Designing a Concrete Mix

As the most commonly used man-made material in the world, concrete mixes are designed to meet the demands of today’s increasingly complex architectural projects.  A structure’s concrete mix must suit the purpose of the structure as well as accommodate any special features and characteristics of the project. 

In the early planning stages of a project, a concrete mix is designed to meet the criteria for both strength and appearance of the structure.  Additional factors taken into account are local building codes and the kind of weather conditions the structure will be exposed to.  Furthermore, standard molded and standard-cured cylinder samples are used to measure the concrete’s compressive strength.  Other testing methods may include the Hardened Air Void Systems (AVS), Rapid Chloride Permeability (RCP) and Linear Shrinkage limits.  

The slump or consistency of fresh concrete is also considered, and generally there is a trade-off in terms of easy mixing and placement and in achieving the ultimate performance of the concrete.  The design process will include discussion on the type, cost and amount of the various additives to be used in addition to the portland cement.  It will also be decided if the concrete mix will use fine (small) or coarse (larger) aggregates.  Since there is such a wide range of performance requirements for concrete and different types of mixes, sophisticated software programs have been developed to help in the process. 

According to the Portland Cement Association (PCA), “The key to achieving a strong, durable concrete rests in the careful proportioning and mixing of the ingredients. A mixture that does not have enough paste to fill all the voids between the aggregates will be difficult to place and will produce rough surfaces and porous concrete. A mixture with an excess of cement paste will be easy to place and will produce a smooth surface; however, the resulting concrete is not cost-effective and can more easily crack.”   They suggest that a common concrete mix is approximately “10 to 15 percent cement, 60 to 75 percent aggregate and 15 to 20 percent water.”  For concrete mixes with entrained air, it can account for another 5 to 8 percent of the mix.   

The Conco Companies are one of the leading concrete contractors in the Western U.S. and offer a wide range of quality services and products.  Our experience includes providing services for commercial, educational, parking and other construction development as well as public works projects.  We proudly serve California, Washington State, Oregon, Colorado and Nevada.

Sources:en.wikipedia.org/wiki/Types_of_concrete,cement.org/cement-concrete-basics/how-concrete-is-made