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Concrete Casting News from the Hill and Griffith Company

Pre-Concrete Checks for Formwork and Release Agents

Posted by Hill and Griffith Company on Jul 23, 2020 4:02:25 PM

Excerpt from TheConstructor.org

Promising apparatus successfully tested in the laboratory

Before the concrete is poured into the formwork, it must be checked by someone who has been trained to inspect formwork. Depending on how big or complicated the pour is, the inspection may just take few minutes or it could take hours. Only when the formwork has been approved, may the pour take place.

Formwork pressures are function of height (including the height from which concrete is dropped into the forms) and are affected by concrete workability, rate of stiffening and rate of placing. One task of the temporary works co-ordinator is to consider such factors as ambient temperatures and concrete composition, when calculating maximum permissible rate of concrete placing.

 josue-isai-ramos-figueroa-qvBYnMuNJ9A-unsplash
 

Exceeding this limit may lead to unacceptable formwork deflections, loss of grout / concrete at joints, or even collapse. The cost of remedial work due to formwork deflection will usually exceed the original cost of doing the job properly.

Below are the checks that should be verified before pouring begins:

  • Is the formwork erected in accordance with the approved drawings?
  • Is the formwork restrained against movement in all directions?
  • Is it correctly aligned and leveled?
  • Are all the props plum, and at the right spacing?
  • Are bolts and wedges secure against any possible looseing?
  • Has the correct number of ties been used? Are they in the right places and properly tightened?
  • Are all inserts and cast-in fixings in the right position and secure?
  • Have all stop ends been properly secured?
  • Have all the joints been sealed to stop grout loss (especially where the formwork is against the kicker)?
  • Can the formwork be struck without damaging the concrete?
  • Are the forms clean and free from rubbish such as tie wire cuttings, and odd bits of timber or metal?
  • Has the release agents been applied, and is it the correct one?
  • Are all projecting bars straight and correctly positioned?
  • Is there proper access for placing the concrete and compacting?
  • Have all the toe-boards and guard rails been provided?

Release Agents for Formwork

Formwork needs to be treated with a release agent so that it can be removed easily after the concrete has set. Failure to use a release agent can result in the formwork sticking to the concrete, which may lead to damage of the concrete surface when it is pried off.

A single application of release agent is all that is required when forms are then used. Care must be taken to cover all the surface that will come in contact with the surface of concrete. However, if there is an excess of release agent, it may cause staining or retardation of the concrete.

There are different release agents depending on what material is used for the formwork. The three most common release agents for formwork are:

  1. Neat oils with surfactants: used mainly on steel surfaces, but also suitable for timber and plywood.
  2. Mold cream emulsions: good general purpose release agents for use on timber and plywood.
  3. Chemical release agents: recommended for high quality work, applied by spray to all types of form face.

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Self-Compacting Concrete: Materials, Properties and Applications

Posted by Hill and Griffith Company on Jun 25, 2020 4:25:54 PM

Excerpt from the instructional book Self-Compacting Concrete: Materials, Properties and Applications.

3.2.3 Surface Finish of Self-Compacting Concrete (SCC)

Surface-compacting concrete (SCC) is generally used for architectural concrete because the surface finish of SCC is of high quality, often more appealing with sharp edges compared to traditional concrete. The improved surface finish is attributed to the self-leveling and filling capabilities of SCC, which allows concrete to flow smoothly, and thereby fill holes. The surface finish of traditional concrete often has discoloration because of hydration by-products and segregation. Other imperfections such as sand textured areas, honeycombing (aggregate bridging), and some problems caused by mortar loss can also occur (de Schutter et al., 2008). Using SCC can increase the chance of eliminating these surface imperfections. However, a balanced concrete mixture with optimized rheological properties is required to achieve a high-quality surface finish for SCC, i.e. aesthetic appeal for exposed architectural use. Mixtures with lower viscosity, i.e. higher slump flow allow for entrained air to escape more efficiently and thereby provide a better surface finish. The quality of formwork surfaces, type and amount of release agent, as well as production and placement methods also affect the surface finish.

