Methods for Evaluating Pozzolanic Reactivity in Calcined Clays: A Review

Abstract

The search for alternative materials to replace ordinary Portland cement has been the object of work that enhances the investigation of the use of pozzolanic materials and the reduction of the carbon footprint with supplementary cementitious materials. However, not all materials are available to meet the large-scale demand for cement replacement. A relevant exception is the calcined clay, a material found worldwide that, when subjected to appropriate heat treatment, presents pozzolanic reactivity and can be used as a supplementary material to cement. This review presents, through a systematic search, methods for measuring the pozzolanic reactivity of calcined clays, namely, direct, indirect, qualitative, quantitative, chemical and physical methods such as electrical conductivity (Lùxan), the force activity index, the modified Chapelle, R3, Frattini test, thermal analysis, X-ray diffraction and X-ray fluorescence spectrometry. The most usual methods to assess the pozzolanic reactivity of calcined clays were exposed and analyzed. It should be pointed out that there is greater use of the Frattini and modified Chapelle methods as well as the analysis of the mechanical strength behavior of the material in cementitious matrices. X-ray diffraction and thermal analysis were exposed as the most used correlation methods but it was also concluded that different tests are needed to generate accurate results.

Pozzolanic potential of sustainable precursors for engineered geopolymer composites (EGC)

“…Consequently, a considerable correlation exists between the Frattini and SAI tests (figure 6). Nonetheless, the Frattini test values recorded for BOF Slag, FA, and IOT in this study were consistent with the known degrees of their respective pozzolanicity [23,27,53].…”

“…Contrarily, a weak correlation may indicate difference in aspects of pozzolanic activity, making them unreliable [50][51][52]. Also, this relation allows the selection of suitable methods, depending on the time and resource availability alongside improving the intended test methods [23,50,53]. The study also examines the potential of utilizing these industrial wastes, especially the combination of FA and BOF slag, as sustainable precursors for producing EGC.…”

Reactivity of Calcined Clays as SCM—A Review

“…A lot of different test methods to evaluate the reactivity of SCMs with different approaches can be found in literature as compiled in Table 1 (compare [31]).…”

Comprehensive Review of Direct and Indirect Pozzolanic Reactivity Testing Methods

“…The R 3 reactivity test method stands for "rapid, robust, and relevant," based on work by Avet et al [30] and the RILEM Technical Committee 267 [18]. This method was primarily developed to assess calcined clays' pozzolanic reactivity [127]. It is a method that was established based on good Pearson correlations between strength development the and evolution of heat or bound water for detecting the reactivity of SCMs [127,128].…”

“…This method was primarily developed to assess calcined clays' pozzolanic reactivity [127]. It is a method that was established based on good Pearson correlations between strength development the and evolution of heat or bound water for detecting the reactivity of SCMs [127,128]. As this test method is relatively new, it recently underwent some modifications and complement studies were conducted before being standardized in North America as ASTM C1897 for measuring the reactivity of SCMs over a curing time of 7 days [32,128,129].…”