Measures to Improve the Durability of Concrete

The external environment, raw materials, compactness, and impermeability of concrete are important factors for the durability of concrete. Therefore, corresponding measures should be taken in accordance with the specific conditions in the project, from the three materials of concrete, structural design, and engineering construction. Improve the durability of concrete.

Concrete material

1. Coarse aggregateChoose hard, well-graded limestone, granite, diabase, and other spherical, low water absorption, and small porosity crushed stones, the crushing index is not more than 10%, the cubic compressive strength of the parent rock and the design strength of the beam concrete The ratio should be greater than 2, the mud content should be less than 0.5%, the content of flake particles should not be greater than 5%, and the particles should be as close as possible to equal diameter. Use alkali-free active coarse aggregate.
2. Fine aggregateThe fine aggregate should be natural medium-coarse sand with reasonable gradation and uniform and firm texture, with a fineness modulus of 2.6~3.0. The content of mica and soil should be strictly controlled. The sand content should not exceed 1.5%, and the mud content should not be greater than 1.5%. More than 0.1%, use alkali-free active fine aggregate.
3. CementThe strength and engineering performance of cement and cement-like materials are formed by the setting and hardening of cement mortar. Once the cement stone is damaged, the durability of the concrete will be destroyed, so the choice of cement needs to pay attention to the specific properties of the cement variety. Choose cement with low alkali content, low heat of hydration, low drying shrinkage, heat resistance, water resistance, corrosion resistance, and good frost resistance, and choose according to specific conditions.

Structural design

1. Concrete mix ratioThe design of the concrete ratio should consider reducing the amount of cement and water consumption as much as possible while meeting the strength and workability of the concrete, reducing the heat of hydration, reducing shrinkage cracks, increasing the density, and using reasonable water reducing agents in concrete and air-entraining agents to improve the concrete. The internal structure is mixed with a sufficient amount of mixture to improve the durability of concrete.

1. Concrete protective layerIn the concrete structure, reinforced concrete is a composite material composed of two different materials: steel and concrete. The good bonding properties of the two materials are the basis for their work together. The requirements for the concrete protective layer are put forward from the perspective of the bonding and anchoring of steel bars. In order to ensure that the steel bars and the surrounding concrete can work together, and to make the steel bars give full play to the required strength of calculation. Different protective layer thicknesses should be designed for different corrosive environments. Concrete structures and components should be cast integrally, and construction joints should not be left. When construction joints are necessary, their position and structure shall not impair the durability of the structure.
2. Node structure designThe joint structure design of the structure should also consider the overall durability of the component after partial damage.

Engineering construction

1. Conveying of concreteThe concrete is transported by a concrete pump or a concrete truck. When pumping is used, the length of the initial horizontal section of the conveying pipeline shall not be less than 15m. Except for the hose at the outlet, the other parts of the conveying pipeline shall not use hoses or tapered pipes. The conveying pipeline should be fixed firmly, and should not be in direct contact with the formwork or steel bars. The concrete should be conveyed continuously, the conveying time interval is not more than 45min, and the slump loss is not more than 10%. The grid of the conveying pump receiving hopper shall not be filled with concrete, and the feed flow shall be controlled, and the over-diameter aggregate and foreign matter shall be removed in time. During high-temperature construction in summer, it is advisable to cover the conveying pipe with wet straw bags to prevent the excessively high temperature of the conveying pipe from causing excessive loss of concrete slump and affecting the construction, until the concrete is blocked. In winter construction, it is advisable to wrap the conveying pipe with thermal insulation material to prevent the concrete from freezing.
2. Concrete mixingThe concrete mix ratio should consider factors such as strength, elastic modulus, initial setting time, workability, and other factors and be determined through experiments. Concrete raw materials should be accurately weighed in strict accordance with the construction mix ratio. Before mixing the concrete, the moisture content of the fine aggregate should be strictly measured, and the change in the moisture content of the coarse and fine aggregates caused by weather changes should be accurately measured in order to adjust the construction mix ratio in time.
3. Concrete curingAttention should be paid to humidity and temperature in the maintenance of concrete. Curing is not only watering and moisturizing but also controlling the temperature change of concrete. At the same time as wet curing, it should be ensured that there is not too big a difference between the concrete surface temperature and the internal temperature and the atmospheric temperature it is in contact with. Take comprehensive measures of heat preservation and heat dissipation to prevent temperature drop and excessive temperature difference. Therefore, comprehensively considered, steam curing can better solve the above two problems.

Kingsun is a professional concrete admixtures manufacturer and supplier.