Autogenous shrinkage of cementitious composites incorporating red mud

Due to the impact on the environment, the construction industry is striving to comply with the EU Green Deal in terms of reducing the natural resources used to produce cement. One of the strategies is the use of industrial by-products such as cement substitutes. In this work, the autogenous shrinkage of cement pastes with red mud (RM), limestone (LS), silica fume (SF), and calcined clay (CC) was investigated. The materials used originate from the same region in South-Eastern Europe. Five different mixtures were tested, in which the replacement level for cement varies up to 20% for RM and up to 10% for SF, LS, and CC. In addition, the behavior in the fresh state was evaluated by testing the workability and setting time and in the hardened state by testing the compressive and flexural strength. The results show that as the amount of supplementary cementitious material (SCM) increases, the deformation of autogenous shrinkage gradually increases. Normalized to the amount of cement, the compressive strength showed higher efficiency of the cement when SCMs were added. The results suggest that the SCMs used, with their fine particle size, provide additional nucleation sites for hydration products, resulting in higher efficiency of the cement in achieving compressive strength and higher autogenous shrinkage when SCMs are present.