Method of Improving Concrete Durability

Concrete durability refers to the ability of concrete to withstand the effects of environmental media and survive long-term use without being damaged if it meets the design requirements. Improving the durability of concrete has important practical and long-term significance for extending the service life of concrete buildings and saving national investment.

The durability of concrete is directly related to its impermeability. The penetration of concrete determines to a large extent that concrete is susceptible to erosion by adverse external factors. Therefore, in order to improve the durability of concrete, the impermeability of concrete must first be improved.

1. Reduce water-cement ratio

When the water-cement ratio is large, after the concrete hardens, the excess water is evaporated to form capillary pores. The greater the water consumption, the more capillary pores left after the cement is hydrated, and the greater the permeability coefficient. On the one hand, it affects the bonding force between aggregate and cement slurry, steel bars and concrete, reducing the compactness and strength of concrete. On the other hand, these connecting pores also become shortcuts for external liquids and harmful gases to invade the interior of the concrete. Therefore, when mixing concrete, while meeting the technical and construction requirements, the water-cement ratio should be reduced as much as possible, the water consumption should be reduced, and the density should be increased to improve the impermeability of concrete.

2. Adding admixtures is the best way to improve the properties of concrete.

One is the air-entraining water-reducing agent. On the one hand, the air-entraining water-reducing agent produces uniform, stable, and interconnected micro-bubbles inside the concrete to prevent liquid penetration; on the other hand, it can also greatly reduce the water consumption of concrete and improve the density of concrete. The second is to mix anti-penetration agent. The impermeable agent forms a colloidal complex in the concrete, filling and blocking the capillary pores inside the concrete, thereby improving the compactness of the concrete. The third is to mix expansion agent. Chemical reactions occur through the addition of expansion agents, causing the concrete to expand and increase the compactness of the concrete under the constraints of external forces.

3.Choose the right material

The cement grade is generally no less than 425#; the fine aggregate is required to be medium sand with an average particle size of about 0.4mm from river sand with uniform, smooth and hard texture, a mud content of less than 3%, and an appropriate amount of silt; The maximum particle size of coarse aggregate should be selected reasonably. Except for large volumes, 5 to 30 mm is generally suitable. The maximum particle size should not exceed 40 mm, and the mud content should not exceed 1%. It requires fine organization, neat particles, and hard texture. In addition, the gradation should be excellent to improve the workability of concrete.

4. Strengthen maintenance

the early curing is not done well, the cement will not be hydrated normally, which will reduce the compactness of the concrete and then affect the impermeability. Therefore, the early wet curing of concrete must be strengthened, and the curing time shall not be less than 14 days.