The proportion of various materials in the construction of foam concrete

Overview of foam concrete

Foamed concrete is a foaming agent that is fully foamed mechanically by the foaming system of the foaming machine, and the foam and cement slurry are evenly mixed. Then use the foaming machine pumping system for cast-in-place construction or mold forming, and a new type of lightweight thermal insulation material formed by a large number of closed-cell thermal insulation materials. As a new type of energy-saving and environmentally-friendly building material, scholars at home and abroad have conducted a lot of research and development on it, making it widely used in wall materials. Advantages: low density, light weight, good heat insulation, sound insulation, and seismic performance.

1. Cement ratio

The main raw material of foamed concrete is cement. Since foamed concrete is mostly cured at room temperature and a large amount of foam is added, these two factors determine its higher cement ratio. This is fundamentally different from aerated concrete. Because autoclaved aerated concrete mainly relies on the hydration reaction of fly ash and lime under high temperature and high pressure to produce gel, cement is a supplement. However, when foamed concrete is produced at room temperature, the active micro-aggregates will not quickly undergo hydration reaction, and the solid foam still depends on the cementing effect of the cement. Therefore, the mix ratio of foamed concrete must be cement as the main body, and the cement ratio is high. Under normal circumstances, the amount of cement should account for 50% to 100% of the total dry material, and the minimum solidification at room temperature should be 50%. When pouring on site, the proportion of cement should account for more than 80% of the total dry material. For normal temperature foamed concrete with a density below 600kg/m3, the proportion of cement should not be less than 70% of the total material. When the density is below 400kg/m3, the proportion at room temperature should account for more than 90% of the total dry material, preferably 100%. The low cement ratio must reduce the cement ratio on the basis of satisfying the product performance under the premise of ensuring the strength of the product. Can be minimized, but also consider the stability of pouring (pouring). Too low cement content will cause collapse. Can not deviate from the technical requirements to reduce the specific gravity of cement.

The cement ratio design should consider the following factors:

① The type of cement. Cement types with high early and late strength (such as dual-fast Portland cement) can appropriately reduce the cement ratio, and cement types with low late strength or low early strength should increase the cement ratio;

② Cement strength grade. High-strength cement can reduce the ratio, and low-strength cement should increase the ratio;

③ Cement quality. The specific gravity of Dachang's famous brand new dry-process rotary kiln cement can be appropriately reduced, while the specific gravity of vertical kiln cement or cement with a large amount of mixed materials can be appropriately increased;

④ Density and strength requirements of the product. The cement ratio should be increased if the density is low or the strength requirement is high, and the cement ratio can be reduced if the density is high or the strength requirement is low;

⑤ Initial growth temperature. The initial curing temperature after pouring (pouring) is low (<25°C). The proportion of cement should be increased. When the original curing temperature was high (25°C ~ 45°C), the cement ratio can be appropriately reduced. If steam curing or autoclave is used, reducing the proportion of cement is still powerful;

⑥ The type and activity of active microaggregates (additives). The use of high-activity micro-aggregates can reduce the specific gravity of cement (such as ultra-fine slag), while the use of low-activity micro-aggregates (such as secondary fly ash) can increase the specific gravity of cement.

2. Active micro-aggregate ratio

When curing at room temperature, especially when curing at low temperature, the active micro-aggregates should not be designed or less designed in the formula, because it will affect the initial setting of the slurry. If the amount is large, it may cause collapse. In general, adding active micro-aggregate with a cement content of less than 10% has little effect on coagulation and can be added in proportion. In summer normal temperature production, the highest mix ratio is about 30% of cement. During steam curing, the highest mix ratio is about 60% of cement. The ratio is related to the type of active micro-aggregate. When using slag powder for pulverization, the high value can be used; when using the first grade fly ash, the median value can be used; when using the second grade fly ash, the lowest value can be used.

Foam concrete construction is generally not suitable for large-volume active micro-aggregates, because it is mostly constructed at room temperature, and there are many factors that affect the stability of grout pouring. Therefore, the maximum amount of active micro-aggregate should be designed to be less than 20% of cement.

