One is: the exact amount or the maximum amount of consumption is recommended by the manufacturer, which is determined during laboratory tests and is included in the technical specifications of the product. (Note that you can get the most accurate answer this way)

And another: the maximum consumption of concrete additives is 5% of cement weight.

But there are more precise answers.



Allowed amount of concrete additives (for each specific sample)

If you didn't get your answer in the previous paragraph, don't skip this section. In the following, we have checked the allowed amount of concrete additives for each specific additive.

Microsilica

This highly pozzolanic material reduces cracks caused by cement hydration, increases the durability of concrete against sulfates and acid waters, and increases its resistance. Microsilica (Silica Fume) is used in piers, piles, columns, prefabricated parts, machinery foundations, etc.

The amount of this concrete additive is 10 to 15% of the weight of cement used. Therefore, the amount of cement used can be reduced by the same amount.

Microsilica gel

This innovative product is widely used to increase slump, increase mechanical resistance and reduce permeability, as well as in all structures that must be resistant to corrosive chemical agents, such as docks and chemical tanks.

The permitted amount of concrete additives in the case of this gray gel (Silica Fume Gel), which is not allowed to be used in dried form, is 7-10% of the weight of the cement used.

Super lubricant based on modified lignosulfonate

Unlike the previous two men, whose main function is to increase the durability of concrete, types of lubricants help to lubricate concrete. This liquid additive reduces the permeability, increases the strength and durability of concrete, and is used in the concreting of reinforced structures, roofs, delicate columns and bulky parts.

The amount of concrete additives to use this type of super lubricant is 0.8 to 1.5% of cement weight, which is added to concrete water.

Super lubricant based on melamine sulfonate formaldehyde

This additive is used for hot areas and high-volume concreting, and is produced in two types, liquid and powder.

The permitted amount of concrete additives for the liquid type of this product is 1 to 1.5% of the weight of cement and is added to water. This amount changes to 0.3 to 0.6% of the cement weight for the powder type, and it should be added to the dry materials.

Super lubricant based on modified naphthalene sulfate

The method of use and the amount of concrete additives for this type of super-lubricants are similar to "modified lignosulfonate-based" samples.

Concrete antifreeze

The consumption amount of this substance, with the clear function that its name tells us, has a direct relationship with the ambient temperature. Here, ambient temperature is the minimum temperature that concrete is likely to experience during its setting. In the following, you can see the allowed amount of these concrete additives in different conditions:

Grade of concrete (kg/m3) 350 300 250 Air temperature (degrees Celsius)

consumption (liters per cubic meter)

5

6

8

2-

consumption (liters per cubic meter)

8

9

10

5-

consumption (liters per cubic meter)

11

12

13

10-

consumption (liters per cubic meter)

13

14

15

15-

Precipitator of concrete

Precipitators enter into a chemical reaction with cement, and by accelerating hydration, they reduce the setting time of concrete. In the following, you can see the allowed amount of concrete additives for this group, which is extracted from the specifications published by the manufacturers:

AS-1 accelerator: This accelerator is based on resin materials, and in addition to accelerator, it also has high lubricating power. This product should be added to the mixing water, and the amount of concrete additives for it is 0.8 to 1.5% of the weight of cement used.

AA-1 accelerator: This product is added to the dry mixture of cement and aggregates. After complete mixing, water is added to the mixture to make concrete. The amount of consumption of this additive is 3 to 4 percent of cement weight.

Precipitator AA-101: This precipitator is used in concrete spraying by dry mix method, and its consumption amount is 2 to 4% of cement weight. Of course, to speed up the setting, the amount of concrete additives can be increased to 5-6% of the weight of cement used. Note that using more than 9% will have a negative effect on the compressive strength of concrete.

Superplasticizers are added on the basis of workability required at site. When you are using superplasticizers you ensure that w/c ratio is low. In that case there is no possibility of shrinkage and cracking.

Om Prakash Chhangani sir thanks for your reply first. Actually in my site, For M40 concrete i have kept w/c ratio as 0.37. So is it okay or not?

For normal concrete mix design you get the w/c ratio based on Target mean strength. This w/c ratio can be reduced if we intend to add superplasticizers in mix. This will increase strength and workability and will reduce the possibility of shrinkage and segregation.

There are many types and functions of Superplasticizers, their use must be adjusted according to needs. Whether for workability or to reduce the free water content of the concrete mix, this is certainly done to improve the performance of the concrete. For the usage needs of superplasticizers based on the amount of cement used in the concrete mixture and the amount of doses used for each superplasticizer manufacturer is different, it is better to read the rules for using superplasticizers in the guidelines written on the packaging.

The maximum percentage of usable admixture is mentioned by each manufacturer, and it will differ from product to product. The dosage is within the manufacturer's limit, there will be no problems. Using superplasticizer, you can reduce water cement ratio and achieve more workability, and it has the advantage of less Shrinkage cracks and high strength.

It depends on the type of superplasticizer and the liquefaction method used (steric effect, electrostatic effect, lubrication effects, etc.). It is definitely worth taking into account the manufacturer's recommendations. However, I must honestly admit that nowadays we almost never use amounts exceeding 1.0% of the cement mass, because modern superplasticizers are very active and effective. Too much of such superplasticizer may lead to segregation of the concrete mix (especially if the w/c ratio is high) and actually adversely affect the quality of the hardened concrete.

That's right Mrs Joanna...must be taken in the use of superplasticizer