In concrete pavement construction, the reasonable control of concrete slump directly affects the construction quality and mechanical operation efficiency. The specific standards are as follows
1. Conventional slump range
Ordinary concrete pavement
Slump: 120~180mm (about 150mm is appropriate)
Applicable scenarios: Applicable to laser leveling machine or paver construction to ensure that the fluidity of concrete meets the requirements of mechanical paving and vibration.
Special requirements pavement
High slump: 180~220mm (when adding water reducer)
Applicable scenarios: Complex reinforcement structure or high temperature dry environment, it is necessary to improve the fluidity of concrete to avoid segregation.
Low slump: 80~120mm (dry hard concrete)
Applicable scenarios: Construction with slipform paver, or projects with high early strength requirements.
2. Key factors affecting slump selection
Construction process
Laser leveling machine: requires a higher slump (120~180mm) to facilitate mechanical vibration and leveling.
Slipform paver: The slump should be strictly controlled at 80~120mm to avoid deformation of the structure due to excessive fluidity.
Environmental conditions
Hot and dry weather: The slump can be appropriately increased (+20~30mm) to reduce the slump loss caused by water evaporation.
Low temperature or rainy season: The slump can be appropriately reduced (-10~20mm) to prevent concrete segregation.
Material properties
When the coarse aggregate particle size is large and the grading is poor, the slump needs to be increased to ensure workability.
Adding water reducer can reduce the water-cement ratio and improve strength while maintaining the slump.
3. Construction precautions
Slump test
Each truck of concrete needs to be tested for slump before unloading. If the deviation exceeds ±20mm, it needs to be adjusted (such as adding admixtures or secondary mixing).
Time control
The mixing and pouring of concrete must be completed before the initial setting (usually ≤2 hours) to avoid slump loss due to too long time.
Common Problems
Slump is too large: it is easy to cause bleeding and segregation, which can be improved by adding fly ash or reducing the water-cement ratio.
Slump is too small: poor fluidity, it is necessary to add water reducer or increase the water consumption appropriately (need to be verified by the laboratory).
4. Reference Standards
"Technical Specifications for Construction of Highway Cement Concrete Pavement" (JTG/T 3650-2020): The recommended slump is 100~180mm, which is adjusted according to the construction machinery.
"Concrete Structure Engineering Construction Quality Acceptance Code" (GB 50204-2015): The slump detection frequency is required to be no less than once every 100m³.
Reasonable control of slump can ensure the construction quality, durability and appearance smoothness of concrete pavement. The specific parameters need to be determined in combination with design requirements, construction technology and environmental conditions.
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