Performance-based specifications focus on properties such as consistency, strength, durability and reduced costs. Traditional bag mix specifications treat concrete as a commodity, assuming a mix of components produces virtually identical performances. However, not all bag mixes are the same and measuring the cement content of concrete is not the best way to measure quality. This is why in 2002, the National Ready-Mix Concrete Association launched the P2P initiative to change the way concrete is specified. Strength is one very good way to measure how well the concrete fits the required purpose. Performance-based specifications focus on how a material will perform rather than on what it contains. Performance Concrete utilizes materials not found in standard bag mixes. Slag, fly ash, and water reducers are the most popular components used a cement substitute. These materials are less expensive than cement and at the same time produce a higher quality concrete than 100% cement mixes. A few advantages are listed below:


Cost

Performance mixes utilize materials that are more cost effective.


Strength

Performance concrete can produce ultimate strengths that are greater than Portland cement alone. This is especially true when looking at 28 day strengths and longer. The improved strength and durability of concrete is attributed to increased Calcium Silicate Hydrates and paste density. The use of fly ash and slag produces a denser paste which reduces the permeability of the concrete. The lower permeability is especially important when considering resistance to chlorides such as de-icing salts.


Color

Concrete that contains slag is lighter in color than 100% Portland cement mix concrete.


Workability

Ease of placement and consolidation are inherent in performance mixes that utilize slag.


Shrinkage

Since performance concrete uses less cement, the amount of water needed in the mix is reduced. In addition, water reducers will lower the need for water even further. By reducing water content, the performance mix design will have substantially less shrinkage issues than the standard 100% cement mixes.



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