River sand is one of the most commonly used natural materials in construction. It plays a vital role in making concrete, mortar, plaster, and other essential building works. In this blog, we will explore what river sand is, why it is preferred in construction, and how to test it to ensure its quality. This information is especially useful for civil site supervisors, engineers, and anyone interested in building with strong and reliable materials.
What is River Sand?
River sand is a type of fine aggregate collected naturally from the beds of rivers. It is formed by the weathering of rocks over thousands of years and carried by river currents. It usually has a smooth texture, rounded particles, and is light brown to white in colour.
Why is River Sand Used in Construction?
River sand is widely used in construction for several reasons:
- Good Strength: It gives strong bonding when mixed with cement and water.
- Clean Particles: Natural river sand is often cleaner than manufactured alternatives.
- Smooth Finish: It provides a neat and fine finish to plaster and concrete work.
- Workability: Easy to mix and spread on site.
However, due to increasing demand and environmental concerns, excessive mining of river sand has caused ecological damage, leading to restrictions in many regions.
How is River Sand Test Performed?
Testing river sand ensures its quality before it is used in construction. One of the most common and crucial tests is the silt content test, followed by bulking, fineness modulus, and organic impurities test.
1. Silt Content Test (Field Method)
Apparatus Required:
- 250 ml measuring cylinder
- Water
- 1% Salt Solution (to settle particles faster)
- Sample of river sand
- Marker or scale
Procedure:
- Fill the measuring cylinder with sand up to 100 ml mark.
- Add water up to the 200 ml mark.
- Add a pinch of common salt or 1% solution (optional but speeds up settling).
- Shake the cylinder vigorously for 1 minute to mix.
- Place it on a flat surface and leave it undisturbed for 3 hours.
- Observe and measure the thickness of the silt layer that settles on top of the sand.
Precautions:
- Ensure the measuring cylinder is clean.
- Let it settle in a vibration-free environment.
- Don’t disturb the cylinder while settling.
Result:
Let’s say:
- Thickness of sand layer = 100 mm
- Thickness of silt layer = 6 mm
Then,
Silt content = (6 / 100) × 100 = 6%
Determination of Usability:
- If silt content is ≤ 8%, the sand is usable as per IS 2386 Part II.
- If it is > 8%, it should be either washed or rejected.
2. Bulking of Sand Test
Bulking happens due to moisture forming thin films on sand particles, increasing their volume.
Apparatus Required:
- Beaker or measuring cylinder
- Sand sample
- Water
Procedure:
- Fill a beaker with moist sand and note the volume.
- Pour water and stir until saturation.
- Note the reduced volume.
Result:
Bulking (%) = (Initial Volume – Final Volume) / Final Volume × 100
Usability:
This helps adjust the volume of sand while batching concrete to maintain the correct mix ratio.
3. Fineness Modulus (Sieve Analysis)
This test determines the grain size distribution of sand.
Apparatus Required:
- IS sieves (4.75 mm, 2.36 mm, 1.18 mm, 600 µm, 300 µm, 150 µm)
- Weighing machine
- Sieve shaker
Procedure:
- Take 1 kg dry sand sample.
- Sieve it for 10–15 minutes using a sieve shaker.
- Record the weight retained on each sieve.
Result:
Fineness Modulus (FM) = Sum of cumulative % retained on each sieve / 100
Usability:
- FM for good river sand should be between 2.2 to 3.0.
- If FM is too low: sand is too fine → use caution in concrete mix.
4. Organic Impurities Test
Checks for decayed vegetation or organic matter in sand.
Apparatus Required:
- Glass bottle
- 3% Sodium Hydroxide solution
- Sand sample
Procedure:
- Fill half the bottle with sand.
- Add sodium hydroxide solution till ¾ full.
- Shake well and allow it to stand for 24 hours.
Result:
Compare the colour of the solution with standard reference.
