The cell structure is an important index that affects the performance and appearance of concrete, and good cell parameters are a necessary condition for the establishment of a reasonable cell structure.

There are three parameters that characterize the characteristics of concrete cell structure: air content stability, cell size distribution and cell spacing coefficient. Common control measures for bubble structure include: raw material control, mix ratio adjustment, and the use of defoamers and air-entraining agents. Among them, the use of defoamers and air-entraining agents is the most efficient.

The defoamer eliminates harmful air bubbles in concrete through defoaming and foam breaking. As the amount of defoamer increases, the air content of concrete decreases, and the lubricating effect of air bubbles between slurry and aggregate is weakened, resulting in poor workability of concrete. . The air-entraining agent can reduce the air-liquid interfacial tension, so that a large number of uniform, stable and closed micro-bubbles can be introduced into the concrete during the mixing process, which can enhance the lubrication and viscosity of the slurry, and significantly improve the workability and cohesion of the concrete.

At home and abroad, there have been many studies on the influence of defoamers and air-entraining agents alone on the performance of concrete, but the research on the effects of defoamers and air-entraining agents combined is still relatively rare.

With the increasingly higher requirements of modern engineering for concrete performance and appearance quality, it is difficult to meet the requirements of concrete performance indicators with a single use of defoamers or air-entraining agents, and the compounding of defoamers and air-entraining agents can not only improve The comprehensive performance of concrete can also effectively improve the concrete bubble structure, which is of great benefit to enhancing the appearance quality of concrete.

A large number of air bubbles introduced in the fresh concrete during the mixing process approach each other during the standing process and coalesce into larger air bubbles. Under the action of buoyancy, they overcome the viscous resistance of the grout and rise and discharge, resulting in the loss of air content in the concrete, and the longer the standing time , the greater the possibility that a large number of independently existing air bubbles in the concrete will meet and coalesce, the greater the loss of air content.

By mixing air-entraining agent and defoaming agent, not only can the structure and distribution of air bubbles inside the concrete be changed, but also the viscosity of the slurry will be affected, thereby affecting the stability of the air content of the concrete.

When the defoamer is used alone, the space coefficient of concrete hardened concrete bubbles increases, while the average pore size decreases. When the content of defoaming agent is high, as the content of air-entraining agent increases, the spacing coefficient and average pore size of hardened concrete decrease first and then increase. Appropriate amount of defoamer and air-entraining agent used in combination can improve the stability of air content in concrete, reduce the spacing coefficient and average pore size of hardened concrete bubbles, and effectively improve the appearance of concrete.