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Precast Concrete Procurement Needs To Pay Attention To What?

- Aug 29, 2018 -

Structural material

cement

 

Different types of cement have different properties

 

1) Portland cement (silicon water)

Features: early strength and high, hydration heat release, compact structure, dry shrinkage, good anti-freezing; but resistant to sulfate corrosion and soft water corrosion;

Applications: High-strength, prestressed concrete and concrete engineering with early strength requirements; concrete works subject to freeze-thaw cycles and concrete works with wear resistance requirements.

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2) slag cement

Features: early strong bottom, high late strength; small hydration heat release, good heat resistance, good corrosion resistance, poor frost resistance, large shrinkage, poor impermeability, poor carbonation resistance.

Application: Mass concrete engineering; concrete engineering with heat and corrosion resistance requirements; prefabricated components for steam curing; concrete works in general underground and underground rivers.

3) Volcanic ash cement

Features: poor heat resistance, good impermeability, dry shrinkage, other properties with slag cement.

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Application: Mass concrete engineering in underground and water; steam curing components; concrete works with corrosion and impermeability requirements; not suitable for dry areas.

4) Fly ash cement

Features: poor heat resistance, dry shrinkage, good crack resistance.

Application: Mass concrete engineering in underground and water; steam curing components; concrete engineering with corrosion resistance requirements; general concrete engineering.

Buying cement considerations

1) Does the manufacturer have a "cement production license" issued by the national "work permit"?

2) Does the cement of this number have a cement factory inspection list; whether there is a qualified inspection report of the provincial quality inspection department or the provincial industry cement quality inspection station.

3) Whether the packaging bag is a plastic woven bag with a flat appearance, no cracks, no degumming, clear and complete printing and a brand, registered trademark, cement production license number, product name, code number, implementation standard, strength grade, Net content, date of use, conditions of use, cement manufacturer. The product name and strength level are printed on both sides. The back of the bag is printed with the standard, code, factory number, date of manufacture, name and address of the bag making company.

4) Weighing the bag: The national standard stipulates that the net content of bagged cement is 50kg per bag, not less than 98% of the mark quality, that is, the net content of each bag is not less than 49kg, and the net content of 20 bags randomly selected shall not be less than 1000kg. .

 

Precautions

 

1. The strength grade of concrete, when it is different from the comprehensive base price, is allowed to be converted;

2. When the type and particle size of the stone used in concrete are different from the comprehensive base price, conversion is allowed;

3. For the precast concrete members produced on site, when the commercial concrete is actually used, the project may be used to calculate the off-site transportation cost of the commercial concrete.

4. In the comprehensive base price, when the project quantity is calculated by “m3” or “m2”, when the concrete dosage is different from the comprehensive base price, the concrete amount difference adjustment may be performed separately, and the others are unchanged.

5. When the amount of reinforced iron parts is designed to be different from the comprehensive base price, the adjustment of the difference between steel bars and iron parts is uniformly performed in units of units.

6. When the prefabricated components are actually steam-cured, the cost is additionally increased.

 

Features:

 

1. Good structural performance, factory-made production can effectively guarantee structural mechanics and small dispersion.

2. The construction speed is fast, the product quality is good, the surface finish is high, and the decorative effect of the clear water concrete can be achieved, so that the structure and the building are unified and coordinated.

3, factory production energy-saving, is conducive to environmental protection, reducing noise on-site construction.

4, good fire performance.

5. The overall performance of the structure is poor, and it is not suitable for buildings with high seismic requirements.