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Concrete Casting News from the Hill and Griffith Company

Technical Questions: Concrete Form Release Agents

Posted by Hill and Griffith Company on Jun 18, 2020 5:31:30 PM

Excerpt from the ACI Website Technical Articles.

Concrete Form Release Agents

Q. I need to select a form release agent for a new project requiring an architectural finish. Can you provide information on different types of form release agents and recommendations for using them? Does ACI have a publication on form release agents I could use as a reference?

 
A. Form release agents ease formwork removal, extending the useful life of a form and improving the smoothness and texture of concrete surfaces. Two main types are available: barrier and chemically active.
 
Bond Breaker Application for Tilt-Up

Barrier-type agents (examples include diesel oil, wax, and silicone) create a barrier between the form and the concrete. These are not recommended for architectural concrete, because they can cause stains, surface air voids, and problems with form removal in very cold or very hot weather; they also may prevent subsequent adhesion of coatings to the hardened concrete. While diesel oil was once commonly used, it’s now prohibited because the associated volatile organic content (VOC) emissions contribute to smog. (Note: In the United States, form release agents have to meet federal VOC limits of 450 g/L [3.8 lb/gal.] and may have to meet more restrictive limits of 250 g/L [2.2 lb/gal.] in some states.)

Chemically active form release agents (certain types of fatty acids) react with calcium ions in the cement paste to produce a soap that prevents concrete from bonding to the formwork. Based on the reactivity, they are divided into buffered (partially) reactive and fully reactive. Buffered agents produce an improved soap film that helps remove entrapped air and may promote better flow of a thin skin of cement paste at the surface of the form. Fully reactive agents can provide a good basic soap film that, depending on the brand, works well in most cases. Because chemically active form release agents produce fewer bugholes, stains, and surface irregularities than barrier type of form release agents, they are commonly used for architectural concrete.

For more information on this topic refer to ACI 347R “Guide to Formwork for Concrete”, ACI 303R “303R-12 Guide to Cast-in-Place Architectural Concrete Practice”, and ACI 533R “Guide for Precast Concrete Wall Panels”.

References: ACI 347R-14; ACI 303R-12; ACI 533R-11

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Hill and Griffith Customer Service

We're known for our hands on approach. Let us visit your plant and recommend concrete release agents, packerhead concrete form releases, concrete form seasoning, potable water concrete form release, non-petroleum concrete form release, biodegradable concrete form release, rust inhibitors and concrete dissolver products that suit your needs.

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On-site casting defect investigations, product testing, machine start-ups and much more. Also, lab facilities are available to provide testing upon request.
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Bulletins and Technical Papers for Concrete Casting Products

 

Tags: Concrete Form Release Agents, Biodegradable Concrete Form Release, Concrete Release Agents, Concrete Forms, Concrete Form Seasoning, Concrete Casting Supplies, Concrete Pipe, Concrete Form Release, American Concrete Institute, ACI

Specifications for Structural Concrete: Form Release Agents

Posted by Hill and Griffith Company on Jun 11, 2020 4:36:46 PM

Excerpt from the ACI 301 Field Reference Manual

4.9 Form release agents

4.9.1 General - Release agents are materials applied to the form sheathing to prevent the bonding of concrete to the sheathing, keep the formwork clean, and assist the successful production of high-quality architectural surfaces.

4.9.2 Selection - Release agents help produce the concrete surfaces specified in the design reference sample, contract documents, and mockup. Additionally, the following should be considered:

  • Compatibility of the release agent with the form or form liner, admixtures in the concrete mixture and, if used, the form sealer or coating;
  • Possible interference with the adhesion of other materials such as sealants, architectural coatings, and curing compounds to the hardened concrete surface;
  • Allowable amount of any discoloration or staining and the permissible number and size of bugholes on the concrete surface;
  • Effect on stripping time, ease of stripping, and cementitious buildup on the form;
  • Effect of seasonal temperature extremes on application procedures when the concrete placing portions of the project overlap more than one season, which may affect both concrete color and bughole blemishes on the surface;
  • Effect with accelerated curing procedures (especially steam) on stripping and the appearance of the concrete surface;
  • Uniformity of appearance: the same release agent should be used for all the architectural concrete surfaces;
  • Local and federal and federal environmental regulations, especially on volatile organic compounds (VOCs);
  • Dew point of water-borne materials; and
  • Entrapped air migrations in the consolidation process.
Release Agent Applied to Forms 
 

The safest approach to evaluate several different release agents is under actual use conditions on a test panel, mockup, or non-architectural portion of the project concrete. Information should also be obtained from the release agent manufacturer as to the kind of form surface for which the product is intended and the proper method of application to produce the desired surface appearance because the thickness of the application may affect the quality of the finished surface and air voids.

4.9.3 Types of release agents - Release agents fall into two main classes: barrier and chemically active. Barrier types are water-insoluble materials that include oils without additives (neat oils), diesel oil, paraffin wax, and silicone oils. The EPA prohibits use of uncut or straight diesel oil as a release agent. Barrier-type release agents are not recommended for architectural effects. They tend toward more stains, bugholes, and difficulty with releasing in both very cold and very hot weather, and they can cause problems with adhesion of coatings and other construction materials to the hardened concrete.

Chemically active release agents are the most common for architectural concrete surfaces. Fatty acids chemically react with the basic materials in concrete and produce soap. Soap is a better lubricant than oil for the removal of entrapped air in fresh concrete.

The formation of the soap film from the ingredients in the cement paste and the chemically active release agent prevents the concrete from bonding to the formwork. Applied at the right rate recommended by the manufacturer, the chemical reaction only consumes a very small quantity of the free lime from the fresh concrete. During consolidation, the soap film on the form face is an excellent channel for the migration of the entrapped air out of the fresh concrete.