- Light Yellow/Colourless: Acceptable
- Brown or Dark: High organic matter → Not suitable
Summary of River Sand Test Usability
| Test | Criteria for Usability |
|---|---|
| Silt Content | ≤ 8% acceptable |
| Bulking | Adjust sand volume based on bulking % |
| Fineness Modulus | Between 2.2 to 3.0 preferred |
| Organic Impurities | Colourless/light yellow solution = Pass |
Final Determination of Sand Usability
After conducting all the essential tests:
- If all values are within IS Code limits, the sand is fit for use in construction.
- If one or more results fail, the sand must be either washed, blended, or rejected based on severity.
Types of Sand Used in Construction
While river sand is common, here are other types of sand you might come across:
- M Sand (Manufactured Sand) – Crushed stone sand, an eco-friendly alternative to river sand.
- P Sand (Plastering Sand) – Fine-grade sand used mainly for plastering walls.
- Desert Sand – Generally not suitable for construction due to its round particles.
- Sea Sand – Not preferred due to salt content, unless properly washed.
Important River Sand Tests
Before using river sand on site, it must pass certain tests to ensure quality. Below are the key tests:
1. Sieve Analysis
This test determines the particle size distribution. Proper gradation ensures better compaction and strength.
- Standard sieve sizes are used.
- Fine sand passes through 4.75 mm sieve.
2. Silt Content Test
Silt particles reduce the bonding strength of sand. Excess silt can weaken concrete.
- Fill a measuring cylinder with sand and water.
- Shake it and let it settle.
- If silt layer is more than 8%, the sand is not suitable.
3. Specific Gravity Test
It tells how heavy the sand particles are compared to water. The ideal range is 2.5 to 2.8.
4. Moisture Content Test
Moisture affects the water-cement ratio. The sand should be tested to adjust water quantity during mixing.
5. Bulking of Sand Test
When moist, sand increases in volume. This test helps in measuring the exact volume for batching.
6. Organic Impurities Test
Organic matter like leaves or roots can reduce the strength of concrete. This test is done by comparing colour in a sodium hydroxide solution.
7. Visual Inspection
Just by looking at the sand, you can tell a lot:
- Should be free from clay, dust, and other foreign particles.
- Colour should be consistent.
IS Codes Relevant to Sand Testing
- IS 2386 (Part I to VIII) – Methods of test for aggregates including sand.
- IS 383:2016 – Specification for coarse and fine aggregates from natural sources.
Precautions While Using River Sand
- Always check the source of the sand.
- Ensure the sand is clean and properly stored.
- Do not use sand from polluted or industrial zones.
- Compare sand test results with IS code standards.
Alternatives to River Sand
Due to environmental regulations, river sand is being replaced by:
- M-Sand – Made by crushing granite.
- Recycled Sand – Produced from demolition waste.
- Crushed Rock Fines – A by-product of stone crushing.
These options are cost-effective and eco-friendly when tested and used properly.
Environmental Impact of River Sand Mining
Excessive river sand mining has led to:
- Riverbank erosion
- Lowering of water tables
- Habitat destruction for aquatic life
To reduce this damage, governments have imposed strict regulations and promoted alternative materials.
Conclusion🎯
River sand is an essential material in the construction industry due to its natural qualities and suitability for a variety of works. However, testing river sand before using it on site is crucial for long-lasting and safe structures. As natural sand becomes scarce, switching to alternatives like M-Sand is not just practical but also responsible.
FAQs on River Sand
Q1. What is the main difference between river sand and M-Sand?
River sand is naturally occurring, while M-Sand is manufactured by crushing rocks. M-Sand has angular particles, while river sand is smoother.
Q2. How can I check if the sand contains too much silt?
Perform the silt content test using a measuring cylinder. If silt exceeds 8%, the sand should be rejected.
Q3. Is sea sand suitable for construction?
No. Sea sand contains salts which corrode steel in concrete. It must be washed thoroughly if used.
Q4. Can I use desert sand in concrete?
Desert sand is too smooth and does not bind well. It is generally not suitable for construction.
Q5. What is the cost difference between river sand and M-Sand?
River sand is usually costlier due to transport and scarcity. M-Sand is cheaper and locally available in many areas.
Q6. Why is bulking of sand important?
Bulking causes an increase in sand volume due to moisture. If ignored, it leads to incorrect batching.