Low Hydration Heat with High Strength in LHPC Composite Binders Governed by Hydration Efficiency and Matrix...

Area of Science:

• Materials Science
• Civil Engineering
• Construction Materials

Background:

• Controlling early-age temperature-cracking in concrete necessitates binders with low hydration heat without compromising strength.
• Optimizing supplementary cementitious material (SCM) combinations is key to balancing heat generation and mechanical performance.

Purpose of the Study:

• To design and evaluate a novel binder system using low-heat Portland cement (LHPC), fly ash (FA), ground-granulated blast-furnace slag (GGBS), and silica fume (SF).
• To identify a low-heat/high-strength pathway for concrete applications requiring early-age temperature-crack control.

Main Methods:

• Formulation of LHPC-FA-GGBS-SF binder systems with fixed LHPC (80 wt.%) and SCMs (20 wt.%).
• Characterization using compressive strength tests (3, 7, 28 days), isothermal calorimetry with Krstulović-Dabić (K-D) modeling, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM).

Main Results:

• The mixture F10G3S7 (10% FA, 3% GGBS, 7% SF) yielded the highest 28-day strength (58.2 MPa).
• The mixture F10G9S1 (10% FA, 9% GGBS, 1% SF) balanced low 7-day heat (203.5 J/g) with high 28-day strength (54.2 MPa).
• K-D modeling indicated FA reduced heat potential, while GGBS/SF blends increased it, showing composition-dependent hydration efficiency. Bound water content strongly correlated with compressive strength (R²=0.75-0.78).

Conclusions:

• The optimal low-heat/high-strength pathway involves efficient heat-to-hydrate conversion and microstructural densification, as evidenced by SEM analysis of the F10G9S1 mixture.
• This research provides critical mechanistic insights and practical guidelines for developing advanced concrete binders for crack control.