🏗️ Tensile Strength Test of Cement
📘 Aim
To determine the tensile strength of cement using the briquette method as per IS 4031 (Part 7):1988.
🔍 Purpose
The tensile strength of cement indicates its ability to resist tension (pulling forces). Although cement is rarely subjected to direct tension in structures, the test indirectly helps to assess the adhesive strength and quality of cement. A cement with higher tensile strength generally gives concrete and mortar with better compressive strength.
⚙️ Apparatus Required
- Briquette moulds (as per IS specifications)
- Tensile testing machine
- Trowel
- Balance (accuracy ±1 g)
- Glass plate and steel float
- Mixing tray
- Water measuring jar
🧱 Materials
- Cement sample (Ordinary Portland Cement)
- Standard sand (as per IS 650:1991)
- Potable water
🧪 Procedure
- Take cement and standard sand in the proportion of 1:3 by weight.
- Add water equal to (P/5 + 3)% of the combined weight of cement and sand, where P is the percentage of water required for standard consistency.
- Mix the materials thoroughly to obtain a uniform mortar.
- Fill the prepared mortar into the briquette moulds in two layers, each layer compacted with 20 strokes of the trowel.
- Remove excess mortar and smoothen the surface with a trowel.
- Store the moulds in a moist environment for 24 hours.
- After 24 hours, remove the briquettes and immerse them in clean water for curing.
- Test the briquettes for tensile strength after 3 days, 7 days, and 28 days.
- Place the briquette in the tensile testing machine and apply load uniformly until failure occurs.
🧮 Formula
Tensile Strength (T) = P / A
Where:
- P = Breaking load (in N)
- A = Cross-sectional area of briquette (in mm²)
Example:
If P = 500 N and A = 650 mm²,
T = 500 / 650 = 0.769 N/mm²
📊 Observation Table
| Sample | Age (Days) | Breaking Load (N) | Cross-section (mm²) | Tensile Strength (N/mm²) |
|---|---|---|---|---|
| 1 | 3 | 500 | 650 | 0.77 |
| 2 | 7 | 600 | 650 | 0.92 |
| 3 | 28 | 700 | 650 | 1.08 |
📋 Permissible Values (as per IS: 269)
- 3 Days: Minimum 2.0 N/mm²
- 7 Days: Minimum 2.5 N/mm²
📖 Significance
- Helps determine the adhesive and cohesive properties of cement.
- Acts as an indicator of cement’s compressive strength.
- Ensures cement meets quality standards before use in construction.
⚠️ Precautions
- Mix mortar uniformly to avoid segregation.
- Ensure moulds are properly oiled before filling.
- Maintain curing temperature at 27 ± 2°C.
- Apply load gradually and uniformly during testing.
✅ Result
The average tensile strength of cement after 7 days = 0.92 N/mm².
📘 Conclusion
The Tensile Strength Test of Cement was conducted as per IS 4031 (Part 7):1988. The average tensile strength obtained was 0.92 N/mm² at 7 days, which is within the permissible limit. Hence, the tested cement is of good quality and suitable for construction works.