What is concrete slump
Concrete slump is an important indicator to measure the fluidity and working performance of concrete and is widely used in construction projects. It directly affects the construction quality of concrete and the durability of the final structure. This article will introduce in detail the definition, testing methods, influencing factors and application scenarios of concrete slump, and help readers fully understand this concept through structured data.
1. Definition of concrete slump
Concrete slump refers to the degree to which concrete slumps freely under its own weight, and is usually measured through a slump test. This test uses a standard slump cylinder. The concrete is loaded into the cylinder and lifted vertically. The height difference between the sinking of the top of the concrete is measured, which is the slump value (unit: mm). The larger the slump value, the better the fluidity of the concrete.
| Slump range (mm) | Liquidity description | Applicable scenarios |
|---|---|---|
| 10-40 | low liquidity | Foundation, mass concrete |
| 50-90 | medium liquidity | Floor slabs, beams and columns |
| 100-150 | High liquidity | Pumping concrete, complex structures |
| >150 | self-compacting concrete | Areas with dense steel bars |
2. Test method for concrete slump
Slump test is a commonly used detection method at construction sites. The specific steps are as follows:
1. Place the slump cylinder on a flat, hard base.
2. Load concrete into three layers, and tamp each layer evenly with a tamping stick 25 times.
3. After scraping the mouth of the cylinder, lift the slump cylinder vertically.
4. Measure the height difference of the top of the concrete sinking, which is the slump value.
| Test tools | Specification requirements |
|---|---|
| slump cylinder | Height 300mm, upper opening diameter 100mm, lower opening diameter 200mm |
| tamper | Diameter 16mm, length 600mm |
| measuring ruler | Accuracy 1mm |
3. Factors affecting concrete slump
Concrete slump is affected by many factors, including:
1.water-cement ratio: The larger the water-cement ratio, the higher the slump, but it will reduce the strength of the concrete.
2.Aggregate properties: The particle size, gradation and water absorption of aggregates affect the workability of concrete.
3.Admixture: Water reducing agent, plasticizer, etc. can significantly increase the slump.
4.environmental conditions: Changes in temperature and humidity will cause slump loss.
| factors | degree of influence | Adjustment method |
|---|---|---|
| water-cement ratio | high | Control water consumption and add water reducing agent |
| Aggregate moisture content | in | Determine the moisture content in advance and adjust the mix ratio |
| Stirring time | low | Control the mixing time between 90-120 seconds |
4. Engineering application of concrete slump
Different projects have specific requirements for concrete slump:
1.Prefabricated components: Usually low slump (30-50mm) is used for easy molding.
2.cast-in-place structure: Medium slump (70-100mm) ensures dense pouring.
3.pumping construction: High slump (120-180mm) is required to reduce pipe resistance.
4.underwater concrete: The required slump is 180-220mm to prevent segregation.
5. Measures to deal with abnormal slump
When the slump does not meet the requirements, the following measures can be taken:
| Problem phenomenon | Possible reasons | solution |
|---|---|---|
| Slump is too small | Insufficient water consumption and high water absorption rate of aggregates | Add an appropriate amount of water reducing agent or adjust the mix ratio |
| The slump is too large | Excess water use, measurement errors | Add dry ingredients and mix again |
| quick loss | High temperature environment, cement sets quickly | Use retarder to shorten transportation time |
By scientifically controlling concrete slump, construction efficiency and quality can be significantly improved. In actual projects, appropriate slump values should be selected based on specific construction conditions, structural requirements and environmental factors, and quality control should be carried out throughout the process.
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