NANOENCAPSULATION-DRIVEN MICROBIAL HYDROGEL SPRAY FOR AUTONOMOUS CONCRETE CRACK HEALING

Concrete microcracking still poses a significant problem that cuts down the
durability of the structure, lets water in, and raises the cost of
maintenance. In order to solve this problem, a novel, nanoengineered
hydrogel system that is sprayable has been created by putting together
nanoencapsulated Bacillus subtilis spores, urease-loaded nanogels, and
mesoporous silica nanoparticles for the purpose of autonomous healing of
cracks. Spores were encapsulated by means of a layer-by-layer (LbL)
nanoshell technique using chitosan and alginate bilayers, which included
6–10 layers, thus increasing the resistance to UV radiation, desiccation,
and alkaline conditions, while still allowing more than 80% germination.
Urease immobilization in alginate nanogels (150–300 nm) gave the high
catalytic activity so that the early precipitation of calcium carbonate was
thus initiated. The mesoporous silica nanoparticles formed the urea
reservoirs and the nucleation sites giving a boost to the mineral deposition
in the cracks. A two-phase spray is used in the delivery of the system: Phase
A comprises the biological nanocomponents in an alginate-xanthan
hydrogel and Phase B provides calcium ions. At the time of application, the
phases intermix at the crack surface, thereby stimulating microbial
proliferation and mineralization at the nanoscale. The planned evaluations
will cover nanoscale characterization (DLS, zeta potential, SEM, TEM),
biological assays (colony recovery, urease activity), and mechanical
performance tests (crack closure, permeability reduction, reinforcement).
This concept showcases the synergy of nanoencapsulation and microbial
self-healing leading to sustainable and high-performance construction
materials.