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Concrete Casting News from the Hill and Griffith Company

Properly Applying Concrete Release Agents

Posted by Hill and Griffith Company on Dec 13, 2019 8:31:59 AM

Reprinted from the National Precast Concrete Association Tech Notes

Release agents, when properly used, aid in the stripping process, assist in producing sound defect-free concrete surfaces, simplify form cleaning and increase the working life of quality form surfaces.

There are two main categories of form release agents:
• Barrier – those that provide a physical barrier between the form and the concrete (such as petroleum-based products, soaps, synthetic resins, waxes) 
• Reactive – those containing fatty acids or other ingredients that react with the free lime in fresh concrete to produce a metallic soap interface between the form and the concrete (such as proprietary products and vegetable oils that are typically found in petroleum-based carrying agent products).

Concrete_From_Release_1.pngApplying 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. He who holds the wand determines the amount of material being applied, so proper training is crucial. As a rule of thumb, remember: Less is better. The amount needed to affectively coat a form is only about 0.005 inches thick. 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 it is 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 (viscosity) throughout the year.

Spraying

Spraying is probably the most efficient and common method for applying release agents. Keep the wand moving when applying form release. Broad nozzle/ flat spray tips have been found to give the thinnest and most uniform cover. It should be noted that as the temperature drops and viscosity increases, the spraying pressure should be increased and the nozzle orifice size reduced. As temperatures rise, reduce pressure and increase nozzle size. It is a good practice to soak or mop up any puddles that may have formed at the bottom of the form Remember: Less is better. Only through experience and training will you learn what works best for your plant’s production line.

CAUTION: Fatty acids will react with brass, bronze, aluminum, grey ductile and malleable iron and mild steel, as well as some petroleum-based products used for making blockouts and other embedded items. It is best to use stainless steel, nickel or plastic for your spraying systems and to test for possible reaction of embedded materials prior to full implementation.

Swabbing and Painting

Swabbing and painting by hand is an acceptable application method, with the benefit of eliminating the majority of airborne particulate. On the negative side, applications tend to be thicker than necessary, leading to wasted material and the potential for additional problems.

Wiping

Wiping is often the method of choice for architectural precasters concerned with a blemish-free surface. Wiping on release agents with a sponge or rag will normally result in the thinnest coating, but it is very labor intensive.

Dipping

Automated dipping systems are fast, labor efficient and ensure complete coverage. Excess material will usually drip back into a holding tank, reducing material waste. The application coat is often thicker than necessary, however, again creating the potential for future problems.

Concrete_From_Release_2.pngSeasoning

Reactive form release agents, the most commonly used release agents in precast and pipe production, typically contain fatty acids. Fatty acids are mild acids composed of animal fats and vegetable oils. These fatty acids have a natural affinity for metal. They react with metal to form a protective barrier, which is a coating of metallic oleate. This process is known as seasoning. This protective layer prevents further application of fatty acids from migrating to the metal of the form and allows the fatty acid to remain on the surface of the form to react with the free lime on the surface of the casting. Seasoning serves two purposes. First, it enhances the easy separation of the form from the castings. Second, it enables free air to rise more easily on the vertical surfaces of the castings, resulting in fewer surface defects. Seasoning of forms is a very basic requirement to help minimize the amount of labor involved when forms are stripped or pipes are tipped out. If forms, pallets and headers are properly maintained, labor cost and better looking castings are the end result.

New forms, pallets and headers will frequently arrive with a protective coating on them to help prevent rusting in transit or until the forms are sold and delivered. In order to season these forms, the protective coating can be removed with solvents or grinding and the form release applied liberally, allowing it to set for a minimum of four hours. A 24-hour period is better, as it allows more seasoning to take place. Also, forms that are exposed to the sun will season more quickly, as higher temperatures increase the reactivity with the metal forms and rings.

Care of forms and rings

At times, you may be storing forms inside or outside for short or long periods of time. Release agents can be used to protect this vital equipment from damage. For short-term or long-term storage, a good quality VOC-compliant petroleum solvent-based form release can be used by applying a liberal coating on the form. If the forms are stored outside, even for a short period of time, a quick walk-by is often necessary to ensure that the form release has not washed off from rain. If any evidence of rust is present, apply another coat of the form release on the forms and rings as quickly as possible. A biodegradable form release is preferred, as over-application is desired and some of the material will end up on the ground.

