Here’s a detailed mix design for M30 grade concrete following the guidelines of IS 10262:2009 and IS 456:2000:
1. Stipulations for Proportioning:
- Grade designation: M30 (characteristic compressive strength of 30 MPa at 28 days)
- Type of cement: Ordinary Portland Cement (OPC) 53 Grade conforming to IS 12269
- Maximum nominal size of aggregate: 20 mm
- Minimum cement content: 340 kg/m³ (as per IS 456:2000)
- Maximum water-cement ratio: 0.50 (as per Table 5 of IS 456:2000 for moderate exposure conditions)
- Workability: 100-120 mm slump (suitable for most casting applications)
- Type of aggregate: Crushed angular aggregates conforming to IS 383
2. Target Strength:
- As per IS 10262:2009, the target strength should be higher than the characteristic strength to account for variations in material properties and construction practices.
- Standard deviation (s) for M30 grade concrete is typically 5 N/mm² (from Table 1 of IS 10262:2009).
- Therefore, the target average compressive strength (f’ck) at 28 days is calculated as:
f'ck = fck + 1.65s
f'ck = 30 MPa + 1.65 * 5 MPa
f'ck = 38.25 MPa
3. Water Content:
- From Table 2 of IS 10262:2009, the maximum water content for 20 mm aggregate and a 25-50 mm slump range is 186 liters/m³.
- For a 100 mm slump, the water content can be estimated by adding 6% of the base value:
Water content = 186 liters/m³ + (6/100) * 186 liters/m³
Water content ≈ 197 liters/m³
4. Cement Content:
- The minimum cement content is 340 kg/m³ as per IS 456:2000.
- However, achieving the target strength with a water-cement ratio of 0.50 might require a higher cement content.
- Trial mixes can be prepared with different cement contents (e.g., 360 kg/m³, 380 kg/m³) to determine the optimal amount needed for achieving the desired strength and workability.
5. Aggregate Proportions:
- The volume of coarse aggregate can be estimated using Table 3 of IS 10262:2009 for a water-cement ratio of 0.50 and fine aggregate grading Zone II (typical for most regions).
- For a water-cement ratio of 0.45 (as assumed in this example), the volume of coarse aggregate needs to be slightly increased to compensate for the lower water content.
- The final proportions of coarse and fine aggregates can be adjusted based on trial mixes and sieve analysis results of the specific aggregates used.
6. Admixtures:
- Superplasticizers can be used to improve workability while maintaining a low water-cement ratio.
- This can lead to higher strength and reduced permeability of the concrete.
- The dosage of superplasticizer should be determined based on the manufacturer’s recommendations and trial mixes.
7. Trial Mixes and Adjustments:
- Prepare several trial mixes with different proportions of cement, coarse aggregate, and fine aggregate, and with or without admixtures.
- Test the compressive strength, workability, and other properties of each mix to determine the optimal combination of materials for achieving the desired performance.
- Adjust the proportions and admixture dosages as needed based on the test results.
8. Quality Control:
- Implement proper quality control procedures during concrete production and placement to ensure consistent material properties and workmanship.
- This includes regular testing of the concrete mix, aggregates, and hardened concrete.
Note: This is a general outline of the mix design process for M30 grade concrete. The specific proportions and materials may need to be adjusted based on the specific project requirements, available materials, and local standards.
Example
Here’s an example mix design for M30 grade concrete, following the guidelines of IS 10262:2009 and IS 456:2000:
Assumptions:
- Exposure condition: Moderate (protected from harsh chemicals and weather)
- Placing method: Hand placement
- Degree of supervision: Good
- Fine aggregate type: Zone II
- Target slump: 100 mm
- Superplasticizer used: Yes (to improve workability at a lower water-cement ratio)
Materials:
- Ordinary Portland Cement (OPC) 53 Grade conforming to IS 12269
- Crushed angular aggregates (20 mm nominal size) conforming to IS 383
- Zone II fine aggregate
- Superplasticizer conforming to IS 9103
Design Calculations:
- Target Strength:
f’ck = fck + 1.65s (as per IS 10262:2009)
f’ck = 30 MPa + 1.65 * 5 MPa
f’ck ≈ 38.25 MPa - Water Content:
Maximum water content from Table 2 of IS 10262:2009 for 20 mm aggregate and 25-50 mm slump range = 186 liters/m³
Water content for 100 mm slump ≈ 197 liters/m³ (with 6% increase) - Cement Content:
Minimum cement content from IS 456:2000 = 340 kg/m³
Trial mix with 380 kg/m³ cement assumed for target strength with low water-cement ratio - Coarse Aggregate Volume:
From Table 3 of IS 10262:2009 for water-cement ratio 0.50 and Zone II fine aggregate = 62%
Increase slightly for water-cement ratio of 0.45 (approx. 63%) - Fine Aggregate Volume:
100% – Cement volume – Water volume – Coarse aggregate volume
≈ 100% – (380 kg/m³ / 3.15) * (1/1000) – 197 liters/m³ * (1/1000) – 63%
≈ 33.5%
Mix Proportions:
| Material | Quantity per m³ of concrete |
|---|---|
| OPC 53 Grade | 380 kg |
| Water | 197 liters |
| Coarse Aggregate (20 mm) | 1194 kg |
| Fine Aggregate (Zone II) | 646 kg |
| Superplasticizer | According to manufacturer’s recommendations (typically 0.5–1.0% of cement weight), |
Mixing Instructions:
- Mix dry ingredients (cement and aggregates) thoroughly in a clean mixer.
- Add water gradually and mix until a uniform consistency is achieved.
- Add superplasticizer and mix for an additional 2-3 minutes.
- Adjust water content or superplasticizer dosage if necessary to achieve the desired slump.