Concrete is gray, not green, right? Well, there are many ways that concrete is becoming much more environmentally friendly. The green movement is a great way to better our current products and spawn innovation for new creations. As these new, more efficient products gain speed and drop to a reasonable price, people will be much more motivated to upgrade to sustainable materials and replace the old, less efficient products. This can be seen when comparing the cost to light a room, or heat your water. However, there is a great misunderstanding about the use of concrete and how it affects our communities and natural resources. The progress of concrete mix designs is not a hot topic at the dinner table or on the evening news, so it often gets ignored or overlooked by the masses.
Let’s begin with the basics: Water, Rock, Sand and Cement.
Water is used for the hydration process – how everything binds together. The water needs to be good clean water, but does not need to be potable (drinkable) according to the Portland Cement Association. Thus, this ingredient requires no additional purification or processing to be used. After the hydration process is complete, the majority of the water will evaporate or return to the groundwater system, making it a completely renewable source.
Rock found in concrete can come from anywhere. That means that it can come from down the road and be locally provided. It is true that some rock has a greater compression strength than others, but many states require local materials be used for government jobs. The local use reduces excess transportation costs and saves other resources, making it a favorite material for LEED certified buildings. Recycled materials such as blast furnace slag and reused glass are making a steady appearance in both the construction industry and the art world.
Sand is even easier to come by and is not only dirt cheap and plentiful, but also is often a local mineral and highly favored for all projects. Rock and sand make up about 70% of concrete mix and can be a very good choice for earth friendly construction because they are naturally occurring materials and require little to no processing. The main energy consumption comes into play when they need to be transported great distances, which was already discussed.
Cement does require a fair amount of energy to process. That is one reason other sources of cementitious material is becoming more popular. Fly ash, for example has similar properties as portland cement, but is a by-product of power plants and is therefore a reused material. There are many other materials that are making their way into concrete that are less energy intensive to refine into a usable bonding agent. Some of these materials include naturally occurring pozzolans, microsilica, fly ash, and other proprietary ‘crete products.
I foresee a continual change in the actual mineral recipe of the cementitious materials used in concrete in the future. Along those lines, I don’t see any lack of demand for this diverse and beneficial construction material in the next decade or century. Concrete will be used in the future just as we currently use the dirt, timber and steel of the past. As we continue to make improvements in our products, we will be able to save money and reduce our impact on the world’s resources.