Decarbonization in Cement Manufacturing-The Role of Calcined Clay for the Achievement of Environmental Neutrality by the Cement Industry: Its Reactive Alumina Content (Al2O3r–) or Key Chemical Parameter for Verifying Its Quality

¹PhD student, Salamanca University, Spain

²Retired, Cement Manufacturer, Cali, Colombia

³Retired, Eduardo Torroja Institute of Construction Science – CSIC – Madrid, Spain

Corresponding author: Rafael Talero , Retired, Eduardo Torroja Institute of Construction Science – CSIC – Madrid, Spain, Phone: 617 819 911, E-mail: [email protected]

Received Date: January 29, 2026
Published Date: April 29, 2026

Citation: Talero R, et al. (2026). Decarbonization in Cement Manufacturing- The Role of Calcined Clay for the Achievement of Environmental Neutrality by the Cement Industry: Its Reactive Alumina Content (Al₂O₃r–) or Key Chemical Parameter for Verifying Its Quality. Material Science. 8(1):43.

Copyright: Talero R, et al. © (2026).

ABSTRACT

The large-scale thermal activation of clays to produce highly reactive pozzolans is a critical technology for reducing CO₂ emissions in cement manufacturing and make it much more sustainable. This document establishes the scientific and technical principles for producing high-quality supplementary cementitious materials (SCMs) from thermally activated clays. The quality of these SCMs is primarily determined by their reactive silica content (SiO₂^r⁻ (%)) and, most importantly, their reactive alumina content (Al₂O₃^r⁻ (%)). We examine key manufacturing aspects, including pyro-processing and separate grinding technologies, and discuss the optimized use of these materials in novel blended cements. These cements exhibit superior sustainability, being more eco-efficient and environmentally friendly than conventional Portland cement. Furthermore, they demonstrate enhanced mechanical performance and durability, particularly showing improved resistance to chloride-induced corrosion of steel reinforcement, sulphate attack (with replacement amounts greater than 40-55%), seawater exposure, and alkali-silica reaction (ASR). This paper highlights that the reactive alumina content (Al₂O₃^r⁻ (%)) is the key chemical parameter for verifying the quality and performance of activated clay” (AC) in sustainable cement applications. Because the higher this content, the greater the PC replacement amount that can be achieved, regardless of whether the kaolinite content of its matrix clay is greater or less than 40%. Because against the subsidiary generation of CO₂, when decarbonating the limestone from the Portland clinker raw material in its kiln, in 1st phase, the subsidiary generation of H₂O vapor from the dehydroxylation of the clay when it is thermally activated in its kiln is also taken into account, in such a way that, as long as higher the quality of the matrix clay, greater Al₂O₃r− (%) content will have activated and greater percentage of replacement will allow by OPC, which make the manufacture of the new OPC/AC blend cements much more sustainable: directly and indirectly.

Keywords: Calcined Clays, Thermal Activation, Dihydroxylation Process, Reactive Alumina, Pozzolanicity, Quality Control; Joint Grinding, Separate Grinding, Blending Station