Understanding How the Aggregate Influences a Concrete Mix

The Portland Cement Association (PCA) states that, “Aggregates strongly influence concrete's freshly mixed and hardened properties, mixture proportions, and economy.”   Furthermore, while choosing the proper aggregate in a concrete mix is important, the type of aggregate used affects the concrete more while it is wet than once it has cured. 

Concrete mixes are made up of aggregate, cement, water, and sometimes chemical admixtures.  The aggregate’s size or type of stone used in the mix can impact the strength, durability, workability, hardening, and ultimately the cost of the concrete.  It also accounts for up to 60 to 75% of the volume and 70 to 85% of the weight.

Most aggregate comes from sand, gravel or crushed stones and helps to determine the amount of cement paste added to the mix, which is the most costly part of concrete.   Before the aggregate is ready to go into the concrete, it is put through a cleaning and grading process.  Fine aggregate is usually defined as a mix of natural sand or crushed stones with a majority of particles smaller than 3/16th of an inch or 5mm (although sometimes it is defined as less than 4.75mm).  For coarse aggregate, the crushed stones or gravel particles are usually larger than 3/16th of an inch or 5mm (or larger than 4.75mm.).     

Aggregate used in concrete is derived from natural sand or gravel pits, rivers, seas or lake beds, hard-rock quarries, and underground mines.  If the gravel used in an aggregate is extremely rough or irregularly shaped, it will require that more water and cement be added to the concrete mix for a proper consistency.

During our many decades in the industry, The Conco Companies have encountered and successfully used a variety of concrete mixes including “green” concrete.  See our website to learn more about our large portfolio of projects.    

At Conco, we 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 serve California, Washington State, Oregon, Colorado and Nevada.

Source: cement.org/cement-concrete-basics/concrete-materials/aggregate