PORTLAND CEMENT - Materials for Civil and Construction Engineers - page 218

T ABLE 6.7 Summary of Effects of Water Impurities on Concrete Quality

Impurity Effect

Alkali Carbonate Can retard or accelerate strength test setting and 28-day strength

and Bicarbonate 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 concentrations 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.

This waste water is usually generated from truck wash systems, washing of
central mixing plant, storm water runoff from the ready-mix plant yard,
waste water generated from water sprayed dust control, and conveyor wash
down. According to the Water Quality Act (part 116), waste water from