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Concrete Casting News from the Hill and Griffith Company

Innovative Solutions for Formlining, Lifting, and Reinforcing Precast Concrete

Posted by Hill and Griffith Company on Feb 11, 2021 8:39:55 PM

Excerpt from the December 2019 issue of Concrete Plant International by Michael Khrapko

The precast technique is practical and economical. This is proven by the very existence of the precast concrete industry and the numerous successful building projects achieved using precast concrete. A number of aspects make concrete precast different from in-situ concrete. Precast elements must be joined with each other to form a complete structure. A precast concrete structure is an assemblage of precast elements which, when suitably connected together, form a 3D framework capable of resisting gravitation and wind (or even earthquake) loads. Another unique concrete precast feature is vertical patterned texture, achieved by using formliners, which are essentially molds for giving texture and design.

New Zealand is a relatively young country. Europeans only started settling in New Zealand in any significant numbers of the past one hundred years. Being isolated geographically and having no cultural traditional building systems to change, New Zealand has been quick to adopt innovative precast building systems, which now enjoy a relatively high market share. Some of these innovative building systems, such as on-site precasting and moment-resisting precast building frames, have evolved their own style and character to meet New Zealand's unique needs. Over the years, innovative and unique systems to support precast concrete construction industry have been developed.

Precast Concrete Bridge Spaning Over 150 Feet

The precast concrete industry controls about 25 percent of the multi-story commercial and domestic building marketing, including frames, floors and cladding (facades). Precast concrete has many advantages over in-situ concrete and other materials. Precast concrete components are produced in controlled conditions that enable to manufacture units to tight tolerances, varying shapes and highly attractive architectural finishes. Controlled production processes allow for faster and most effective implementation of advanced material technologies, like self-compacting concrete and fiber composites. Compared with other materials, precast concrete can provide benefits in fire resistance, durability, thermal and acoustic properties, installation time and can perform its function immediately upon arrival at a construction site, therefore eliminating on-site curing time.

Precast concrete production and construction require efficient, effective and safe lifting and transporting methods. Growing concerns about safety on construction sites, together with escalating demands on cost efficiency, encouraged new developments in this area. Efficient and safe lining systems have been designed and successfully used.

Precast Concrete Made with 3D-Printed Forms

One of the characteristic features of precast elements is that they must be joined together to form a complete structure. The connections for precast concrete are important components of the building envelope and frame systems. The primary purposes of the connection are to transfer load to the supporting structure and provide stability. Connection of precast elements becomes an essential component for construction in seismic areas like New Zealand. Precast connections for seismic resistance is another area where innovative systems have been developed.

Architectural facades using formliners

One of the greatest advantages of working in concrete is its versatility. When viewed as an artistic medium rather than simply a construction component, the material offers infinite possibilities for creativity. Many tools for expressing this creativity have been around for a long time, but they are finding new uses. One proven system receiving renewed attention is formliners.

Formliners are essentially molds for giving texture and design to vertical concrete surfaces. Formliners can be described as "reverse stamp." Instead of pouring the concrete and applying a texturing tool, the tool (the formliner) is attached to the form and concrete is poured onto it. Formliners have been widely used for years to beautify buildings and otherwise ordinary structures such as highway walls, sound barriers, bridge supports and retaining walls. This market continues to grow as more and more communities demand beauty as well as functionality from their buildings and highway systems. In many cases, budgets for these projects include a required amount of art, a requirement that can be met with form liners. Decorative formliners have been further developed in recent years, and certain times can be reused 100 times or more. This is partially due to formliner quality and improvements in the technology of adhesives and concrete release agents. Significant advancements in concrete admixture technology have played an integral role in producing concrete mixes that minimize surface blemishes, enabling the production of the specified surface finish. The new generation of polymer-based admixtures have ensured that concrete placing is easier than in the past, enabling quicker, continuous pouring. It is possible to achieve a high-quality, dense surface finish using self-compacting concrete (SCC). This further increases the life of the formliner as vibrating apparatus is not used. 

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Tags: Hill and Griffith, Concrete Form Release Agents, Concrete Release Agents, Concrete Casting Supplies, Precast Concrete Form Release, Concrete Form Release Application, Concrete Form Release, Concrete Form Release Agent, Concrete Plant International Magazine

The Seven Precast Wastes: Waste #7 Defects

Posted by Hill and Griffith Company on Feb 4, 2021 2:27:41 PM

Article excerpt from the November/December 2020 issue of Precast Inc. magazine by Eric Carleton, P.E.

