The purpose of concrete curing is to create suitable temperature and humidity conditions to ensure or accelerate the normal hardening of concrete. Different curing methods have different effects on concrete performance. Common curing methods include natural curing, steam curing, dry-wet curing, autoclaving curing, electric heating curing, infrared curing and solar curing.
The time of maintenance experience is called maintenance cycle. In order to facilitate comparison, it is stipulated that the specimens for measuring concrete performance must be cured under standard conditions. The standard curing conditions adopted in China are: the temperature is 20 2℃; ; Humidity is not less than 95%.
Extended data:
Concrete has the characteristics of abundant raw materials, low price and simple production technology, so its consumption is increasing day by day. At the same time, concrete also has the characteristics of high compressive strength, good durability and wide range of strength grades.
These characteristics make it widely used, not only in various civil engineering, but also in shipbuilding, machinery industry, marine development, geothermal engineering and so on. Concrete is also an important material.
The function of concrete:
1, workability
The most important performance of concrete mixture. The properties of the mixture, such as consistency, fluidity, plasticity, anti-delamination, segregation and bleeding, and easy plastering, are comprehensively shown. There are many methods and indicators to measure and express the workability of mixture. The slump (mm) measured by truncated cone slump cone and Weibull time (sec) measured by Weibull instrument are mainly used as the main indicators of consistency in China.
2. Strength
The most important mechanical properties of concrete after hardening refer to the ability of concrete to resist pressure (such as compression, tension, bending and shearing). Water-cement ratio, variety and dosage of cement, variety and dosage of aggregate, and mixing, molding and curing all directly affect the strength of concrete.
The strength grade of concrete is based on the standard compressive strength (cube with side length of 150mm is taken as the standard specimen, which is cured for 28 days under standard curing conditions, and measured by standard test method, with a guarantee rate of 95%). Improving the tension-compression ratio of concrete is an important aspect of concrete modification.
3. Deformation
Concrete will be deformed under load or temperature and humidity, mainly including elastic deformation, plastic deformation, shrinkage and temperature deformation. The elastic deformation of concrete under short-term load is mainly expressed by elastic modulus.
Under long-term load, the phenomenon of constant stress and increasing strain is creep, while the phenomenon of constant strain and decreasing stress is relaxation. The volume deformation caused by cement hydration, carbonation and cement stone dehydration is called shrinkage.
4. Persistence
Generally speaking, concrete has good durability. However, in cold areas, especially in the engineering parts where the water level changes, concrete is easy to be destroyed under the action of frequent freezing and thawing in saturated state.
Therefore, there should be certain frost resistance requirements for concrete. When used in seepage control engineering, concrete is required to have good impermeability and corrosion resistance. Impermeability, frost resistance and erosion resistance are the durability of concrete.
Baidu encyclopedia-concrete