- Proper Mix Design: When incorporating silica fume into your mix design, it’s essential to adjust other mixture components to achieve the desired workability and performance. A typical dosage of silica fume in a concrete mix is 5% to 15% by weight of cement.
- Water Content: Silica fume generally requires more water than conventional concrete due to its high surface area. However, adding more water can result in a lower strength mix. Therefore, water-reducing admixtures are often used in combination with silica fume to achieve the necessary workability without decreasing strength.
- Mixing: Silica fume should be added slowly to the mix to avoid clumping and to ensure thorough dispersion. The mixing time after the addition of silica fume should be enough to ensure that the silica fume is completely dispersed throughout the mix.
- Curing: Silica fume concrete needs to be cured properly to achieve its full potential strength. Curing should be started as soon as possible and continue for a longer period compared to conventional concrete.
- Use of Admixtures: High-range water reducers (HRWR), or superplasticizers, are usually needed in silica fume concrete mixes to improve workability. Without these, the mix can be very stiff and difficult to handle and place.
- Safety: Silica fume is a fine powder, like cement, and is harmful if inhaled. Therefore, necessary safety precautions, including masks and eye protection, should be used when handling silica fume.
- Quality Control: As with all components of concrete, it is crucial to have a rigorous quality control program in place to ensure consistency and meet the project’s specifications.
- Training: All personnel involved in the mixing, placement, and curing of silica fume concrete should be properly trained to understand the characteristics of the material and the need for accurate proportioning, thorough mixing, proper placement, and extended curing.
