⛰️ Aggregate sand equivalent
Determination of sand equivalent of 0/2 mm fine aggregate fraction. Assessment of aggregate cleanliness — ratio of sand fraction to silt-clay.
Overview
Sand equivalent (SE) is a parameter assessing the cleanliness of fine aggregate, specifically the proportion of sand to silt-clay particles (clay, silt, organic dust). It is one of the basic quality parameters of aggregates used in road, railway and building construction.
Aggregates contaminated with excessive amount of clay particles show reduced adhesion to asphalt binder or cement, leading to deterioration of pavement and concrete durability. Requirements for sand equivalent are specified in standards PN-EN 13043 (aggregates for asphalt mixtures), PN-EN 12620 (aggregates for concrete) and PN-EN 13242 (aggregates for engineering works).
The method consists of placing a 0/2 mm aggregate fraction sample in flocculation solution (calcium chloride + glycerin + formaldehyde in water), shaking, then sedimentation for 20 minutes. Flocculation solution causes separation of fine clay particles from sand grains — clays float in suspension and sand settles at bottom. Sand equivalent is the percentage ratio of sand sediment height to total sediment + suspension height.
The test is fast (approx. 40 min), does not require expensive equipment and is commonly performed in road laboratories, concrete plants and aggregate quarries.
Method principle
A 0/2 mm aggregate sample (approx. 120 g) is placed in measuring cylinder with flocculation solution. After 10-minute soaking, 90 shaking cycles are performed (manually or mechanically). Cylinder is filled with solution to height 380 mm and left for 20 min for sedimentation. Clay particles form suspension/colloidal solution above sand sediment. Measured: h₁ — upper suspension boundary (from bottom), h₂ — upper sand sediment boundary (read with piston with 1 kg weight). Sand equivalent SE = (h₂/h₁) × 100%. Value SE = 100% means clean aggregate (no clay dust), low SE indicates strong contamination.
Applications
- Quality control of aggregate for asphalt mineral mixtures (PN-EN 13043)
- Assessment of fine aggregate for concrete (PN-EN 12620)
- Testing of soils and aggregates for earthworks (PN-EN 13242)
- Aggregate acceptance control on construction site (raw material acceptance)
- Production quality monitoring in sand and gravel quarries
- Road subgrade and sub-base testing
Key parameters
| Parameter | Value |
|---|---|
| Fraction tested | 0/2 mm |
| Sample mass | ~120 g (after drying) |
| Sedimentation time | 20 min ± 15 s |
| Result SE | 0–100% (higher = cleaner aggregate) |
| Typical requirement (asphalt mix) | SE ≥ 50–60% (depending on pavement layer) |
| Repeatability | ±5% (between duplicates) |
Standard
- Standard number
- PN-EN 933-8:2012+A1:2015
- Title (PL)
- Badania geometrycznych właściwości kruszyw — Część 8: Ocena zawartości drobnych cząstek — Badanie wskaźnika piaskowego
- Title (EN)
- Tests for geometrical properties of aggregates — Part 8: Assessment of fines — Sand equivalent test
Step-by-step procedure
1. Sample preparation
Dry aggregate sample at 105±5°C to constant mass. Sieve through 2 mm sieve. Weigh ~120 g of 0/2 mm fraction.
2. Flocculation solution preparation
Dissolve 125 mL concentrated solution (CaCl₂ + glycerin + formaldehyde) in 5 L distilled water. Mix until homogeneous.
3. Cylinder filling
Pour flocculation solution into cylinder to height 100 mm. Pour in aggregate sample. Tap bottom on table to remove bubbles.
4. Soaking
Leave cylinder with sample for 10 min ± 15 s. Aggregate saturates with solution.
5. Shaking
Stopper cylinder. Perform 90 shaking cycles in 30 s (manually or on mechanical shaker).
6. Filling and sedimentation
Insert washing tube to cylinder bottom. Fill with solution while raising tube until level reaches 380 mm. Start 20 min countdown.
7. Reading h₁
After 20 min read level of upper suspension boundary (h₁) on cylinder scale.
8. Reading h₂ (with piston)
Lower piston with 1 kg weight onto sand sediment. Read level of piston head lower edge (h₂).
9. SE calculation
SE = (h₂ / h₁) × 100%. Perform at least 2 determinations. Difference between duplicates ≤5%.
10. Documentation
Note: h₁, h₂, SE for each determination, average, solution temperature. Compare with specification requirements.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Sand equivalent test kit | Controls 65-L0023, Matest A063, ELE/Soiltest | 3 000–8 000 PLN |
| Measuring cylinder ∅32 mm × 420 mm | Glass cylinder with scale, according to EN 933-8 | 300–600 PLN |
| Piston with weight (1 kg) | Brass piston ∅25 mm with 440 mm guide, mass 1 kg | 500–1 200 PLN |
| Mechanical shaker (optional) | Controls 65-L0025, 90 cycles in 30 s | 5 000–15 000 PLN |
| Laboratory dryer | Binder FD 56, Memmert UF55, 105±5°C | 5 000–12 000 PLN |
| Laboratory sieves 2 mm | Retsch, Endecotts, ∅200 mm, wire mesh | 200–500 PLN/pc. |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Anhydrous calcium chloride | 10043-52-4 | CaCl₂, pure, flocculation solution component — 480 g per 1 L concentrated solution |
| Glycerin (glycerol) | 56-81-5 | Pure, flocculation solution component — 2 050 g per 1 L concentrated solution |
| Formaldehyde 37% | 50-00-0 | Aqueous solution, preservative — 47 g per 1 L concentrated solution. Warning: carcinogenic! |
| Distilled water | 7732-18-5 | For preparing working solution: 125 mL concentrated solution per 5 L water |
Health and safety (OHS)
- Formaldehyde — carcinogenic substance cat. 1B! Prepare solution in fume hood, nitrile gloves
- Calcium chloride — irritating to eyes and skin, hygroscopic
- Aggregate dust — P2 mask when drying and sieving, workstation ventilation
- Hot dryer 105°C — heat-resistant gloves