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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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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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Bulletins and Technical Papers for Concrete Casting Products 

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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.

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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

Double Curved Concrete Surface

Posted by Hill and Griffith Company on Oct 15, 2020 5:02:06 PM

A case study in reinforced concrete

Excerpt from the May 2018 issue report by Luis Pedro Sarmento Esteves and Goncalo Castro Henriques

This paper deals with digital integration between design and fabrication in order to construct a complex double-curved concrete surface. This research focuses on the practical application of CNC technology to polyurethane (EPS), as an alternative to concrete formwork. The influence of specific EPS properties as deformability under compression, water tightness and finish on concrete pre-fabrication was analyzed. This enabled high flexibility of architectural forms and textures, integrated in structural elements. Limitations were found on the mold reuse for several elements.
 

1. Introduction

Since industrialization, construction of complex non-standard structures in concrete considerably diminish. These structures became less common due to the lack of construction and design processes capable of generating viable concrete elements and shapes, according to the mass production of elements in series. Specialization and a lack of collaboration between architecture, engineering and material science led to segregation of investigation on the field. Concrete structures are usually narrow and integrate production techniques that are optimized for linear elements. When facing more complex forms, concrete is seen as a non-flexible material, which is bonded to limitations of molding options and solutions.

Double Curved Concrete Surface

Buildings like the "Sagrada Família" designed by Gaudí in 1926, seem difficult to attain or complete due to the economic restraints and skill limitations of the workers. Recently with the digital revolution, CAD-CAM (computer aided design, computer aided manufacture) technologies offer us the possibility to regain a new integration of disciplines, Kieran (2004). The building "Zollhof Towers" (2000) in Dusseldorf, by Frank Gehry was overlooked as a practical example of the use of different pre-cast panels built off the site.

In this case study, we developed a complex double-curved surface in concrete, and the CAD-CAM process integrated design, engineering and fabrication. Data flow in a non-linear process accompanied all the stages from conception until the final product was made.
 
We used two molds to pre-cast the double-curved surface in self-compactable concrete. The molds were milled with the help of a CNC four axes machine that translated the data in 3D trajectories and made successive paths, subtracting material until obtaining the desired form. After that, they were filled with concrete and dried in the mold to gain resistance.
 
The digital integration can provide a shorter production process and the integration of disciplines engaged in collective intelligence. One could start to think about a building information model to be used by the collaborating disciplines, Kolarevic (2005). With the development of parametric design, fabrication and materials science integrated with digital collaboration, a wider range of solutions will be available. From this, a different logic of production is derived regarding the limitation of mass production, the mass-customization:
 
"Things used to be made to order and made to fit. But they were labor-intensive and expensive. Mass production came along and made things more affordable, but at a cost of the sameness, the cost of one-size-fits-all.
 
Technology is beginning to let us have it both ways. Increasingly we're getting more personalization at mass production prices. We’re moving towards mass customization," McTeer (1998). This new situation enables us to think of complex concrete structures, in a differentiated pre-fabrication process where choice is present.

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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

3D-Printed Tooling Offers Durability for Precast Concrete

Posted by Hill and Griffith Company on Oct 8, 2020 4:24:36 PM

As an alternative to wooden tooling, 3D-printed forms for precast concrete are proving to be more durable and better able to support a large-scale renovation project.

Article excerpt from the May 2018 issue of Additive Manufacturing by Stephanie Hendrixson

There are certain applications today where 3D printing makes sense. An injection molder might choose to print a small batch of plastic parts that would be cost-prohibitive to mold. A machine shop might invest in a 3D printer to make jigs to aid in inspecting short runs of parts. A service bureau might rely on 3D printing for product development work, as a way to make prototypes quickly and easily.

What these scenarios have in common is that 3D printing makes it easier to produce a small, custom quantity: A few dozen parts, a couple of temporary fixtures, one prototype. There are exceptions, but manufacturers today don’t necessarily see 3D printing as the solution for repeatable, high-volume jobs.

Precast Concrete Made with 3D-Printed Forms


One of those exceptions is proving to be the precast concrete industry. Gate Precast, a supplier of precast structural and architectural concrete, is finding that 3D-printed tooling is exactly the right solution for a job requiring high repeatability over many concrete pours: manufacturing hundreds of punched windows for the façade of a 42-story building in New York City. For this large-scale project, 3D-printed forms have proved their worth in terms of faster lead times, increased durability and better quality in the end product.

Precast Concrete 3D Printed Form

Enter 3D Printing

Gate Precast manufactures precast concrete in nine locations nationwide. Some of these facilities focus on structural concrete—weight-bearing items like the beams and columns that make up parking garages—which is produced with metal forms, often in very large quantities. Others, like its Winchester, Kentucky, plant, specialize in architectural pieces that are typically made in smaller batches.

