By Sue McCraven
Billions of dollars in economic stimulus funding have been approved for new infrastructure projects in the United States and Canada. A resuscitating infusion of state and federal money will be spent this year and next to repair and rebuild roads and bridges and to jump-start a number of renewable energy initiatives. What potential public projects provide the greatest opportunity for newly developed precast concrete systems? Which materials will be given priority for public funding, and why? This article presents some of the most promising precast concrete technologies for building a more durable and environmentally friendly infrastructure.
Projects to receive stimulus funding
In Washington, D.C., hundreds of billions of dollars in stimulus bill funds have been enacted since the beginning of 2009. Canadian government officials also expect to spend nearly $20 billion on infrastructure construction. While not meant to be inclusive, here are some of the infrastructure projects with potential precast concrete applications that are included in the $787 billion American Recovery and Reinvestment Act (ARRA) signed into law in February by President Obama:
- $10 billion to modernize a failing national electric grid and transmission facilities for renewable energy;
- $48 billion for transportation infrastructure, including bridges and roads;
- $22 billion to construct energy-efficient public housing retrofits and weatherizing;
- $6.7 billion to renovate federal buildings with energy-efficient systems;
- $3 billion for homeland security and military applications;
- $14 billion in tax breaks for wind and solar electricity with a grant program to help finance projects; and
- 30 percent federal tax credit for eligible renewable energy construction projects.
New precast technology fits the (stimulus) bill
Precast concrete systems have significant advantages over competing materials (cast-in-place concrete, steel, plastic) for building infrastructure projects that are energy efficient and environmentally friendly. Advantages include: local labor and materials; plant-fabricated quality and consistency; long service life; durability and low maintenance; rapid installation and minimum site disruption; recycled components; light weight for lower transport costs; impact resistance; exceptionally strong Ultra-High Performance Concretes (UHPC); product availability and stable market pricing; proven performance record; and remarkable material flexibility in form and function.
Precast applications for infrastructure stimulus funding could include:
- Durable precast concrete bridge and pavement systems offering long service life and rapid installation;
- Lightweight, strong precast UHPC components for hundreds of miles/kilometers of new high-voltage transmission towers and FHWA and DOT pavement and bridge projects;
- Insulated precast wall panels for energy-efficient buildings;
- Precast concrete components with recycled materials, white cements for solar reflectance, and numerous material and design LEED (Leadership in Energy and Environmental Design) points;
- UHPC blast-resistant precast solutions for public security and military installations;
- Precast concrete systems that offer high availability with stable pricing, lower transport cost, and proven strength and durability for repetitive infrastructure use – as compared with competing materials like steel, timber and plastic; and
- Precast concrete wind turbine tower sections.
FHWA instituting precast pavement solutions
The U.S. Federal Highway Administration (FHWA) recently published two technical briefs on the use and application of precast pavement slabs. One of these focuses on Precast/Prestressed Concrete Pavement (PPCP) while the other features a summary of the development of Jointed Precast Concrete Pavement Slabs (JPCPS). Both briefs present a condensed synopsis of how these products are used for repair, rehabilitation and construction of rigid pavements. For simplicity we will use AASHTO Technology Implementation Group’s (TIG) broader acronym, PCPS (Precast Concrete Pavement Slabs) to include both systems.
“Generic specifications have been developed for the design, fabrication and construction of PCPS,” says Timothy LaCoss, FHWA pavement and materials engineer. “An excellent primer outlines the uses, applications and benefits of PCPS.” These documents can be found at www.aashtotig.org via the Precast Concrete Pavement Slabs link under the Active Projects dropdown.
In New York where LaCoss works, as well as in other states, DOTs were putting together “shovel-ready” projects that were let and awarded by early spring 2009 (visit the government’s site to current information on ARRA projects). According to LaCoss, many of these projects, funded by ARRA, “focus on improving the condition of existing pavements” as well as a significant amount of projects “focused on bridge repair, rehabilitation and replacement projects that are shovel ready.”
With the ARRA funding in addition to yearly appropriations to state DOTs, FHWA engineers expect to see a surge in spending for transportation infrastructure projects over the next 12 to 18 months.
