining admixture (AEA). This study investigates using ground recycled rubber (GRR) as an eco-friendly alternative to AEA to improve the freeze-thaw performance of mortar mixtures incorporating two different types and ratios of fly ash. Two different sizes and ratios of GRR were used in this study. The results were compared with mixtures having two different types and dosages of AEA as well as a reference mortar mixture having neither GRR nor AEA. Foam indices were determined for both types of fly ash and compared with cement. The compressive strength retention values of mortar cubes after exposing them to 36 freeze-thaw cycles were determined and linked to the air content of each mixture. This study revealed that the GRR outperformed the AEA in terms of the freeze-thaw durability where all mixtures retained their compressive strengths. However, the performance of mixtures including AEA was inconsistent depending on the chemical composition of the fly ash, fly ash replacement ratio, and AEA dosage.

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