Bughole Diameters with and without release agents courtesy of Liu, B., Yang, T., 2017

Three main types of surface imperfections of SCC are bugholes, honeycombing and surface cracking. These issues are explained below and some solution to rectify these problems are provided.

Bugholes are small cavities which result from air bubble entrapment between the concrete and formwork, or the trace of bubbles escaping from the free surface of concrete during the hardening stage, whereby the self-leveling property is no longer available. It was discussed previously that the method of placement, formwork and mixture design of concrete is essential to reduce air entrainment. There is a higher chance of air escape while the concrete is still plastic, which can recover its surface. The interrupted delivery of concrete, very long or very short flow length, very high viscosity, the rough internal surface of formwork, inappropriate application or choice of release agent are the main causes of bugholes. Image analysis has been developed for the quantitative evaluation of bugholes on the surface of concrete (Liu and Yang, 2017). Different grades of bugholes on the concrete surface, based on the Concrete Industry Board of American Concrete Institute, are shown in Fig. 3.4.

Bugholes in Concrete

Imperfections in the internal surface of the formwork can cause severe flaws in the surface finish of SCC compared to traditional concrete whereby these imperfections are less noticeable. In order to achieve a better surface finish, a permeable lining inside the formwork is typically used for escaping air bubbles and for limiting bugholes in the surface finish (Kothandaraman et al., 2016). However, the excellent flow properties of SCC can produce a good surface finish even in the case of using steel formwork with an impermeable surface. Dry, uncoated wooden formwork can excessively absorb water, which may result in staining discoloration or retarding of the surface of the concrete. The surface cleanliness of the formwork and use of an appropriate type and amount of release agent are also critical in order to achieve a better surface finish. Dirty formwork can increase the chance of producing a rough surface finish.

Also, using wax- or oil-based release agents, as well as the application of a thick layer of a release agent, increase the formation and retainment of air bubbles on the surface of concrete, which creates bugholes. A thin layer of water-based release agent, which is applied evenly on the surface of formwork, is highly recommended to achieve the highest quality surface finish. Release agents should fully adhere to the internal surface of formwork. Detachment of the release agent and then blending it with SCC can cause severe reductions in mechanical properties and durability, as well as issues with the surface finish of concrete.

The incompatibility of hydrophobic release agents (oil-based) with water can cause stabilization of air bubbles in concrete after casting, which can potentially increase the air content and porosity of the concrete. The amount of release agent should be adequate in order to easily remove the formwork and to create a perfect surface finish but should be controlled to prevent other issues. The excess amount of release agent can also run to the bottom of the formwork due to gravity (especially for a sprayed release agent) and then blend with the concrete mixture. In this case, air entrapment will be considerably higher because of the high pressure of SCC placement and bubble stabilization of release agents.

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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

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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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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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

Experimental Formwork for Facing Concrete – Benefits for Research and Practice

Posted by Hill and Griffith Company on May 28, 2020 1:01:37 PM

Excerpt from the December 2012 article from Concrete Plant International by Ludger Lohaus and Karen Fischer

Promising apparatus successfully tested in the laboratory

Facing concrete can be perceived in its complexity only by taking into account the original materials and the entire construction method. Yet, this construction material, concrete, is subjected to varying influences beginning with the composition of its source materials, continuing with processing right up to hardening. Careful planning and vigilant execution of construction work can counteract such influences but they are not always controllable. As a consequence, undesired effects crop up repeatedly. Among these are to be found: surface pore holes, marbling, clouding, ridges, misalignments and coloration deviations which can occur over broad areas, locally, in fill layers or as a result of leaking formwork.

 Screen Shot 2020-05-28 at 11.50.12 AM
 

The smooth facing concrete surfaces which currently find approbation (see Fig. 1) are manufactured with non-absorbent formwork skin material which favors certain effects, like pores and coloration differences for example (see Fig.2), in contrast to absorbent formwork material. In addition, it is almost impossible to draw on past experience with stiff to plastic freshly mixed concrete consistencies, since the tendency to slim down construction component geometry and to create curved molds demands very soft to running fresh concrete consistency. 

