This book takes an in-depth look at the influence of calcium oxide and hydrated calcium sulfate on the mechanical and physical properties of mortar used for masonry joints. Based on a rigorous experimental analysis with 21 samples and multiple admixture ratios, it reveals how these compounds impact key aspects such as compressive strength, density and structural failure behavior.The results provide clear insight: while calcium oxide can reduce mortar strength versus a standard sample, hydrated calcium sulfate improves its mechanical performance up to a certain threshold. This study provides valuable data for civil engineers, researchers and practitioners seeking to innovate in the formulation of more efficient and sustainable mortars.An indispensable technical guide to optimize materials in contemporary masonry.