Methods for Evaluating Pozzolanic Reactivity in Calcined Clays: A Review.

Area of Science:

• Materials Science
• Civil Engineering
• Sustainable Construction

Background:

• Ordinary Portland cement (OPC) production has a significant carbon footprint.
• Supplementary cementitious materials (SCMs) are investigated to reduce environmental impact.
• Calcined clay is a globally abundant pozzolanic material suitable for cement replacement.

Purpose of the Study:

• To systematically review and analyze methods for measuring the pozzolanic reactivity of calcined clays.
• To identify the most common and effective techniques for assessing calcined clay suitability as an SCM.
• To highlight the importance of calcined clay in sustainable construction materials.

Main Methods:

• Systematic literature search for pozzolanic reactivity assessment methods.
• Categorization of methods into direct, indirect, qualitative, quantitative, chemical, and physical.
• Analysis of specific techniques including Lùxan, force activity index, modified Chapelle, R3, Frattini test, thermal analysis, XRD, and XRF.

Main Results:

• Common methods for assessing calcined clay pozzolanic reactivity include the Frattini and modified Chapelle tests.
• Mechanical strength testing in cementitious matrices is frequently used.
• X-ray diffraction (XRD) and thermal analysis are prevalent for correlating results.

Conclusions:

• Multiple testing methods are necessary for accurate assessment of calcined clay pozzolanic reactivity.
• Calcined clays are a viable SCM for reducing the carbon footprint of cement.
• Further research and standardization of testing protocols are recommended for widespread adoption.