Hybrid Nucleation Acceleration Method with Calcium Carbonate and Calcium Silicate Hydrate for Fast-Track Construction

Abstract

This research focuses on achieving early strength of cement-based materials through the hybrid nucleation acceleration method. Through the study of various mortar mixtures, which incorporate components such as ordinary Portland cement (OPC), fine limestone powder (with a particle size of d50: 1 μm), coarse limestone powder (with a particle size of d50: 12 μm), calcium silicate hydrate (C-S-H) nucleation seeding agent, and calcium nitrate (CN), the effect of the hybrid nucleation acceleration method was investigated. When OPC was substituted with 20% fine limestone powder, a strength of 13.5 MPa was achieved at 6 h, whereas the use of coarse limestone powder only yielded 3.5 MPa within the same time frame. The mortar containing 2% C-S-H nucleation seeding agent reached an impressive 16 MPa at 6 h. Meanwhile, through the synergistic combination of fine limestone powder and C-S-H nucleation seeding agent, the 6 h early strength attained an impressive 19 MPa. The micrograph revealed that the hybrid nucleation acceleration method significantly promoted the formation of a dense network of C-S-H within the paste, thus enhancing the packing density. Measuring the heat release demonstrated that the samples accelerated with the C-S-H nucleation seeding agent and fine limestone reached the peak 160 min earlier than the OPC sample, indicating a faster hydration process. The hybrid nucleation accelerated concrete (HNAC) achieved strengths of 20 MPa and 27 MPa within 6 and 8 h, respectively, whereas the 28-day strength surpassed 70 MPa. The concrete equivalent mortar (CEM), derived from concrete, attained a compressive strength of 25 MPa within 8 h, making it suitable for repair applications. The modulus of rupture (MOR) was 7.31 MPa at 8 h and increased to 17.27 MPa at 28 days. Overall, the developed concrete and CEM with the novel hybrid nucleation acceleration method allowed for high early and long-term strength for fast-track construction to be attained.