4.7 QUALITY CONTROL OF WATER FOR CONCRETE MIXING
Water used for concrete must be clean and free from harmful quantities of oils, acids, alkalis, salts, organic matter, or other impurities that may adversely affect the properties of concrete or steel reinforcement. Ensuring the quality of mixing and curing water is therefore a crucial part of concrete quality control.
4.7.1 Sources of Water
| Source Type |
Typical Characteristics |
Precautions / Remarks |
| Potable water (drinking water) |
Usually safe and suitable for mixing and curing concrete |
No further testing generally required |
| Groundwater (wells, boreholes) |
May contain dissolved salts or minerals |
Must be tested for chlorides, sulphates, and alkalinity |
| Surface water (rivers, ponds) |
May contain organic matter, silt, or suspended impurities |
Filtration or sedimentation required before use |
| Recycled / treated water |
Water recovered from concrete batching plants |
Acceptable if it meets IS 456 and IS 3025 limits |
4.7.2 Requirements as per IS 456
Water shall be free from deleterious materials in amounts that could cause:
- Reduction in strength of concrete,
- Corrosion of reinforcement,
- Efflorescence or surface discoloration, and
- Unacceptable volume stability.
The general rule is:
“Water fit for drinking is fit for concrete.”
4.7.3 Laboratory Quality Tests for Water
| S. No. |
Test Name |
Description / Objective |
Typical Requirement / Acceptance Criteria |
Standard Reference |
| 1 |
pH Test |
Measures acidity or alkalinity of water |
pH ≥ 6.0 |
IS 3025 (Part 11) / IS 456 |
| 2 |
Organic Impurities Test |
Determines presence of decaying vegetation or humic acid by color comparison |
Should be lighter than standard solution |
IS 3025 (Part 9) / IS 456 |
| 3 |
Suspended Matter Test |
Checks for turbidity and suspended solids that affect workability |
≤ 200 mg/L |
IS 3025 (Part 17) |
| 4 |
Inorganic Solids Test (Total Dissolved Solids) |
Measures the amount of dissolved salts in water |
≤ 2000 mg/L |
IS 3025 (Part 16) |
| 5 |
Chloride Content Test |
Determines chloride ions that may corrode reinforcement |
≤ 500 mg/L for RCC; ≤ 2000 mg/L for PCC |
IS 3025 (Part 32) / IS 456 |
| 6 |
Sulphate Content Test (as SO₃) |
Excess sulphate may cause expansion and cracking |
≤ 400 mg/L |
IS 3025 (Part 24) / IS 456 |
| 7 |
Alkalinity Test |
Determines total alkalinity due to carbonates and bicarbonates |
≤ 600 mg/L (as CaCO₃) |
IS 3025 (Part 23) |
| 8 |
Sugar Content Test |
Detects the presence of sugar, which retards setting |
≤ 0.05% by mass |
IS 3025 (Part 37) |
| 9 |
Oil and Grease Test |
Determines oil contamination that affects bond and hydration |
≤ 10 mg/L |
IS 3025 (Part 39) |
| 10 |
Hardness Test |
Measures calcium and magnesium content |
≤ 500 mg/L (as CaCO₃) |
IS 3025 (Part 21) |
4.7.4 Field Quality Control Measures
- Use potable water wherever possible for mixing and curing.
- For non-potable water, carry out full chemical and physical analysis as per IS 3025.
- Avoid water from swamps, marshes, or stagnant sources.
- Periodically verify water quality, especially when the source changes.
- Record test results, sampling date, and water source in the site QA logbook.
4.7.5 Acceptance Criteria (as per IS 456, Table 1)
| Property |
Maximum Permissible Limit |
| Suspended matter |
200 mg/L |
| Inorganic solids (TDS) |
2000 mg/L |
| Organic matter |
200 mg/L |
| Sulphates (as SO₃) |
400 mg/L |
| Chlorides (as Cl⁻) for RCC |
500 mg/L |
| Chlorides (as Cl⁻) for PCC |
2000 mg/L |
| pH value |
≥ 6.0 |
4.7.6 Effect of Impurities on Concrete Properties
| Type of Impurity |
Effect on Concrete |
| Organic matter |
Retards setting and reduces strength |
| Excess chlorides |
Corrosion of reinforcement steel |
| Excess sulphates |
Expansion and cracking due to ettringite formation |
| Acidic water (low pH) |
Reduces strength and affects hydration |
| Oily or greasy matter |
Hinders bond between cement paste and aggregates |
4.7.7 Relevant BIS and ASTM Standards
| Standard No. |
Title / Description |
| IS 456 |
Code of Practice for Plain and Reinforced Concrete |
| IS 3025 (Parts 1–44) |
Methods of Sampling and Testing of Water |
| IS 9103 |
Specification for Admixtures (for compatibility testing) |
| ASTM C1602 |
Standard Specification for Mixing Water Used in the Production of Hydraulic Cement Concrete |
| ASTM D512 / D516 |
Determination of Chlorides and Sulphates in Water |
4.7.8 Summary of Quality Assurance Practice
- Establish testing frequency – at least once per new water source or every 3 months.
- Maintain traceability records of test reports.
- Reject water not meeting IS 456 limits.
- Educate site staff about visual inspection indicators – odor, color, oil film, turbidity.
- Document compliance in the Material Quality Register.