Effect of CSH-PCE nanocomposites on early hydration of the ternary binder containing Portland cement, limestone, and calcined coal gangue

Abstract

In this work, the impact of lab synthetic addition agent, CSH-PCE nanocomposites (CPNs), on the early hydration property of the ternary binder containing Portland cement, limestone, and calcined coal gangue was investigated. CPNs were added in partial substitution of Portland cement by mass at 0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5% and 3.0%. X-ray diffraction (XRD), isothermal calorimetry, mercury intrusion porosimetry, and scanning electron microscopy were used to characterize the hydration and hydrates of the CPNs-modified pastes systematically. The workability and compressive strength of this ternary system was also studied. The obtained results indicated that the use of CPNs continuously improved the workability of the ternary mortar. The compressive strength of the ternary mortar increased with CPNs additions until the threshold limits of 3.0% and 2.5% before and after 12 h, under which the strength values were even higher than the reference OPC mortar at each age. Isothermal calorimetry results indicated that CPNs promoted cement hydration and produced more hydrates, which were also verified by the qualitative XRD analysis. This promotion effect leads to significant reduction in porosity as well as densification in microstructure within the ternary paste, ultimately resulting in enhanced early-age compressive strength. These findings provide valuable insights for designing lower carbon footprint ternary blends incorporating calcined coal gangue and limestone while maintaining comparable early-age compressive strength to traditional cement.