Modeling and Optimizing Recycled Concrete Properties Using Central Composite Design: The Impact of Parent Concrete

Document Type : Regular Paper

Authors

1 Faculty of Civil Engineering, Semnan University, Semnan, Iran

2 Department of Mechanical Engineering, Khatam Ol Anbia University, Tehran, Iran

Abstract

Recycled aggregates have gained popularity in the recent decade. In this paper, central composite design and response surface methodology as an analytical approach were implemented to determine experimental design and prepare models of concrete properties made by recycled aggregates in the lab. Three important factors were chosen: the compressive strength (fc) of parent concretes, the rate of substitution of parent concretes, and the amount of cement. In contrast, compressive strength (fc), tensile strength (ft), and water absorption of recycled concrete were considered target responses. Statistical analyses reveal that models were acceptable with R2 values. Both statistical and experimental studies represent that fc, ft, and water absorption of concrete mainly relied on fc of parent concretes. The increase in the fc of parent concretes from 19 MPa to 36 MPa led to the rise in the fc of new concretes from 27 MPa to 38 MPa. In addition, when the substitution rate changed from 8% to 92%, fc of concretes changed from 26 MPa to 30 MPa. Recycled concretes with higher strength could be generated if the fc of parent concrete is high enough, mainly because of the better bond between paste and aggregates. The optimization of multiple responses reveals that a high percentage of parent concretes with high fc could be used in concrete mixtures without a considerable fall in mechanical properties.

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History

  • Receive Date: 14 October 2024
  • Revise Date: 15 November 2024
  • Accept Date: 03 February 2025

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