Editor’s Note: This is the final article in a year-long series about how seven common types of waste in manufacturing can create unprofitable activity and how to address them in your plant.

A precast concrete defect can be defined as a product not meeting a standard or a customer’s expectation. Like all wastes, defective products create additional problems and add costs throughout the production process. They also generate environmental wastes not identified in this series. For these reasons, many lean quality management experts consider defects to be the worst of the seven wastes.

However, defects are one of the easiest wastes to identify. Does the product meet all aspects of its respective ASTM, Department of Transportation or municipal standards? Does it display the aesthetics and company reputation as intended? If the answer is “no” to one of these questions, you have a defect that needs correction.

Precast Concrete Defects

While identifying a defect can be straightforward, understanding the cause and corresponding remedy can prove to be more difficult. When attempting to tackle defects, four guidance activities are often recommended1 by lean manufacturing experts2:

  • Determine one defect on which to place your primary emphasis. For example, a precast inlet was stripped from the form and has rough vertical wall edges that appear honeycombed or jagged. This defect not only creates issues with appearance and acceptance, but it can also affect long-term durability and possibly structural integrity. This type of defect often requires repair.
  • Determine when in the production process this defect occurs and identify the cause. If the product in question is wet-cast, is the issue related to stripping? Are you experiencing a paste leakage issue caused by forms not being connected or latched correctly, properly maintained or checked for dimensional tolerances? Are forms being damaged during production, crane operation or storage? Use root cause analysis procedures to identify where the problem originates and determine the appropriate solution. Ensure the solution totally corrects the identified problem at the source such that the problem does not proceed in some manner down the production line.
  • Revise the process and/or provide training to correct the defect. Investigate the form tolerances, ensure latch mechanisms are working properly and perform the necessary maintenance on the forms. Conduct form dimensional checks and maintenance at a greater frequency or add chamfers at the corner sections, which may prevent the loss of concrete paste at the form joints and improve appearance. Train your employees on proper production techniques and talk about why the issue has been occurring and why it’s imperative to make process changes. You can engage crews in helping to identify what other tools or resources may be needed to prevent the defect in the future.
  • Standardize the process to eliminate the defect. Leverage the data gathered during the process revision and training phase and include that information into the new process or method. For instance, incorporate the maximum allowable gap tolerances of form joints into the pre-pour dimensional inspection checklist. Develop simple gauges for your workers to verify tolerances are not exceeded. Ensure form dimensional compliance and latch connections are verified in good working order prior to production activities. When you’ve standardized your new process to eliminate the root cause of the defect, conduct ongoing and refresher training on the new process and correct techniques.

Precast Concrete Defects and Remedies

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Questions from the Field


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Tags: Concrete Form Release Agents, Concrete Release Agents, Concrete Casting Supplies, Precast Concrete, Precast Concrete Form Release, Concrete Form Release, Concrete Contractor Magazine

Form Oil on Concrete Rebar

Posted by Hill and Griffith Company on Jan 28, 2021 12:55:40 PM

Article excerpt from the August 2013 issue of Concrete Contractor magazine by James R. Baty II

The Concrete Foundations Association explains the code reference and common misconceptions regarding oil on rebar for residential concrete.

Question

On several of our most recent residential projects, the inspector in our area has been complicating our pour schedule when finding form oil over-sprayed on the rebar in our walls. Is it our misunderstanding that form oil on rebar shouldn’t pose a problem to the wall performance or the acceptance of our pre-pour inspection? – Concrete Contractor (Ohio)

Concrete Release Agent and Rebar

Answer

Your question addresses a common problem across the construction industry that is created as codes are modified over time. Regardless of the comparison of residential to commercial work, code edition after code edition presents challenges to professionals throughout the industry to remain current with the latest acceptable practices and minimum requirements. In the specific case of the acceptability of form oil sprayed on rebar for residential applications, this is both a question of appropriate code reference applying more properly to the residential concrete code — ACI 332 — rather than ACI 318, and of referencing the most recent version, ACI 332-10, instead of older versions -04 or -08.

