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Three construction technologies directly affect the performance of refractory castable
Refractory castables are often supplied in the form of bulk mixtures, and lining construction is carried out on site. This kind of refractories are mainly used as renewal materials of kiln lining and repair materials of old lining with premature corrosion. Because of the different shapes of lining and mending kilns, different parts of lining and different types of materials.
Generally speaking, when we talk about the influence on the service performance of refractory castable, we will surely think of the material, physical and chemical indexes, content and composition of castable, etc., but in addition to the quality of castable itself, the on-site construction is also the key to affect the delivery and service performance of refractory castable.
一.Control of water consumption
By adding a certain amount of water into the refractory castable, the dry powder is mixed with appropriate water to make the refractory castable water system slurry, and then the construction can be carried out. The construction performance of the refractory castable slurry directly determines its fluidity. It can be seen that water is also the key binder in the refractory castable. It plays a media role in the pouring process of the refractory castable, which can ensure that the refractory castable has a certain thixotropy and fluidity. After hardening, it can obtain dense casting components or linings, so that it has a good combination Energy and mechanical strength, etc. However, in order to obtain a better refractory casting component or lining, its water consumption needs to be strictly controlled. Because the increase of water consumption will lead to the separation and deposition of aggregate and powder, and make the refractory casting components or linings produce more air holes due to a large amount of water escaping during the drying process, which will lead to its loose structure, performance degradation, and some important properties after firing, such as strength reduction, erosion resistance reduction, etc.
Under the condition of limited water consumption, in order to ensure the construction performance of the refractory castable slurry, it is often necessary to use surfactant, namely water reducer or dispersant, to improve the thixotropy and fluidity of the refractory castable slurry, so that the refractory castable slurry can obtain the ideal injection performance. Generally, composite surfactant is used to improve the thixotropy and fluidity of refractory castable slurry to achieve good water reducing effect and improve the pouring performance of slurry.
二. Mixing and mixing mechanism of injection materials
It is a very important process to make refractory castable slurry by mixing refractory castable with water. Mixing is done at a constant speed in a specialized mixing device. During the mixing process, the mixing force, the time needed for the mixing uniformity and the temperature of the refractory castable slurry will increase.
There are a certain amount of fine powder and micro powder in the mixture of refractory castable, and the powder generally has natural agglomeration. Van der Waals force and capillary force in the presence of water are the forces of adhesion and agglomeration of particles, and their roles in different powders are more complex.
At the beginning of adding water, the particles will be covered by the liquid membrane of the so-called adsorption layer, and at the same time, there will be a liquid bridge between the particles. When the adsorption layer overlaps, the adhesion will be produced and the particles will agglomerate. The adsorption force increases with the expansion of the contact surface of the particles, and then the strength of the aggregates is increased.
When the water content reaches a critical level, a liquid bridge will be formed between the particles. The shear strength of the system increases sharply. Generally, the shear force increases with the increase of particle surface area.
At the initial stage of water mixing, the refractory castable will form water containing aggregate, which will seriously affect the rheological properties of the refractory castable slurry. Therefore, only when these agglomerates are broken up to form small mobile monomers can the refractory castable slurry have rheological properties.
三. Drying of refractory castable
The construction body (lining) of the refractory castable needs to be dried after hardening to remove the internal moisture before it can be delivered for use. In the process of KTC drying, the quality reduction caused by water discharge is related to the time. As a result, the apparent porosity and permeability of the material increase. Theoretically, different PSD may produce different porosity, but the experimental results show that different PSD cement-free all aluminum refractory castables modulated by the same water consumption have similar apparent porosity, and the open porosity is formed when the water is removed during the drying process of the refractory castables.