IS 2720:1973 Part 2 is the Indian Standard (BIS) for methods of test for soils - determination of water content. This standard covers laboratory and field methods for determining the water (moisture) content of soils. It establishes the oven-drying method as the standard reference test while detailing rapid alternative methods like the sand-bath and alcohol methods for field applications.
Specifies methods for determining the water content of soil samples, essential for various geotechnical calculations.
Methods, oven temperature, drying duration, sample mass by particle size and calculation of soil water content.
| Reference | Value | Clause |
|---|---|---|
| Test | Determination of water content (moisture content) of soil | Cl. 1 |
| Method (a) — oven-drying | Reference method for fine-grained soils | Cl. 3.1 |
| Oven temperature | 105 – 110 °C | Cl. 3.1.1 |
| Oven-drying duration (min) | 16 hours (≥ to constant mass) | Cl. 3.1.3 |
| Cooling — before reweigh | In desiccator until room temperature | Cl. 3.1.3 |
| Min mass — particles ≤ 425 µm | 25 g | Cl. 3.1.2 (Table 1) |
| Min mass — particles ≤ 2 mm | 50 g | Cl. 3.1.2 (Table 1) |
| Min mass — particles ≤ 4.75 mm | 200 g | Cl. 3.1.2 (Table 1) |
| Min mass — particles ≤ 20 mm | 1000 g | Cl. 3.1.2 (Table 1) |
| Min mass — particles ≤ 40 mm | 5000 g | Cl. 3.1.2 (Table 1) |
| Calculation — water content w (%) | (M2 − M3)/(M3 − M1) × 100, with M1 = container | Cl. 3.1.4 |
| Pycnometer method | Quick method for granular soils (sand) | Cl. 4 |
| Sand-bath / hot-plate method | Field quick method (less accurate) | Cl. 5 |
| Calcium-carbide (Speedy moisture) method | Field rapid method per IS 2720-2 supplement | Cl. 6 |
| Reporting precision | 0.1 % (oven method) | Cl. 3.1.5 |
IS 2720 Part 2 (1973) provides Methods of Test for Soils — Part 2: Determination of Water Content. The foundational test for soil moisture / water content used in compaction control + geotechnical investigations.
Use when: foundation design, embankment compaction control, soil characterization, PMGSY rural road construction, slope stability analysis.
Oven-drying method (most common): 1. Take fresh sample (50-100 g typical) 2. Weight wet sample (W₁) 3. Oven dry at 105-110 °C for 24+ hours 4. Weight dry sample (W₂) 5. Water content = (W₁ - W₂) / W₂ × 100 (in %)
Speedy moisture meter (calcium carbide): - Field test; faster but less accurate - Calibrated against oven-dry result - For routine quality control
Microwave drying: modern faster method
Typical soil water contents: - Sand (dry to natural): 0-10 % - Sand (saturated): 15-25 % - Clay (dry): 5-15 % - Clay (natural): 15-40 % - Clay (saturated / soft): 40-70 % - Peat / organic: 100+ %
OMC (Optimum Moisture Content): for compaction; typically 8-20 % depending on soil
Test accuracy: ± 0.5-1 % water content
Sample size: 50-100 g for fine; 200-500 g for coarse
Compaction control: - Field moisture at compaction within OMC ± 2 % - Below OMC: dry compaction; lower density achievable - Above OMC: over-saturated; pumping + poor stability
Per IS 2720 (Part 8): Compaction - Modified Proctor: higher density target - Standard Proctor: routine projects
Acceptance criteria: - Per IRC:36:2010 for road embankments - Per IRC:34:2011 for waterlogged areas - Per IS 1080 for foundations
Quality control: - Field density per 500-1000 m² for embankment - Nuclear gauge correlation with oven-dry - Multiple readings for accuracy
1. Sample contaminated → wrong result. 2. Drying temperature too high → loss of clay-bound water (over-estimate). 3. Drying time insufficient → moisture remaining (under-estimate). 4. Sample size too small → not representative. 5. Stored sample loses moisture before test → field value wrong. 6. Microwave / speedy meter without calibration → systematic error. 7. Sample taken at wrong depth → not representative for compaction.
1. Geotechnical investigation: water content per borehole + depth. 2. Mix design / compaction: OMC determination. 3. Construction: field water content monitoring at compaction. 4. Quality control: per IRC + IS specifications. 5. Long-term: water content variation seasonally; foundation + slope monitoring.
IS 2720 Part 2 is the routine soil moisture test for India's geotechnical + civil construction — applied on every foundation + embankment + slope project.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Standard Drying Temperature | 105°C to 110°C | 110 ± 5°C (105°C to 115°C) | ASTM D2216-19 |
| Drying Temp. (Gypsum/Organic Soil) | Not exceeding 80°C (typically 60-80°C) | 60 ± 5°C (suggested) | ASTM D2216-19 |
| Min. Sample Mass (100% passing 2mm sieve) | 50 g | 20 g | ASTM D2216-19 |
| Min. Sample Mass (100% passing 9.5-10mm sieve) | 200 g (for 10mm) | 500 g (for 9.5mm) | ASTM D2216-19 |
| Constant Mass Check Interval | 4 hours (after initial 24h) | ≥ 1 hour (after initial 12-16h) | ASTM D2216-19 |
| Balance Sensitivity (for 50g sample) | 0.01 g | 0.05 g (readable to 0.1% of mass) | ASTM D2216-19 |
| Reporting Precision | To the nearest 0.1% | To the nearest 0.1% | ASTM D2216-19 |