Flexural Behaviour of Reinforced Concrete Beams with HCL-treated Recycled Aggregate

Mohammed ALIBADI; Ali Ghanim Abbas AL-KHAFAJI; Awad  JADOOE

doi:10.71229/3bs37d71

Authors

Mohammed ALIBADI Department of Civil Engineering, College of Engineering, University of Kerbala, Karbala, Iraq
Ali Ghanim Abbas AL-KHAFAJI Department of Civil Engineering, College of Engineering, University of Kerbala, Karbala, Iraq
Awad JADOOE Department of Civil Engineering, College of Engineering, University of Kerbala, Karbala, Iraq

DOI:

https://doi.org/10.71229/3bs37d71

Keywords:

Reinforced concrete beams, Flexural behaviour, Recycled concrete aggregate, Hydrochloric acid treatment, Metakaolin

Abstract

Recycled concrete aggregate supports more sustainable concrete, but the old mortar on its particles weakens the bond with fresh paste; metakaolin is a reactive pozzolan that densifies the cement matrix. This study examined the flexural behaviour of reinforced concrete beams containing hydrochloric acid treated recycled concrete aggregate with metakaolin. Seven beams were cast with recycled concrete aggregate (0%, 25%, 50% of coarse aggregate) and metakaolin (0%, 5%, 10% of cement), the recycled concrete aggregate first soaked in 0.6 Molarity hydrochloric acid for 24 hours. All beams were loaded to failure under four-point bending, with first crack load, ultimate load, mid-span deflection and failure modes recorded. Without metakaolin, the first crack load fell from 18 kN to 13 kN, ultimate load decreased by 2.8% and 8.3% at 25% and 50% recycled concrete aggregate. With 10% metakaolin, the cracking load at 25% recycled concrete aggregate returned to the control value, ultimate load reached 142.90 kN (about 36% higher than the control), while all beams failed in a ductile flexural mode. The results suggest that combining hydrochloric acid treatment with metakaolin preserved, and in several cases improved, the flexural performance of beams containing recycled aggregate.

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