The role of fly ash hollow microspheres in concrete

2022-04-30

The role of fly ash hollow microspheres in concrete

 

Key words

Fly ash, floating beads, hollow beads, self-shrinking concrete, internal curing agent, porous hollow beads

 

Fly ash hollow particle microbeads are the main raw material, and the nano-film shell on the surface of fly ash hollow particle microbeads is corroded and removed by a special method, and finally a new type of high-performance concrete internal curing agent with the best pore structure is obtained - porous Hollow microbeads can use their own water absorption and water release characteristics to implement internal curing of high-performance concrete, improve the mechanical properties of concrete to a certain extent, and improve the cracking problem of concrete caused by self-shrinking.

 

Autogenous shrinkage is a common phenomenon in early high performance concrete. In this phenomenon, water can quickly make cement enter the hydration process. However, more water will produce very small capillaries in high performance concrete. The high surface tension will cause the concrete to undergo self-shrinking, which will lead to the premature cracking of the concrete, making the concrete more easily attacked by potentially aggressive substances (sulfates, chlorides, carbonates, etc.), and seriously reducing the durability of the concrete. High-performance concrete (HPC) has a low water-cement ratio, and the early cracking caused by autogenous shrinkage is particularly serious. These cracking problems cannot be alleviated by traditional water spray curing.

 

The internal curing method of adding a saturated internal curing agent into the concrete, the internal curing agent is used as a water storage carrier, and the water is gradually released during the cement hydration process, which can maintain a high relative humidity in the concrete pores to prevent Self-shrinking cracking. As a result, the self-shrinkage of concrete can be reduced or eliminated, minimizing cracks and significantly improving the structural durability of concrete. Since the internal curing agent provides additional curing water, more complete and complete hydration of the cement paste can also be achieved through internal curing, thereby making the cement-based paste denser after hardening and reducing its permeability. As a result, the service life of concrete structures can be significantly extended.

 

In addition, the application of porous hollow microspheres in high performance concrete has great potential.

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