Development of Self-Healing Cement Mortar Through the Integration of Sodium Silicate-Impregnated Expanded Vermiculite

Cracks in concrete structures are common which compromises its structural integrity, durability, by permitting the penetration of detrimental elements such as water and chemicals, resulting in accelerated deterioration. Over the past decades, extensive research has been conducted to address this problem with the introduction of self-healing concrete. However, existing self-healing approaches often face limitations such as reduced efficiency for wider cracks, limited availability of healing agents, and poor long-term performance. Therefore, there is a need to develop efficient self-healing systems capable of enhancing healing performance without compromising the strength and durability. The current study examined the influence of sodium silicate impregnated expanded vermiculite as a fine aggregate in cement mortar, which can act as a self-healing agent. Here, raw vermiculite heated at a temperature of 1000 ℃, expanded vermiculite, was impregnated with sodium silicate solution using a vacuum impregnation process and, coated with polyvinyl alcohol to prevent premature leakage of sodium silicate during mixing and curing. The coating enables controlled release of the healing agent upon crack formation, thereby enhancing the self-healing efficiency. The fine aggregate is partially substituted with expanded vermiculite and impregnated expanded vermiculite in 5, 10, 15, and 20% proportions. The study evaluated the strength, durability, and crack-healing efficiency of the developed cement mortar. The crack width was examined and assessed at every 7, 28, 56, and 90 days using ImageJ software. Test results revealed that mix containing 15% expanded vermiculite impregnated with sodium silicate (IEV-15) achieved a healing efficiency of 75% within 90 days. Thus, the ideal dosage of expanded vermiculite was determined to be 15% replacement to fine aggregate, indicating improved self-healing efficiency. The improved crack-healing efficiency is attributed to the controlled release of sodium silicate from the expanded vermiculite. Once released, sodium silicate reacts with the available calcium hydroxide in the surrounding cement matrix to form additional C–S–H gel within the crack region, thereby enhancing crack sealing and durability. The study provides insight into the healing mechanism and contributes to the development of efficient self-healing cementitious materials.