Easing Logistic Challenges with Structural Lightweight Concrete Components

Precast concrete components are emerging as a key solution for bridge deck construction and repairs. Manufactured in controlled, factory conditions, precast bridge components like girders, seats, wing walls and piles consistently meet high-quality standards and contribute to a more precise construction process. Their off-site production enables concurrent construction, eliminating time for extensive on-site formwork and curing.

But because precast, prestressed concrete must be shipped to the job site, it can contribute to higher transportation costs. Plus, other logistics limitations around the need for larger on-site equipment can cause construction delays in a project. One innovative approach to address these logistical challenges with enhanced performance is the use of precast, prestressed members made with structural lightweight concrete (SLWC).

Lighter SLWC Components Ensure Transportation Efficiency  

Precast, prestressed components made with normalweight concrete (NWC) typically weigh between 145-155 pounds per cubic foot (PCF). This may cause members to exceed truck load limits without reaching optimal span lengths and may also necessitate a higher number of shipments to transport the required number of bridge components to the site.

Conversely, components made with SLWC weigh a more manageable 110-115 PCF. Additionally, when SLWC is made with expanded shales, clay or slate lightweight aggregates, the mix has improved physical and chemical properties that allow precast elements to be made larger in spans but leaner in section and lighter in weight as compared to similar-sized NWC components. As a result, these large components can still fit within truckload limits, helping reduce the number of shipments required to complete a project.

In “A Holistic Approach to Sustainability for the Concrete Community,” two projects by (pre-Arcosa Lightweight) Big River Industries are analyzed to determine the differences in projected shipping costs between normal weight and lightweight concrete products. In the first project, the number of truckloads of precast concrete was reduced from 431 to 287 and from 87 to 66 in the second, as more elements could be loaded on each truck due to the lowered density. By needing fewer truckloads, these projects spent less on transportation costs.

SLWC-Made Precast Components Support Time- and Cost-Efficient Installation

The installation of SLC precast prestressed components is more straightforward. Unlike heavier NWC components that often require large overhead cranes, SLWC components can be placed with smaller rated cranes, which are generally more readily available. This flexibility helps streamline installation requirements and timelines. Additionally, SLWC’s larger yet lighter component sizes reduce the number of parts to be placed, allowing teams to ensure more efficient installation, resulting in faster completion of bridge girder and deck construction as well as repair projects.

For instance, the I-5 southbound Puyallup River Bridge near Tacoma, Wash. used precast SLWC components to extend the length of the bridge girders to an unprecedented 223 feet and 4.5 inches, surpassing conventional girder lengths by more than 13 feet. The record-breaking size enabled construction crews to manage tight schedules, as a railway directly below a portion of the bridge required crews to halt work whenever a freight train passed underneath. Streamlining this aspect of construction helped minimize labor hours and revenue lost due to interruptions, ensuring the project’s efficient completion.

A Win-Win Investment

When used in precast concrete components, SLWC made with ESCS LWA offers construction teams significant benefits in easing logistics. These advantages support shorter construction timelines, contributing to cost-effectiveness. Additional properties of SLWC with ESCS further enhance component performance and support an extended service life. This combination helps teams not only meet immediate project objectives but also lay a foundation for a more resilient and longer-lasting infrastructure in the country.

To leverage the benefits of SLWC with ESCS lightweight aggregate in precast components, contact a local aggregate producer to learn more.