A Study on Mechanical and Microstructural Characteristics of Concrete Using Recycled Aggregate

Area of Science:

• Civil Engineering
• Materials Science
• Sustainable Construction

Background:

• Construction and demolition waste presents a significant environmental challenge.
• Recycled aggregates offer a potential solution for sustainable concrete production.
• Limited research exists on the performance of concrete using raw, unprocessed mixed coarse recycled aggregate (MCRA).

Purpose of the Study:

• To evaluate the performance of concrete incorporating MCRA as a substitute for natural aggregate (NA).
• To assess the impact of varying MCRA replacement levels (0-100%) on concrete properties.
• To determine the optimal MCRA replacement percentage for concrete with a characteristic strength of 30 MPa.

Main Methods:

• Concrete mixes were prepared with 0%, 30%, 60%, and 100% MCRA replacement.
• Workability was assessed using the slump test.
• Mechanical properties (compressive, split tensile, flexural strength) were tested on cubes, cylinders, and beams.
• Microstructural analysis was conducted using SEM, EDAX, XRD, and FTIR.

Main Results:

• Higher MCRA content improved concrete workability.
• 30% MCRA replacement significantly enhanced compressive strength (up to 14.24% at 90 days).
• Split tensile and flexural strengths increased by 2.92% and 6.26% respectively at 30% MCRA replacement.
• Microstructural analysis revealed a denser microstructure in the optimum mix.

Conclusions:

• A 30% replacement of NA with MCRA is suitable for concrete with a 30 MPa characteristic strength.
• MCRA incorporation positively influences concrete's physical, mechanical, and microstructural properties.
• This research supports increased utilization of construction and demolition waste, promoting a circular economy in construction.