What kind of sand is good for concrete
In construction projects, the quality of concrete is directly related to the strength and durability of the structure, and sand is an important part of concrete, and its choice is particularly critical. This article will analyze the selection criteria for concrete sand selection based on popular topics and hot contents in the past 10 days of the entire network, and provide structured data for reference.
1. Classification of concrete sand
Sand is mainly divided into two categories: natural sand and mechanical sand. Each sand has different characteristics and is suitable for different concrete mixing needs.
| Sand type | source | Features | Applicable scenarios |
|---|---|---|---|
| Natural river sand | River sedimentation | Smooth particles and low mud content | High-strength concrete |
| Natural sea sand | Coastal Sedimentation | High salt content, need to be desalted | Non-critical structural concrete |
| Mechanism Sand | Rocks broken | Many edges and angles, controllable grading | Ordinary concrete, masonry mortar |
2. Key indicators of concrete sand
When choosing concrete sand, you need to focus on the following indicators to ensure the strength and durability of concrete.
| index | Standard value | Detection method | Influence |
|---|---|---|---|
| Mud content | ≤3% (concrete above C30) | Washing method | Reduce concrete strength |
| Fine Module | 2.3-3.0 (Zhongsha) | Screening method | Impact and ease and strength |
| Chloride ion content | ≤0.02% (reinforced concrete) | Chemical titration method | Causes steel bar rust |
3. Suggestions for sand use of concrete of different strengths
The choice of sand needs to be adjusted according to the strength level of the concrete. The following is the matching plan hotly discussed in the engineering forum in the past 10 days.
| Concrete strength | Recommended sand types | Sand dosage (kg/m³) | Things to note |
|---|---|---|---|
| C15-C20 | Mechanical or mixed sand | 700-800 | Can appropriately relax the mud content |
| C25-C30 | Natural river sand | 600-700 | The fineness modulus is around 2.6 |
| C35 or above | Grade river sand | 500-600 | The chloride ion content needs to be strictly tested |
4. Tips for using mechanism sand
With the shortage of natural sand resources, the use of mechanical sand has become a hot topic. The following is the mechanism sand optimization plan summarized by engineering experts:
1.Grading adjustment: Improve and ease by mixing mechanism sand with different particle sizes (such as mixing 0.15-0.3mm with 0.3-0.6mm at 3:7).
2.Stone powder control: The content of stone powder in the mechanism sand should be controlled at 7-10%. Too much will increase the water demand, and too little will affect the density.
3.Admixture adaptation: The use of polycarboxylic acid water reducing agent can effectively improve the fluidity of mechanism sand concrete.
5. Controversial topic: Can sea sand be used in concrete?
The recent incident of illegal use of sea sand in a coastal city has caused heated discussion. Test data of professional institutions show:
| How to deal with it | Chloride ion content | 28-day intensity | Risk of corrosion of steel bars |
|---|---|---|---|
| Untreated sea sand | 0.08-0.15% | Meet the standards | Extremely high (3 months of rust spots) |
| Fresh water 3 times | 0.03-0.05% | Meet the standards | Medium (corrosion occurs after 2 years) |
| Professional equipment fading | ≤0.01% | Meet the standards | Low (compliant with standards) |
6. Expert advice
1. Natural river sand is preferred for important structures, and the mechanism sand needs to undergo strict mix ratio tests.
2. Sea sand must be professionally desalted and is limited to non-load-bearing structures.
3. It is recommended to establish a sand source archive system, and each batch of sand should be kept in testing reports.
From the above analysis, it can be seen that the selection of concrete sand requires comprehensive consideration of material characteristics, engineering requirements and cost factors. Against the backdrop of stricter environmental protection policies, the optimized use of mechanism sand will become a key research direction in the industry.
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