Appropriately referencing ACI 332-10, your inspector and you can develop a common understanding of this issue based on the presented reference. Stated in section 4.2.4 of ACI 332-10, the code provides:

4.2.4 Surface conditions of reinforcement—At the time concrete is placed, deformed bar and welded wire reinforcement shall be free of materials deleterious to development of bond strength between the reinforcement and the concrete.

R4.2.4 Common surface contaminants such as concrete splatter, rust, form oil, or other release agents have been found not to be deleterious to bond.

This version of the residential concrete code presents two issues that are significant to this topic and to the successful resolution of the argument. The first is that during construction, nothing should be found on the reinforcement that would adversely affect the bond strength of the reinforcement in the concrete. The inspector on your project is rightly wanting to make sure the purpose for the steel present in the concrete is successfully achieved, or at the very least, not voided by preventing such a bond. However, the second issue is equally as important even though it occurs in the commentary. Referencing significant industry research, the explanation is given as to what common site conditions found on rebar are not to be considered deleterious to bond. As you might expect, form oil is one such surface contaminant that is not to be considered deleterious to bond.

The obvious next question in your discussion might be why such a surface contaminant is not deleterious to bond. This is the purpose of the reference to the type of reinforcement found in the code section. Deformed bar and welded wire are both designed to achieve a mechanical bond with the concrete rather than a chemical or adhesive bond. The mechanical bond relies on a keying action with the deformations along the length of the reinforcement bar. Therefore, as long as the surface contaminants do not effectively eliminate the presence of those deformations, they would not be considered deleterious to bond.

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Precast Shine in Treatment Plant Project

Posted by Hill and Griffith Company on Jan 22, 2021 3:41:16 PM

Article excerpt from the January 2018 issue of Precast Solutions magazine by Shari Held

Knox Borough, Pa., is a quaint community of approximately 1,000 residents tucked away in the northwestern quadrant of the state. Its original cast-in-place wastewater treatment plant was built in the 1930s and had only been upgraded twice – once in the ‘50s and again in the ‘70s.

The plant’s tanks showed evidence of spalling so severe that the reinforcement in the walls was exposed. The plant didn’t have the hydraulic or organic capacity to handle its customer base. It needed to be expanded or replaced quickly to keep Knox Borough in compliance with the Pennsylvania Department of Environmental Protection.

Wastewater-Plant-1

A winning solution

Replacing the wastewater treatment plant was the less expensive and more practical option. One of the first decisions to be made was what building material to use. The capacity of the new plant was 500,000 GPD, making it too large for steel, which poses issues with durability. Steel plants have a lifespan of 25-to-30 years, while concrete plants can last more than 50 years.

Martin English, P.E., an engineer with the EADS Group of Clarion, Pa., considered using cast-in-place concrete. Ultimately, though, he chose post-tensioned precast.

"Preventing leakage was our number one priority," English said. "The post-tensioning support available with precast concrete makes it a very advantageous product for both strength and durability in environmental structures."

The design for the new extended aeration plant called for two 45-foot (outside diameter) circular clarifier tanks and a 153-foot-by-76-foot rectangular tank subdivided into two aeration chambers, two digester chambers, a flow-splitter chamber and a return-activated sludge chamber. Precast caps on the wall tops create a walkway around the tanks.

Mack Industries' headquarters plant in Valley City, Ohio, produced the precast for the treatment plant, built it, and installed the tanks and equipment. The company, which had worked with English before, began consulting on the project more than two years prior to receiving official approval to begin.

"We are unique in that our salespeople are working with the engineer in the early stages of a project," said Betsy Mack Nespeca, president, Mack Industries. "The key to a customized solution is working hand-in-hand with the engineer."

Mount Braddock, Pa.-based Global Heavy Corporation served as the general contractor for the project.

Challenges along the way

Timing was a big challenge. English was concerned about meeting DEP-imposed deadlines. "We had an implementation schedule that had to be met from start to finish," English said. "It definitely helped knowing we could meet our schedule for installing the tanks."

Wastewater-Plant-2

On-site construction began in February 2016 under frigid conditions. Sub-freezing temperatures can impact the grouting and sealing process. Fortunately, precast panels can be set in the ground until there’s a deep frost, unlike cast-in-place concrete.

Because the original plant remained operational during construction, workers had to contend with space constraints. And making a safe conversion from the old system to the new one involved some tricky logistics.

