The Experience of Cuba TRC on the Survey of Kaolinitic Clay Deposits as Source of SCMs—Main Outcomes and Learned Lessons

Color control in industrial clay calcination

“…In the raw clay sample the Al 2 O 3 /SiO 2 = 0.53 and the LOI ≥ 7%. For samples with kaolinite contents higher than 40%, the lower limit values for those ratios are 0.3 and 0.1 respectively[34]. Therefore, kaolinite content values as determined by TGA are in good agreement with chemical composition.…”

Properties and occurrence of clay resources for use as supplementary cementitious materials: a paper of RILEM TC 282-CCL

“…Kaolin is also frequently used as a commercial term to describe a low-iron claystone comprised mostly of kaolinite or related clay minerals, characterized by being white or nearly white, even when calcined, and its commercial value being determined by its whiteness and particle size [24]. This industrialoriented classification of kaolin reflects its traditional application and includes high-grade kaolin, used in the paper industry and manufacture of glass fibers; bauxitic kaolin, with relatively high contents of alumina and low content of alkalis and iron oxides, mainly used for refractories; sandy kaolin, with variable contents of quartz and feldspars, used for obtaining pigments and additives; and kaolin with high contents of plastic clays, used by the ceramics industry [15].…”

“…Their abundance and wide global distribution, low activation temperature and large thermal activation window in comparison to other clay minerals are advantageous factors for their processing at industrial scale [6,24,26,27]. Moreover, calcination products of clay minerals from the kaolinite group are an excellent source of reactive alumina, unmatched by any other currently available SCMs.…”

“…Among the minerals of the kaolinite group one may find nacrite and dickite in addition to kaolinite in this setting. Relatively high contents of sulfides or aluminum sulfates such as alunite are potentially present [24,25,32,33]. Occurrence of iron oxides or hydroxides depends on the iron content on the parent rock.…”

“…The absence of selection criteria for evaluation of kaolinitic clay deposits as source of SCMs is a major limitation for their identification and industrial exploitation. Although there are currently no specified kaolinitic clay characteristics for use as a source of SCMs, a minimum content of clay minerals from the kaolinite group of 40 wt.% has been proposed by several authors [24,28,29], including the authors of this paper. This threshold criterion corresponds to the content of reactive material needed to obtain a mechanical performance at seven days comparable to PC by a 30 % substitution of PC by calcined kaolinitic clay, or by a 50 % substitution of clinker by a calcined kaolinitic clay-limestone blend in a limestone-calcined clay cement (LC 3 ) [6,28,29].…”