There's no mystery as to why concrete is environmentally unfriendly. In fact, gaining insight into that question is fairly simple. Let's start the discussion on how concrete is made.
Concrete is "of the earth". We extract the elements that go into making concrete out of rock and earth. The next step after collecting the rock is to grind it into a powder. So far, so good. In the most elemental sense, powdered cement is "green". In its powdered form, cement is also biodegradable. Its environmentally friendly ways go downhill from there.
We make concrete by mixing cement material with sand or fly ash and gravel, limestone or granite, and enough water to allow the material to "set", thereby binding it together. We make cement for that recipe by fusing together limestone and clay, subjecting them to great heat, and then grinding the combination into a powder.
Why concrete is not environmentally friendly. In general, it is not the ingredients, so much as the processes we use to make concrete that fail the sustainability test.
- Quarrying for the sand and other aggregate materials like limestone or granite can destroy and pollute the mine area.
- To make cement takes a lot of energy and water.
- There's a lot of waste in the mixing process. The concrete hardens quickly and if there's not enough time to lay it down before it hardens, builders just throw it away.
- Concrete is known for its high carbon emissions into the atmosphere, which contributes to greenhouse gases. This occurs in the process of making cement when the clay burns at high temperatures and the limestone burns to create the high temperatures. Big carbon footprint here.
But what would we do without concrete? Concrete is the most common building material in the world. We use it for our building footers and our basement walls and floors. We build our homes on slabs made of concrete. We use concrete to finish our driveways. We create sidewalks and stairs and porches around our home from concrete. We wouldn't have our built-in pools without this versatile building material. We use concrete for the mortar that holds our brick fireplaces and brick walls together, and for our patios and even benches to sit on. Is there anything to replace concrete in a sustainable way? The answer is yes.
Three Advances in Concrete
Pervious Concrete. One environmentally friendly product that replaces traditional concrete as a paving substance is pervious concrete.
Traditional concrete is environmentally unfriendly with respect to the health of our water supply. As concrete covers more of our ground, less rainwater soaks into the soil. Traditional concrete is impervious to water and so the water just runs off the paved surfaces. This creates lots of problems, the most notable soil erosion, flash flooding, depleted water table resources, and pollution from our oil-soaked and deicing-chemical-filled roadways.
More and more businesses and localities have switched to pervious concrete. Pervious concrete is a porous material that helps hold stormwater runoff so that it percolates into the ground and refills the water table. So instead of gushing down your driveway to the street gutters and sewers, your porous driveway, sidewalks, patio and pool areas snag the rainwater and hold it in tiny voids until it slowly seeps into the ground like nature intended.
CO2 Absorbing Concrete. A British manufacturer called Novacem claims that it has developed a new kind of concrete that absorbs large amounts of carbon dioxide during the hardening process instead of emitting carbon gases. Novacem claims its product can absorb .6 tonnes of CO2 compared to traditional concrete which emits .4 tonnes of CO2.
The product is still in trial stages but would significantly impact the building market if it were available for builders to use and designers to require.
Composite Cement. The Bautex wall system is based on a composite material that combines EPS foam beads with cement to provide an improved method of constructing walls. The Bautex wall system provides the storm resistant strength, fireproof properties and ease of construction of traditional concrete walls. It also provides insulalting, sound absorbing, weight saving, moisture resistance of foam.
The use of foam in the composite also reduces the amount of cement required to provide a more environmentally friendly solution. The result is a high performance wall system that saves energy, is faster to install, has less chance of installation errors and is more environmentally friendly.
To talk more about this, or anything else, please contact us. We look forward to sharing our ideas with you.