Concrete Form Testing Facility

There are still no separate standards available for facing concrete in Germany. The leaflet "Sichtbeton" [1] (facing concrete) provides the only national recommendations. Testing facilities are necessary for assessing facing concrete construction methods and their further development. For this purpose, at the institute of construction materials at Leibniz University, Hanover, two sets of experimental formwork were developed [2] and put to the test in the research department [5]. Their benefits in possible fields of application in laboratory and practice are described in the following report.

Experimental formwork for facing concrete

The experimental formwork types developed and tested by the institute of construction materials at Leibniz University, Hanover, are represented in figures 3 and 4. Their objective is to create test conditions in the laboratory which reflect conditions in practice as closely as possible. Differentiation is made between column formwork and wall formwork. For the column formwork, "column" type test specimens measuring HxWxD = 60cm x 20cm x 20cm were produced, and for the wall formwork, "wall" type test specimens with measurements of HxWxD = 150cm x 60cm x 20 cm. The experimental formwork types are basically set up in the same way. The front side consists of a transparent plastic panel for observing the behavior of the concrete while it is poured. The other three sides can be arranged with different formwork skin materials and release agents, and also exhibit various predefined surface defects. Horizontal formwork skin joints which have not been sealed off and a kerf in the formwork board are all to be found on each side. In addition, there are tie bars with sheathing and tie bar cones, and a reinforcement cage with spacers in the specimens. 

Experience from research and practice with facing concrete

Facing concrete construction methods produce concrete surfaces whose outer appearance is almost irreparably determined by the entire manufacturing process. Blemishes like pores and coloration variations can only be rectified by removing the surface or applying further layers. For this reason, risks of error must be confronted as far as is possible at both a concrete engineering, organizational level (operations planning, quality management, protection measures, etc.) and a sociological level (identification of employees with their company, creating a team spirit, etc.).

Read More


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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, Concrete Plant International Magazine

Concrete Release Agent Classification

Posted by Hill and Griffith Company on May 21, 2020 5:32:09 PM

Excerpt from the June 2019 article from Concrete Plant International

The Dutch construction industry uses concrete release agents in manufacturing a variety of concrete products.

These concrete release agents ensure the easy removal of concrete from molds. Concrete release agents are mainly processed in the prefab concrete industry, but also a construction sites. Due to the wide diversity of concrete products and processing methods, more than 100 different concrete release agents are currently available on the market. As with many other products in the construction and concrete industry, these release agents may have adverse effects on the health of the user and environment. The suppliers of concrete release agents take responsibility in ensuring occupational health and safety, as well as protecting the environment. By offering work and environmentally friendly concrete release agents, they are able to greatly reduce  the chance of adverse effects.

 Concrete Release Agents
 

People and the Environment

Health and environmental risks can be defined through the following measurable characteristics:

  • Health risks for users are represented through H-/EUH-phrases (Hazard) and symbols.
  • The presence of solvents (VOC) is evident when the flashpoint reaches <100° C.
  • Concrete release agents can make an important contribution to a circular economy by using renewable resources (vegetable oils and water) instead of petroleum-based products (process oils and solvents).

Biodegradability has been omitted as a criterion, as it seems to give the impression that the concrete release agents are human and environmentally friendly. If it is readily biodegradable, the concrete release agents are usually safe for the environment, but not always for humans. This is especially true when working with petroleum-based products, which are also biodegradable. As these are not always safe, they can lead to certain health problems through the (prolonged) inhalation of oil fog and through skin contact. A prolonged exposure to solvents may cause OPS (Organic Psychosis Syndrome by Solvents).

Concrete Release Agent Classification

Each classification has their own set of criteria for the above-mentioned characteristics. These criteria have been defined in such a manner that the health and environmental impact increases, starting with classification 1 up to classification 7. Concrete release agents under classification 1 are the most human and environmentally friendly, while concrete release agents under classification 7 are damaging to the environment and health.

