Silica Fume Effect on Hydration Heat and Compressive Strength of High-Performance Concrete

The objective of this study was to evaluate the influence of silica fume (SF) on the rate of compressive strength and hydration heat in high-performance concrete. Portland cement was replaced by SF in amounts ranging front 10 to 30% by mass in concrete with water-binder ratios (w/b) ranging from 0.25 to 0.45. A high-range water-reducing admixture was used to maintain a fluid consistency. The improvement of the compressive strength tends to reduce in the long term. SF plays a positive part up to approximately 20% content and has the most important effect when reaching 10 to 15% content, regardless of the water-cementitious material ratio (w/cm) (cement and SF). The heat of h hydration was monitored continuously by a semi-adiabatic calorimetric method for 10 days at 68 degrees F (20 degrees C). The calorimetric study indicated that the hydration is modified by the presence of SF In the early stages, the SF showed a high activity and accelerated the hydration rate as compared with that of the reference concrete. The fine SF particles provided nucleation sites for hydrates' growth, then the pozzolanic activity took over and increased both strength and the It hydration heat. A substitution of portland cement by 10% with SF produced greater strength and cumulative heat of hydration as compared with that of the reference concrete.