Thermal behaviors of clay minerals as key components and additives for fired brick properties: A review

Clay minerals are critical components for fired bricks because they provide plasticity, porosity and adequate strength for desired products. Investigations on clay minerals have been extensively published but those relevant to bricks have not been systematically reviewed in recent decades. Nowadays, the global brick industry faces critical challenges from energy costs, regulatory policies, and competing materials. A full understanding of raw materials for brick making is crucial for precise quality control and mitigation of waste streams. The innovative use of non-clay additives has substantially enhanced performance or processing conditions. However, moderating existing clay minerals may provide a more practical solution for many producers. This review summarizes recent progress in clay mineral-related brick production. Firstly, eight typical clay minerals are grouped according to their roles in the brick-making raw material. Research progress on the thermal behaviors of these clay minerals is summarized, including thermal mass loss, thermal phase transition, thermal expansion/shrinkage, etc. Then, relationships between clay minerals and critical physical, mechanical, and thermal conductivity/diffusivity characteristics of clayey raw materials and obtained brick products are comprehensively reviewed. Relevant studies on mineralogy and porcelain/earthenware products have also been perused to present an interdisciplinary conclusion. Finally, the current challenges in clay mineral-related brick production and potential suggestions are proposed. This review aims to provide a reference for designing clay mixtures and clay-based additives that deliver enhanced properties of bricks produced at an industrial scale.