Concrete Release Agents Classification Chart

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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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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, Concrete Plant International Magazine

The Right Choice and Correct Use of Formwork Release Agents

Posted by Hill and Griffith Company on May 14, 2020 11:01:26 AM

Excerpt from the February 2020 article from Constro Facilitator

New types of form release agents comply with latest environmental and safety regulations

Release agents are coatings applied on the formwork surface, prior to concreting, in-order to facilitate easy removal the formwork or shuttering. If the appearance of the concrete surface is of significance, it is important that care is taken with the finish surface of the shuttering. Release agents provide the critical barrier between a molding surface and the substrate, facilitating separation of the cured part from the mold. Without such a barrier in place, the substrate would become fused to the mold surface, resulting in difficult clean-up and dramatic loss in production efficiency. Even when a release agent is used, factors such as irregular applications or improper release agent choice may have a dramatic effect on the quality and consistency of the finished product. In the concrete construction industry, form release agents prevent the adhesion of freshly placed concrete to the forming surface, usually plywood, overlaid plywood, steel or aluminum. In this application, there are two types of release agents available: barrier and reactive.

Release agents should have a reasonably long and stable storage life and should not be susceptible to damage from extreme tempera t u re changes or from rough or repeated handling. Care should be taken to ensure that release agents are stored in accordance with the manufacturer ‘s recommendations, particularly with regard to temperature extremes Before using the release agents should be checked for sediment. To ensure uniformity it may be necessary to stir them adequately. Care must also be taken to ensure that they do not become contaminated. Release agents containing volatile solvents must be stored in airtight containers to prevent a change in concentration. Release agents should not be diluted at the job site unless specifically permitted by the manufacturer. Some oils have a critical emulsifier content and dilution makes the emulsion unstable and causes poor performance.

Release-Agent

 

Tips on Choosing the form release agent

One valuable standard for evaluation and selection of a release agent is prior experience. However, the safest approach is to evaluate different commercial release agents under actual use conditions, either on a test panel or on a non-architectural portion of the concrete on the project. In addition, information should be obtained from the manufacturer of the release agent about the kind of form surface for which the product is intended and the proper method of application. In making the selection, consider the following:

  • Release agent compatibility with the form material or form sealer; that is, whether the release agent softens the plastic from face.
  • Final surface requirements. If surfaces are to be plastered or painted, the form contact area should be treated with materials that don’t leave oily or waxy residue that interfere later with adhesion of plaster or paint. Some contractors consider it sufficient to wet the forms with water if surfaces are to be plastered. If the stripped surface is slightly rough the plaster will adhere better.
  • Durability of the final surface. The release agent should not cause the concrete surface to soften and dust. Moreover, it should not impede wetting of surfaces that are to be water cured nor should they otherwise hinder the proper functioning of curing compounds
  • Discoloration and staining. On forms for architectural concrete, regardless of the kind of concrete finish, a 100-percent non-staining form release agent free from pigments should be used. It will prevent uneven coloring of the concrete. The type of release agent used is of less importance for exposed aggregate concrete because the discoloration usually does not penetrate to any great depth.
  • Time period before stripping.
  • Environment of the cast concrete.
  • Uniformity of performance of the release agent.

Benefits of Releasing Agents

Releasing agents mean coatings which are provided on the formwork surface, before starting of concreting to allow smooth detachment of the formwork or shuttering. Consideration should be given on the finish surface of the shuttering as it reveals all the flaws on the form surface. Some flaws include: vibrating poker known as burns, changeable properties in the form-face material, marks of irregular water absorption in timber. There are several benefits of applying release agents.

  • It allows smooth elimination of shuttering.
  • Minimizes the occurrence of blowholes.
  • Supplys the recommended surface finish for the concrete member cast.
  • Minimizes the loss of water from the concrete caused by absorption in timber forms.
  • Minimizes seepage of water and moisture throughout curing of concrete.
  • Safeguards the formwork and helps in reuse.
  • Minimizes the cracks because infernal restraints.

Application of formwork release agents

Release agents should be applied to a clean form before the reinforcement has been placed to reduce the likelihood of inadvertently applying it to the reinforcement. If the release agent does come in contact with reinforcement it should be wiped clean before placing the concrete. When applying a release agent, it is best to follow the manufacturer’s instructions. When too much form release is used, it is not only wasteful and inefficient, but it leads to a number of other associated problems with the finished product. Those who hold the spray wand determine the amount of material applied, so proper training is crucial. The actual cover thickness will depend on the application method and viscosity of the product, which is related to the ambient temperature. Typically, the colder it is in the plant, the thicker, or more viscous, the release agent will be. The warmer the plant, the thinner or less viscous it will be. Different measures can be taken during the application process to account for changes in material temperature throughout the year.