Identifying Potential Problems

Concrete is a highly variable material because it is comprised of raw materials that potentially have a lot of variability. It is often difficult to pinpoint exactly what causes a problem because it may be a combination of a number of factors. The following are two examples of common problems often associated with excessive form release agent coverage.

• Staining has been linked to the use of excessive release agents and the use of dirty forms. Dirt, dust, rust or grease can easily be transferred from a dirty form to the finished surface of the concrete product. Once a form has been properly cleaned and coated with release agent, proper measures should be taken to minimize the potential for dust and debris to collect on the form before casting.

• Excessive bugholes occur when barrier-type release agents are applied to heavily. Barrier-type release agents tend to encapsulate free air along the vertical sidewalls, which leads to surface defects. In contrast, the metallic soap formed when using a reactive release agent allows the free air on the vertical walls to rise more easily to the surface. Proper vibration practices also reduces bugholes. The potential for bugholes and staining can be reduced by selecting an application method that produces the thinnest coat of release agent in accordance with the manufacturer’s recommendations. Release agent should not be allowed to collect and pool in the forms. Applying a thin coat, wiping up puddles and avoiding contact with reinforcing steel greatly improves the odds of producing a defect-free concrete product.

This publication is designed to provide accurate and authoritative information, however the National Precast Concrete Association does not guarantee the validity or accuracy of any data, claim or opinion appearing in this publication. If engineering, legal or other professional services are required, the services of a competent professional should be obtained. The National Precast Concrete Association does not assume and hereby disclaims liability to any person for any loss or damage caused by errors or omissions in this publication, regardless of whether such errors result from negligence, accident or any other cause whatsoever.

Read the NPCA whitepaper in its entirety.


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Tags: Concrete, Concrete Casting Products, Concrete Release Agents, National Precast Concrete Association, NPCA

Coating Tilt Up Concrete Walls

Posted by Hill and Griffith Company on Oct 24, 2019 3:55:17 PM

Originally published in the March 2011 issue of Concrete Construction

Q: The painted surfaces of some of the tilt-up concrete walls on our projects seem to develop blisters, peeling, or flaking shortly after application. Sometimes this occurs after it rains. Is there anything different about tilt-up walls that makes this happen?

A: As with any paint or coating project, the key to good results is paying attention to the three Ps: Prep, Prime, and Paint. Procedures for painting and coating concrete surfaces are different from other surfaces, and tilt-up concrete surfaces do require special preparation.

Causes of Defects on Tilt Up Concrete Walls

Surface Preparation: The most likely reason for blistering and peeling in a tilt-up wall, especially if it occurs shortly after it rains, is failure to remove the mold release agents and bond breakers used for casting the concrete component.

This is the big difference between tilt-up concrete and other forms: It is cast on the jobsite in concrete forms. After the concrete wall or column has cured, a mobile crane tilts the piece up and moves it into place, where it is braced into position and secured. Painting contractors may not always be fully aware of this because they arrive on the jobsite after the walls are in place.

To prevent the concrete from adhering to the molds, contractors apply release agents, or bond breakers, to the mold before the concrete is poured. These release agents can be solvent-based, water-based, oil-based, silicone-based, silicone-free, silicone water-based and many other proprietary combinations. But they all perform the same function—they create lower surface energy between the concrete form and the concrete to mitigate adhesion. The objective is to be able to lift the cured concrete from the casting mold smoothly and cleanly.

Unfortunately, release agent residue also can inhibit adhesion of coatings and paint to the concrete surface. Most painting contractors are aware of this, and paint companies do a good job of educating painters about the need to remove release agent residue before painting or coating tilt-up concrete surfaces. Power washing at the specified pressure using the specified cleaning solvent should do the trick, but there are two cautions.

One, be methodical and thorough when power washing. Two, there is a trend toward making release agents and paints/coatings more compatible, but it is always prudent to power wash the surface first. Even with “compatible” release agents, if too much was applied to one area, it could swamp the system and adversely affect coating adhesion.

All concrete surfaces must be washed before coating to remove dirt, dust, and excess sand anyway, so always take the extra step of power washing tilt-up concrete to remove any release agent residue, whether they are compatible or not.

