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Requirements with water mixed concrete

Technical requirements for water used for mixing concrete, grouting, washing aggregate and curing concrete are specified in National Standard TCVN 4506: 2012.

Technical requirements for water used for mixing concrete and mortar

Accordingly, water for mixing concrete , mortar, aggregate washing and curing of concrete should meet the following requirements:

• Does not contain oily scum or grease.

• The amount of organic impurities is not greater than 15 mg / L.

• pH is not less than 4 and not greater than 12.5.

• No color when used for concrete and decorative mortar.

For the purpose of use, the content of dissolved salts, the amount of sulfate ions, the amount of chlorine ions and the insoluble residue cannot be greater than the values specified in Table 1 (for concrete and mortar mixers) and Table 2 (for with water used for washing aggregate and curing concrete).

In addition, there are other technical requirements for concrete and mortar mixing water:

• The setting time of cement and the compressive strength of the mortar must meet the values specified in Table 3.

• The total equivalent amount of alkali converted to Na2O should not be greater than 1 000 mg / L when used with aggregates likely to cause alkali - silicon reactions.

Table 1 - Maximum permissible levels of dissolved salts, sulfate ions, chloride ions and insoluble residues in concrete and mortar mixers

Unit in milligrams per liter (mg / L)

Uses	Maximum content allowed
Uses	Salt dissolved	Sulfate ion (SO 4 -2 )	Chlorine ion (Cl-)	The insoluble residue
1. Concrete-mixing water and water-mixing grout pump protect reinforcement for pre-stressed reinforced concrete structures.	2 000	600	350	200
2. Concrete mixing water and mortar-mixing water insert joints for reinforced concrete structures .	5 000	2 000	1 000	200
3. Concrete mixing water for non-reinforced concrete structures. Water mixed with construction mortar and plaster.	10 000	2 700	3 500	300
NOTE 1 When using high alumina cement as a binder for concrete and mortar, the water used for all areas of use must comply with the provisions of Section 1, Table 1. NOTE 2 In case of necessity, water with chloride ion content in excess of Clause 2 of Table 1 may be used to mix concrete for reinforced concrete structures, if the total chlorine ion content in concrete is used. Not exceeding 0.6 kg / m3. Note 3: In the case of water used to mix masonry, plastering structures that require surface decoration or in parts that are frequently exposed to moisture, the chlorine ion content is controlled not exceeding 1 200 mg / L. .

Table 2 - Maximum permissible levels of dissolved salts, sulfate ions, chloride ions and insoluble residues in water used for washing aggregate and curing concrete

Unit in milligrams per liter (mg / L)

Uses	Maximum content allowed
Uses	Salt dissolved	Sulfate ion (SO 4 -2 )	Chlorine ion (Cl-)	The residue does not dissolve
1. Concrete curing water of structures that require surface decoration. Washing water, watering and wet sieving aggregate.	5 000	2 700	1 200	500
2. Concrete curing water of structures without surface decoration (except water discharge works)	30 000	2 700	20 000	500
3. Wet water stops before pouring concrete to wet concrete surfaces before inserting joints. Water curing concrete in the works of discharging and cooling concrete in the heat exhaust pipes of large blocks	1 000	500	350	500
Note: When using high alumina cement as a binder for concrete and mortar, water used for washing aggregate and curing of concrete must comply with the provisions of Section 1, Table 1.

Table 3 - Requirements for setting time of cement and compressive strength of mortar

Targets	Limited value
Setting time of cement, min - Start, not less - Finish, not bigger	45 420
The compressive strength of mortar at 7 days should not be less than,% (percentage compared to the control sample)	90
Note: The control sample using domestic water (meeting QCVN 02: 2009 / BYT) is conducted in parallel and using the same cement with the test sample.