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Tips to Minimize Concrete Consolidation Issues with Forming Projects

Posted by Hill and Griffith Company on Jan 14, 2021 5:38:43 PM

Avoid repair costs and aesthetic disputes in concrete forming projects by minimizing consolidation-related surface blemishes.

Article excerpt from the June 2012 issue of Concrete Contractor magazine

Honeycomb, subsidence cracks, cold joints and excessive surface air voids are common surface blemishes associated with ineffective concrete consolidation. In addition to being unsightly, formed surfaces with blemishes may not conform to the requirements of the contract documents. When this occurs, surface blemishes become defects and subsequently must be repaired. Along with the expense of repairing surface defects, it is difficult and sometimes impossible to make repairs match the color and texture of the surrounding concrete. By understanding the causes and using effective consolidation techniques, contractors can avoid repair costs and aesthetic disputes due to consolidation-related surface blemishes.

Concrete Bug Hole Porosity

Stages of consolidation

Consolidation using an internal vibrator occurs in two stages: 1) leveling and 2) de-aeration. During the first stage, concrete is temporarily liquefied due to the rapid oscillatory motion transmitted to the concrete by the vibrator. Due to the energy imparted to the concrete, coarse aggregate particles become suspended, large voids between aggregates fill with mortar and concrete settles due to gravity.

In the second, or de-aeration stage, the remaining entrapped air bubbles rise to the surface and escape, especially the large bubbles. It is not possible to remove all the entrapped air bubbles; however, vibration should continue until the cessation of large air bubbles occurs.

Use the largest and most powerful internal vibrator, systematically vibrate the concrete area through the full depth of the lift being sure to penetrate the previous lift, and limit the distance between insertions so the area visibly affected by the vibrator overlaps the adjacent just-vibrated area. Continue vibrating until the coarse aggregate particles become embedded, a thin film of mortar forms on the top surface and along the form faces, and large air bubbles stop escaping from the surface.

Also, listen to the pitch or tone of the vibrator. When the vibrator is first inserted into the concrete, vibrator frequency drops but then increases and finally becomes constant when the concrete is free of entrapped air bubbles.

Many times, untrained operators only level the concrete and fail to complete the de-aeration phase of consolidation resulting in unwanted surface blemishes. It is important for operators to understand the stages of vibration and indicators of well-consolidated concrete.

Surface air voids

Commonly called bug holes, surface air voids are small, regular or irregular cavities, usually less than 5/8 inch in diameter, caused by entrapment of air bubbles in the surface of formed concrete. Bug holes are normal for vertical cast-in-place concrete and not considered a defect unless voids exceed the maximum size specified by the contract documents.

Minimize bug holes by using: smooth, impermeable formwork; the thinnest coat possible of an appropriate release agent; limited lift thicknesses; high-frequency vibrators; and proper vibrating procedures with sufficient periods of vibration to de-aerate the concrete.

Honeycomb

Honeycomb occurs when mortar fails to completely fill the spaces between the coarse–aggregate particles leaving irregular voids or stony zones in the concrete. Typically, honeycombing occurs along the form face and in many cases is limited to the region between the form face and reinforcement. Causes include: congested reinforcement and narrow forms, insufficient paste due to segregation of the concrete, improper fine to coarse aggregate ratio, improper placement procedures (excessive concrete free fall and lift thicknesses), trying to place stiff and dry concrete, difficult construction conditions, and insufficient consolidation efforts.

Concrete Consolidation Honeycomb

Subsidence cracks

Sometimes called plastic settlement cracks, subsidence cracks occur when additional settlement or consolidation occurs after the freshly placed concrete has been vibrated and finished. Causes of delayed settlement include excessive bleeding and incomplete concrete consolidation. Cracks form in the plastic concrete because of some type of restraint that restricts concrete settlement. Subsidence cracking in columns and walls commonly occurs over fixed items such as tie bolts and reinforcement and in columns and walls where settlement is restrained by wedging or arching of the concrete. Deep concrete sections are more prone to subsidence cracking.

This form of plastic cracking can be minimized by using proper placing and consolidation procedures and essentially eliminated by re-vibration. Re-vibration is not harmful, can mend subsidence cracks and reconsolidate concrete after delayed settlement has occurred. If the vibrator can be inserted into the concrete and removed without leaving a hole, it is not too late to re-vibrate the concrete.

