The incorporation of silica fume powder into concrete has been a subject of global research for over 70 years, with China taking a leading role in studying its application since the early 1980s. Notably, the Ministry of Water Resources in China has recognized the benefits of silica fume powder in water conservancy projects, promulgating temporary provisions for its quality standards. This article explores the chemical composition and properties of silica fume powder and presents experimental results demonstrating its positive impact on cement performance.
I. Chemical Composition and Properties
The chemical composition of silica fume powder reveals a low loss on ignition (L.O.I) at 1.69%. The predominant component is SiO2 at 95.62%, with minimal proportions of Al2O3, Fe2O3, CaO, and MgO. The principle behind using silica fume powder in concrete lies in its ability to fill particle voids, increase bulk density, and reduce porosity. Additionally, the powder undergoes a volcanic ash reaction, forming silica-rich gel during hydration, which, when combined with cement hydration gel C-S-H, results in superior strength compared to Ca(OH)2 crystal.
II. Experimental Methods and Results
In experimental trials, 5% and 3% of silica fume powder were added to P.O42.5 and P.C32.5 strength grade cement, respectively. The results illustrate several key findings:
Limited Impact on 3d Strength: The addition of 3% or 5% silica fume powder shows minimal influence on the 3-day strength of cement.
Substantial 28d Strength Increase: Adding 5% silica fume powder led to a 10MPa and 8.6MPa increase in 28-day strength for P-O42.5 and P.C32.5, respectively. Meanwhile, a 3% addition resulted in a 7.9MPa and 6.0MPa increase for the same cement grades.
Enhanced Concrete Performance: Concrete exposed to harsh environments can face significant damage, threatening project quality and reducing service life. By formulating concrete with cement, silica fume, fly ash, and a water-reducing agent, high-performance stick concretes meeting diverse requirements have been successfully developed. These concretes exhibit improved performance, with durability and freeze-thaw resistance demonstrated in large-scale applications.
Energy Consumption Reduction: The addition of a certain percentage of silica fume powder to cement not only improves performance but also contributes to reduced energy consumption.
Cost Efficiency: Practical application reveals a reduction of approximately 10 yuan in the cost of cement production. This cost-effectiveness makes it a viable option for widespread adoption, particularly in areas with favorable conditions.
In conclusion, the inclusion of silica fume powder in cement showcases a promising avenue for enhancing concrete performance, reducing energy consumption, and promoting cost efficiency. As research continues, the positive impact of silica fume powder on the construction industry is poised to grow, offering sustainable solutions for high-performance concrete applications.