Quality of Water

1. Quality of Water Materials of Construction Dr. TALEB M. AL-ROUSAN

2. Quality of water • Very important • Impurities in water may: • interfere with the setting of cement. • Adversely affect strength of concrete. • Cause staining of concrete surface. • Lead to corrosion of reinforcement. • Cause efflorescence. • Reduce durability. • Volume instability.

3. Mixing Water • Water should be fit for drinking. • Limits may be set on chlorides, sulfates, alkalies, and dissolved solids. • Dissolved solids < 2000 ppm • If drinking water has high concentration of Sodium or Potassium it will be unsuitable to be used for mixing because of danger of Alkali-Aggregate reaction. • Alkali Carbonate & bicarbonate (Na, K) affect setting times of different cement (accelerate or retard), and if available in higher contents may cause strength reduction. • Sulfates: High sulfate content may cause expansive reactions and deterioration.

4. Mixing Water Cont. • Oils: Mineral oils (Petroleum) has less effect than animal or vegetable oils. Oils > 2.5% by mass of cement tends to reduce strength. • Water carrying sanitary sewage: Treated water that has up to 20 ppm solids is OK to be used. • Acid water : depends on pH (< 3 cause handling problems). • Water used to wash out truck mixers can be used because solids in it are concrete ingredients. • Wash water & industrial water: can be used but high solid content will reduce strength.

5. Mixing Water Cont. • Sugar: • Small amounts of sucrose (0.03 – 0.15% by mass of cement) retard setting of cement, and may improve 28 days strength and reduce the 7 days strength. • Sugar > 0.25% of cement may cause rapid setting and reduce 28 days strength. • Water not fit for drinking can be used. • Rule: Any water of (pH = 6.0 – 8.0 which doesn’t taste saline or brackish) is suitable for use.

6. Mixing Water Cont. • Sea water can be used but generally inadvisable. • Leads to higher early strength but a lower long-term strength (15% loss). • Sea water or any water with high chlorides content tend to cause efflorescence and persistent dampness. Should not be used where appearance of concrete is of importance. • Sea water increase the risk of corrosion of reinforcement. • When reinforced concrete is permanently in water (sea or fresh) the use of sea water seems to have no ill-effects.

7. Curing Water • Generally, water satisfactory for mixing is also suitable for curing purposes. • Iron or organic matter may cause staining. • Curing water should be free from substances that attack hardened concrete such as: water containing free CO2 (water formed by melting ice or condensation), which dissolves Ca(OH)2 and causes surface erosion.

8. Tests on Water • To determine water suitability for mixing compare setting time of cement and strength of mortar cubes using water in question with results obtained using known good water. • 10% variation is tolerated for strength. • Such tests are also recommended when water contains dissolved solids in excess of 2000 ppm or alkali carbonate or bicarbonate in excess of 1000 ppm. • For curing water, performance tests involving simulated wetting and evaporation can be done to check for staining which can not be done using chemical analysis.