Increasing the Strength of Concrete

There are several ways to control the strength of concrete.  One of the easiest is to add more cement to the mix and reduce the ratio of water to cement in the cement paste.  In fact the Portland Cement Association states that, “Every desirable physical property that you can measure will be adversely affected by adding more water.”

In addition to the water/cement ratio affecting the strength of concrete, it is also influenced by the quality of raw materials, the ratio of coarse/fine aggregate, temperature, relative humidity, compaction of concrete and the curing process.   Factors such as how the cement is stored (should be under dry conditions) and whether it was manufactured to the appropriate standards, the quality of the aggregate regarding size, shape, texture and strength, to the purity of the water, can all impact the strength of the concrete. 

The coarse/fine aggregate ratio will determine the amount of water that is needed.  When the fine aggregate is increased in relation to the coarse aggregate, the aggregate surface increases and demands more water.  This higher water demand means the water/cement ratio is increased, which in turn decreases the compressive strength of the concrete. 

Another factor that can impact strength is compaction of concrete.  If there is poor compaction of the plastic concrete, air is entrapped and reduces the strength of the concrete.  It is estimated that the strength of concrete that contains 10% trapped air can be affected by as much as 30 to 40%. 

Concrete contractors also consider air temperatures and relative humidity as both can affect the strength of the concrete.  While higher temperatures allow concrete to gain strength more quickly, the final strength of the concrete is actually lower when hydration occurs at a faster pace.  This is due to the hardened cement paste being less structured as well as more porous. 

At The Conco Companies, 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.

Sources:cement.org/for-concrete-books-learning/concrete-technology/faqs

theconstructor.org/concrete/factors-affecting-strength-of-concrete/6220/