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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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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, Constro Facilitator

VOC-Compliant Form Release Agents

Posted by Hill and Griffith Company on May 7, 2020 8:08:16 PM

Excerpt from the October 1992 article from Concrete Construction by Marilyn Palmer

New types of form release agents comply with latest environmental and safety regulations

Environmental concerns and worker health and safety issues influence many aspects of the construction industry. The use of form release agents is no exception. Where once a contractor could use a few gallons of diesel fuel from the local filling station, regulations may now require the use of a volatile organic compound (VOC)-compliant form release agent.

Traditionally, form release agents have been grouped into these categories: petroleum oils, emulsions, nonreactive coatings with volatile solvents, waxes, and chemically active agents. Many newer form release agents, however, do not fit neatly into one of these categories. For example, an emulsion and a chemically reactive ingredient may be combined in one product to gain the advantages of both. Though products in these categories are still available, environmental regulations are steering the form release agent industry toward producing products with fewer VOCs.

Proper application of a water-based, chemically active form release agent can yield a smooth, relatively unblemished concrete surface.

 Proper application of a water-based, chemically active form release agent can yield a smooth, relatively unblemished concrete surface
 

Lower VOC levels and hazard ratings

Many of the new types of water-based form release agents are the industry’s answer to the latest environmental and safety regulations for VOC levels, toxicity, carcinogens, flammability, and hazard ratings. A few oil-based agents on the market also comply with the new regulations.

Lower VOC levels are a key feature of the latest water-based agents. The products produce fewer aerosols and help to minimize odors, air contamination, and damage to the ozone layer. Workers breathe fewer vapors and generally have fewer skin irritations. Water-based products are nonflammable and have low hazardous material ratings for transportation, storage, and personal protection. Several are biodegradable, allowing product and container disposal in non-hazardous landfills.

Other advantages of water-based agents

Most water-based release agents contain a chemically reactive ingredient that forms a barrier film between the form and the concrete to inhibit adhesion. Manufacturers claim the chemical reaction at the form concrete interface minimizes bugholes and staining of the concrete, producing a smooth, relatively blemish-free finish that requires little touch-up. Many water-based products are nonresidual and will not adversely affect subsequent use of curing agents, sealers, and coatings applied to the formed concrete.

Form type compatibility claims for water-based agents show few limitations. Manufacturers indicate some agents should not be used with expanded polystyrene or natural rubber forms. To ensure adequate compatibility, apply the agent to a test panel under actual job conditions.

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Selecting and Using Form Release Agents

Choosing and Using a Form Release Agent


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Concrete Forms - Types and Selection of Concrete Forms

Posted by Hill and Griffith Company on May 1, 2020 4:24:36 PM

Excerpt from the instructional website, The Constructor.

Bond Breakers

Concrete forms can be defined as a solid barrier that helps to hold the fluid concrete in place until it hardens and acquire a particular shape. The concrete takes the shape of the form or the mold in which it is contained. Now new concrete form systems are developed that provides additional properties like insulation, surface patterns and effects to the concrete cast.

The different types of concrete forms used in concrete casting are:

  1. Wooden Forms
  2. Insulated Concrete Forms
  3. Foam Concrete Forms
  4. Concrete Wall forms
  5. Steel Forms
 
Wooden Concrete Forms

Wooden Concrete Forms

Wooden form is the basic and the most conventional type of concrete form. It is employed mainly for concrete casting that does not exceed 6 inches of height. The wooden form types consist of wooden boards. These are either nailed or screwed together to the desired mold or formwork shape. Special leveling devices are used to properly level or slope the form based on the requirement.

In order to cast concrete with curves or any sort of free-form designs, thinner cross-sections are employed to make the form. Before pouring concrete, the inner surfaces are applied with low-grade oil or any form releasing agent so that concrete does not stick to the surfaces.

