A. The role of micro-silica powder in concrete.
Micro-silica powder mixed into concrete can be fully dispersed and filled between the gaps in the cement particles, making the paste more dense. The volcanic ash activity index of micro-silica powder can reach 110, with an effective substitution factor of 3-4, especially for the Ca(OH)2 generated after hydration of cement has a strong absorption, forming a well-developed calcium silicate gel, greatly improving the strength of concrete.
1. Increase the strength: when mixed with 5-10%, the compressive strength of concrete can be increased by 10-50% and the flexural strength by more than 10%.
2. Increase density: When mixed with 10%, impermeability increases by 5-8 times and carbonation resistance increases by more than 4 times.
3. Increase frost resistance: concrete mixed with 10% micro-silica powder has a 1-2% reduction in relative dynamic elastic modulus after 300-500 freeze-thaw cycles, while ordinary concrete has a 36-73% reduction in relative dynamic elastic modulus after 25-50 cycles.
4. Increased resistance to abrasion and cavitation: Micro-silica powder concrete is 0.5-2.5 times more resistant to abrasion and 3-16 times more resistant to cavitation than ordinary concrete. It is the best material for hydropower stations, reservoirs and dams for anti-abrasion repair and surface protection.
B. The role of micro-silica powder in refractory castables.
1. Since micro silica powder has obvious spherical particles, it is easy to enter the tiny voids in the castable, plus the particle size is small, so it not only has good water reducing effect, but also improves the dense degree of the refractory castable, so that the pores left after drying are reduced and the porosity is lowered, thus improving the strength and high temperature use performance.
2. Micro-silica powder can form colloid in water, and the colloid particles adsorb dispersant around it to form a soluble layer, thus increasing the fluidity of the castable and improving its molding performance.
3. Because of the fine particles of microsilica powder, large surface free energy, many lattice defects and high activity, it is easier to occur solid phase sintering reaction in medium and high temperature, and it can occur mullitization reaction with Al2O3 in high alumina refractory materials, thus improving the post-fire strength of low cement refractory castables.
C. Micro-silica powder in refractory materials to enhance the life increasing effect.
Micro-silica powder produced by micro-silica powder manufacturers is a kind of ultra-micro solid material. Micro-silica powder as a new raw material in the refractory industry, the role played by the indefinite refractory materials in which is crucial:.
1. Because of its small size and high density, it can easily fill the gaps in the refractory material, so that the density of the refractory material is improved, while reducing the pores in the refractory material also increases the strength of the refractory material.
2. By it has volcanic ash activity, the activity is very strong, it can form colloidal particles in water after melting with water, after adding the right amount of dispersant, it can achieve the effect of making its liquidity enhanced.
3. It has a strong hydrophilic, after adding water, can make stronger cohesion in the refractory materials, so that the refractory materials to improve the high temperature resistance, but also can extend the service life of refractory products.
D. The quality control of micro-silica powder.
Micro-silica powder is essentially a “by-product” or “waste product” in the smelting process, not through deliberate production and processing, so its quality will be more affected by external factors. In order to make the product quality relatively stable, we have done a lot of exploration and research, and come up with a set of effective quality control methods mainly as follows:
I. Quality control of generating source.
①. The choice of furnace size: the size of the furnace determines the stability of product quality. Too small furnace, furnace conditions change more frequently, resulting in unstable quality of SiO2, and more than 12,500KVA furnace, the output is less, can not ensure the continuity of product supply, so 6300KVA to 12,500KVA industrial silicon furnace is preferred, can ensure that the engineering micro-silica powder SiO2 content ≥ 85% and the corresponding impurity content is less, all indicators can meet the relevant standards.
②. The smelting furnace load size, ore raw material origin quality, reducing agent category and other factors of the mineral heat furnace itself will be initially classified, and the micro-silica powder samples will be collected for analysis, and the product classification will be made according to the assay results.
II. Quality control of production process.
①. In the field of automatic control of the micro-silica powder “production line” (environmental protection equipment), through observation of the on-site furnace conditions and communication with the technical personnel in the plant, the main fan control parameters are adjusted to change the air speed at all levels for different furnace conditions and to change the pressure difference between the inside and outside of the filter bag to control the filtration effect without affecting the effect of the environmental protection dust removal equipment, so as to The purpose of adjusting the silica fume content and other parameters. In addition, it is also possible to upgrade the dust collection equipment, add temperature-regulated air catcher sets, expand the filtering area of the bag filter, etc., to change the entire dust collection system SiO2 condensation time, molding properties, etc., and finally the parameters of the micro-silica powder can be adjusted and controlled within a certain range.
②. Before the product is unloaded and sealed, the operator must visually inspect the bag to ensure that the color of the micro-silica powder is uniform and the product is free of lumps, and a quality card with a unique number is sewn onto the bag. This makes each bag of micro-silica powder traceable, strengthens the operator’s responsibility, and also facilitates the identification of each link of production and storage, which greatly enhances the quality assurance of the product.
③. The inspection of the production site is an important part of the quality control process. Dedicated site inspection personnel will conduct daily routine inspection of the material yard and smelting site records to ensure that the smelting process, raw materials and finished products have not changed to ensure the stable quality of micro-silica powder products. In case of changes in the process, raw materials, furnace conditions and other conditions that may affect the quality of micro-silica powder, the products of the day need to be stored differently in time, and the samples will be analyzed for indicators in time, and then classified according to the laboratory results.
III. Quality control of products leaving and entering the warehouse.
①. When the products are stacked in the warehouse, the products of different furnace types shall be sorted and stacked; the products of the same equipment shall be stacked separately as a batch of products produced within a week. The storekeeper shall make records of the origin and stacking location of different batches of products. The laboratory personnel shall take a whole truck (25-30 tons) as a batch and then conduct a sampling inspection, the number of samples shall not be less than 20 bags, the weight of each bag shall not be less than 100g, and the samples shall be mixed evenly and sent for inspection. Each inspection is required to record the test time, index data and other relevant information.