Cold joints

Cold joints are different than lift or layer lines. Lift lines occur when successive lifts of concrete are not completely knitted together. In many cases, lift lines occur because of color variations between loads of concrete and do not indicate there is a joint or discontinuity in the concrete.

In contrast, a cold joint is a discontinuity between two lifts of concrete. They occur when, due to a concrete placement delay, the earlier lift of concrete hardens sufficiently to preclude knitting and bonding of the two lifts. Except for the unsightly appearance, cold joints are typically not a concern unless the concrete is unreinforced or an environmental tank.

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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 and non-petroleum concrete form release, biodegradable releases, 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, Concrete Release Agents, Concrete Casting Supplies, Precast Concrete, Precast Concrete Form Release, Concrete Form Release, Concrete Constructor Magazine

Save Your Concrete Forms With Proper Use of Concrete Form Release

Posted by Hill and Griffith Company on Nov 19, 2020 5:58:44 PM

Concrete formwork is a major investment for a precast or prestress plant. Taking care of the forms extends form life and protects a valuable investment and contributes to a healthy bottom line.

Concrete-Form-Release-Agent-Application-1.jpg

Care of concrete forms needs to be considered every time they are used. Steel form damage can occur with lack of cleaning or with too much use of wire brushes and sandblasting. Vibrators can damage form surfaces.

Proper selection and application of release agents is necessary for lower cost, producing the best product possible and for minimizing form clean up.

Grifcote-Concrete-Form-Release-Agent-Sizes.jpg

There are two types of release agents but they can also be combined for some applications.

The first is the barrier type. They provide a barrier between the concrete and the form. Originally form oils were barrier types of diesel fuel, greases, used motor oil, etc. These produced a good release but lowered product quality by causing bug holes, and staining, resulting in poor product appearance. They hard to apply due to their high viscosity.

The second type of release agent is chemically active and react with lime in the concrete to produce a soap-like film on the form. This type of release agent is the most widely used. Because they are easily applied in a very stable thin film by spraying, wiping, or brushing, you can produce stain-free, void-free concrete surfaces even after the form has been exposed for a day or two. Reactive type release agents applied in a thin film allow the form to strip cleaner which saves on labor costs related to form cleaning and extends the life of the form.

Concrete-Form-Rust-Preventative.jpg

In September of 1999 release agent manufactures and concrete producers were required by the EPA to make and use limited VOC products. Some companies, including Hill and Griffith, saw this coming years in advance and were already producing VOC compliant products. Some states, such as California have stricter rules than that passed nationally.

There are four main application methods-spraying, wiping, mopping or brushing and dipping. Spraying is the most common method of application. Avoid over application to reduce your cost. An extremely thin film of release agent is all that is needed, "The thinner the better." Pump unit sprayers or centralized systems with air pressure regulators give a good consistent pressure and work well. Spray pressures of 35 to 50 psi are best. Higher pressures put more airborne particles in the air throughout the plant and can be harmful to personnel in the plant. Lower pressures cause puddling in the form, and wasted release agent. A flat fan spray nozzle of .1 or .2 gpm will spray a good thin release agent. Many of these thin, chemically active release agents are more expensive per gallon. But with coverage rates at 2000-2500 sq. ft. per gallon the cost is much less than a cheaper barrier release agent. A second type of application is wiping on the release agent. Architectural precasters like wiping the release agent on the form because over application is eliminated. Burial vault manufactures use a sponge for application because they clean the form each time as well. A third type of application is with mop or brush with which over application can be a problem. The mop or brush must be wrung out in order to achieve the desired results. Wipe up puddles. Dipping systems are fast, labor efficient, and assure total coverage of the form. And they collect the excess release agent that drains off the form.

The investment in forms needs to be protected from rust and corrosion, use grease, diesel fuel, or release agent. A better choice is a good rust preventative that offers quality protection, long life, ease of application, and easy removal.

Taking care of forms each time they are used can save thousands of dollars and make a concrete business more profitable.


