Modeling the Effect of Alternative Cementitious Binders in Ultra-High-Performance Concrete

Concrete production contributes significantly to global CO₂ emissions. To reduce this impact, researchers seek alternatives to traditional Portland cement. It was already known that cement replacements like fly ash or slag could lower emissions. However, the specific effects of alternative binders on ultra-high-performance concrete remained unclear. This gap motivated a closer look at how these binders alter UHPC's chemical structure. The modeling of phase assemblages had not been fully explored in this context. No prior work had resolved how different binders affect hydration and solid volume. That uncertainty drove the need for computational analysis. This study aims to address these unresolved questions.

The goal was to assess how alternative cementitious binders influence UHPC's chemical composition and hydration. The researchers focused on binders like calcium aluminate cement and blast furnace slag. They wanted to determine how these materials affect phase formation and water demand. The motivation stemmed from the need to improve UHPC sustainability without compromising performance. They aimed to model phase assemblages after replacing Portland cement. This approach allows predicting hydration outcomes before physical testing. The study also sought to compare water requirements across binders. This comparison could guide material selection for UHPC production.

The research used computational modeling to simulate UHPC phase assemblages. Portland cement was replaced with four alternative binders. The team calculated hydration products for each scenario. They considered phases like C-S-H, strätlingite, and ettringite. The model tracked changes in solid volume and water demand. No physical experiments were conducted in this study. The focus was on hydration chemistry and phase stability. The results were based on thermodynamic calculations and known reaction mechanisms.

Replacing Portland cement with calcium aluminate cement reduced C-S-H volume. It increased the overall solid volume due to strätlingite formation. Calcium sulfoaluminate cement showed a similar effect with ettringite. The model predicted higher water demand for these binders compared to plain UHPC. Blast furnace slag and metakaolin required similar or less water. This suggests lower hydration water needs for these materials. The findings highlight differences in hydration behavior among binders. These results may inform material selection for sustainable UHPC.

The study concludes that alternative binders alter UHPC hydration and phase formation. Calcium aluminate and sulfoaluminate cements increase solid volume through new phases. These binders may require more water than traditional UHPC. Blast furnace slag and metakaolin show lower water demands. The authors propose that these findings could guide sustainable UHPC design. They suggest that hydration modeling is useful for predicting binder effects. No essential role was assigned to any specific binder in the abstract. The implications are limited to the model's predictions.