Biopolymeric microcapsules containing different concentrations of sodium silicate as admixture in cement pastes for autonomous self-healing

Portland cement concrete faces challenges related to durability, strength, and repair costs, and it also contributes to CO₂ emissions. Although sodium silicate and biopolymeric microcapsules have already been reported in the literature, this study focuses on the autonomous self-healing of the cementitious matrix by evaluating the effect of different sodium silicate concentrations encapsulated within biopolymeric microcapsules: MC.A (0%), MC.SS10 (10%), and MC.SS20 (20%). It prepares cement pastes with approximately 16% (v/v) of microcapsules. The characterization of microcapsules employs optical microscopy, particle size distribution analysis, and SEM-EDS, confirming their spherical morphology and the presence of sodium silicate in the core. The characterization of cement pastes and specimens employs rheology, calorimetry, compressive strength tests, water absorption, and SEM-EDS microstructural analysis. The results indicate that incorporating microcapsules does not compromise the fresh or hardened properties of the pastes. Calorimetry shows reductions in maximum heat flow of 54%, 17%, and 16% for MC.A, MC.SS10, and MC.SS20, respectively, compared to the reference sample (REF). The compressive strength test reveals that, except the MC.A, the inclusion of microcapsules does not negatively affect axial compressive strength over time. In pre-cracked specimens, especially MC.SS10 and MC.SS20, strength recovery is comparable and, in some cases, superior to the control samples. Although the effect is more pronounced at early ages and immediately after crack formation, the microcapsules promote a more efficient strength recovery process than systems without their inclusion. This behavior highlights the healing potential of microcapsules, establishing them as a promising alternative for strengthening cracked cementitious materials. • Biopolymeric microcapsules with sodium silicate enhanced autonomous self-healing in cement pastes. • Calorimetry showed reduced heat flow and modified hydration due to microcapsule incorporation. • Sodium silicate microcapsules preserved compressive strength and improved crack recovery. • SEM-EDS confirmed silicate release and healing product formation in cracked regions. • Integrated tests confirmed strength recovery without mechanical performance loss.