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 Solutions, Concrete Casting Products, Concrete Casting Supplies, Precast Concrete, Gricote, Concrete Form Release

Concrete Form Removal Time, Specifications and Calculations

Posted by Hill and Griffith Company on Nov 12, 2020 5:07:24 PM

Excerpt from The Constructor

The removal of concrete forms also called as strike-off or form stripping should be carried out only after the time when concrete has gained sufficient strength, at least twice the stress to which the concrete may be subjected to when the forms are removed. It is also necessary to ensure the stability of the remaining forms during form removal.

Concrete Form Removal Time

The rate of hardening of concrete or the concrete strength depends on temperature and affects the form removal time. For example, time required for removal of concrete in winter will be more than time required during summer.

Special attention is required for form removal of flexural members such as beams and slabs. As these members are subjected to self-load as well as live load even during construction, they may deflect if the strength gained is not sufficient to handle to loads.

To estimate the strength of concrete before form removal, the tests on concrete cubes or cylinders should be carried out. The concrete cubes or cylinders should be prepared from the same mix as that of the structural members and cured under same circumstances of temperature and moisture as that of structural member.

When it is ensured that the concrete in the structural members has gained sufficient strength to withstand the design load, only then forms should be removed. The forms should be left for longer time if possible as it helps in curing.

Concrete Form Released After Curing

Removal of forms from the concrete section should not make the structural element:

  • Collapse under self load or under design load
  • deflect the structural member excessively in short or the long term
  • physically damage the structural member when the form is removed.

The following points must be kept in mind during form removal whether the structure will be prone to:

  • freeze thaw damage
  • cracks formation due to thermal contraction of concrete after form striking.

If there is a significant risk of any of the above damages, it is better to delay the removal time of forms. If forms have to be removed for optimizing the concrete construction activities, then these structures must be well-insulated to prevent such damages.

Calculation of Safe Form Striking Times:

Structural members are constructed based on designed load. But before a structure is complete and subjected to all loads assumed during structural design, the structural members are subjected to its self weight and construction loads during construction process.

So, to proceed with construction activities at a quicker rate, it is essential to calculate the behavior of structure under is self load and construction load. If this can be done and structural member is found to be safe, forms can be stripped-off.

If these calculations are not possible, then following formula can be used for calculation of safe form striking times:

Characteristic strength of cube of equal of maturity to the structure required at time of form removal

Form Removal Formula

This formula was given by Harrison (1995) which describes in detail the background of determination of form removal times. Another method to determine the strength of concrete structure is to conduct the non-destructive tests on structural member.

Factors Affecting Concrete Form Striking Times

The striking time of concrete forms depends on the strength of structural member. The strength development of concrete member depends on:

  • Grade of concrete – higher the grade of concrete, the rate of development of strength is higher and thus concrete achieves the strength in shorter time.
  • Grade of cement – Higher cement grade makes the concrete achieve higher strength in shorter time.
  • Type of Cement – Type of cement affects the strength development of concrete. For example, rapid hardening cement have higher strength gain in a shorter period than the Ordinary Portland Cement. Low-heat cement takes more time to gain sufficient strength than OPC.
  • Temperature – The higher temperature of concrete during placement makes it achieve higher strength in shorter times. During winter, the concrete strength gain time gets prolonged.
  • A higher ambient temperature makes the concrete gain strength faster.
  • Forms help insulate concrete from surroundings, so longer the forms remain with the concrete, the less loss of heat of hydration and rate of strength gain is high.
  • Size of the concrete member also affects the gain of concrete strength. Larger concrete section members gain strength in shorter time than smaller sections.
  • Accelerated curing is also a method to increase the strength gain rate with the application of heat.

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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."
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Hill and Griffith Customer Service

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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, Casting Solutions, Concrete Casting Products, Concrete Casting Supplies, Precast Concrete, Gricote, Concrete Form Release, The Constructor Magazine

Form Coatings and Mold Linings

Posted by Hill and Griffith Company on Nov 5, 2020 1:02:16 PM

Excerpt from the book, Formwork for Concrete Structures by Kumar Neeraj Jha

Mold surfaces of wood and steel in due course, after repeated use, warp and rust, respectively, making the molds unserviceable if unprotected. It is common to treat the sheathing materials with some coating or release agent for easy removal. Only a few special form face materials, such as expanded polystyrene, do not need release agents.

The coating or release agents are temporary coatings and composed of fatty acids that react with the alkali in cement. The reaction produces a soap-like substance on the contact surface, which helps remove forms easily. Coating agents can also help enhance the mold life. The form surface remains smooth, provides good abrasive resistance, makes the wooden surface moisture resistant and retards the rusting of steel.

