Construction Of Concrete Slabs

- Jan 29, 2019-

Heat Insulated Precast Sandwich Concrete Panel.jpg

The concrete of the floor is characterized by its thin thickness and large area. The construction steps are as follows:

1. Stakeout and clearing the foundation. The method is the same as the slurry block stone bottom plate.

2. Vertical model. The template of the bottom plate is generally short, and the pile head support is commonly used, and its structure is as shown in the following figure. If the bottom of the rock foundation is over-excavated, it is uneven, and it is filled with cement bag paper or slurry block stone to prevent slurry leakage. The boundary of the concrete surface should be drawn on the formwork to control the engineering standard.

3. According to the design requirements, the bottom plate steel bar is tied, and the bottom layer steel bar can maintain the thickness of the protective layer with a small stone pad. If you use your hands, the surface reinforcement can be hung on your hands with lead wire. If there is no scaffold, the concrete should not be sunk when the concrete vibrates.

4. For concrete mixed with concrete, it is best not to use cement with too much admixture. Because the admixture is light, it is easy to concentrate the surface and it is not good for the panel to resist impact. Sand and stone should be screened and the surface is not allowed to carry dirt or other debris. Stones are generally classified according to the size of Xiaoshi 0.5~2, medium stone 2~4, and big stone 4~8 cm. Crushed stone or gravel can be used. Some blocks of stone can also be buried in the concrete.

5. Artificially mixed concrete is carried out on the mixing board. First, dry the cement and sand with iron shovel, and mix at least three times until the color is uniform. No sand or cement is observed. Then add stones, gradually sprinkle a specified amount of water with a watering can, and use two iron shovel to turn the opposite side of the worker. A worker mixes with four teeth and turns it back and forth several times until it is completely uniform. The already mixed concrete must be used immediately and it is not allowed to be stacked on the workbench for more than half an hour.

For larger concrete construction, the concrete can be mixed with a mixer, and the mixing time should not be shorter than 1 minute.

6. Pouring concrete, artificially mixed concrete can be directly pushed into the warehouse with a crucible, vibrated with a vibrator or manually tamped with iron braze. When the bottom slope of the panel is slower than 1:3, the general surface does not need a template, and it can be smoothed with mud. If the slope is steep, it should be temporarily blocked with wooden planks. After the vibration is stopped, it should be removed. If it is smoothed with mud, it can also be used as a dry and hard concrete.

7. Maintenance. After concrete is poured, it is covered with straw, straw or cement bag paper. Sprinkle water conservation. Maintenance time is at least 14 days.

In the construction of concrete panels, pay attention to the following issues:

(1) It is better to lay a layer of cement mortar first in contact with the foundation to avoid the formation of honeycomb and increase the adhesion to the foundation.

(2) The pouring work of concrete should be carried out continuously, and the interval time should not exceed 2 hours, such as the interval time. It should be treated as cold seam, and the concrete strength should reach 12 kg/cm 2 or more. After the surface is chiseled, cleaned, and covered with a layer of the same grade mortar, the concrete will continue to be poured.

(3) Newly poured concrete, it takes at least one day and night in spring and autumn, and it takes three days in winter to build a lane board on the concrete surface for material transportation.

(4) When the minimum temperature in winter is lower than -3 °C, the lining concrete should not be poured to prevent the concrete from being damaged by freezing. Although concrete can be constructed in winter, it has special requirements for equipment and materials. Therefore, it is best to consider the spillway of small and medium-sized reservoirs in advance when planning the project, and to pour concrete before the temperature is lowered.