For most jobs, the Winchester plant builds its own concrete forms from plywood and fiberglass through an in-house carpentry department. These forms are not highly durable, but they don’t need to be. A wood form will start to break down, typically after 15 to 20 castings. But for a typical job where only 5 to 10 castings might be needed, this is no problem. It’s larger jobs that are the challenge when multiple forms must be built to support many concrete pours—which is where 3D printing comes in.

Pouring Concrete with a 3D-Printed Form

In practice, pouring concrete with a 3D-printed form is not much different from pouring with a wooden one. The windows are typically cast three together on top of a large platform in Gate Precast’s Winchester facility. The 3D-printed forms actually represent the front and inner sides of the window cavities, with the outer edges formed by removable plywood walls. Both the forms and sides are treated with a form release oil to help with the unmolding process.

Although they are not structural features, the punched windows still require reinforcement in the form of rebar, which helps to support the windows during stripping and shipping. The rebar is set into the empty form before the pour, along with lifting inserts and tiebacks that will serve to enable shipping, lifting and eventually hold the windows onto the building.

An overhead crane carries buckets of concrete to the platform; it takes about three buckets of concrete to fill one of the three-window forms, Schweitzer says, with each concrete cast weighing 20,000 to 30,000 lbs. depending on the profile. The pour stops periodically to allow the platform to vibrate and consolidate the concrete around the rebar, removing any air pockets from the face. Once the form is filled, workers manually smooth the top surface of the concrete (which will be the back of the windows) and clear the areas around the lifting and tieback inserts.

Inspecting Precast Concrete

Concrete pours take place each day in the afternoon, and then cure for 12 to 14 hours. The plywood walls are stripped from the cast first, and then the concrete pieces are lifted from the forms around 3 a.m. each morning. Each window frame is manually cleaned with an acid wash spray that exposes the sand in the mix. Then, some of the front faces are polished to expose the sand and aggregate. The resulting finish sparkles—quite intentionally—like sugar cubes.

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Cleveland Rocks: Precast Concrete

Posted by Hill and Griffith Company on Oct 1, 2020 4:44:51 PM

Allega Cos. answers Corps contract commanding nearly 120,000 tons of wave-worthy precast

Article excerpt from the January 2017 issue of Concrete Products

A weather front emanating from Superstorm Sandy in October 2012 tested infrastructure well inland of metro New York and New Jersey, the area hardest hit by precipitation, wind and storm surge. Among federal and state agencies contending with long-term responses to Sandy-level exposure is the U.S. Army Corps of Engineers Buffalo District. It capped the 2015 and 2016 construction seasons closing repair and upgrade contracts—Oswego Harbor Detached Breakwater, New York; Cleveland Harbor East Breakwater, Ohio—using non-proprietary precast concrete structures known as dolosse, in tandem with limestone or granite armor block.

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District engineers outlined finished structure air content, flexural and compressive strength, plus surface quality specifications for respective Oswego and Cleveland project precasters, Lakelands Concrete Products of Lima, N.Y., and Allega Cos. of Valley View, Ohio. Both determined that highly fluid, self-consolidating mixes are the best solution for accelerated production of structures that will be submerged or subject to frequent Great Lakes wave exposure through a service life plausibly extending into the next century. Early indicators suggest the dolosse installations contribute to a Corps roster proving the efficacy of SCC for structures prone to extreme weather or temperature events, sharp freeze-thaw cycles, and rare, but catastrophic loads.

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Dolosse resist breakwater or shoreline erosion from waves and undercurrent through their mass and energy-dissipating geometry. Known as dolos individually, the monolithically cast structures comprise three members of octagonal cross section: Uniformly sized shanks connect fluke ends. The latter are flared, tapered members running in opposite directions, along X and Y axes. Dolosse are fabricated in four- to 16-ton sizes, sans lifting hardware, and placed by sling so each structure interlocks such that even the most forceful waves or undercurrents meet long plain or reinforced precast concrete chains of inordinate tonnage.

The Corps Buffalo District used a formula factoring statistical 20-year wave height and 10-year water level to determine 16-ton and 6.5-ton dolos sizes for the New York and Ohio installations. Located near the southeastern corner of Lake Ontario and serving the first U.S. port from the St. Lawrence Seaway, the upgraded Oswego Harbor structure marks the District’s first use of 16-ton dolosse. Lakelands Concrete fabricated 997 of the 11-ft. long structures with conventional reinforcement (Concrete Products, July 2015). The dolosse represented the bulk of a $19 million contract Michigan’s Durocher Marine completed in November 2015.

Slightly trailing the New York engineering and casting schedule were preliminaries for the much more ambitious Cleveland Harbor work, centered in Lake Erie about two miles east and one-half mile north of downtown Cleveland. Buffalo District engineers specified the 6.5-ton dolosse, plain and 8.3-ft. long, for 4,400 feet of breakwater structure, which sustained more than $31 million in damage attributable to the Superstorm Sandy-spurred weather system. The Corps found that the intensity of the winds over Lake Erie created extraordinarily rare waves, measured at nearly 18 feet offshore of Cleveland.