Read More


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5 Options for Dry-Cast Concrete Pipe Dip Tank Maintenance

Posted by Hill and Griffith Company on Oct 10, 2019 2:24:06 PM

Originally published in the May-June issue of 2015 PRECAST INC, by Bob Waterloo

Maintaining the optimum reactive level of form release agents in pipe production dip tanks ensures performance and quality. 

Dip tanks play a critical role in the dry-cast pipe production process for many manufacturers. The reactive properties of the fatty acids in the form release agent enable the pipe to release from the pallet/header smoothly. Here’s the problem. The cement/concrete residue left behind when headers are dipped starts to negate the reactive properties of the fatty acids.

Left unchecked, the form release agent eventually begins to lose its effectiveness, pipes will not pull easily from the headers and quality could suffer. The solution: implement a regular program of monitoring and maintenance that keeps the form release at the optimum reactive release level and reduces replacement and disposal costs.

Precast Pipe Dip Tank Maintenance

Benefits of a dip tank
Reactive form release agents are the accepted standard in today’s precast and pipe-forming operations. Fatty acids, which are found in an infinite number of blends, are the most commonly used reactive material. Fatty acids have the unique ability to react with the free lime on the surface of the concrete, which results in a nonviolent chemical reaction. This neutralization (or saponification) forms a metallic soap, allowing the product to release easily.

There are several benefits to using a dip tank to apply form release during pipe-forming operations, including complete coverage, proper release and reduced chance of operator error. However, a common occurrence when using this method of manufacturing is increasing difficulty with “pulls” or “tip-outs” during stripping over a period of production time. This is generally the result of decreased reactive material in the dip tank as contaminants enter the system and negate some of the reactive material.

Maintaining the dip tank
Two areas must be addressed in the preventive maintenance program for this type of equipment:

  1. Regular maintenance to remove sludge that accumulates in the bottom of the dip tank
  2. Regular maintenance of the release agent’s reactive levels for effective release

The sludge generated in the dip tank includes contaminants from previously dipped headers/joint rings. These contaminants negate the reactive portion of the form release. As the reactive portion of the release agent gradually decreases, the possibility of concrete sticking to the headers increases, causing a more difficult release. The rate of decrease is gradual and depends on many factors, including rate of production and amount of contaminants allowed to enter the dip tank.

Ring-Oiling

Removing contaminants
Rather than disposing of the entire tank of form release, transfer it to a holding tank and shovel out the sludge. Because the sludge typically contains petroleum hydrocarbons, disposal should be in compliance with local regulations. Then, transfer the recovered form release agent back into the dip tank and top it off with fresh release agent.

Remember that by adding fresh release agent to the recovered material, rather than using all new release agent, reactive levels will be reduced and release problems will occur sooner unless the reactive portion is tested and brought back to a normal level. The discoloration of the recovered material from the dip tank is not relevant to the release characteristics, or levels of reactive material.

Maintaining reactive release levels
Maintaining the correct level of reactive agent in the form release is quite simple. Test the recovered material and bring the reactive portion back to optimum levels.

Test a sample from the dip tank (less than one ounce is sufficient) for the reactive level through either titration or infrared analysis. Your release agent supplier should be able to tell you the optimum level of reactive material required and may be able to run the analysis for you. Once you determine the level of fatty acids, a number of simple calculations determine the amount of pure reactive agent to be added to the dip tank to bring it back to the optimum reactive level.

After adding the recommended amount of reactive material to the dip tank, use an air lance for mixing for a minimum of two minutes, making sure to cover the entire area of the dip tank. Then top off the dip tank with fresh release agent and air lance again for good distribution.

Depending on the amount of contaminants and reduced reactive material, the timeframe between tests will vary. One way to determine the frequency between tests is to establish a baseline. Begin with tests every 30 days, which should be recorded, until a history can be compiled to determine the needed frequency. The normal frequency of adding more reactive ingredients is typically five gallons for every six weeks of regular production.

In many cases, production workers can see the reduced effectiveness of release agents. It’s important to train them to notify management to add additional reactive material to the dip tank. As usual, science is best, but practical application and analysis are also important.

Total replacement of form release
While removing sludge and maintaining dip tanks by adding new release as needed make sense from an environmental and cost perspective, on occasion, you may feel it necessary to clean the entire dip tank to remove all residual sludge and refill the cleaned dip tank with fresh release agent.

