In the concrete industry, generally the concrete between C60 and C100 strength level becomes high-strength concrete, in the preparation of ordinary concrete, although the mixing of silica fume is not mandatory, but the preparation of high-strength concrete, silica fume is essential.
High strength concrete in the use of silica fume protocols
- The silica fume used in high-strength concrete should be in line with the current national standard “high-strength high-performance concrete with mineral additives” GB/T18736 provisions;
- When formulating high-strength concrete of C80 and above, the SiO2 content of silica fume should be greater than 90%, and the specific surface area should not be less than 15 × 10 ³ ㎡/kg;
- For high-strength concrete mineral admixture can include fly ash, granulated blast furnace slag powder, steel slag powder, phosphate slag powder and silica fume compounding;
- Silica fume and other mineral admixtures of radioactivity should comply with the current national standard “Limit of Radionuclides in Construction Materials” GB6566 of the relevant provisions;
- Mixed with silica fume high-strength concrete, in order to ensure the water-cement ratio, must also use high-performance water reducing agent.
- The preparation of high-strength concrete mixed with silica fume should be used high-performance water reducing agent, the preparation of C80 and above strength grade concrete, high-performance water reducing agent water reduction rate should not be less than 28%.
High-strength concrete ratio design requirements
The design of high-strength concrete ratio should comply with the provisions of the current industry standards, and should meet the design and construction requirements. High-strength concrete ratio should be determined by the test, in the absence of test basis need to comply with the following provisions:
1.Water-cement ratio, the amount of cementitious materials and sand rate should be selected according to the following table, and should be determined by test fitting;
| Water-binder ratio, amount of cementitious material and sand rate | |||
| power level | water-binder ratio | Amount of cementitious material（kg/m³） | sand rate（%） |
| ≥C60，＜C80 | 0.28~0.34 | 480~560 | 35~42 |
| ≥C80，＜C100 | 0.26~0.28 | 520~580 | |
| C100 | 0.24~0.26 | 550~600 | |
2. Admixtures and silica fume and other mineral admixture species, admixture, should be determined by trial, other mineral admixture admixture should be 25% to 40%, silica fume admixture should not be greater than 10%;
3. For the prevention of concrete alkali aggregate reaction design requirements of the project, the alkali content of high-strength concrete should not be greater than 3.0kg/m³, the alkali content of fly ash can be 1/6 of the measured value, granulated blast furnace slag powder and silica fume alkali content can be taken respectively 1/2 of the measured value;
4. The mix should be used for the actual use of raw materials, concrete mix performance, mechanical properties and durability test, the test results should meet the design and construction requirements;
5. Bulk high-strength concrete proportioning and adjustment, it is appropriate to control the adiabatic temperature rise of concrete not more than 50 ℃;
6. High-strength concrete design ratio should be adapted before production and construction, should be adjusted to the adjusted ratio as the construction ratio;
7. High-strength concrete production process, should be timely measurement of coarse and fine aggregate moisture content, and because of its changes in accordance with the timely adjustment of the weighing.
It can be seen from the above that in the preparation of high-strength concrete, the requirements for the use of silica fume are relatively high, one is the requirement of the amount of admixture, the other is the requirements of the ratio. If you need, please leave a message on our website or call our customer service for more information.
