Influence of water-repellent admixtures (Sitren and Stearate materials) on the microstructure and mechanical performance of conventional Portland cement paste and mortar

The longevity of mortar and concrete structures can be compromised by the absorption of water and other fluids, leading to deterioration and aesthetic issues. To address this, water-repellent admixtures are employed to enhance the service life of mortar and concrete components by improving their mechanical and microstructural characteristics. This study focus on the effects of incorporating Sitren P 750 and various stearate materials (calcium, zinc, aluminum, and barium) as admixtures with ordinary Portland cement at mortar and paste dosages of 0.5 %, 1.0 %, and 1.5 % of the cement content. We found that mortars with water-repellent admixtures exhibited competitive mechanical properties at all curing ages. Additionally, the study confirmed the contribution of these admixtures to the production of hydration products and the structural development of the mortars, as investigated through scanning electron microscopy, thermogravimetric–derivative thermogravimetric, and X-ray diffraction analyses. Despite alterations in several physical properties and hydration kinetics due to the water-repellent compounds and their dosages, all admixtures provided effective water-repellent protection. This was further corroborated by water contact angle tests and the measurement of the capillary water absorption coefficient for all samples. Identifying the optimal mixture ratio for construction technology and effectively incorporating repellence features is a crucial aspect of this research.