Compressive strength ratios of concretes containing pozzolans under elevated temperatures

Area of Science:

• Materials Science
• Civil Engineering
• Environmental Science

Background:

• Cement production is a significant source of pollution due to high energy consumption and emissions.
• Elevated temperatures can negatively impact concrete infrastructure, necessitating performance studies under such conditions.

Purpose of the Study:

• To investigate the post-heat performance of concrete with zeolite and bentonite additives.
• To evaluate the effect of elevated temperatures (28°C to 700°C) on concrete specimens containing 6% and 10% zeolite and bentonite.

Main Methods:

• Concrete specimens were prepared with varying percentages of zeolite and bentonite.
• Specimens were exposed to temperatures of 28°C, 150°C, 300°C, and 700°C.
• Compressive strength, tensile strength, C-S-H peak intensity, and Portlandite content were analyzed using XRD.

Main Results:

• Replacing cement with 6% and 10% zeolite and bentonite increased compressive strength at 90 days under ambient conditions.
• Concrete with 10% bentonite heated to 150°C showed a 40% increase in compressive strength.
• Tensile strength decreased at 300°C and 700°C for specimens with pozzolans.
• C-S-H peak intensity decreased significantly at 700°C, while remaining similar up to 300°C.
• Specimens heated at 150°C exhibited the highest compressive strength, while those heated at 700°C showed the lowest.

Conclusions:

• Zeolite and bentonite additives can enhance concrete's ambient compressive strength.
• While 150°C exposure can boost compressive strength, higher temperatures (300°C-700°C) degrade tensile strength and C-S-H structure.
• The study provides insights into concrete's thermal performance with mineral admixtures for infrastructure resilience.