We know that silica fume in concrete is mainly mixed with internal and external blending, but in actual use, the simple blending of silica fume is difficult to directly meet the requirements of concrete use, often use some other technical means to cooperate with the use of silica fume, here HSA has compiled a few common reasonable blending technology of silica fume for your reference.
Compounding technology
The fineness of silica fume is very fine, can fill most of the pores in the cement particles, but there will still be some pores in the concrete can not be filled directly with silica fume, or fill the effect is not good, then the use of silica fume and other mineral admixture compounding technology, through different microscopic forms, different fineness, different surface activity, different amounts of reasonable collocation of complementary strengths and weaknesses, the so-called superposition effect optimization, such as silica fume and fly ash. Such as silica fume and fly ash double blending and slag powder and fly ash, silica fume triple blending technology, can substantially improve the strength and ease of mineral admixture and other effects, but also reduce the cost of cement, while inhibiting the occurrence of alkali aggregate reaction of concrete.
Particle grading technology
In determining the amount of silica fume and other mineral admixture compound, only consider the gradation between them is not enough, should also consider the addition of cement after the cementitious material particle gradation. If the cement clinker and silica fume and other mineral admixtures are spheres of equal diameter, in order to make each admixture particles around the cement clinker particles in close contact with them, then the volume of cement clinker and mineral admixture volume should be 1 to 1, but there will be 26% of the pores are not filled, so it should use smaller particle size to fill, then silica fume and other mineral admixtures should be at least two different sizes of particle size . Therefore, according to the grading point of view, not only silica fume and other mineral admixture requirements for the number and particle size, and even if the use of silica fume alone, should also try to be divided into coarse and fine two particle sizes, and the volume ratio of the two particle sizes should be about 0.5 as appropriate.
Compound exciter technology
In the use of silica fume compounding technology, often because of the number of large and lead to the number of cement clinker hydride is not enough to reduce the alkalinity of the interparticle water film, so that silica fume and other mineral admixture activity is difficult to get full excitation, the specific performance is the early strength of concrete is not high, poor durability of reinforced concrete, so you need to add some excitation agent to increase the activity of silica fume and other mineral admixture, generally Including:
Sulfate exciter
Gypsum can excite the activity of fly ash and other admixtures with high AL2O3 content, and the formation of weak cementing ability of cubic crystals CAH6, while sulfate can further react with CAH6 to form a strong cementing ability of needle hydrate calcium alumina.
Lime exciter
Cement clinker or cooked lime powder can excite the activity of SiO2-based silica fume, slag, steel slag and other admixtures, formed under the excitation of cement hydration products Ca (OH) 2 is hydrated calcium silicate with cementing ability, etc.
Alkali metal excitation agent
Salts containing potassium, sodium, lithium can promote the silica fume and other mineral admixture surface layer of silica-oxygen tetrahedral network structure loosening, so that they enter the solution, which is conducive to their volcanic ash reaction.
Reduce the water-cement ratio
Increase the amount of silica fume and other mineral admixture will lead to its surface adsorption of water film Ca (OH) 2 concentration is reduced, is not conducive to hydration, but also cause low concrete early strength, surface sand, not wear-resistant defects, so the use of large admixture to reduce the mixing and water, that is, reduce the water-cement ratio, which not only can make the adsorption of water film between the particles thin, so that the solution layer is easy to reach supersaturation precipitation crystals, and between the particles Distance closer to produce a small amount of hydrated colloid can be interwoven with each other to form crystals and produce bond strength. The use of high-efficiency water reducing agent (high-performance water reducing agent) can make the mixing and water consumption significantly reduced to become possible.
Adding nucleating agent
In silica fume and other mineral admixture compound a small amount of nucleating agent is also very meaningful, it is generally believed that the addition of about 3 to 5% of the crystal nuclei is beneficial, such as limestone micronized powder, wollastonite micronized powder, recycled cement net slurry finely ground micronized powder, etc., will not only induce crystal precipitation, reduce the concentration of ions in the adsorbed water film, promote the dissolution of the surface layer of admixture, conducive to the formation of hydration products to promote the early strength of concrete, but also the cementitious materials There are filling and conditioning effect, formulated concrete with excellent mechanical properties, small loss of collapse degree by time, excellent corrosion resistance. Can also be pre-hydration treatment of silica fume and other mineral admixtures, so that the surface of the formation of corrosion spots or crystal embryo, conducive to nucleation to promote hydration.
All of the above several reasonable blending techniques of silica fume are means to improve the use performance of silica fume and at the same time increase the amount of blending to make the concrete use higher performance, especially in the higher performance concrete formulation, more need or use these techniques at the same time. As a silica fume manufacturer, Henan Superior Abrasives (HSA) also cooperates with many scientific research institutions, and can provide high grade silica fume with different contents and different uses for different projects, which can meet different blending techniques, if you need, you can leave a message on our website, or call our customer service for detailed consultation.
