Formwork, the temporary or permanent molds used to hold wet concrete until it sets, is a crucial element in concrete construction. Just as important is selection of the right formwork because it greatly affects the schedule, labor requirements, quality, and total cost of a project.

Concrete formwork access platforms for the Hoover Dam Bypass Bridge piers featured custom brackets.

Over the years, formwork molds have evolved from traditional job-built timber to pre-engineered systems composed of a combination of steel, aluminum, manufactured timber, plywood, and plastics. These advancements in formwork molds have led to increased jobsite production and safety, with less labor, while producing a better finished product.

Formwork trends
Less than 15 years ago, there were approximately a dozen major formwork systems readily available in the United States. However, during that short time period, an influx of European forming companies entered the U.S. market, more than doubling the number of systems available.

The increase in competition is pushing innovations to a rate previously unseen in the industry. Thirty-year-old systems that have enjoyed wide use and popularity are being supplanted by new, modern systems that offer greater productivity and a higher quality product.

Presently, the most prevalent system in use for handset wall forming are steel-framed, wood-faced panels that require consumable ties at 2-feet-on-center and one connection per square foot. These are being replaced with larger, two-person handset systems that require less labor and eliminate consumable purchases with the use of reusable taper ties. Gang forming has completely changed during the last 10 years. Older systems of steel-framed wood or steel-faced panels with double channel stiffbacks that connect with bolts/pins have been overtaken by clamp connection forms with wood or plastic form faces that provide tremendous labor savings in assembly and use. These standard systems assemble and reconfigure very quickly to meet changing structure dimension while also providing a consistent concrete finish.

Unique formwork challenges are faced every day. In one of the most outstanding cases, the Hoover Dam Bypass Bridge — also known as the Mike O’Callaghan-Pat Tillman Bridge — required several innovative formwork solutions from Doka and the general contractor, Obayashi. Doka supplied the Framax framed formwork system to pour the large anchor footings for the cranes. This equipment then was moved over the canyon’s edge and reused to pour the pier footings and abutments. Later, the first of the two skewbacks was poured on the Nevada side and the forms were flown across the canyon in large sections. This quick move saved the contractor the cost of multiple sets of forms.

The skewback footings presented Doka with a unique challenge because of the sloped face of the structure and the requirement for rebar penetrations to anchor the concrete arches. The design required the general contractor to support the forms for the sloped face using sacrificial steel posts inside the footings. To aid in placement of the Framax framed formwork on the sloped face, the design solution included a continuous row of hinged corners that allowed the forms to be clamped while being held vertical by the crane and then laid into position. These were all creative solutions that allowed for the safe, efficient completion of a historic structure.

Selecting the right formwork
Because conditions vary for each project, there is no simple formula for choosing the right formwork supplier or system. Formwork typically accounts for 40 to 60 percent of the total cost of a project’s concrete frame. These percentages include the cost of material and labor, with the largest cost for labor. It is important to analyze labor costs thoroughly because this is the bigger number and reducing this number will have a much greater impact on bottom-line costs.

To help determine the most efficient solution for a project, a contractor will evaluate several forming systems. As available and capable labor shortages continue in the construction marketplace, it has become even more important to select the right forming system. Simply stated, a contractor has two choices: an inexpensive forming material that is labor-intensive or a forming system that is more expensive, but provides high productivity, built-in safety features, and is more labor efficient.

Other factors the contractor will evaluate when choosing a formwork system include:

• Is the required material readily available? Does the supplier manufacture the material or purchase it from another company?
• Can the formwork supplier pre-assemble some or all of the formwork prior to delivery? This can reduce rental cost, save labor requirements, and minimize assembly area requirements.
• Does the supplier provide onsite field service to train and reduce the learning curve of the formwork crew?
• How safe is the system to install, use, and dismantle? Can the forms easily be climbed and are tie-off points built into the system where required?
• What experience does the firm have with your type of project?
• Does the supplier offer engineering services? Will the supplier provide formwork assembly drawings specifically for the project or only provide general drawings of the system?

Another consideration is whether to purchase or rent a system. This decision should be based on the duration of the project and the overall strategy of the construction company. Typically, if a form system has to be rented for more than eight to 10 months, purchasing the system might be more economical. However, along with the purchase of a system, there are additional costs such as maintenance and storage. Some formwork companies, however, offer services for customers who purchase their equipment.

Formwork is in place for the concrete pier caps of the Hoover Dam Bypass Bridge.

The quality of the product also must be considered in the decision-making process. Steel-framed wall formwork with standard plywood facing will require more maintenance and repair throughout the life of the form than hot-dipped galvanized steel frames with specially manufactured plywood designed for longer life.

Forming a relationship
In order to consider formwork in the overall design, it is important for the structural engineer to have a good handle on the standard products available in the marketplace. This can be accomplished by contacting the major formwork suppliers. They are more than eager to provide assistance to educate the industry on forming products available and how the structure’s design affects overall costs.

Contacting formwork suppliers at the very early design stage of the project can allow for as much information as possible to be incorporated into the bid documents, which will provide a more accurate cost to the owner. Formwork suppliers can advise on sizing structural concrete members to meet standard form dimensions. And, because major form suppliers typically are involved in a large number of projects in a wide variety of construction markets, they can draw upon their resources to suggest formwork means and methods.

Also of importance is to ask concrete-forming contractors to be involved early in the design stage of the structure. They are ultimately the people who will be physically constructing it and can provide a tremendous amount of knowledge as to the most economical means and methods.

There are many considerations to take into account at the design phase, and considering formwork is of prime importance. Product quality, material and labor costs, and worker safety are all part of the total cost of forming. With better, faster, and safer formwork available, designing for the formwork is a crucial component to ensuring the success of an economical concrete construction project.

Michael Schaeffer, senior manager at Doka USA Ltd., is responsible for national sales management, Northeast/Mid-Atlantic area management, sales/product training, product development, and marketing support. He can be contacted at michael.schaeffer@doka.com or 201-853-0553.