Cost-effectiveness
Dip tank maintenance comes down to five options. Option 1 is the least cost-effective, while Option 5 is the most cost-effective.

Option 1: Drain the dip tank, dispose of the sludge and old release material, then refill only with fresh form release agent.
Option 2: Remove the form release from the dip tank, dispose of the sludge, refill the dip tank with fresh form release, then use the recovered form release to replenish the dip tank as necessary.
Option 3: Remove the form release from the dip tank, dispose of the sludge, refill the tank with recovered form release, then top off with fresh form release.
Option 4: Remove the form release from dip tank, dispose of the sludge, test the recovered form release, add reactive ingredient to bring it back to an optimum level, then top off with fresh form release.
Option 5: If there is not enough sludge to remove but the release is not as good as it should be, test for the reactive level of the release agent in the tank, then add reactive material to return it to an optimum level.

In the long run, a little care and attention to the reactive content level in the dip tank will help to reduce labor costs and maintain or improve casting appearance.


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Tags: Concrete Form Release Agents, Concrete Casting Products, Concrete Casting Supplies, Concrete Pipe, Concrete Safety, Precast Concrete, Grifcote FR 50 Concrete Form Release, Bio Gold Concrete Form Release, Grifcote, Precast Inc Magazine

Preventing Bug Holes in Precast Concrete

Posted by Hill and Griffith Company on Sep 26, 2019 4:40:25 PM

From the June 2, 2014 PRECAST Magazine post Causes and Fixes for SCC Bug Holes, by John Pelicone

bugholes_th.jpgLike a persistent mosquito, one question has plagued precast concrete producers for years: “How can I eliminate bug holes?” In the past, this question was much harder to answer, because concrete was placed at a stiffer consistency that required excessive vibration. And excessive vibration sometimes caused more bug holes. After the introduction of self-consolidating concrete (SCC), bug holes(ii) became a less common occurrence. Yet, as a recent online industry discussion revealed, this perturbing problem is still with us.

"Two types of release agents

  1. Chemically reactive agents: When a chemically reactive form release agent is used, a nonviolent chemical reaction takes place when fatty acids react with free lime on the surface of fresh concrete. This reaction results in the formation of a metallic soap, a slippery material that allows air bubbles to rise along the vertical surface. This “soapy” film also prevents the hardened concrete from adhering to the forms during stripping.
  2. Barrier release agents: Thicker coatings on forms are typical of the older barrier-type materials, like heavyweight used motor oil, vegetable oils, diesel fuel and kerosene. Barrier type release agents are less expensive than chemically reactive agents, but they are not generally recommended for reducing SCC bug holes."

SCC-Bug-Holes-1

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In summary,

"Bug Hole voids are formed during placement. Small pockets of air or water are trapped against the form. The problem increases with the height of the lift. Vibration may not be adequate or well spaced. The mix may be sticky.

  • Primarily caused by the way concrete is placed and compacted
  • Entrapped air not removed by vibration, air bubbles move to the form
  • Improper application of Form Release agent or wrong type 

SOLUTION I PREVENTION: Avoiding Bug Holes

  • Work the voids at the form face up and out of each lift
  • Let the vibrator drop through the lift, then vibrate upward
  • Don't overvibrate at the center of the wall
  • Move the vibrator as close to the form as possible
  • Add upward external vibration if necessary
  • Reduce the height of each lift to make void removal easier
  • Aggregate - consult ready mix producer and review aggregate size and shape
  • Reduce sand content
  • Use low slump concrete"

Hill and Griffith Customer Service

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The Influence of Form Release Agent Application to the Quality of Concrete Surfaces

Posted by Hill and Griffith Company on Sep 19, 2019 11:00:54 AM

ACI 318-19 was published in response to new engineering practices and industry changes.

Excerpt from a technical paper by A. Klovas and M. Daukšys 2013 IOP Conf. Ser.: Mater. Sci. Eng. 47 012061.

