I think yes

in the short time period the effect is negligible,,,the effect is more pronounced in long time period...regards

Dear Dr. Amjad

In calculating losses, no one mention effects of concrete additives. Is that right ?

Dear Dr. Abbas, would you please explain your thinking ?

may be additives contain organic material that affect strength on the long term.

I prefer to check out the technical data sheet TDS for each admixture and figure out its chemical composition.

Organic materials not accepted at all.

Dear Researchers: my question are there any chemical interaction between additives and the strands ?

Dear Dr. Mohanned,

Per ASTM C 494/C 494M – 04 (Standard Specification for Chemical Admixtures for Concrete). 

NOTE 3—Admixtures that contain relatively large amounts of chloride may acceleratee corrosion of prestressing steel. Compliance with the requirements of this specification does not constitute assurance of acceptability of the admixture for use in prestressed concrete.

5. General Requirements

5.4 At the request of the purchaser, when the admixture is to be used in prestressed concrete, the manufacturer shall state in writing the chloride content of the admixture and whether or not chloride has been added during its manufacture.

And according to what mentioned above, every addmixture contains a relatively large amounts of chloride should be avoided.

Hope the best Dr.

Thank you Mr. Ali for this information.

 hope the colleagues benefit from it.

Concrete additives are added to the mixture of water cement and aggregate in small quantities to increase the durability of the concrete, to fix concrete behavior and to control setting or hardening. They can either be liquid or powdered additives.

These additives are supplied in ready-to-use liquid form and are added to the concrete at the plant or at the jobsite. Successful use of additives depends on the use of appropriate methods of batching and concreting.

Also Read:High Performance Admixtures

Concrete additives have various functions depending on what the contractor wants to achieve. There are two main types of concrete additives which are chemical and mineral.

Chemical additives reduce the cost of construction, modify properties of hardened concrete, ensure quality of concrete during mixing/transporting/placing/curing, and overcome certain emergencies during concrete operations.

Mineral additives make mixtures more economical, reduce permeability, increase strength, and influence other concrete properties. Mineral admixtures affect the nature of the hardened concrete through hydraulic or pozzolanic activity. Pozzolans are cementitious materials and include natural pozzolans (such as the volcanic ash used in Roman concrete), fly ash and silica fume. They can be used with Portland cement, or blended cement either individually or in combinations.

Any used material with the ordinary concrete composition, (cement, fine aggregate, coarse aggregate and water), shall have positive or negative side effect on the concrete properties (physical, chemical and mechanical) and that will affect positively or negatively the reinforcement performance.

A. Some of additives increase the heat of hydration that for sure increase the initial prestressing losses for pretensioned strands due to the difference of temperature between the sections inside (i.e.,through the span) and outside (i.e.,at anchorages).

B. Some of additives decrease the shrinkage of concrete that will minimize the time-dependent losses of strands (pretensioned or posttensioned).

C. Some additives are increasing the corrosion resistance of reinforcing steel to reduce the risk of rusting steel that causing cracking of concrete.

I think the question should be specific not general (i.e., for a specific type of additives what is the side effect of using it).

Thank you colleagues

Suitable concrete additives should be used in prestressed concrete.

Mohannad H. Al-Sherrawi .... Technically, concrete additives made to be compatible with all reinforcement type,... so As I think it has no harmful effect on the strands

I think each type of additive is used for a specific purpose, this means a specific type of additive can be positive or negative depending on the purpose. An additive used for shrinkage reduction can result in strength losses and vice-versa. But anyway, the foremost step is to assess the chemical composition of the additive and evaluate its reactivity with the cement one.