Effect of air-entraining agents on concrete properties

Air-entraining agent, also known as air-entraining agent, is an admixture that introduces air into the concrete mixture during the mixing process to form a large number of tiny, closed and stable bubbles. Because of its significant effect in improving the performance of concrete, air-entraining agent is one of the commonly used concrete admixtures.

1. Improve the workability of concrete
Air-entraining agents introduce countless tiny and independent bubbles into the concrete, increasing the volume of cement mortar and reducing The friction of aggregates enhances the lubrication effect, thereby greatly improving the workability of concrete. Due to the reduction of unit water consumption, the amount of bleeding water is reduced. When making air-entrained concrete, the workability of concrete can also be significantly improved when coarse aggregate with poor particle shape and fine aggregate with poor particle size are used. For every 1% increase in the air content of concrete, the slump increases by approximately 10mm. Adding air-entraining agents can reduce the unit water consumption of concrete. When the slump of concrete and the amount of cement are constant, for every 1% increase in air content, the unit water consumption will be reduced by 2% to 4%. For lean concrete, the improvement effect of air-entraining agent on workability is more significant.

2. Improve concrete homogeneity
Due to the introduction of micro-bubbles, the settling of solid particles and the rise of moisture are prevented, and the film of bubbles consumes part of the Moisture, coupled with the air-entraining and water-reducing effect of the air-entraining agent, reduces the amount of water that can move freely, thereby greatly improving the water retention of fresh concrete, and the bleeding and settlement shrinkage during setting and hardening will be significantly reduced. The resulting segregation of the various components of the concrete is significantly reduced, resulting in a significant improvement in the homogeneity of the concrete.

3. Improve the durability of concrete

Concrete mixed with air-entraining agents requires less water , the bleeding settlement is reduced, thereby reducing gaps, reducing the number of capillary pores and reducing the capillary pore diameter. A large number of closed independent micro-bubbles cut off the capillary channels, thereby improving the impermeability of concrete. Among the effects of improving the durability of concrete, air-entraining agents contribute the most to improving the freeze-thaw resistance of concrete. The frost resistance of concrete mixed with air-entraining agents is several times higher than that of standard concrete, which greatly extends the life of concrete materials under the influence of freeze-thaw damage conditions. </p