From its high compressive strength to its ability to be formed into countless shapes, concrete is one of humankind’s most useful construction products. As concrete producers know, though, the material’s great weight creates a host of challenges, such as high transport and installation costs, and worker fatigue.

To overcome these and other issues, people throughout history have sought to reduce concrete’s weight without negatively affecting its performance. An early example is the Ancient Romans’ addition of pumice and air-filled clay pots to the Pantheon’s domed concrete roof. In recent years, additives have become much more sophisticated, notably with the introduction of ultra-lightweight synthetic aggregates.

Among these are lightweight polystyrene and expanded polystyrene (EPS) beads. These small foam beads sometimes are mistakenly referred to as “Styrofoam,” but are a different material.

Polystyrene-based lightweight additives reduce the weight of concrete, while conferring beneficial mechanical properties.
CityMix Polystyrene-based lightweight additives reduce the weight of concrete, while conferring beneficial mechanical properties.

Benefits of lightweight polystyrene additives

Ultralight polystyrene-based additives serve as a partial volume substitution material for the heavy sands and gravels in concrete. Such additives reduce the unit weight of concrete, which in turn reduces the weight of structures, reduces hauling costs and lessens worker fatigue – resulting in lower costs and potentially higher profits for concrete producers. The possible weight reduction depends on the concrete product to be produced – with on the order of a 5% - 15% reduction for structural concrete building panels, but potentially up to 80% for non-structural concrete objects such as veneer stone, decorative moldings and landscape block.

In addition to decreasing the weight of concrete products, polystyrene-based additives can also enhance concrete’s performance in several key areas. Chief among these properties are enhanced flexibility and resilience, improved crack resistance and freeze/thaw durability, and improved fire and thermal performance.

Depending on the additive, polystyrene-based aggregate substitution materials can be used in a host of structural and non-structural applications, including:

  • Stucco
  • Veneer stone
  • Cement board
  • Architectural and industrial precast concrete
  • Pumpable lightweight flooring
  • Precast
  • Landscape block
  • Soil additives
Coated EPS beads disperse evenly throughout concrete.
CityMix Coated EPS beads disperse evenly throughout concrete.

Challenges of polystyrene additives

Although ultra-lightweight polystyrene-based additives offer many benefits, until recently they shared a number of drawbacks, such as:

  • Ultra-lightweight beads can become airborne in the wind or during general agitation, which can make handling and mixing them messy in the field or in a factory
  • Inherent high static charge makes beads cling to skin, clothing and other surfaces, which can make the additive a hassle to work with
  • Bead clumping within the concrete mixture, or a tendency to float to the surface, which prevents the additive from evenly dispersing throughout the concrete
  • Use of virgin foam plastic in some additives can both increase the additive’s cost and burden on the environment

A new technology emerges

Building industry scientists recently have developed a new class of polystyrene-based additive, which provides all of the lightweight and mechanical benefits discussed above, while removing the drawbacks. Currently manufactured by Insulfoam for CityMix, this unique and patented additive uses recycled EPS particles encased in a performance-enhancing outer shell. In this economical and ultra-light product, static has been eliminated and just enough particle weight added to enable the material to be easily handled and mixed.

Recycled vs. virgin EPS

The EPS particles used in this new lightweight additive can either be from virgin material or recycled from other EPS products (such as building insulation, geofoam used in civil engineering jobs, or product packaging), which enables the diversion of large volumes of waste foam from public landfills.

Concrete is often considered to be humanity’s first composite building material. Through trial and error, ancient civilizations figured out how to combine sand, aggregates and cements to produce an exceptionally strong, yet adaptable building material. Today, science has discovered ways to further enhance concrete with synthetic lightweight additives, which continue to improve year after year.