4.2.7 in order to prevent the concrete from segregation, when the free falling height of the concrete is more than 2m, a tumbling barrel or chute shall be set to ensure that the concrete will not be separated when falling.
4.2.8 control the pouring speed of concrete, ensure the continuity of concrete pouring and prevent construction cold joints.
Therefore, increasing the inventory of cement will relatively prolong the cooling time of cement, so as to ensure the stability of cement performance and concrete performance.
The upper layer of concrete shall be poured before the initial setting of the next layer of concrete.
After tamping, the upper layer shall be poured.
The formwork in contact with the concrete shall be coated with lubricant or liner film material.
4.2.1 the mortar used to moisten the pipe shall not be poured to the column, wall, beam and other parts.
4.2.4 when the floor slab is poured together with the beam, pour the beam first and then the floor slab.
If necessary, a series of concrete cooling measures are required, which will not be described here.
4.2.5 during pouring, the movement and deformation of reinforcement, formwork and positioning reinforcement shall be prevented.
03 delivery control of concrete before delivery, the delivery inspection of concrete shall be carried out to visually inspect the delivery slump of concrete, estimate the transportation time and slump loss of concrete, and ensure the incoming slump of concrete.
It is a systematic project.
During pouring, pay attention to vibrating in place to make the concrete fill the ends and corners.
Generally, the warehousing temperature of cement is 40 ~ 60 ℃, and the temperature in summer is above 25 ℃.
02 mix proportion design and control the mix proportion design of concrete in summer, according to the performance of raw materials and considering the characteristics of rapid hydration of cementitious materials caused by high temperature in summer, make full use of this performance, adjust the proportion of cementitious materials in the concrete mix proportion and appropriately increase the amount of admixture, so as to control the hydration speed of concrete (calculate the hydration heat), It can also increase the durability of concrete, reduce the production cost of concrete and improve the construction performance of concrete.
In addition, the characteristics of high temperature in summer can easily lead to large slump loss of concrete.
4.2.6 when pouring concrete in layers, pay attention to the integration of the upper and lower layers of concrete.
The delivery and use of concrete are affected by many factors, which are prone to adverse conditions such as rapid setting and large drying shrinkage.
If the method of increasing the amount of cement is used to supplement the requirements of water consumption, the setting time and early hydration heat will have a greater impact on the concrete, and there will be more cracks caused by too fast shrinkage.
4.1.2 the formwork and reinforcement shall not be stained with debris and dirt, and the formwork shall not have joints.
When pouring the upper layer of concrete, the vibrator must be inserted into the next layer of concrete for about 5cm to form a whole.
If the problem is caused by non accidental causes, all concrete production processes shall be subject to unified and comprehensive inspection.
Therefore, the slump should be reduced as much as possible on the premise of meeting the construction requirements..
The conventional reasons for this situation are: first, the large mud content of sand and gravel leads to large adsorption capacity of materials to water and admixtures; Second, the plastic preservation performance of concrete admixtures is poor; Third, during the rush period of project construction, the retarding composition of admixture is insufficient due to the short setting time of concrete.
4.2.2 when pouring walls, columns and other high components, the height of one pouring shall be subject to the fact that the concrete does not separate.
If effective measures are not taken in the construction and maintenance process, quality problems may be caused.
More attention should be paid to the above situation in the process of mass concrete construction.
4.2 the pouring sequence is reasonable.
Identify QR code, pay attention to me and learn more information 4.3 reasonable vibration 4.3.1 when the concrete temperature rises, in order to facilitate construction, the slump is generally required to be large, resulting in the increase of concrete shrinkage and the significant reduction of strength.
Generally, each layer shall not exceed 500mm.
4.1.4 concrete pouring shall be arranged at night as far as possible.
4.2.3 when the floor slab, beam, wall and column are poured together, the wall and column shall be poured first, and then the beam and floor slab shall be poured after the concrete is settled.
In addition, the transportation of concrete should also be controlled.
In addition, effective measures and means should be established in the production process of concrete to ensure the strict implementation of concrete mix proportion.
04 concrete construction control is the key to ensure the quality of concrete works 4.1 preparation before construction 4.1.1 before concrete pouring, check the thickness of foundation, formwork and its protective layer, as well as the position and size of embedded parts, confirm that they are correct, and rectify any abnormalities found.
Summer has the characteristics of high temperature, more precipitation, large precipitation and fast drying.
Therefore, the concrete engineering construction in summer is divided into several stages: the incoming of raw materials, the design and control of mix proportion, the outgoing control of concrete and the construction control of concrete.
4.1.3 the foundation and formwork in contact with concrete shall be watered before construction to reduce the surface temperature, but the formwork shall be prevented from storing water.
Due to the possible problems of transportation vehicles, traffic control, slow construction speed and other reasons, it is easy to increase the transportation time of concrete; Therefore, this situation can be effectively improved by configuring (can be barreled) 5 ~ 10 kg concrete admixture in each transport vehicle.
Under such temperature, the cooling speed of cement slows down, and the problem of false setting of concrete or large slump loss of concrete is easy to occur in the use of hot cement.
01 incoming control of concrete raw materials the quality control of raw materials in summer construction focuses on the use temperature of cement, the performance of admixture and the control of mud content of sand and stone.
In the process of delivery inspection, when the slump and workability of concrete are found to be abnormal, the concrete shall be prohibited from leaving the factory and adjusted after analyzing the causes.
