Nucleation Seeding for Performance Enhancement of Cementitious Materials
Advisor: Professor Nishant Garg
Abstract
Emerging blended cements and concrete mixes with a high volume of SCMs often suffer from slow hydration and reduced early strength. Conventional chloride-based accelerators can mitigate this strength reduction yet may introduce corrosion risks and late-age penalties, limiting their use. Over the past decade, a new form of accelerators based on nucleation seeding has been introduced in the admixture market. Fundamental and systematic investigation of these “seeding” approaches are needed in the lab and the field before widespread deployment.
This thesis addresses that gap by (i) quantifying the effects of two commercial C-S-H seed admixtures (X-Seed 44/55) on early-age kinetics, microstructure, and strength in Type IL systems using coordinated lab–field studies, and (ii) developing a scalable, grinding-free co-precipitation route for ultrafine, novel ettringite (AFt) seeds stabilized with polycarboxylate ether (PCE), then evaluating those seeds in Type IL and LC3 binders.
Commercial C-S-H seeds successfully increased the degree of hydration by ~15%, reduced open porosity, and advanced strength development. Field placements in Illinois conducted with IDOT followed lab trends, with seeded concrete mixes reaching ~5,400 psi in 2 days, whereas the unseeded control required 7 days to reach ~5,300 psi – reducing cure times. Novel AFt seeds synthesized via a PCE-stabilized route yielded sub-100 nm particles (D50 ≈ 68 nm) without drying or milling, reducing the cost of production. These ultrafine, lab-grown AFt seeds also accelerated hydration, refined the pore structure, and boosted early strength in both Type IL and LC3 systems, achieving performance comparable to commercial C-S-H seeds at the optimized dosage.
Overall, this nucleation seeding approach offers a potential pathway to accelerate setting and hardening, while densifying the microstructure and enhancing strength at both early and later ages. This thesis opens up a pathway for further scaling and deployment of seed-based admixtures.