Rock.Paper.Scissors.

Green building is all the rage across the country, especially in the San Francisco Bay Area where high tech companies seek environmentally-friendly materials and sustainable practices on nearly all new construction projects.

Concrete is a major component of green building.

Concrete is the most used construction material in the world and contributes to about 6 percent of the world’s carbon dioxide emissions. The chemical process of converting limestone to Portland cement concrete releases CO2 into the air and is very energy intensive.

However, concrete made with reclaimed industrial byproducts – fly ash and slag – reduces CO2 emissions, which significantly contributes to a project’s sustainability and provides LEED points.

We sat down with Graniterock’s director of geological and environmental sciences, Jon Erskine, for insight on the trend and what makes Graniterock concrete some of the greenest around.

Q. What exactly is green concrete, and how did it get started?

When we talk about the environmental impact of concrete, we’re primarily talking about the cement portion and how far it takes to import the aggregate portion to the plant.

Converting limestone into Portland cement is an extremely energy-intensive process, which adds carbon dioxide into the atmosphere. Every mile of travel it takes to move aggregate from its source to the plant also adds pollution.

Every sack of cement saved directly reduces greenhouse gases; every mile of travel saved does the same.

Environmentally-friendly concrete involves replacing a portion of cement with reclaimed industrial byproducts, primarily fly ash and slag, and using locally-sourced aggregate.

Green concrete has been around for several decades because of its great engineering properties, but it only started being called “green” in the early 2000s with the advent of Leadership in Energy and Environmental Design by the U.S. Green Building Council.

Even the Hoover Dam was constructed with what’s now considered green concrete because the material is stronger and more durable than traditional concrete.

In addition to superior strength, concrete with slag and fly ash has greater workability and chloride resistance.

Technology companies, in pursuing their environmental ethos, are the primary market for green concrete in building their large campuses. Their employees and customers expect green.

Green concrete with an environmental product declaration helps earn LEED points.

Q. What is an environmental product declaration (EPD) and why should we care?

Using a product with an EPD gives a project one LEED point, and approximately 80 percent of all new construction in the SF Bay Area is seeking some kind of LEED certification – certified, silver, gold or platinum.

You can think of an EPD like a nutritional label for concrete as it assesses the lifecycle impact of a particular concrete mix.

The assessment includes everything that goes into your concrete as it relates to the environment: energy, materials, transportation, waste generated and water.

An EPD is a document, verified by a third party, that’s used as a metric to show how green you actually are.

An EPD allows direct comparisons between your product and others in the marketplace.

It’s not enough to say you’re green, you have to prove it. Our EPD shows Graniterock concrete beats regional industry averages, which allows our customers an additional one LEED point.

Q. What is Graniterock’s role in the green concrete market?

Graniterock is one of nine ready-mix suppliers in the country with a product-specific EPD.

The company produced a product-specific EPD in 2015, including 30 mix designs, which helps set us apart because all of the sustainable elements that go along with being a local concrete supplier with local aggregates are spelled out and compared against other ready-mix suppliers.

Graniterock mines aggregate from its quarries in Aromas and Hollister and ships the aggregate, largely by rail, to the company’s concrete plants in Redwood City, San Jose, Seaside, Salinas and Santa Cruz.

When it comes to serving the San Francisco and Monterey Bay areas, we can beat anybody in those markets.

Q. What changes are on the horizon for green concrete?

The demand in green concrete is to get higher strengths earlier as concrete made with SCMs typically takes longer to cure. There’s a push being made to find new supplemental materials and admixtures that would act more like Portland cement but keep the green elements and engineering advantages. Some of the materials being explored are rice husks and silica and different sources of slag.