What are the water quality requirements for concrete mixing plants to produce concrete?
The quality of water used for concrete mixing has a great impact on the quality of precast concrete wall panels or precast concrete floor panels! When using precast concrete wall panel machines and precast concrete panel manufacturing machines to produce concrete components, the water quality must be strictly controlled to ensure that the qualified rate of concrete products meets the requirements!The Quality of Water for Concrete is the key.
According to the “JGJ63-2006 Concrete Water Standard” and related specifications, the technical requirements for concrete water mainly include the following:
Ⅰ. Requirements for concrete mixing water
1. Water quality indicators
pH value: prestressed concrete ≥5.0, reinforced concrete and plain concrete ≥4.5.
Chloride ion (Cl⁻):
– Prestressed concrete ≤350 mg/L;
– Reinforced concrete ≤1000 mg/L;
– Plain concrete ≤3500 mg/L;
– Structural concrete with a design service life of 100 years ≤500 mg/L.
– Sulfate (SO₄²⁻):
– Prestressed concrete ≤600 mg/L;
– Reinforced concrete ≤2000 mg/L;
– Plain concrete ≤2700 mg/L.
– Alkali content: calculated as Na₂O+0.658K₂O, ≤1500 mg/L (non-alkali-active aggregates are exempt from testing).
– Insoluble/soluble matter:
– Prestressed/reinforced concrete: insoluble matter ≤2000 mg/L, soluble matter ≤2000/5000 mg/L;
– Plain concrete: insoluble matter ≤5000 mg/L, soluble matter ≤10000 mg/L.
2. Other requirements for water used in concrete
– Radioactivity: surface water, groundwater, and recycled water must comply with the “Sanitary Standard for Drinking Water” (GB 5749).
– Setting time and strength: Compared with drinking water, the difference between initial setting and final setting time is ≤30 minutes, and the strength of cement mortar at 3d and 28d is ≥90%.
– Sensory requirements: No obvious grease, foam, color or odor.
3. Special water source restrictions
– Seawater: It is strictly prohibited to use it in reinforced concrete and prestressed concrete; it can be used in plain concrete, but it is not suitable for decorative concrete.
– Washing water: It must not be used in alkali-active aggregate concrete, and should be used with caution in prestressed, decorative or corrosive environment concrete.
Ⅱ. Requirements for water used for concrete maintenance
1. Simplified inspection: Insoluble matter, soluble matter, setting time and mortar strength can be omitted, but other indicators must meet the standards for mixing water.
2. Water quality requirements: Key parameters such as pH value and chloride ion must still meet the requirements of the corresponding concrete type.
Ⅲ. Inspection rules and frequency of water for concrete mixing
1. Sampling and testing:
– Water quality inspection water sample ≥5L, radioactivity, setting time and strength tests must be completed within 7-10 days after sampling.
– Surface water is tested once every 6 months, groundwater once a year, and recycled water and washing water are tested once every 3 months (extended after stabilization).
2. Exemption conditions: Water that meets drinking water standards can be used directly without additional testing.
Ⅳ. Prohibition and precautions
1. Industrial wastewater: must be treated before use.
2. Seawater and washing water: strictly limit use to avoid chloride ion corrosion and alkali aggregate reaction.
Ⅴ. Priority of testing indicators for water for mixing concrete
The pH value, chloride ion, sulfate, insoluble matter, soluble matter and alkali content of mixing water need to be tested, and the testing of curing water can be simplified.
The above specifications are intended to ensure the strength, durability and corrosion resistance of concrete. When implementing them, the water source should be selected and strictly tested in combination with the actual project.
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