Document Type : Research Paper
Authors
1
MsC Graduate student, Department of Civil Engineering, University of Science and Technology of Mazandaran, Behshahr, Iran
2
Assistant Professor, Department of Civil Engineering, University of Science and Technology of Mazandaran, Behshahr, Iran
3
Faculty of Civil Engineering, University of Science and Technology of Mazandaran, Behshahr, Iran.
Abstract
The increasing use of concrete in concrete pavements is accompanied by serious environmental, economic and technical challenges. The high consumption of Portland cement and natural aggregates leads to the destruction of natural resources, greenhouse gas emissions and waste management problems caused by construction waste. The use of recycled concrete aggregates (RCA)1 as a partial replacement for natural aggregates is considered a sustainable solution, but due to high water absorption (5-10% higher than natural aggregate), higher porosity and weak interfacial transition zone (ITZ)2, it reduces the compressive strength of concrete by 10-20% and weakens its durability against environmental factors. The present study investigated the effect of simultaneous use of recycled concrete aggregates (with 25 and 50 percent replacement levels), Class F fly ash as a cement supplement (with 25 and 50 percent levels), and polypropylene macrosynthetic fibers (with 0.4 and 0.6 percent volume percentages) on the mechanical properties and durability of pavement concrete. Ten mix designs including a control sample were designed and manufactured. Fresh concrete slump tests, compressive strength at 7 and 28 days, tensile strength, elastic modulus, and water absorption were performed on cubic and cylindrical samples. The results showed that RCA replacement alone reduced compressive strength and increased water absorption, but the simultaneous addition of fly ash and macrosynthetic fibers significantly compensated for this performance loss. The optimal design combination (T8) (25 percent RCA + 25 percent fly ash + 0.4 percent macrosynthetic fibers) provided the best results; So that the 28-day compressive strength reached 31.48 MPa (8.5% higher than the control sample), tensile strength reached 2.81 MPa, and water absorption reached 1.41%. This combination, by creating a synergistic effect in improving the microstructure of the cement paste, strengthening the interfacial transition zone, and reducing porosity, provides a sustainable, economical, and resistant pavement concrete suitable for Iran's climatic
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