The Weight of Sustainability – Does Weight Matter?

By John Ries, ESCSI

In many cases it does. The use of expanded shale clay and slate (ESCS) lightweight aggregate concrete for building and bridge construction has intrinsic and easily documented benefits that contribute to the sustainability of our built environment.The traditional benefits associated with a 20 to 40% reduction in density as compared to normalweight concrete are well known. Now that the traditional lightweight concrete building industry has matured, a service record has been established.This clearly shows that repair and replacement of the infrastructure is minimized when lightweight concrete is used which accounts for its enhanced sustainability as compared to normalweight concrete.

What is less well known about ESCS is the multitude of other uses that have become an important addition to sustainability.For example, internal curing where pre-wetted ESCS provides improved cementitious hydration resulting in better durability and extended service life.Another is using ESCS as the growing media for horticultural and green roofs that reduces the heat island effect in urban areas.In the purification of water, the use of ESCS provides enhanced area for the development of bacterial growth that is particularly effective in lowering phosphate content in storm water runoff. The use of ESCS in geotechnical applications reduces the lateral forces by approximately 50% and in asphalt chip seal ESCS provides safer roads by improving skid resistance and practically eliminating windshield damage.

Sustainable Benefits of Using ESCS Over Conventional Normalweight Sand, Stone and Gravel Aggregates Are:

In Concrete and Concrete Masonry

  • Less weight (reduced dead load)
  • Less overall material used (thinner walls and floors use less material themselves and allow smaller foundations, beams and columns)
  • Reduced seismic inertia (more economical design, less materials)
  • Longer spans increasing design flexibility
  • Reduced number of trucks (more building products per load)
  • Easier placement (all products are lighter)
  • Improved workforce sustainability (masons have fewer injuries and safer jobsites)
  • Increased mason productivity
  • Better fire ratings (thinner walls and floors)
  • Improved energy performance with thermal mass, higher thermal inertia and lower thermal bridging
  • Increased durability and service life with improved concrete properties
    • Improved concrete properties through internal curing
    • Improved contact zone between aggregate and cementitious matrix
    • Better elastic compatibility between aggregate and cementitious matrix
    • Fewer overall micro-cracks and macro-cracks
    • Reduced autogenous shrinkage
    • Reduced chloride ion permeability

In Lightweight Asphalt Chip Seal

  • Practically eliminates damage towindshields, headlights and paint
  • Reduces motorist complaints and insurance claims
  • Superior skid resistance, wet or dry, and will not polish as it wears (safer roads)
  • Extends chip seal and roadway service life

In Lightweight Geotechnical Fills

  • Convert unstable soil into usable land
  • Half the weight, higher internal friction angle (reduced dead load & lateral forces)
  • Free draining
  • Provides Insulation and is chemically inert

In Horticulture and Green Roofs

ESCS is the perfect soil media because it is non-toxic, odorless, 100% inert and will not compress, degrade, decompose, or react with agricultural or horticultural chemicals. ESCS is use as a soil conditioner in plantings, golf course greens, potting soil and as a soil media in both intensive and extensive green roofs. ESCS is also incorporated into engineered structural soil to support healthy plant growth and improve drainage while allowing access by heavy emergency vehicles to the edges of buildings.

  • Promotes strong root development
  • Improves aeration and drainage
  • Reduces nutrient loss and improves moisture retention
  • Enhances soil resiliency to climate changes
  • Resists compaction

Storm Water Management and Water Treatment

ESCS can be used to construct vegetated filter strips, rain gardens, rain basins, constructed wetlands and bioswales to treat and reduce the amount of storm water runoff. The voids within ESCS provide an environment suitable for beneficial microbial action that will help to filter storm water. ESCS is also used as the underground-layered aggregate filtering fill beneath permeable pavements.

  • Increased surface area with better porosity
  • Larger interstitial space and greater water storage
  • Improved removal of suspended solids, hydrocarbons, metals, nitrogen and phosphorous.

In addition, ESCS can be used as part of an onsite sewage treatment system. The void structure within ESCS allows microbes to live, flourish and improve septic system efficiency. It can also be used in living machines that process a generated waste stream through the use of innovative natural environments that filter and digest waste in many different stages.ESCS can also be used as filter media in packaged nutrient removal systems and in constructed wetlands.

Regional Material

ESCS is used at numerous manufacturing facilities in close proximity to almost every building site. The 500-mile radius from ESCS aggregate plants encompasses most major markets all across the United States. ESCS products have lower transportation requirements and use fewer trucks to transport the same amount of product when compared to normal weight aggregate or concrete.

By Definition

Sustainability must be looked at with a long-term perspective. A product that is considered “green” today but lowers durability and long-term performance is not sustainable. Conversely, when the energy invested in the production of ESCS is quickly recovered, both in first and ongoing life cycle costs, the material is undoubtedly sustainable. ESCS has been contributing to the sustainability of the site and structure of building projects long before the current green movement came to the forefront. It’s beneficial properties will continue to improve the sustainability of past, current, and future projects.