Foam concrete additives are crucial materials in the production of foam concrete, and the ability to produce foam concrete with the appropriate density hinges on selecting the right foam concrete additive. There is a wide variety of foam concrete additives on the market, with prices varying greatly. Many people choose additives without a clear direction or simply opt for the cheapest option. In reality, the cost of foam concrete additives in the overall production is relatively low, and relying solely on price when selecting foam concrete additives is not advisable, in the editor's opinion.
Currently, foaming agents for cement are generally categorized into synthetic cement foaming agents, cement foaming agents derived from animal and plant proteins, composite cement foaming agents, and rosin soap cement foaming agents. Each type of foaming agent has its own advantages and disadvantages. Synthetic cement foaming agents are widely chosen due to their low price, particularly in the roof insulation market. Those transparent and cost-effective foaming agents typically belong to this category. The primary reason is that the roof insulation market does not prioritize quality, as construction companies often say, "Roof insulation is just like making substandard tofu." However, if this continues, the market is bound to deteriorate sooner or later.
Animal protein cement foaming agents offer advantages such as good foam stability and closed cell rate. Plant-based cement foaming agents have a relatively balanced foaming power and stability. Many people believe that cement foaming agents are merely for foam reduction and densification, which is a very one-sided view. In reality, cement foaming agents are related to the strength, thermal conductivity, setting speed, water absorption rate, pouring height, and other properties of foamed concrete products. Therefore, when selecting cement foaming agents, one should not solely focus on price but consider the overall cost. The cost of cement in foamed concrete is the main cost. Reducing cement cost is crucial for lowering the cost of foamed concrete. To reduce cement cost, one can increase strength to decrease cement usage. By improving the strength of the same-density foamed concrete, if the strength is maintained, the cement usage can be reduced while still achieving the original strength. For instance, if a 400-density foamed concrete previously had a strength of 0.6 MPa, by enhancing the strength, it can reach 0.6 MPa with 350. This saves 50 kg of cement, achieves the strength, and also improves thermal insulation properties. However, one key factor is to choose a good cement foaming agent.
The Impact of Cement Foaming Agents on the Performance of Foam Concrete
One, strength
The strength of foamed concrete is a critical indicator. As foamed concrete is an artificial stone material that has been foamed, its low density naturally leads to a decrease in strength, with lower density resulting in a greater decrease. How to enhance the strength of foamed concrete has become a key factor in improving its performance. Choosing a good cement foaming agent can effectively increase the strength of foamed concrete. A good cement foaming agent can form bright, closed pores in foamed concrete, significantly enhancing the compactness of the bubble walls and thereby increasing strength. Good cement foaming agents can be used at low water-cement ratios, with lower ratios leading to higher strength. Many cement foaming agents on the market today can only be used at high water-cement ratios, which is why many construction teams opt for high ratios, claiming it as "self-leveling." However, this sacrifices the strength of the foamed concrete, resulting in "mushy" construction. The compatibility of the cement foaming agent with cement also affects its strength. If the foaming agent is not matched with the cement, a common issue is that the foaming agent becomes a barrier layer for the cement, leading to "false setting" where the cement does not actually solidify. This barrier layer prevents the cement from fully reacting, resulting in a product that is particularly crumbly with little strength.
Absorption Rate
Many foamed concrete products on the market have a high water absorption rate, with some reaching up to 50%. The reason lies in the low closed pore rate of foamed concrete, caused by bubble leakage and poor foam stability of the cement foaming agent, leading to bubble bursting and the formation of through-pores. This is all due to the low closed pore rate of the cement foaming agent. Therefore, a good cement foaming agent is one that reduces the water absorption rate of foamed concrete products.
III. Pouring Height
The pouring height of foamed concrete is directly related to the foam stability of the cement foaming agent. Higher foam stability in the cement foaming agent allows for greater pouring heights, and vice versa. The higher the pouring height, the greater the pressure the slurry exerts on the foam. Poor foam stability can lead to collapse.
Density
The key to controlling the density of foamed concrete lies in the amount of foam added, making the cement foaming agent a direct factor affecting density. The more stable the foam of the cement foaming agent, the better the density can be controlled, allowing for the production of lower density foamed concrete. Conversely, if the stability of the cement foaming agent is poor, it's possible to design a 400-density concrete, only to find it's 500 kg after pouring. There's also the possibility of uneven density from top to bottom, resulting in inconsistent density. Such issues are particularly evident in wall casting.
Thermal Conductivity
The direct influencing factor of thermal conductivity is the density of foam concrete, with the key factor for density control being the cement foaming agent. Correcting a common misconception in the industry: many believe there is a direct relationship between thermal conductivity and closed cell rate. However, our tests on foam concrete samples with a density of 200 kg/m³ and varying closed cell rates have shown that there is no significant difference in thermal conductivity between high and low closed cell rates, both being 0.059.
In summary: Foaming agents for cement can affect performance indicators such as the strength of foam concrete, water absorption rate, pouring height, density, and thermal conductivity. It is evident that selecting a high-quality foaming agent is crucial in the construction of foam concrete.