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Cincinnati's State-of-the-Art West End Stadium Progresses

Posted by Hill and Griffith Company on Aug 13, 2020 12:21:28 PM

Exerpt from the June 2020 issue of Construction Equipment Guide by Cindy Riley

Construction crews in Ohio are working to complete a $250 million project created to bring an unprecedented fan experience to Cincinnati. Designed by the renowned architecture firm Populous, West End Stadium will serve as the home field of FC Cincinnati of Major League Soccer (MLS).

"West End Stadium will be Cincinnati's newest sports stadium, and the anchor for neighborhood revitalization in the West End, as the city continues its remarkable renaissance," said Lizz Summers, FC Cincinnati vice president of communications. "A world-class venue with a design unlike anything in North America, West End Stadium will have clear and close views from every single seat in the building.

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"The fan experience is central to the design of the building, creating an intimate atmosphere that will create a true home field advantage for FC Cincinnati. With considerations also made to accommodate other events, both sporting and cultural, West End Stadium is set to become a key destination for patrons from all over the Midwest."

According to Summers, West End Stadium is envisioned to be the jewel in the Queen City's crown.

"With a fan-forward strategy, the stadium will draw eyes and attention to Cincinnati. Soccer is a global game, and West End Stadium will provide a platform to bring Cincinnati to people around the world. MLS is already broadcast in more than 170 countries, but when you then layer in national team games, international friendlies and other cultural events, Cincinnati will gain global attention. With the growth of corporate business and acclaimed cultural enterprises here in the city, we believe that West End Stadium will become another attraction that sets Cincinnati apart from other similar cities."

Jeff Berding, FCC president, had a vision for what FC Cincinnati could mean to the area.

"First, launching the club as a minor-league franchise and realizing that it would not only succeed, but flourish and set new business and on-field standards was rewarding and eye-opening for the entire region," said Summers. "It was a source of immense pride for an area that truly embraces hard work and community success. The resounding success of Jeff's vision helped launch FC Cincinnati into Major League Soccer in record time. Now, after the long hours, hard work and collaboration to get the stadium project approved and under way, seeing West End Stadium rise so quickly out of the ground and take shape is really inspiring.

"The club is very excited about the lighted fin structure that will make up the external skeleton of the facility. Each fin will have an LED light system built into it that, when programmed, will allow animation and motion graphics to appear on the east side of the building. It will be unique to any sports facility in North America, and is being prepared by SACO, the same company that installed the system on Burj Khalifa in Dubai."

 

The entire east side of the stadium is designed to serve as an entryway to the community. A grand staircase will lead to the main gates through a large open plaza. Both the northeast and southeast corners of the stadium also will serve the community, both with open, programmable areas and the largest team store in the city and Major League Soccer.

 

"The project team also is being considerate and thoughtful in the smaller touches throughout the stadium, including seating choices in every section and design themes in the four premium clubs and suites, as well as concourse layout and design to accommodate the 26,000 fans who'll be on site for each event," said Summers.

 

The owner's representative is Machete Group, while Turner Construction serves as the general contractor.

"To this stage, we've had two main challenges, but both have really boosted the project to make it better," said Turner Construction project manager David Bareswilt. "The first was collaborating with the city, county, state and the two immediate neighborhoods to gain project buy-in and approval so quickly. We worked hard to put a great community benefits agreement in place with the West End, unlike any other sports project in the city, to help ensure our actions and intentions of being a supportive citizen in our new neighborhood. We've received a lot of tremendously positive feedback from the overall West End neighborhood about our commitment and actions to support the revival of the West End.

"The other major challenge was that we changed architects midway through the design work and after site work began, but as Populous came on board with Jonathan Mallie as the lead architect, we worked hard to make a lot of really amazing adjustments and changes to reach the point we're at today. When it opens, through so much hard work from a tremendously dedicated stadium staff, the stadium is going to be world-class and garner worldwide attention. We're really excited about that, and it will make not only the city exceptionally proud, but make all the hard work worth the end product."

Site work began in the summer of 2018. After the completion of the high school football season, workers were able to deconstruct the existing high school stadium and stage the formal groundbreaking on Dec.18, 2018. MLS Commissioner Don Garber was among the attendees.

Now that all steel work for the lower bowl is complete, Turner is working on construction of the upper bowl and structure, including work on the canopy roof. Steel work for the 360-degree roofing system is expected to be complete in early July.

 

Simultaneously, concrete work is being performed on flooring levels. Fireproofing and other internal work is being carried out throughout the stadium non-public and team campus areas, and the precast is being installed in the lower bowl, with the upper bowl set to start installation.

 

Weather has not been a major factor, to date.

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.

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.
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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, Construction Equipment Guide

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