Many manufacturers often use a large amount of active micro-aggregate, especially fly ash, for cost reduction considerations, which is still not enough to add 50% of the total dry material ratio, which is not feasible under normal temperature curing. It is difficult to guarantee Stable pouring (pouring). There have been some reports and papers on room temperature foamed concrete containing a large amount of fly ash (more than 50% of the total dry material), but according to our experience, this is not easy to achieve at room temperature.

3. Lightweight aggregate ratio

Lightweight aggregates are characterized by high porosity, so high water absorption, low density, and large volume per unit weight. Therefore, its addition has the greatest influence on the water absorption and density of the product, and also has a great influence on the thermal conductivity. When designing its ratio, the following points should be paid attention to:

① There should not be too much adverse effect on the water absorption of the product. It is best to choose light aggregates with low water absorption (such as waste polystyrene particles), and do not use light aggregates with high water absorption (such as expanded perlite). When the water absorption rate of light aggregate is high, its specific gravity should be reduced, or hydrophobic sealing pretreatment should be carried out;

② It should be able to reduce the density of the product as much as possible. When choosing light aggregate, the lower relative density should be preferred, the lower the better;

③It is helpful to reduce the thermal conductivity of the product. Lighter aggregates with lower thermal conductivity are more preferred. It is recommended to use waste polystyrene foam particles;

④The proportion of lightweight aggregates should be based on product density, strength, and thermal conductivity requirements. To achieve the coordination and unity of these three aspects, one cannot only consider unilateral needs. The greater the specific gravity of the lightweight aggregate, the worse the strength, but the lower the density and thermal conductivity. Density and thermal conductivity require a larger proportion of lightweight aggregate, while strength requires a lower proportion of lightweight aggregate. This is a big proportional contradiction. Therefore, these aspects should be coordinated and unified.

4. The proportion of heavy aggregate

Foamed concrete with a density below 700kg/m3 generally does not use heavy aggregates, and most of them are only used for high-density foamed concrete. The influence of heavy aggregate ratio on product performance and process is as follows:

①The larger the proportion of heavy aggregate, the worse the stability of pouring (pouring), the easier it is to cause the heavy aggregate to sink and collapse; if heavy aggregate is not used or the proportion of heavy aggregate is smaller, pouring is more stable ; Considering the stability of pouring (casting) material, the proportion of heavy aggregate should be small rather than large;

②The larger the particle size of the heavy aggregate, the worse the pouring (pouring) stability, because the larger the particle size, the easier it is to sink; when designing the ratio, a smaller particle size should be selected on the premise of meeting the technical requirements;

③The appropriate proportion of heavy aggregate is beneficial to improve the strength of the product. From the perspective of product strength, it is advantageous to mix a certain amount of heavy aggregate.

Application of foam concrete

Lightweight concrete is widely used in energy-saving wall materials due to its good characteristics, and has also been used in other areas. Currently, lightweight coagulation the application of soil in China is mainly cast-in-place roof insulation, lightweight wall panels, and compensation foundations. However, making full use of the good characteristics can continuously expand its application in construction engineering, speed up the project progress, and improve the quality of the project.

The price of foam concrete

The price of lightweight concrete varies randomly with production costs, transportation costs, international conditions, exchange rates, and the market supply and demand of lightweight concrete. Tanki New Materials Co. Ltd aims to help all industries and chemical wholesalers find high-quality products by providing a full range of products. If you are looking for lightweight concrete, please contact us for the latest price of lightweight concrete.

Supplier of foam concrete

As a global supplier of lightweight concrete, Tanki New Materials Co., Ltd. Has extensive experience in the performance, application and cost-effective manufacturing of advanced and engineering materials. The company has successfully developed a series of foam concrete additives (including lightweight concrete, CLC blocks provide concrete foaming agents, superplasticizers, foam concrete strength enhancers, etc.), high-purity targets, and functional materials. Ceramics and structural equipment, and provide OEM services.