In vertical casting, undesirable striping effects are sometimes produced when an immersion vibrator is improperly placed very close to the release agent. It is caused by over application of the release agent. The excess release agent is consumed by the basic materials in the concrete raising the w/cm at the points of tangency as the vibration stimulates the reaction. At the secant points, there is not sufficient stimulation of the vibration to change the x/cm; consequently, a striping effect is created. This striping effect will not bleach out. For this reason, control of vibrator intersections is critical to the overall appearance. Other unrelated causes of striping effects exist, such as shadows of reinforcement, porous form facings, and overly wet concrete mixtures.

Each brand of release agent exhibits its own fingerprint of final surface color, although vibration and form surface texture also have a pronounced effect. Using the same release agent throughout a project is recommended for achieving uniform color.

The two common categories of chemically active release agents include both buffered reactive (partially reactive) and fully reactive types.

Buffered for release agents tend to produce an improved soap film that not only helps remove entrapped air but may promote better flow of a thin skin of cement paste at the very surface of the form. This may help explain why, in vertical castings, these release agents tend to minimize or eliminate the striped effect from vibrator insertions.

Fully reactive form release agents can provide a good basic soap film that, depending on the brand, works well in most cases. Because buffered and fully reactive release agents are similar and proprietary, specifying absolute differences between them is difficult. Generally, the buffeted release agents produce a slightly different type of soap film that, with some brands, assists in improving the visual impact.

Properly formulated, both oil-based and water-based form-release agents can meet the Federal Volatile Organic Content regulations of 450 g/L and even the more restrictive value of 250 g/L required in some areas.

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Hill and Griffith Customer Service

We're known for our hands on approach. Let us visit your plant and recommend concrete release agents, packerhead concrete form releases, concrete form seasoning, potable water concrete form release, non-petroleum concrete form release, biodegradable concrete form release, rust inhibitors and concrete dissolver products that suit your needs.

Hill and Griffith Samples

Product Samples

We are pleased to provide samples in quantities large enough to allow you to "try before you buy."
Contact Us »



Hill and Griffith Customer Service

Technical Services & Support

On-site casting defect investigations, product testing, machine start-ups and much more. Also, lab facilities are available to provide testing upon request.
Contact Us »

 

Bulletins and Technical Papers for Concrete Casting Products

 

Tags: Concrete Form Release Agents, Biodegradable Concrete Form Release, Concrete Release Agents, Concrete Forms, Concrete Form Seasoning, Concrete Casting Supplies, Concrete Pipe, Concrete Form Release, American Concrete Institute, ACI

Precast Concrete Form Release Agent Q&A from ACI

Posted by Hill and Griffith Company on Jul 25, 2019 8:00:00 AM

Technical Questions - Precast Concrete Form Release Agent 

American Concrete Institute

Q. I need to select a precast concrete form release agent for a new project requiring an architectural finish. Can you provide information on different types of form release agents and recommendations for using them? Does ACI have a publication on form release agents I could use as a reference?

A. Form release agents ease formwork removal, extending the useful life of a form and improving the smoothness and texture of concrete surfaces. Two main types are available: barrier and chemically active.

Barrier-type agents (examples include diesel oil, wax, and silicone) create a barrier between the form and the concrete. These are not recommended for architectural concrete, because they can cause stains, surface air voids, and problems with form removal in very cold or very hot weather; they also may prevent subsequent adhesion of coatings to the hardened concrete. While diesel oil was once commonly used, it’s now prohibited because the associated volatile organic content (VOC) emissions contribute to smog. (Note: In the United States, form release agents have to meet federal VOC limits of 450 g/L [3.8 lb/gal.] and may have to meet more restrictive limits of 250 g/L [2.2 lb/gal.] in some states.)

Chemically active form release agents (certain types of fatty acids) react with calcium ions in the cement paste to produce a soap that prevents concrete from bonding to the formwork. Based on the reactivity, they are divided into buffered (partially) reactive and fully reactive. Buffered agents produce an improved soap film that helps remove entrapped air and may promote better flow of a thin skin of cement paste at the surface of the form. Fully reactive agents can provide a good basic soap film that, depending on the brand, works well in most cases. Because chemically active form release agents produce fewer bugholes, stains, and surface irregularities than barrier type of form release agents, they are commonly used for architectural concrete.

For more information on this topic refer to ACI 347R “Guide to Formwork for Concrete”, ACI 303R “303R-12 Guide to Cast-in-Place Architectural Concrete Practice”, and ACI 533R “Guide for Precast Concrete Wall Panels”.


Precast Concrete News from the American Concrete Institute

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Seminar – ACI 318-19: Changes to the Concrete Design Standard

ACI Foundation is Now Accepting Fellowship and Scholarship Applications


Hill and Griffith Customer Service

We're known for our hands on approach. Let us visit your plant and recommend concrete release agents, packerhead concrete form releases, concrete form seasoning, potable water concrete form release, non-petroleum concrete form release, biodegradable concrete form release, rust inhibitors and concrete dissolver products that suit your needs.

Hill and Griffith Samples

Product Samples

We are pleased to provide samples in quantities large enough to allow you to "try before you buy."
Contact Us »

 

Hill and Griffith Customer Service

Technical Services & Support

On-site casting defect investigations, product testing, machine start-ups and much more. Also, lab facilities are available to provide testing upon request.
Contact Us »

 

 Bulletins and Technical Papers for Concrete Casting Products

Tags: Concrete Casting Products, Concrete Release Agents, Concrete Casting Supplies, Precast Concrete, ACI

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