Fired clay bricks made by incorporating organic additives: A review

The incorporation of organic additives in the manufacture of fired clay bricks represents a promising approach to promoting sustainable construction, making it possible to reduce the carbon footprint while improving the performance of these materials. The aim of this study is to synthesize and critically analyze existing research on the impact of various organic additives on the properties of fired clay bricks. The methodology adopted includes a systematic review of the available literature with a comparative analysis of performance according to different incorporation parameters. The strength of this review lies in the establishment of a classification of 19 types of organic additives based on their differentiated impacts. This approach makes it possible to define optimal incorporation ranges (2–25 % by weight) and to identify the best-performing additives according to multiple criteria. The study also introduces a multi-criteria optimization methodology that simultaneously integrates mechanical, thermal and environmental performance, representing a significant methodological advance in the field. The results show that the addition of organic additives (2–25 %), such as sawdust, rice husks or industrial sludge, reduced density by up to 10 %, significantly increased porosity by up to 35 %, led to a 40 % reduction in thermal conductivity and resulted in a progressive reduction in compressive strength as a function of the percentage of additives added. Increased porosity improves thermal insulation, but leads to a reduction in mechanical strength when incorporation rates are high. By establishing quantitative relationships between manufacturing parameters and final properties, the incorporation rate and the firing conditions, it has been possible to achieve an optimum compromise between thermal and mechanical performance in some of the cases studied. Simultaneously, the use of additives derived from agricultural and industrial residues has great environmental potential, as it recovers waste products while reducing the use of natural resources and the associated carbon footprint. The main benefits of this approach include waste recovery, reduced production costs and improved energy performance of buildings. This study is relevant to international research because it proposes a systematic approach to multi-scale characterization of organic additives, transferable to different geographical contexts and local clay types. The innovative methodology developed makes it possible to optimize formulations according to environmental, economic and technical criteria simultaneously, providing a reference framework for the recovery of organic waste available in many countries. It makes a significant contribution to the advancement of knowledge in the engineering of sustainable construction materials, and paves the way for practical applications in the construction industry worldwide. This work has highlighted the need to strike a balance between porosity, which improves thermal performance, and mechanical strength, which is often reduced by the excessive use of additives. Optimizing incorporation rates, particle size distribution of additives and drying and firing parameters is therefore essential to guarantee bricks that combine mechanical durability and thermal efficiency. Hence the need to continue exploring the use of organic additives in the production of fired clay bricks remains paramount.