Understanding the longer-term effects of C-S-H seeding materials on the performance of limestone calcined clay cement

The application of C-S-H seeding offers great potential for improving the early age strength of cement. However, the fundamental understanding of longer-term effects of C-S-H seeding on the properties of cementitious ma-terials is still limited, partly due to the complex composition of C-S-H seeding materials. This paper studied the effects of purified C-S-H seeding and impurities separated from synthesized C-S-H seeding suspensions on the hydration and strength of limestone calcined clay cement (LC3) over a period of 90 days. The results showed that compared to reference, the addition of purified C-S-H seeding leads to an average increment of 16.5% in the compressive strength of LC3 at the first 7 days and does not significantly affect the strength development af-terwards, while the presence of impurities can cause a 5.7% decrease in compressive strength at 90 days. The reason for this later-age discrepancy was attributed to the lower degree of hydration of alite and less reaction of metakaolin in the system with impurities compared to the system without impurities. The findings offer a new perspective to better understand the longer-term effects of C-S-H seeding materials on the performance of cementitious materials.