SUSTAINABILITY

Sustainability, as defined in Webster’s Dictionary is: “To keep up: Prolong.” Sustainability should be viewed as a process and not a goal. Viewing sustainability as a process is essential for “Green Designers”, as designers are challenged to evaluate the full life-cycle of the products.

Concrete is a green material—it always has been, and is a friend of the environment in all stages of its life span. From raw material production to demolition, making it a natural choice for sustainable home construction. Here are some of the reasons why, according to the Portland Cement Association and the Environmental Council of Concrete Organizations:

• Resource efficiency. The predominant raw material for the cement in concrete is limestone, the most abundant mineral on earth. The predominant materials in concrete; cement, sand and aggregate are all generally locally available, and have been for some time.
  
  
• Durability. Concrete builds durable, long-lasting structures that will not deteriorate, rot, rust, or burn. Life spans for concrete building products can be at least double or triple those of other common building materials. Roman buildings over, 1,500 years old such as the Coliseum and more recently the discovery of the ruins at Gobekli Tepe in Turkey, uncovered mortar between stones and concrete floors that date back some 12,000 to 14,000 years, provide living examples of the strength and durability of concrete.
  
  
• Thermal mass. Homes built with concrete walls, foundations, and floors are highly energy efficient because they take advantage of concretes inherent thermal mass, or ability to absorb and retain heat. This means that homeowners can significantly cut their heating and cooling bills, and install smaller-capacity HVAC equipment.
  
  
• Low maintenance. Concrete, being inert, compact, and non-porous, does not attract mold or lose its key properties over time, and maintenance costs are almost non-existent.
  
  
• Minimal waste. Concrete can be produced in the quantities needed for each project, reducing waste. After a concrete structure has served its original purpose, the concrete can be crushed and recycled into aggregate for use in new concrete pavements, or as backfill or road base.
  
  

When concrete is mixed in the usual manner in delivery trucks, an excessive amount of water i.e.: a high water to cement ratio above that required to set (hydrate) the concrete must be utilized. This is required in order to provide a capability to the mix to flow out of the trucks, into pumping equipment, into forms, around reinforcing steel and into corners. This excessive water leads to a reduced strength of the concrete, as well as excessive waste of the concrete mix and water.

In the concrete bag system of construction, only the exact amount of dry concrete mix required to fill the sacks for the walls is required, thereby producing no waste of the mix in the process. The role of water is important because the water to cement ratio is the most critical factor in the production of “perfect” concrete. Too much water above the optimum amount required for hydration provides workability to the concrete, but at the same time reducing its strength. In the concrete bag system of construction, the concrete dry mix is positioned in the walls at the exact place where it will be hardened. It doesn’t need to flow to get there. The amount of water used to harden the dry mix is only that required to set the mix and no more. There is no flow requirement thereby saving on the dry mix and the water over conventional methods.

Using the lowest water/cement ratio to set the pre-positioned mix, assures the development of the highest concrete strength attainable, for the mix design.

Once a home is built using the concrete bag system of construction, it will be serviceable for generations. This is the true definition of sustainability i.e.: “to keep up: prolong.”