Effect of Elevated Temperatures on Diverse Properties of Sustainable Concrete with Fine Recycled Refractory Brick Aggregate and Polypropylene Fiber

Utilization of recycled aggregates into concrete has taken a significant stride toward achieving sustainable construction, whereas temperature remains a pivotal factor adversely affecting the diverse concrete properties during service life. Thus, when exposed to elevated temperature, enhancing and evaluating sustainable concrete properties has become essential. The present article concentrates on the physical, destructive, and nondestructive properties of concrete, incorporated with fine recycled refractory brick (RRB) as a replacement of fine aggregate in combination with polypropylene fiber as the reinforcing agent, after exposure to elevated temperatures. To accomplish this, four distinct concrete blends have been prepared, with 10%, 20%, and 30% substitution of fine aggregate with RRB including one conventional (control) mix. Moreover, 1% polypropylene fiber has been incorporated as a reinforcing agent to meet the expected strength parameters. The concrete specimens have been exposed to different temperatures, 200°C, 400°C, 600°C, 800°C, 1,000°C, and 1,200°C. After exposure, different tests (visual appearance, mass loss, density loss, stress–strain profiles and compressive strength, ultrasonic pulse velocity, dynamic modulus of elasticity, degree of damage, failure pattern, and scanning electron microscope analysis) have been conducted to assess the diverse properties of concrete. The experimental findings have conclusively indicated optimal performance when 20% fine aggregate has been replaced with RRB with a compressive strength of 35.02 MPa at ambient temperature. Whereas, the specimen with 10% fine aggregate replacement with RRB has shown a compressive strength of 38.98 MPa at 400°C. All specimens, irrespective of the RRB replacement level, indicated excellent consistency of concrete with an ultrasonic pulse velocity value greater than $4.4\mathrm{km}/\mathrm{s}$ up to 200°C, which was then followed by stepwise degradation with further temperature increases. In the authors’ opinion, natural fine aggregate partially replaced with RRB in combination with polypropylene fiber holds promising potential for the manufacturing of sustainable concrete intended for use under elevated temperature.

The newly developed concrete blend, designed to be both sustainable and heat-resistant, will hold the promise of safeguarding natural resources and saving Mother Earth. By incorporating a particular alternative aggregate (recycled refractory brick), this innovation will not only curtail manufacturing expenses for heat-resistant concrete but also repurpose waste effectively. This sustainable heat-resistant concrete can be applied to concrete structures and members exposed to high temperatures, protecting them from rapid deterioration caused by repeated harsh conditions. Its implementation will not only enhance durability and efficiency of these structures but also lead to significant savings on maintenance costs, particularly in steel making industries.