Concrete engineering is a key project in construction. Its construction process is: construction preparation → concrete mixing → concrete transportation → concrete pumping → concrete pouring → concrete vibrating → concrete curing. There are many options for each step in construction. Usually, the selection should be based on the site conditions and project conditions. Here are some tips for concrete construction.
The transportation method of concrete should be selected according to the amount of concrete poured. It is mainly divided into the following methods.
(1) Manual transportation by wheelbarrow or dump truck. It is often used when the concrete transportation volume is not large and the transportation distance is short, but the transportation speed is the slowest.
(2) Dump truck transportation. It is often used when the concrete transportation volume is large and the transportation distance is long. The vehicle body is sealed, which is convenient for heat preservation and moisture retention. It is mainly used in mixing plants.
(3) Tower crane transportation. It is often used for concrete pouring in large hydropower projects. Usually, the height between the bucket outlet and the concrete bin surface does not exceed 1.5~3.0m, but the transportation speed is slow.
(4) Belt conveyor transportation. Generally, it is better to transport the concrete in a horizontal direction, and the transportation speed should not exceed 1.2m/s, so as to avoid the concrete separation caused by too fast transportation speed.
(5) Concrete pumping transportation. Including piston type and pneumatic type, it is often used in the case of inconvenient transportation and large amount of concrete. The transportation speed is fast, but it will be affected by the site conditions.
Selection of concrete pouring method
When pouring concrete, it should be selected according to the site conditions and specific engineering conditions. It is usually necessary to calculate the interval time of concrete layering, which should not be greater than the setting time of concrete. Commonly used concrete pouring methods are mainly divided into three methods: full layering, segmented layering and oblique layering. Full layering is often used for large-volume concrete; segmented layering is suitable for the case where the structure thickness is not large but the area or length is large; oblique layering is mostly used for large-volume concrete, and the inclined angle of the structure with a long length is generally less than or equal to 45°.
Selection of concrete vibrating machinery
When vibrating concrete, the vibration range of the selected machinery should be considered and selected according to the site conditions. Usually, concrete vibrators can be divided into internal vibrators and external vibrators according to their vibration mode. The former is mostly used to vibrate cast-in-place foundations, columns, beams, walls and other structural components and concrete for later volume foundations. When vibrating, it should avoid collision with steel bars, formwork, core tubes, hanging rings or embedded parts; the latter is often suitable for thin plates and is used for component surface vibration. When vibrating, the moving spacing of the external vibrator should ensure that the vibrator bottom plate can cover the edge of the vibrated part.
Selection of concrete curing methods
Concrete curing methods should be selected according to the construction site conditions, construction conditions and weather conditions, and are mainly divided into natural curing and thermal curing. Natural curing is usually carried out by covering concrete with appropriate materials at room temperature, and taking measures such as watering, wetting, windproof and dry, and heat preservation and anti-freezing. It mainly includes covering watering curing and plastic film curing. The former can be covered with materials such as straw mats, reed mats, sacks, sawn wood, wet soil and wet sand; the latter is usually covered with plastic film. Thermal curing mainly involves hardening concrete at a higher temperature to accelerate the hardening process, which generally includes steam chamber curing and hot mold curing. In addition, attention should be paid to temperature calculation during winter construction.
