What sand is used for concrete mixing? Comprehensive analysis of the selection criteria for construction sand
In construction projects, the quality of concrete is directly related to the strength and durability of the structure, and as one of the main aggregates of concrete, the selection of sand is crucial. This article will combine hot topics and industry data in the past 10 days to provide a detailed analysis of the types, standards and precautions for concrete mixing sand to help you make a scientific choice.
1. Main types and characteristics of sand for concrete
| sand type | source | Particle characteristics | Scope of application | Advantages and Disadvantages |
|---|---|---|---|---|
| natural river sand | River erosion and sedimentation | Round and smooth, well graded | high strength concrete | Advantages: low mud content; Disadvantages: shortage of resources |
| Machine-made sand | Rock crushing processing | Sharp edges and corners, controllable gradation | Ordinary concrete | Advantages: stable source; Disadvantages: need to control the content of stone powder |
| sea sand | coastal sediments | Uniform particles and high salt content | Need to be diluted | Advantages: Rich reserves; Disadvantages: High risk of corrosion |
| Recycled sand | Construction waste recycling | The ingredients are complex and need to be screened | low grade concrete | Advantages: environmentally friendly; disadvantages: unstable strength |
2. Key indicators of sand quality standards
| Detection indicators | National standard requirements | Detection method | Impact of nonconformity |
|---|---|---|---|
| Fineness modulus | Coarse sand: 3.7-3.1 Medium sand: 3.0-2.3 Fine sand: 2.2-1.6 | Sieve analysis | Affects workability and strength |
| Mud content | ≤5% (C30 and above) ≤7% (below C30) | elutriation method | Reduce adhesion |
| Mud content | ≤2% (high strength) ≤3% (ordinary) | manual picking | Create weak points of strength |
| Chloride ion content | ≤0.06% (reinforced concrete) | chemical titration | Accelerate corrosion of steel bars |
3. Latest developments in the sand and gravel market in 2023
According to the latest data from the China Sand and Gravel Association, affected by environmental protection policies and infrastructure investment, sand and gravel prices show regional fluctuations:
| area | River sand price (yuan/ton) | Manufactured sand price (yuan/ton) | Year-on-year change |
|---|---|---|---|
| Yangtze River Delta | 120-150 | 85-100 | +8% |
| Pearl River Delta | 140-180 | 90-110 | +12% |
| central region | 90-120 | 65-85 | +5% |
4. 5 practical suggestions for sand selection for projects
1.Strength first principle: For concrete above C40, it is recommended to use zone II medium sand, and the fineness modulus should be controlled between 2.6-3.0.
2.economical balance: Ordinary cushion concrete can be mixed with 30% qualified machine-made sand to reduce costs.
3.Pay attention to special circumstances: Desalinated sea sand must be used in marine projects, and the chloride ion content needs to be rechecked
4.Key points for on-site acceptance: Focus on checking the moisture content and impurity content of the sand to avoid affecting the mix ratio
5.sustainable development: It is recommended to establish a sand and gravel quality traceability system for large projects to ensure reliable sources.
5. New trends in industry technology
1. Intelligent sorting technology: Using AI image recognition to automatically sort harmful impurities in sand and gravel
2. Modification process: polymer modification of low-quality sand to improve performance
3. Application of recycled aggregates: a technological breakthrough that increases the proportion of recycled sand used in construction waste to 40%
4. Standard system update: 2023 version of "Construction Sand" GB/T14684 adds new micro powder content limit requirements
Conclusion: The scientific selection of sand for concrete requires comprehensive consideration of engineering requirements, material properties and economic benefits. With the advancement of technology and the improvement of environmental protection requirements, the application proportion of machine-made sand and recycled sand will continue to increase, but no matter which sand is chosen, strict quality control and standardized construction technology are always the key to ensuring the quality of concrete.
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