Why are PCPS systems becoming more competitive with traditional cast-in-place concrete and asphalt paving? “Speed and phasing of construction are critical to minimize lane closure time and, because safety is a primary driver of accelerated construction practices, precast concrete technologies often provide the means to accomplish these goals,” explains LaCoss. Beyond offering safe and fast installation, precast concrete quality means performance, durability, low maintenance and long service life – all critical elements in FHWA and DOT material selection decisions.
Which states are using PCPS or plan to install them in 2009? It is clear that there is significant interest in precast pavement solutions. In states like New York and New Jersey, where lane restrictions allow contractors only a five-hour occupancy window, PCPS are becoming institutionalized as pavement treatments. Delaware, California, Utah and Virginia will begin utilizing PCPS in 2009. Nevada, Utah, Florida, Illinois and Minnesota have expressed a strong desire to try PCPS. Iowa DOT has successfully completed two replacement bridge approach slabs using a modified PCPS approach. LaCoss believes that the economic climate for precast rigid pavements has improved with ARRA funding and that state DOTs will include PCPS options in evaluating their transportation needs.
PCPS systems available to the precaster
There are a number of avenues precasters can use to become involved in this product depending upon what specification the DOT of a particular state chooses to use.
Currently, three proprietary systems have been developed: The Fort Miller Co. Inc.’s Super-Slab JPCPS System that uses standard load-transfer dowels and tie bars for slab interlock; Uretek USA PCPS & Stitch-in-Time Load Transfer Mechanism; and Hawaii-based Kwik Slab Inc. that employs a proprietary load-transfer coupling. Precasters should learn about licensing and project outcomes for each system.
Precasters may also elect to use nonproprietary systems such as the Full-Depth Repair/Dowel Bar Retrofit system (commonly referred to as the Michigan Method) that was developed at Michigan State University and piloted by Michigan DOT as described in FHWA technical briefs. Applications of this system have used a variety of bedding and load-transfer techniques. In selecting a system, precasters should carefully evaluate which techniques were successful and met, or exceeded, the AASHTO performance criteria.
Lastly, precasters may choose to use the FHWA-sponsored precast/prestressed concrete PPCP system. Precasters should recognize that because this is not a jointed pavement system, they need to become familiar with the benefits and complexities of fabrication and installation before adopting it.
Rapid “shovel-ready” projects ideal for precast pavements
“We are seeing an uptick in orders for precast pavement for this year and next as well as a general increase in interest in the concept for projects in 2010 and beyond,” reports Peter Smith of Fort Miller.
To be specific, by the end of 2008, our orders totaled about eight lane miles of precast pavement since we began production in 2001. We are providing about eight lane miles in 2009 alone.” Most of Fort Miller’s orders are for state DOT projects in New York and New Jersey, but they will also be providing slabs for projects in Virginia, Utah, California and Ontario.
“Right now, because of the stimulus money, the big emphasis is on ‘shovel-ready’ projects,” says Smith. “Pre-engineered precast pavement systems are ideal for this type of project. They are particularly well-suited for maintenance projects, since they can be incorporated in contract documents with a set of specifications and a table of repair locations.”
Templates of specifications that can be made state-specific are readily available on the TIG link. A simple table of repair locations is relatively easy for state engineers to compile; completion of both of these items does not require a lot of time-consuming, up-front engineering time.
In illustrating how quickly a “shovel-ready” process can be accomplished, Smith says: “In early February 2009, Utah DOT developed a new specification to include a proven pre-engineered precast system for a project on I-15 near Ogden that was bid on February 24, just a few weeks later. Maintenance of traffic and other specifications for the project were developed prior to February.”
Innovative HPC bridge solutions
Under the Intermodal Surface Transportation Efficiency Act (ISTEA), the FWHA encourages state DOTs to use high-performance materials through the Innovative Bridge Research & Construction Program (IBRCP). Funding for state building projects with optimized materials is provided by the IBRCP.