Introduction

High quality surface finishes are a feature of self-compacting concrete (SCC), but by careful attention to mix design and job site workmanship, nice surfaces with the conventional concrete mixture could be achieved. The appearance of an element mainly depends on: the type of cement and addition used; the mix composition; the quality of the concrete mold and release agent; and the placing procedure. If compared self-compacting concrete with the conventional–the color is generally more uniform. Also, it is easier to avoid defects due to leakage spots at the location of mold joints. Blowholes, honeycombing and other blemishes can be found in all types of concrete but with more fluid concrete mixture it is possible to improve the surface finish. International Council for Building Research has provided guidelines how the concrete may be defined referring the surface quality:

  • ROUGH class – no special requirements for finishing
  • ORDINARY – surface finishing has a minor factor
  • ELABORATE – definite requirements for visual appearance
  • SPECIAL – highest standards for appearance
Concrete Form Release Agents Help Form Removal
photo credit: Bob Sawyer

Formworks are also very important factors for concrete surface quality. Scientist, J. Sousa Coutinho, has researched using two different formworks: controlled permeability (CP) and five-layer wood-based formworks. The results have shown that by using CP formworks, the pore diameter (nm) of concrete surface has decreased up to 50%, porosity – up to 45%, surface hardness (MPa) increased up to 70%, and blow-hole ratio has decreased up to 90 % compared with those concrete surfaces using five-layer wood-based formworks.
 
A number of studies determine how to achieve better consolidation resulting in fewer surface blemishes [7-15]. To minimize the size and number of bug holes and all other effects, the following practices should be followed:
  • Vibration period should be of sufficient duration
  • Vibrator insertions should be properly spaced and overlapped and the vibrator removed slowly
  • Each concrete layer should be consolidated from the bottom upward
  • Vibration periods should be increased on withdrawal when using impermeable forms that permit air trapped at the form surface to escape through joints as between
  • Inward sloping forms and other complex design details should be avoided
  • Vibrator should penetrate into the previous layer;

The main outcome of this research is to evaluate the usage of different form release agent applications on the formwork. In addition, this paper presents a technique which provides:

  1. A method how to evaluate the concrete surface quality using image analysis process;
  2. An evaluation of concrete surfaces quality by the following documents: CIB report no. 24 [4] and GOST 13015.0-83.
  3. A combined method how to evaluate and divide concrete surfaces into special categories provided by CIB report no. 24 GOST 13015.0-83 and “ImageJ” in respect to the area of blemishes.

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ACI Releases New Building Code Requirements for Structural Concrete

Posted by Hill and Griffith Company on Sep 12, 2019 4:58:19 PM

ACI 318-19 was published in response to new engineering practices and industry changes.

Article excerpt by Jack Moehle published in the Concrete Contractor August/September 2019 issue.

The American Concrete Institute (ACI) published ACI 318-19: “Building Code Requirements for Structural Concrete in July 2019, in response to new engineering practices and industry changes.

ACI 318 presents requirements for design and construction of structural concrete that are necessary to ensure public health and safety. The document is intended for engineers and building officials, but because it addresses materials advancements and applications, it is expected to have an impact on jobsite procedures. It is anticipated the final code requirements of 318-19 will be referenced in the 2021 International Building Code (IBC).

318_19_cover_highres2.5d39ca6a430aa

New Engineering Practices Translate to Changes in the Field

  • ACI was prompted to make updates in the code due to:
    • new technology (computers used for design and analysis by engineers and architects)
    • increased construction of tall buildings
    • the need for seismic resistance
  • New requirements include:
    • minimum reinforcement on interior column-to-slab connections
    • longer bar lengths for thicker, two-way slabs
    • additional transverse reinforcement
  • Updates include
    • expansion of permissible applications of high-strength reinforcement
    • new requirements for material properties of high-strength steels
    • several changes to strut-and-tie method (STM) for design of discontinuity regions
    • clarity on Anchorage-zone reinforcement

New Materials Addressed

  • IBC shotcrete provisions were included
  • Post-installed concrete screw anchors are now recognized

Alternate Cements and Aggregates

  • Now includes provisions for alternate cements and aggregates
  • No details are readily available for these materials because not enough industry testing is available

Read More


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Selecting and Using Concrete Release Agents - Excerpt

Posted by Hill and Griffith Company on Sep 6, 2019 5:35:38 PM

Enhance the quality and economy of precast products by using the right release agent

Article excerpt by John A. Koski published in the Concrete Construction March 1994 issue.

Almost every precaster has had a double-tee or an architectural precast panel crack as it was being removed from a form. In some cases, an ineffective or improperly applied release agent may have been the culprit. At other times, the wrong type of release agent may have been used. Knowing how to properly use form release agents and which agent should be used for a particular application can go a long way toward preventing costly mistakes. In addition, following proper procedures and using the right agent can enhance the quality and economy of a finished precast piece.