Concrete Release Agents

 

There are many release agent chemical compounds that have been developed for use as the coatings for wood and steel. It is, therefore, important to select the right one.

The three most common types of release agents are:

1. Neat oils with surfactants: mainly used on steel faces, but can also be used on timber and plywood.
2. Mold cream emulsions: for use on timber and plywood – a good general-purpose release agent.
3. Chemical release agents: can be used on all types of form face recommended for all high quality work.

These release agents could be oils, emulsified wax, oil-phased emulsions with water globules, petroleum-based products, catalyzed polyurethane foam, etc. Waste oil is also used as a release agent.

The type of composition of the coating or release agent depends on the following:

1. type of sheathing materials
2. conditions under which it is applied
3. type of concrete
4. finish quality
5. form area
6. ease of application

Concrete_form_release_application_1

The primary objective of the coating and release agents is to ensure easy removal of the form material without damaging the form and concrete. The concrete surface should also not get any stain from the application of release agents. It should be possible to apply the form release agent in an even manner on the form surface. The form release agent should not react with the concrete and produce some undesirable substance in the process.

Coatings on all type of forms are employed with the following objectives:

1. Protection of the form for durability
2. On timber, it reacts with organic constituents and provides a uniform surface on each use. Penetration of the chemicals helps control grain or edge effect as well as fill pores in the wood.
3. Chemically active coating reacts with free lime from the fresh concrete and produces water-insoluble soaps. When dried, these soaps act as positive concrete release agents. When wet, they help move air voids along the form.

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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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Product Samples

We are pleased to provide samples in quantities large enough to allow you to "try before you buy."
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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, Casting Solutions, Concrete Casting Products, Concrete Casting Supplies, Precast Concrete, Concrete Form Release for Wood, Gricote, Mold Releases and Release Agents, Concrete Form Release

Using Concrete Form Release Properly Can Save Your Forms

Posted by Hill and Griffith Company on Oct 28, 2020 4:39:24 PM

Concrete formwork is a major investment for a precast or prestress plant. Taking care of the forms extends form life and protects a valuable investment and contributes to a healthy bottom line.

Concrete-Form-Release-Agent-Application-1.jpg

Care of concrete forms needs to be considered every time they are used. Steel form damage can occur with lack of cleaning or with too much use of wire brushes and sandblasting. Vibrators can damage form surfaces.

Proper selection and application of release agents is necessary for lower cost, producing the best product possible and for minimizing form clean up.

Grifcote-Concrete-Form-Release-Agent-Sizes.jpg

There are two types of release agents but they can also be combined for some applications.

The first is the barrier type. They provide a barrier between the concrete and the form. Originally form oils were barrier types of diesel fuel, greases, used motor oil, etc. These produced a good release but lowered product quality by causing bug holes, and staining, resulting in poor product appearance. They hard to apply due to their high viscosity.

The second type of release agent is chemically active and react with lime in the concrete to produce a soap-like film on the form. This type of release agent is the most widely used. Because they are easily applied in a very stable thin film by spraying, wiping, or brushing, you can produce stain-free, void-free concrete surfaces even after the form has been exposed for a day or two. Reactive type release agents applied in a thin film allow the form to strip cleaner which saves on labor costs related to form cleaning and extends the life of the form.

Concrete-Form-Rust-Preventative.jpg

In September of 1999 release agent manufactures and concrete producers were required by the EPA to make and use limited VOC products. Some companies, including Hill and Griffith, saw this coming years in advance and were already producing VOC compliant products. Some states, such as California have stricter rules than that passed nationally.

There are four main application methods-spraying, wiping, mopping or brushing and dipping. Spraying is the most common method of application. Avoid over application to reduce your cost. An extremely thin film of release agent is all that is needed, "The thinner the better." Pump unit sprayers or centralized systems with air pressure regulators give a good consistent pressure and work well. Spray pressures of 35 to 50 psi are best. Higher pressures put more airborne particles in the air throughout the plant and can be harmful to personnel in the plant. Lower pressures cause puddling in the form, and wasted release agent. A flat fan spray nozzle of .1 or .2 gpm will spray a good thin release agent. Many of these thin, chemically active release agents are more expensive per gallon. But with coverage rates at 2000-2500 sq. ft. per gallon the cost is much less than a cheaper barrier release agent. A second type of application is wiping on the release agent. Architectural precasters like wiping the release agent on the form because over application is eliminated. Burial vault manufactures use a sponge for application because they clean the form each time as well. A third type of application is with mop or brush with which over application can be a problem. The mop or brush must be wrung out in order to achieve the desired results. Wipe up puddles. Dipping systems are fast, labor efficient, and assure total coverage of the form. And they collect the excess release agent that drains off the form.

