Ettringite Seeds for Strength Enhancement: Novel Synthesis via One‐Step Co‐Precipitation

ABSTRACT Reduced early strength can be a barrier to the adoption of cements blended with high levels of limestone. Chemical admixtures based on nucleation seeding are emerging as a potential solution. Herein, while synthesis of C‐S‐H‐based seeds has been thoroughly investigated in the literature, there are limited synthesis protocols available on other nuclei such as ettringite (AFt) seeds. Here, we present a one‐step, aqueous co‐precipitation method that produces well‐dispersed AFt nano‐seeds ( D 50 ≈ 68 nm), much smaller than the previously reported studies. In addition, this method does not involve drying and grinding as reported in previous studies. Adding 0.5 wt% seeds to a Type IL mortar shifts the hydration peak forward by 3.6 h and raises 72 h cumulative heat by 20% to 295 J g − 1 . 27 Al NMR confirms faster AFt formation and earlier monosulfoaluminate appearance. These kinetic gains boost compressive strength from ∼14 to ∼17 MPa at 1 day and ∼19 to ∼25 MPa at 3 days, outperforming 100% PLC, PCE‐only, and commercial C‐S‐H seeded mixes through 14 days. Liquid AFt seeding thus offers a scalable, low‐energy route to boost early performance in next‐generation blended cements.