Aerated concrete blocks and plates can be divided into several stages according to the production sequence: raw material preparation, steel processing (aerated plates), batching, pouring, static stopping, cutting, autoclave curing, and kettle discharge.
1. Preparation of raw materials
The production of aerated concrete first involves grinding siliceous materials such as sand and fly ash. Depending on the requirements of raw materials and process characteristics, some are ground dry to powder, others are wet ground with water to make slurry, and some are mixed with lime and other materials. There are two ways to mix and grind: one is to dry mix and grind to prepare binder; One type is wet grinding with water, mainly to improve the characteristics of fly ash or sand, called hydrothermal ball milling. Most of the purchased lime is in block form, therefore, the lime must also be crushed and ground. Gypsum is generally not ground separately, or mixed with fly ash or lime, or can be ground together with a lime wheel using a ball mill. Other auxiliary materials and chemicals are often prepared and used. The raw material preparation process is the preparation process of ingredients, which involves the reprocessing of raw materials to meet the process requirements and the homogenization of storage before completing the ingredients. It is the most basic process that directly affects the smooth progress of the entire production and whether the product quality can meet the requirements.
2. Reinforcement processing
Steel bar processing is a unique process for producing aerated concrete slabs, including rust removal, straightening, cutting, welding, coating preparation, coating impregnation, and drying of steel bars. Steel bars are the structural materials used in the production of aerated concrete slabs. Process control not only affects product quality, but also directly affects the structural performance and safety of buildings.
3. Assembly of steel mesh
The assembly process of steel mesh is to combine the anti-corrosion treated steel mesh with the required size and relative position according to the process requirements, and then install it into the mold and fix it for pouring.
4. Ingredients
Ingredients are the measurement, temperature and concentration adjustment of various raw materials prepared and stored for use, as well as on-site measurement and preparation of a small amount of added materials. Then, according to process requirements, materials are sequentially fed to the mixing equipment. Batching is a key link in the process of aerated concrete, which is related to the proportion of Active ingredient among raw materials, the fluidity and viscosity of slurry whether it is suitable for aluminum powder to air and the normal hardening of green body. In short, it has the most direct impact on gas expansion, hardening process, and product performance.
5. Pouring
The pouring process is one of the unique production processes that distinguishes aerated concrete from other types of concrete. The pouring process involves mixing the materials from the previous batching process into the mixer after measurement and necessary adjustments, to produce a slurry that meets the time, temperature, and consistency requirements specified in the process. The slurry is poured into the mold through the pouring port of the mixer (hence also known as the pouring mixer). At this point, if the assembled steel mesh has already been placed in the mold when producing the board. The slurry undergoes a series of physical and chemical reactions in the mold, generating bubbles, causing the slurry to expand, thicken, and harden. The pouring process is an important process for forming a good pore structure, and together with the batching process, it forms the core link of the production process of aerated concrete.
6. Quiet stop
The static stop process mainly promotes the thickening and hardening process of the poured slurry. In fact, this process starts after the slurry is poured into the mold, including two processes: gas expansion and green body maintenance, to complete the gas generation of the slurry and form a green body, and to achieve a certain strength of the green body for cutting. There are not many operations in this process, so vibration should be avoided. At the same time, strict attention should be paid to the changes in the slurry during the gas generation process, and feedback should be given to the batching and pouring processes, as the main defects of the billet are all generated in this process, such as mold collapse, cracking of the billet, and gas holding.
7. Cutting
The cutting process is to divide and shape the aerated concrete body to meet the requirements of appearance and size. The cutting process reflects the characteristics of aerated concrete, which is easy to form in large volume, flexible and diverse in external dimensions, and can be produced on a large scale through mechanization. It is also a prominent advantage that distinguishes aerated concrete from other types of concrete. Cutting work can be done mechanically or manually. In order to improve production efficiency and product quality, dedicated cutting machines have been designed, forming the core of the aerated concrete production process and forming different patented technologies. The cutting process directly determines the appearance quality and certain internal qualities of aerated concrete products.
8. Autoclave curing
The steam curing process involves high-pressure steam curing of aerated concrete billets. For aerated concrete, only after a certain temperature and sufficient time of curing can the body complete the necessary physical and chemical changes, thereby generating strength and meeting the needs of building construction. This process usually takes place above 174.5 ℃. Therefore, a well sealed autoclave is commonly used, which is heated by saturated steam with a certain pressure to fully complete the hydration reaction of the green body under high temperature and humidity conditions, obtaining the required hydration products, and making the aerated concrete have a certain strength and other physical and mechanical properties. The autoclave curing process determines the final formation of the intrinsic properties of aerated concrete.
9. Leaving the kettle
Leaving the kettle is the final process in the production of aerated concrete. This includes product discharge, lifting, inspection, packaging, and cleaning and oiling of the trolley and bottom plate, ensuring the supply of qualified products to the market and the normal operation of the next production cycle. With the requirements of the market for product appearance and urban management, more and more aerated concrete factories have begun to package aerated concrete products. The corresponding packaging has also shifted from simple packaging and fixation to the addition of packaging machinery, using thermoplastic packaging.