Air-entraining Agent

Air-entraining agents entrain air into concrete mixtures to meet project specifications and develop a stable air-void system to improve durability of the concrete. SIDLEYAir admixtures facilitate the development of a stable air-void system to provide increased resistance to deterioration from cyclic freezing and thawing exposure conditions. These products also reduce segregation and bleeding and improve plastic concrete workability and cohesiveness, facilitating placement.

Purpose and Benefits of Air-Entraining:

• Improves Resistance to Freeze-Thaw Cycles: Air bubbles create space for the expansion of water as it freezes, reducing internal stresses and preventing cracking.
• Enhances Workability: The presence of air bubbles improves the fluidity of the mix, making it easier to place and finish.
• Reduces Permeability: Air entrainment helps in closing the pores and reducing the permeability of concrete, which enhances durability against ingress of aggressive chemicals.
• Improve pumping performance: Using air-entraining admixtures can positively influence the pumping performance of concrete.
• Improves Shock Resistance: Air-entrained concrete can better withstand impacts and vibrations.

Air-entraining agents, functioning as surfactants, have chemical structures as shown in Figure 1. These substances consist of long-chain molecules with a hydrophilic group at one end and a hydrophobic group at the other. In engineering applications, anionic and nonionic air-entraining agents each possess distinct properties, significantly enhancing concrete performance. Common anionic agents include rosin soaps and dodecyl sulfate salts. Based on production raw materials, air-entraining agents can be classified into rosin-based, alkylbenzene sulfonate-based, soap-based, and fatty alcohol sulfonate-based types. Additionally, the market offers fatty alcohol polyoxyethylene ethers, sodium fatty alcohol polyoxyethylene sulfonates, and sodium fatty alcohol sulfates.

【 Effects on Concrete Workability 】
Air-entraining agents enhance concrete’s flowability and workability, commonly used to improve the constructability of mass concrete. When added to concrete, these agents generate numerous micro-bubbles that significantly reduce concrete viscosity while decreasing friction between aggregate particles, thereby substantially improving workability. At a constant water-cement ratio, each 1% increase in air content corresponds to a 10mm increase in slump.
【Impact on Concrete Mechanical Properties】
Air-entraining agents significantly influence concrete compressive and flexural strength. Certain types can mitigate strength loss. Typically, their addition reduces compressive strength, though this loss stems from multiple factors. For high-strength concrete, their application compensates for the decrease in flexural strength.

Air-entraining agents significantly increase the air content in concrete, which in turn reduces the effective bearing area under compression, leading to decreased strength and abrasion resistance. Specifically, when the water-cement ratio remains constant, each 1% increase in air content causes concrete strength to decrease by approximately 3% to 5%. Therefore, when using air-entraining agents to enhance concrete’s freezing resistance, the air content must be carefully controlled to prevent excessive air bubbles from causing a significant reduction in concrete strength.