Compared with sintered brick, industrial waste residue baking-free brick uses industrial waste residue without sintering and steam curing, and its production cost is lower than that of sintered brick. Large amount of slag, outstanding social and environmental benefits; Regular edges and corners, accurate size, high compactness, low water absorption and good durability with compressive strength higher than 7.5MPa.
1, raw material for producing industrial waste residue baking-free brick.
The raw materials for producing industrial waste residue baking-free bricks generally include three parts: industrial waste residue, curing agent and admixture.
1. 1 industrial waste residue
Industrial waste residue mainly plays the role of aggregate in the production of baking-free bricks. Many industrial waste residues can be used to produce baking-free bricks, including: fly ash from power plants, slag from steel mills, slag from non-ferrous metal smelters, various mine tailings, electrolytic copper ponds, chemical waste gypsum and chemical lime, building waste bricks, construction waste, etc.
The chemical composition, mineral composition, harmful substances and positive and negative effects of various industrial waste residues are different. Therefore, when using industrial waste residue to produce baking-free bricks, a reasonable formula should be formulated according to the strength formation mechanism after analyzing the characteristics of various waste residues. Add some industrial waste residue.
After adding a proper amount of curing agent and admixture, it can be used to make baking-free bricks alone: for example, using fly ash, adding river sand, lime, gypsum, cement and composite admixture, it can produce baking-free bricks with 28d strength of 3 1 MPa; Another example is adding proper amount of cement and additives to pretreated lead-zinc tailings.
Manufacturing non-fired bricks with industrial waste residue not less than MU 10. However, most of the research is to make use of several industrial waste residues through mutual matching, complementary advantages or mutual cooperation. For example, in Qin Jin period, fly ash and steel slag were combined to make baking-free bricks, and the active components in fly ash and steel slag were outside the curing agent.
Under the action of additives, it can stimulate and meet the strength requirements of bricks. The material diameter of fly ash is relatively small, and brick making alone lacks the aggregate function of large particles. However, steel slag with large particle size distribution can meet this condition, and the baking-free brick produced by this method has good performance. For example, the baking-free brick of Mu 10-Mu 15 is made of fly ash and steel slag from Baotou Steel.
When determining the formula of industrial waste residue baking-free brick, we should not only increase the content of waste residue as much as possible, but also make full use of the characteristics of various waste residues that are beneficial to the production of baking-free brick, reduce the amount of additives and auxiliaries as much as possible, and effectively reduce the production cost of brick. The main chemicals and minerals of industrial waste residue are more commonly used to produce baking-free bricks.
See table 1.
In addition, some industrial waste residues are not suitable or can't be used in brick making in large quantities because of their radioactivity, so radioactive detection should be carried out before use. Some industrial waste residues, such as fly ash, must be pretreated before use to remove grass roots and impurities, and some need to be ground to the required material diameter before use; Another example is the waste steel slag discharged from the converter, which needs to be removed by magnetic separation and then ground to the required particle size by wet ball milling.
The particle size of waste residue determines whether it is necessary to add additional aggregate when producing industrial waste residue baking-free brick. Adding an appropriate amount of aggregate with appropriate particle size distribution into the batch of industrial waste baking-free bricks can prevent the brick from delamination, reduce shrinkage, improve the exhaust performance of the brick blank during molding, and increase the compactness, thus improving the strength and durability of the brick.
Save the dosage of cementing material and reduce the cost.
There are three kinds of aggregates: river sand, mountain sand and sea sand. Because mountain sand has sharp edges and corners, it can be well combined with cement, which makes the hearing strength of bricks high, so it is better to choose mountain sand. However, it can generally be used as sand for building materials, and can be used to produce industrial waste residue baking-free bricks. In fact, some waste residue itself has the function of aggregate, such as steel mills.
Steel slag, coal gangue and mining tailings.
1.2 curing agent
The curing agent of industrial waste residue baking-free brick refers to cementing materials with certain strength, such as cement, lime, gypsum, etc., which can cure various dispersed raw materials under physical and chemical effects.
1.2 1 cement
Cement is not only a cementing agent, but also an active activator when producing industrial waste residue baking-free bricks. Its effective components, dicalcium silicate and tricalcium silicate, make great contributions to the early strength and later period of brick. Generally, ordinary portland cement with high alkalinity of 32.5 is selected.
The more cement is added, the better the durability of industrial waste residue baking-free brick; But with the increase of cement addition, the cost of brick will increase. In order to reduce the cost, many manufacturers try to use suitable industrial waste residues to cooperate with each other or use additives to add as little as possible without adding cement on the premise of ensuring the strength of bricks.
For example, when red mud and fly ash are used to make baking-free bricks, the strength of bricks can reach above MU 15 only by adding some alkaline activators and sulfate activators.
1.2.2 lime
Calcium hydroxide produced by lime curing plays an important role in the early strength and late strength of cement. It is also a binder and alkaline activator for the formation of industrial waste residue baking-free bricks. However, in some processes, especially the baking-free bricks with industrial waste residue that need steam curing in the later stage, the use of hydrated lime can simplify the process, reduce the residence time of bricks in the factory and shorten the time.
Turnover time of bricks and funds.
1.2.3 gypsum
Gypsum is a sulfate activator for producing industrial waste residue baking-free brick. At the same time, it has synergistic effect with lime, plays the role of accelerator, and plays a direct and indirect role in the strength of industrial waste residue baking-free brick. Generally, natural gypsum works well. Of course, in order to reduce costs, industrial chemical gypsum, such as industrial phosphogypsum, can also be used.
In the production of industrial waste residue baking-free bricks, curing agents, such as cement, can be used alone. In most cases, according to the specific situation, several curing agents can be combined, such as lime and gypsum, or gypsum, lime and cement can be used together, and the effect is good. Of course, curing agents used in industrial waste residue baking-free bricks are far more than the above three, and there are also
Some sulfate and so on. At the same time, some industrial waste residue (such as alkali residue, etc. ) can also play the role of activator in this batch of bricks.
1.3 admixture
The strength, performance and quality of industrial waste residue baking-free brick can be improved by means of exogenous agents. There are many kinds of additives. The main additives used in industrial waste residue baking-free bricks are plasticizer (water reducer), early strength agent, antifreeze and so on.
The uniformity of industrial waste residue baking-free brick ingredients will directly affect the final strength of the brick. Generally speaking, in order to improve the mixing uniformity of batch, in addition to strengthening mixing, adding water reducer can effectively increase the fluidity of batch and greatly reduce the mixing water consumption, thus improving the compactness, strength, frost resistance and impermeability of brick. the other/opposite side
On the surface, due to the dispersion of water reducing agent, the contact surface area of each substance increases, which is beneficial to improve the reaction probability.
When producing industrial waste residue baking-free bricks, water reducing agents are mostly hydrophilic surface active substances, such as lignin, such as calcium lignosulfonate, etc. Early strength agent is an additive to improve the early strength of products. Whether it is inorganic salt, organic salt or inorganic-organic composite early strength agent, the early strength of brick is improved by accelerating the hydration speed of batch.