RADIATION INDUCED SYNTHESIS OF POLY(ACRYLYIC) ACID-ALUMINA NANOGEL COMPOSITES FOR CHLORIDE BINDING AND NANOPARTICLE STABILIZATION IN CEMENTITIOUS SYSTEMS

Abstract

Chloride-induced corrosion of steel reinforcement is a critical challenge of concrete durability. This dissertation puts forth the development and evaluation of an advanced chloride-binding additive for cementitious systems. This additive is a radiation-induced alumina-poly(acrylic acid) (PAA) nanogel composite that is designed to enhance chloride immobilization. The nanogels are synthesized using a high energy (11 MeV) electron beam to drive radiolytic transformations in the precursor solutions. Two distinct radiation-based pathways were systematically explored. One method involved the direct in situ formation of alumina nanoparticles within a crosslinked PAA polymer network, while the other employed post-synthetic hybridization of PAA nanogels with preformed γ-Al2O3 nanoparticles. Comprehensive characterization using FTIR, UV-Vis, DLS, SEM/EDS and XRD elucidated the structure, morphology and composition of the radiation-derived materials. The chloride-binding performance of the nanogels were first evaluated in simulated pore-water solutions, where rapid chloride uptake was driven by the formation of calcium-aluminate-hydroxide (AFm) phases. This was followed by testing in mortar specimens, which demonstrated that the optimized nanogel composites could effectively sequester chloride under more realistic conditions without compromising the mortar’s mechanical properties. To complement this research, prompt gamma activation analysis (PGAA) was explored as a nondestructive method for chloride detection in concrete. Monte Carlo N-Particle (MCNP) simulations were used to model gamma-ray spectra across a range of chloride concentrations and aggregate types. Together, these results show that radiation-engineered nanogels offer a promising strategy for sequestering chloride from cementitious environments, providing a pathway toward more enhanced corrosion mitigation.