FHWA’s High Performance Concrete Technology Delivery Team (HPC TDT) continues to motivate state DOTs to build more economical and durable bridges. One of the HPC TDT’s goals is to establish HPC as standard practice for every state DOT. In addition, ongoing research into innovative new materials at various universities, municipalities and the FHWA has led to the following UHPC infrastructure projects in North America:
- Cat Point Creek Bridge, Virginia: five 80-foot-long (24.4 meters) UHPC girders
- Hawk Lake Bridge, Kenora, Ontario: precast deck panels with UHCP joint fill
- Jakway Park Bridge, Buchanan County, Iowa: first highway bridge in North America built with a new generation of UHPC girders
- Country Hills Pedestrian Overpass, Calgary, Alberta: 100-foot-long (30.5 meters) UHPC drop-in girder
- Mars Hill Bridge, Wapello County, Iowa: three 110-foot-long (33.5 meters) UHPC girders with no steel reinforcing bars for shear stirrups
UHPC bridge development is currently underway in New York, Iowa, Florida, Virginia, Georgia, Ontario and Alberta. For those who missed the UHPC article by Tess Alborn in Precast Solutions magazine July-August 2008 issue, UHPC is made of fine sand, cement and silica fume in a very dense, low water-cement ratio mix with 2 percent (by volume) of steel or polyvinyl alcohol (PVA) fibers. Compressive strengths reach up to 30,000 psi (200 MPa) and flexural strengths reach up to 6,000 psi (40 MPa). The material’s density and tight compaction of component particles result in a remarkably impervious and durable product; the fibers provide both passive reinforcing and ductility.
Precast for miles of new electrical grids
As global steel price and availability continue to vacillate and treated-timber pole availability grows scarce in some areas, there is a huge opportunity for precast UHPC components for extensive new electrical grids needed in North America.
Wind power is the new poster child for renewable energy and has garnered strong public and political support. Precast concrete wind tower hubs, or tower segments, are a developed technology in Europe. An article in Precast Solutions presented the potential for precast wind turbine towers in North America. Precasters who seek production consistency and growth need to anticipate future markets. New federal funding for the expansion of wind power will require a much more extensive, higher-voltage capacity and surge-tolerant electrical grid than that currently in use.
Electrical transmission towers run for hundreds of miles across country and can be built of steel, timber, concrete or composite (reinforced plastic) materials. A recent study1 reports that to comply with the goal of 20 percent of electricity from renewable energy by 2024, more than 15,000 circuit miles (24,140 kilometers) of ultra high-voltage lines are needed in the United States alone. Much of the country over which new electrical grid lines must run is remote, mountainous and sometimes inaccessible by road.
This means construction products must be delivered by helicopter; expensive transport requires lightweight components for project feasibility. UHPC products are lightweight, extremely strong and durable, competitive in price with alternative materials and offer long service life.
Insulated and reflective precast wall panels
Precast concrete applications using newer technologies can provide additional LEED points for new construction through energy efficiencies and resource conservation. Precast concrete establishes LEED points through: innovation in design (lightweight, strong concretes that use fewer resources); use of recycled components; and environmentally friendly materials such as white cement with solar reflectance and insulated or hollow floor and wall panels that optimize concrete’s thermal mass (see “Sustainability and Practicality”
in the May-June 2008 issue of Precast Solutions magazine). Precast products offer outstanding solutions for stimulus-funded projects that increase the energy efficiency of federal, commercial and residential buildings.
Opportunities for product diversification
At The Precast Show in Houston, held in February, one South Carolina precast fabricator – who had successfully grown his business over the years with a significant emphasis as an architectural precast supplier – said that he was considering PCPS to diversify the company’s product portfolio.
This company had an engineering staff that could potentially design pavement projects that would be a change from the commodity-type highway products made in the past.
Economic downturns are daunting, but these times also present opportunities to take advantage of new precast technologies for infrastructure initiatives. As an old saying goes, “Opportunities are never lost; someone will take the one you miss.” (author unknown)
Sue McCraven, NPCA senior technical consultant, is a civil engineer, technical writer and editor, and environmental scientist who has contributed numerous articles and studies to prominent scientific journals.