Concrete is a matrix of cement, aggregate, water, air and additives. The cement bonds together large and small aggregates such as pebbles and sand, while water, air, and additives are introduced in varying quantities to create the desired mixture. The composition of the concrete can vary dramatically depending on what the project requires, and can be altered by changing the ratio of cement to water, the amount and size of the aggregate, as well as the inclusion of additives that change a specific aspect of the concrete’s characteristics. For example, foam concrete uses little to no small aggregate and a foam additive to create lightweight concrete. Regardless of the specific mixture, concrete is porous and is permeable to both water and air, though the level of permeability will vary tremendously depending on the mixture. It can be a benefit to consider permeability as a factor as you plan your next project.
Low permeability concrete
Limiting permeability can extend the lifetime of some concrete and is ideal when concrete would be exposed to harsh conditions, such as chloride exposure in parking garages which can corrode the steel reinforcements in the concrete. A low permeability reduces the amount of gas that can penetrate the concrete, protecting the steel from corrosion for a longer period.
High permeability concrete
Alternatively, increasing the permeability can allow water to pass through concrete itself. Highly permeable concrete has little or no small aggregate and a higher air content. This creates a matrix that is mainly large aggregate bonded together with cement. This structure allows water to pass through quickly – from 3 to 17 gallons per minute for each square foot on concrete. The Green Building Alliance, which manages LEED certifications, records the introduction of highly permeable concrete in the US in the 1970’s. Though it has been used in some areas in the US since then, it did not gain greater adoption until recently. The rise of sustainable development has promoted the use of porous cement for stormwater management. Permeable concrete allows water to enter the soil and eventually water tables, while still mitigating the damaging effects of water runoff during storms.
Conco’s goal is to be the top supplier of concrete services in the Western U.S. and to bring our expertise and professionalism to each project. We continue to upgrade and expand our facilities to better serve the growing market for commercial, industrial, educational, parking structure projects and other development. For the best value and quality, trust your project to one of the area’s leading lightweight concrete contractors.