THE EFFECT OF ULTRAFINE COMPOSITE MINERALS ON THE LONG-TERM PERFORMANCE OF CEMENT-BASED MATERIALS

Abstract

The impact of ultrafine composite minerals (USCMs) on the long-term characteristics of cement-based materials was explored, revealing that USCMs significantly enhance the long-term mechanical strength of these materials and effectively mitigate mortar shrinkage. The findings demonstrated that the shrinkage could be reduced to as low as 0.11% by 90 d, representing a 95.1% decrease compared to the control group. The influence of USCMs on the hydration kinetics of cement was examined using quantitative X-ray diffraction (QXRD), thermogravimetric-differential thermogravimetry (TG-DTG), and scanning electron microscopy (SEM) analyses. The results, in conjunction with the QXRD and TG-DTG analyses, suggest that USCMs intensify the hydration of the C₂S and C₃S phases. Moreover, the pozzolanic reaction of the USCMs increases the concentration of the hydrated calcium silicate gel within the cement matrix during the later stages of hydration, altering the morphology of the hydration products. This not only improves the volume stability of the mortars, but also results in a denser structure for cement-based materials.

Keywords

• long-term shrinkage
• ultrafine composite minerals
• mechanical properties
• microstructure