Less is better with Precast Concrete From Release 3

BASICS OF USE

  • Make sure the release agent you are using is compatible with the form or mold it is being used on. For example, some release agents can cause an adverse chemical reaction when used on foam or rubber forms.
  • Don’t purchase a release agent based on price alone. When examining prices of comparable release agents, compare them based on their cost per square foot of coverage, not by the cost of a 5-gallon pail or 55-gallon drum.
  • Protect form release agents from temperature extremes. Release agents that have frozen and then become liquid again may have had their form release properties altered or destroyed. Extremely high temperatures also can damage the properties of release agents. 
  • Thoroughly mix or agitate release agents that require mixing or agitating. This ensures proper dispersion and continuity of the chemical components within the release agent. Always follow manufacturer recommendations when considering mixing or agitating. Some release agents don’t need to be, or shouldn’t be, mixed or agitated.
  • Make sure workers wear respirators, goggles, face shields, gloves, and other protective clothing as required by the manufacturer and government agencies. Make sure workers are properly trained in all aspects of the application process. This includes not only safety concerns, but also how to properly apply the release agent being used. The application technique workers use, however, may not be appropriate for the new product and can cause it to perform unsatisfactorily or not at all.
  • Before applying the release agent, remove any buildups of concrete, rust, scale, or dirt that may be on the forms.
  • Repair any holes, fractures, or other defects in the forms. Just prior to applying a release agent, make sure that the surfaces of the forms are clean and free of water, dust, dirt, or residues that could be transferred to the surface of the concrete or affect the ability of the release agent to function properly.
  • Make sure that forms are coated uniformly with no gaps, sags, runs, or beads. To avoid these problems, never apply a too-heavy coat. Sags, drips, and runs should be removed as recommended by the manufacturer.
  • Make sure spray equipment is working properly. 
  • Do not over-apply a release agent, especially when using a release agent that is chemically reactive.
  • On new wooden forms, thoroughly saturate the forms according to manufacturer directions before placing concrete.
  • It is best not to wait an excessive amount of time after applying the release agent and before placing concrete as dust and other airborne contaminants can form a light coating over the release agent
  • If the concrete is to be painted, plastered, or have other coatings applied, be sure to use a release agent that won’t prevent the coating from bonding with the concrete.
  • Don’t allow release agents to contact reinforcing steel. Doing so can prevent the concrete from bonding to the reinforcement.

Read More


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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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Please Release Me - Appropriate Use of Concrete Release Agents

Posted by Hill and Griffith Company on Aug 29, 2019 9:24:55 AM

The use of an appropriate release agent, correctly applied, is critical to creating a good, consistent surface quality

by Elaine Toogood

Originally published in the Winter 2018 Issue of Concrete Quarterly.

Applying a release agent to the face of the formwork is like greasing a cake tin. Without it, the formwork cannot easily be removed or released from the hardened concrete.
According to the Concrete Society publication Visual concrete – Planning & Assessment, there are essentially two types of release agent: barrier and reactive. These are further divided into eight categories, though developments in this field mean that some products do not easily fall within these categories.

Not all release agents are suitable for creating visual concrete and selection will be based on many factors, including compatibility with form-facing material, concrete specification and expected site conditions. A good release agent will also help maximize the number of times that a form can be used.

Concrete Form Release Agent

4 Pancras Square by Eric Parry Architects, where the post-tensioned slabs are exposed as soffits. The concrete contractor specified a concrete mold oil release agent for use with the plastic-faced ply lining of the formwork system.

Photo credit: Rory Gardiner

Barrier release agents work by creating a layer between the form face and the concrete. Oils with surfactants are general-purpose release agents for many different types of formwork, including steel, and are often used in the precast industry. None of the other barrier types such as neat oils, mold cream emulsions, water-soluble emulsions and barrier paints are recommended for high-quality finishes. Although barrier paints may be part of a preparatory treatment for timber and plywood before it is first used to extend the life of the formwork.