If properly cleaned and maintained, these forms are suitable for multiple uses.

Insulated Concrete Forms

The insulated concrete forms (ICF) compromises of hollow blocks made of insulating material that is fit together like building blocks as shown in figure-2. These systems are constructed on the foundation slab. This forms a part of the foundation and the wall systems. Reinforcement is placed within these blocks and filled with concrete of required slump and cast. The form and concrete are placed like a sandwich. This system provides high energy efficiency. Removal of forms is not necessary by implementing ICFs. Once the concrete is filled it need not be removed.

Insulated Concrete Forms

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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, The Constructor Magazine

The Construction of Tilt-Up: Bond Breakers

Posted by Hill and Griffith Company on Apr 23, 2020 11:30:41 AM

Excerpt from the instructional book, The Construction of Tilt-Up, published by the Tilt-Up Concrete Association.

Bond Breakers

Bond breaker is one of the most critical materials used on a Tilt-Up project. As the name suggests, the bond breaker will facilitate separation between the wall panel and the casting slab.

Categories

Bond breakers generally fall into one of two major categories: chemically active or non-chemically active. They can be either water-based or solvent-based. Solvent-based bond breakers do not meet U.S. Federal EPA Clean Air Standards and, therefore, require the end user to pay an exceedance fee.

Chemically active bond breakers contain carboxylic acids which chemically react with calcium hydroxide (lime water) in fresh concrete to form metallic soaps, which prevent wall panel sticking. Non-chemically active bond breakers contain organic resins or wax which form a barrier on the casting/floor slab surface to prevent wall panel sticking.

 
Bond Breaker Application for Tilt-Up

 

Chemically active bond breakers have the advantage of being easily removed from floor and wall panel surfaces once the wall panels have been raised, allowing for the application of exterior patching materials, exterior coatings and flooring products. Non-chemically active bond breakers are generally more difficult to remove, and often interfere with adhesion of exterior patching materials, exterior coatings and flooring products.

Application

When the forming is complete and the casting beds are ready for the insertion of reinforcing steel and inserts, it’s time to apply the bond breaker. Before placing anything on the slab, the bond breaking com - pound must be sprayed on the slab surface. The compatibility of the slab curing compound and the bond breaker, if separate items, must be verified before beginning construction. The use of a single bond breaker from the same manufacturer should be used, and dissimilar products should not be used.

A quality, hard steel-troweled slab finish is a prerequisite for any applied treatments and good panel surface. Slabs that are poorly finished, poorly cured or have low strength will exhibit higher permeability, thus increasing absorption of the bond breaker and reducing its effectiveness. All casting slabs should be cured according to ACI 302.1R, ACI 308 and ACI 360R.

Apply the bond breaker in strict accordance with the manufacturer’s recommendations. Bond breaker application rates, application procedures and user instructions vary widely among manufacturers. Although the chemical makeup of bond breakers varies among manufacturers, most bond breakers are reliable and perform properly if used correctly. Make sure the product is within its shelf life, has not frozen and is thoroughly mixed (applies primarily to water-based bond breakers) prior to use. Be sure the surface is clean and free of any sawdust, dirt or other substance that would impede the action of the bond breaker or stain the panel. Most manufacturers recommend that the bond breaker be applied in a minimum of two coats after all wood reveal strips, chamfer strips and blockouts are installed, but before installation of reinforcement and embedments. These coats are sprayed at right angles to each other to ensure complete coverage of the casting slab. Apply the bond breaker inside the forms to the outside face and the perimeter of the formwork. It is well worth the effort to apply additional bond breaker around the outside of the formwork nearby. This ensures easy cleanup of any concrete that was spilled during the placing process.

Although bond breaker manufacturer recommendations vary, in general, the casting/ floor slab should have a uniform film of bond breaker and should exhibit a slightly darkened uniform appearance prior to insertion of reinforcing steel and panel inserts. Avoid puddling the material, as this will cause discoloration and retardation of the panel surface. When in doubt as to the presence of an adequate bond breaker, consult the manufacturer.

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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, Tilt-Up Concrete Association

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