The investment in forms needs to be protected from rust and corrosion, use grease, diesel fuel, or release agent. A better choice is a good rust preventative that offers quality protection, long life, ease of application, and easy removal.

Taking care of forms each time they are used can save thousands of dollars and make a concrete business more profitable.


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 Solutions, Concrete Casting Products, Concrete Casting Supplies, Precast Concrete, Gricote, Concrete Form Release

How Precast Concrete is Made

Posted by Hill and Griffith Company on Oct 22, 2020 3:23:17 PM

A case study in reinforced concrete

Excerpt from the November 2016 article on BuildingSolutions.com

Precast concrete structures are manufactured in a factory then delivered to a job site, ready to be installed. But, have you ever wondered how precast concrete products are made? In this video, you’ll get a behind-the-scenes look at one of our Oldcastle Infrastructure, a CRH Company, plants and gain first-hand experience on the manufacturing process.

Precast concrete structures are used in many types of construction and for many different purposes, including electrical and communication utilities, stormwater storage and conveyance, wastewater applications, bridges, building structures, and more.

There’s good reason for using precast concrete – it provides many benefits on a project, including quick and easy installation since there are no on-site forms to construct or waiting for the concrete to cure in the field, improving job site safety by decreasing the amount of time an excavation is open, and providing a high-quality, higher-strength product since it is produced in a controlled environment.

How Precast Concrete is Made

Engineering & Design

The process starts with engineering. On each project, a design engineer or owner (such as a Department of Transportation, DOT) sets requirements for their precast components. When we get the drawings and requirements, every product is engineered in-house according to the design engineer and owner’s specifications.

The engineers ensure each precast structure has the appropriate steel reinforcement (rebar) and meets the structural requirements for the area in which it will be installed. Some important considerations include the soil type, whether the precast structure will be adjacent to a building or other structure, and the water table of the area.

Once the calculations are complete, the drafting team creates detailed drawings. These drawings, called submittals, are then sent to the design engineer or owner for approval. When the submittal drawings are approved, the engineering and drafting teams create production drawings sent to the factory floor and used to manufacture the product. The production drawing set includes a bill of materials, or BOM, which includes all the components that go into the product, including sizes and lengths of each piece of rebar and how much concrete (measured in cubic yards) will be used.

Prepping the Rebar Cage

When the production team receives the drawings, the first step is to assemble the rebar cage. To do so, they must cut all rebar to the appropriate lengths according to the BOM and then bend and tie them together. Rebar wheelchairs, sometimes called wagon wheels, are round plastic components that hook onto the rebar and ensure it is properly positioned inside the walls of the precast product – not too close to either side of the wall – matching the engineer’s design and meeting the structural requirements.

Prepping the Form

While the rebar cage is made, another team preps the forms. This team reviews the drawings to see if the structure has any openings or knockouts and places foam inserts (removed after the concrete cures) into the form.

Openings are used where pipes connect or where other junctions are needed. Knockouts are thinner wall sections which allow openings to be “knocked out” in the field once the subcontractor knows where electrical conduit or communication lines would enter the vault. These inserts, along with the proper lifting hardware, are embedded and secured to the form so they don’t move when the concrete is being poured.

Next, the team applies a form oil used to ensure the concrete releases easily from the form after curing. Finally, the rebar cage is lifted using a crane and is lowered down into the form. Before concrete can be poured, each product undergoes a pre-pour inspection by a certified quality control technician to ensure it conforms to the production drawings. Once approved, the technician signs off and flags the form, indicating approval to pour the concrete.

Read More


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 and non-petroleum concrete form release, biodegradable releases, 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, Concrete Release Agents, Concrete Casting Supplies, Precast Concrete, Precast Concrete Form Release, Concrete Form Release

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