SUMMARY OF EFFECTS OF WATER IMPURITIES ON CONCRETE QUALITY

Summary of Effects of Water Impurities on Concrete Quality

Impurities VS Effects

Alkali Carbonate and Bicarbonate Can retard or accelerate strength test setting and 28-day strength
when total dissolved salts exceed 1000 ppm. Can also aggravate alkali–aggregate reaction.

Chloride Corrosion of reinforcing steel is primary concern. Chloride can enter the mix through admixtures, aggregates, cement, and mixing water, so limits are expressed in terms of total free    chloride ions. ACl limits water-soluble ion content based   on the type of reinforcement:

                                                            Prestressed concrete 0.06%

                                                            Reinforced concrete exposed to chloride in service 0.15%

                                                            Reinforced concrete protected from moisture 1.00%

                                                            Other reinforced concrete 0.30%

Sulfate Can cause expansive reaction and deterioration.

Other Salts Not harmful when concentrations limited to

                                                            Calcium Bicarbonate 400 ppm

                                                            Magnesium Bicarbonate 400 ppm

                                                            Magnesium Sulfate 25,000 ppm

                                                            Magnesium Chloride 40,000 ppm

                                                            Iron Salts 40,000 ppm

                                                            Sodium Sulfide 100 ppm

Sea Water Do not use for reinforced concrete. Can accelerate strength gain but reduces ultimate strength. Can aggravate alkali  reactions.

Acid Water Limit concentrations of hydrochloric, sulfuric, and other inorganic acids to less than 10,000 ppm.

Alkaline Water Possible increase in alkali–aggregate reactivity. Sodium hydroxide may introduce quick set at concentration higher than 0.5%. Strength may be lowered. Potassium hydroxide in concentrations over 1.2% may reduce 28-day strength of some cements.

Sanitary Sewage Water Dilute to reduce organic matter to less than 20 ppm.

Sugar Concentrations over 500 ppm can retard setting time and alter strength development. Sucrose in the range of 0.03 to approximately 0.15% usually retards setting.

Concentrations over 0.25% by weight of cement can accelerate strength gain, but substantially reduce

28-day strength.

Oils Mineral oil (petroleum) in excess of 2.5% by weight of mix may reduce strength by 20%.

Algae Can reduce hydration and entrain air. Do not use water containing algae.