The use of lightweight aggregate created from expanded shale, clay or slate can enhance concrete performance by supplying water throughout a mix and slowly releasing moisture to facilitate internal curing. William Wolfe, a senior engineer at Norlite and an active member of several ACI and ASTM committees, examines the benefits of lightweight aggregate and internal curing, which include lower permeability, reductions in early age cracking and shrinkage and reduced curling and warping in slabs. 



Contractors can increase the speed and ease of placing concrete with the latest technologies. But even the most advanced equipment cannot significantly enhance the quality of concrete. To do this, the actual materials that make up the concrete should be considered—especially the type of aggregate used within the mix.

Using lightweight aggregate made from expanded shale, clay or slate (ESCS) is a simple, economical and sustainable way to help concrete reach its maximum potential. Because ESCS develops and retains a pore structure while being heated in a rotary kiln, it can supply water throughout the concrete mix when saturated. After the concrete has set, this water slowly releases to cure the concrete from the inside.

The process is known as internal curing and provides several benefits to concrete, including lowered permeability, reduced early age shrinkage, reduced warping, and improved curing conditions in the field.

All these benefits can help contractors increase the quality of concrete they place as well as their ability to work with challenging applications and field conditions, allowing them to secure more business due to their improved efficiency and final product. Let’s look at the internal curing process and explain the details behind its ability to maximize concrete’s potential.


What Is Internal Curing?

In general, internal curing refers to the process through which concrete is cured from the inside out. Whereas conventionally cured concrete cures from its surface to the depth the curing water penetrated, internal curing ensures an even moisture distribution throughout the concrete.