Most of the reactive types of release agents are suitable for visual concrete and are categorized as chemical release agents, surface retardants and other specialist release agents, including those based on vegetable oil (VERA). They allow the formwork to be struck by creating a very thin layer of unhardened concrete or “soap” on the surface that must be brushed away when the formwork is struck. Chemical release agents are a popular choice but can lead to dusting if over-applied. Although recommended for high-quality finishes, they may not be appropriate for concrete containing silica fume or high amounts of admixtures. VERA fall under the category of other specialist release agents and are recommended for visual concrete, with the added advantage of being non-toxic and biodegradable, and reportedly with a low incidence of blowholes and blemishes.

Design professionals do not need to specify the release agent that is to be used, but rather provide a performance specification. This directs the contractor to select one appropriate for creating high-quality visual concrete surfaces, that has little or no detrimental impact on the appearance of the concrete and that suits the choice of formwork facing and concrete used. Consultation with the manufacturer and form-facing material supplier will be necessary to select the best product and method of application for the specific project. Biodegradable and non-toxic products may also be identified for health and safety reasons.

The selected product or products should then be tested with a full-scale mock-up panel or in a non-critical location of the structure to review the results and trial the method of covering the formwork before final selection. Release agents should be applied in accordance with manufacturers’ guidance – they are often sprayed or applied with a soft brush – to create a thin, uniform and complete coating. Once satisfactory results have been established, the standard of workmanship must be rigorously maintained to ensure consistency. Incorrect application, whether too much or too little, can lead to abrupt color or tone changes in the concrete surface. The surface of the formwork should be cleaned and a coating of release agent applied before every use.

Read More.


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 Bulletins and Technical Papers for Concrete Casting Products

Tags: Concrete Casting Products, Concrete Casting Supplies, Concrete Safety, Precast Concrete, Grifcote FR 50 Concrete Form Release, Concrete Form Release for Wood, Bio Gold Concrete Form Release, Gricote, Concrete Form Release Agent, Concrete Quarterly

Wood Form Concrete Release Agents

Posted by Hill and Griffith Company on Aug 22, 2019 1:04:51 PM

(This week's post comes from a HOMEGUIDES' article, "How to Keep Concrete From Sticking to Wood." It has a unique perspective from the homebuilder's point of view. You can read the full article here.)

How to Keep Concrete From Sticking to Wood

Concrete-Form-Release-For-Wood.jpgConstruction professionals routinely use plywood panels as shaping forms when pouring concrete for new home foundations. If the wood forms were treated properly with a form release agent, you can easily pull them away after the concrete dries. A do-it-yourselfer can pour concrete between 2-by-4 forms when installing a new sidewalk or patio, but for best results, pretreat the wood in the same way the pros do.

(Caption: Hill and Griffith recommends Grifcote Bio Gold concrete form release for wood. A non-petroleum, non-staining concrete form release that is both VOC compliant and biodegradable.)

Oil-Based Release Agents

At one time, construction professionals would create their own oil-based form release agents using materials such as diesel fuel, home heating oil and mineral oil to keep poured concrete from sticking to wood. Today's homebuilders often select stick-resistant plywood or OSB panels pretreated at the lumber mill with proprietary chemical blends that may include parafin, mineral oil and linseed oil. Some concrete contractors extend the stick-resistant life of the plywood by using a refresher coating of a commercial release agent or a solvent-thinned linseed oil.

Water-Based Barrier Agents

Water-based release agents can also keep concrete from sticking to wood forms, and unlike oil-based formulas, they do so without releasing high levels of volatile organic compounds into the air. VOC-releasing chemicals are highly regulated in some regions because they contribute to atmospheric smog. Commercial water-based release agents are produced from plant-based materials and are less likely to discolor the concrete's surface. Ordinary vegetable oils can serve the same purpose if applied in two or three successive coats.

Reactive Release Agents

Chemically active release agents react with the alkalinity of the concrete to prevent the concrete from sticking to wood molds and forms. Commercial products of this type are formulated with a fatty acid and a soapy surfactant that react chemically with the concrete to help create a clean, unstained concrete surface with a smooth edge. At the same time, they create their own thin chemical membrane that blocks the concrete from infiltrating the wood's pores.


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 Casting Products, Concrete Casting Supplies, Concrete Safety, Precast Concrete, Grifcote FR 50 Concrete Form Release, Concrete Form Release for Wood, Bio Gold Concrete Form Release, Gricote, Concrete Form Release Agent

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”.


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

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