Influence of silica fume content on castable properties

Silica fume, high strength castable, refractory and wear-resistant castable

At present, silica fume is commonly used in low cement castable to reduce the amount of water added to the product, reduce porosity and improve product strength.As silica fume is an industrial by-product produced in smelting process, the level of silica fume content and impurities contained are uncertain, and the presence of impurities has a significant impact on the production performance of castable.

Through the test:

The main raw materials used in the test are brown corundum, white corundum, silicon carbide, spherical asphalt, a alumina powder, silica fume, pure calcium aluminate cement, etc.Above is the main resistant material.

Based on a kind of Al2O3, SiC, C low cement castable, according to the design comparison test, the batting is poured into cement mortar mixer, and clean tap water is added to mix evenly, stirring for about 3min until the mixture is plastic.Firstly, measure the flow value of the pouring material under the same amount of water. The method is to use a conical mold with a height of 50mm, a diameter of the lower orifice of 100mm and an upper orifice of 70mm.Second, the physical properties of test under the same flow value, the method is to mix pour mixture within 40 mm x 40 mm x 160 mm steel form, the cement mortar vibration table 1 min molding, hardening after demoulding, 24 h curing, drying under 110 ℃ for 24 h, then in the air condition was detected in 110 ℃ * 3 h, 24 h, 1100 ℃, 1450 ℃ by 3 h after cold bending, compression and heat treatment line rate and high temperature 1450 ℃ by 3 h flexural strength.

Effect of different content of silica fume on flow properties of materials

The comparison of the influence of three silica fume on the flow value of materials under the same adding water amount.It can be seen that the content of silica fume has a direct impact on the fluidity of materials, and the flow value increases with the increase of silica fume content at the same amount of added water.Because silica fume contains a large number of active ultrafine silica powders, it is considered that these active ultrafine silica powders form colloids in water, and the colloidal particles adsorb dispersants around them to form solvent layer, thus increasing the fluidity of pouring material, reducing water consumption and improving its fluidity.

Effect of silica fume content on physical properties of materials

Sample hitches in air is 110 ℃ for 24 h, 1450 ℃, 1100 ℃ by 3 h x 3 h heat treatment after cold bending, compression strength diagram, know the content of silica fume on the flexural strength of materials at room temperature has a certain impact, especially at 110 ℃ and 1100 ℃, with the improvement of silicon ash grade its flexural strength will increase, and by 110 ℃, 1100 ℃ and 1450 ℃ after crushing strength of the sample is also rising with the rising of grade silicon ash.

With silica fume has a direct impact on castable liquidity, high content of silica fume is advantageous to the material liquidity enhancement, the flow under the premise of the same value, bound to lead to use of low content of silica fume castable with the increase of water added and the high water content in castable leaves after drying the porosity increased, sample porosity increases, the volume density decreased, physical strength is reduced, resulting in products in order to ensure the same flow value under the premise of materials needed to add water and the volume of the sample after 1100 ℃ heat density, on the premise of guarantee the same flow value, water added in castable with up and lower content of silica fume,The volume density also decreases.

Because silica fume contains active ultrafine silica powder with fine particles, large specific surface area (20 ~ 28m2/g) and high activity, solid phase sintering reaction is relatively easy to occur at medium and high temperature, and mullite phase is formed with Al2O3 in high-alumina refractory material, which improves the physical strength of the product.At the same time, low content silica fume has high impurity content, and the low melting point phase produced by it reduces the high temperature flexural strength of the material.

The above experiments show that:

The level of silica fume content has a direct impact on the fluidity of castable. On the premise of consistent addition of water, the higher SiO2 content is, the higher the flow value is.Due to the presence of active ultrafine silica powder in silica fume, colloids are formed in water, and colloidal particles adsorb dispersants around them to form a solvent layer, which increases the fluidity of castable, reduces the water consumption, and improves the fluidity of castable.

The main physical properties of castable increase with the increase of silica fume content.Therefore, under the condition that the flow values are consistent, the higher silica fume content requires less water, and the reduction of added water is conducive to the reduction of porosity of products.At the same time, more active ultrafine silica powder in high content silica fume can more easily take place solid phase sintering reaction at medium and high temperature, and generate mullite phase with Al2O3 in high alumina refractory material, improving the physical strength of products.

Remarks: the above information is about "influence of silica fume content on castable performance", which is professionally organized and provided by zibo yuneng kiln technology co., LTD. (http://zbyuneng.cn).