The preparations required for expansion joints, settlement joints, post cast strips or reinforced strips have been completed.
It is not applicable to the construction of mass concrete with ambient temperature higher than 80 ℃ or corrosive medium endangering the concrete.
Various cooling and crack prevention measures for construction have been prepared, and temperature measuring elements or buried pipes have been prepared and passed the inspection.
The content of the construction process standard only designs the special requirements for mass concrete construction.
Cold aggregate and cold water shall be used to mix concrete without freezing in winter.
After the concrete is unloaded from the mixer, it shall be transported to the pouring place in time; During transportation, the “segregation” of concrete, loss of cement slurry, change of slump and initial setting shall be prevented.
The reinforcement, formwork and embedded parts have been installed, and various inspections and quality acceptance have been completed.
If the failure stop time exceeds 45 minutes or the concrete has “segregation”, the residual concrete in the pipe shall be washed with pressure water or other methods immediately.
In case of abnormal operation, slow down the pumping speed, pump and push back and forth for several times to prevent pipe blockage.
Construction roads, construction sites, water, electricity and lighting have been arranged, and construction scaffolding and safety protection have been erected.
The duration from the discharge of concrete from the mixer to the completion of pouring shall not exceed the time specified in the specification.
In order to mix the concrete evenly, the mixing time shall not be less than 90 seconds.
Jianzhongtong media ID: jianzhong0011 The preparation is based on unified standard for quality acceptance of building engineering – gb50300-2013 code for quality acceptance of concrete structures – gb50204-2015 code for quality acceptance of underground waterproof Engineering – gb50208-2011 code for winter construction of building engineering – jgj104-2011 technical code for concrete structure of high rise buildings – jgj3-2010 technical code for mass concrete construction of block foundation – ybj224-91 technical specification for construction of pumped concrete – JGJ / t10-2011 code for design of concrete structures – gb50010-20102 Scope of application the construction process standard is applicable to the construction of mass concrete in construction engineering.
The speed should be slow when starting to press the concrete.
Contact, the command system is ready.
4.2 medium and low heat cement, fly ash and high-efficiency retarding water reducer can delay the release rate of hydration heat and reduce the heat peak value.
The distance between the upper surface of concrete in the hopper and the upper opening should be about 200mm to prevent pumping air.
The sand and gravel yard shall be equipped with simple shading device, and cold water shall be sprayed on the aggregate when necessary.
During pouring, the end hose shall move evenly to make the distribution of each layer uniform and avoid pouring in piles..
Under the condition of meeting the requirements of concrete pumping, stones with large particle size and good grading shall be selected as far as possible; The sand rate should be reduced as much as possible, and should generally be controlled between 42-45%.
If any, it shall be reported to the technical department immediately for measures.
Installation process flow 4 Construction methods and technical measures 4.1 construction conditions the construction scheme of mass concrete has been prepared, and the disclosure has been made according to the construction process flow determined in the construction scheme, the division of flow operation section, pouring procedures and methods, concrete transportation and distribution methods, methods and quality standards, safe construction, etc.
Concrete mixing tank truck or loader shall be used for horizontal transportation of concrete, and concrete pump truck shall be used for vertical transportation.
Add an appropriate amount of U-shaped concrete expansion agent to prevent or reduce the shrinkage cracking of concrete, densify the concrete and improve the impermeability of concrete.
In case of abnormal sound or pump pipe runout, stop the pump in time to eliminate the fault.
The elevation line has been inspected and qualified.
The outgoing temperature and pouring temperature of concrete shall be controlled.
The concrete supply has been implemented, the corresponding supporting equipment, measuring instruments and meters, and the supply channels of various raw materials required have been implemented and have entered the site.
Personnel who need to work with certificates have been trained and have complete certificates.
4.3 mass concrete mixing and transportation concrete mixing shall be strictly measured according to the mix proportion, and truck weighing is required; Loading sequence: Stone → cement → sand; If there are additives, they shall be added together with cement; Powdery admixtures are added together with cement, and liquid admixtures are added together with water.
Before pumping concrete, first pump the clean water in the receiving hopper out of the pipeline to wet and clean the pipeline, then press pure water slurry or 1:1-1:2 cement mortar to lubricate the pipeline, and then pump concrete.
When winter construction or additives are added, it shall be extended for 30 seconds.
It has coordinated with the community, urban management, transportation and environmental supervision departments and has gone through the necessary formalities.
When the pumped concrete is poured into the formwork, the distance from the concrete outlet at the end of the pump pipe to the formwork shall be greater than 500mm.
When the concrete is sent out of the end of the pipe, the speed can be gradually accelerated and switched to the normal speed for continuous pumping.
4.4 the pump receiving hopper for on-site transportation and distribution of concrete must be equipped with a hole diameter of 50 × 50mm vibrating screen to prevent individual large particle aggregate from flowing into the pump pipe.
All mechanical equipment, instruments, machines, tools, etc.
Concrete delivery pump and pump pipe have been laid and commissioned.
The mass concrete involved in the construction process standard usually refers to the concrete whose minimum size of concrete structure is equal to or greater than 1m, or which is expected to produce cracks due to cement hydration heat without taking corresponding technical measures to reduce the concrete temperature.
When pumping concrete, it must ensure that the concrete pump can work continuously.
required for construction have been prepared.
In summer, if the temperature is high at that time, the sand and gravel shall also be insulated.
For general and general requirements in concrete construction, please refer to the construction process standard for concrete structures.
Professionals in place.
The cooling water pipe is embedded in the foundation and cooled by circulating low-temperature water.
Strengthen the patrol inspection of concrete pump and pipeline.