Awesome Sauce usually refers to a food ingredient that 
makes the dish so delicious that you just can’t resist indulging in the dish with the awesome ingredient. For concrete, prewetted Expanded Shale, Clay or Slate aggregates (ESCS) is the Awesome Sauce to which I am referring. If you are reading this, chances are you have already known this for a long time. Internally Cured Concrete (ICC) has been around well over 100 years with projects world-wide. A few of the more popular applications for ICC are paving and bridge decking.
The American Concrete Institute defines internal curing as the “process by which the hydration of cement continues because of the availability of internal water that is not part of the mixing water.” (Ref. ACI Concrete Terminology – 2018)
“Curing Concrete from the Inside Out”
Why use ICC? Because the service life of projects with ICC can be extended by 30% or more. Put simply, a concrete project with a life expectancy of 30 years with standard maintenance may last 39 years, adding 9 years to the project life. The internal curing reduces concrete shrinkage, resulting in fewer, smaller cracks, delaying the onset of corrosion of reinforcing steel that causes degradation of the interior structure. This makes it cost effective and sustainable. ICC is made by replacing roughly 30% of the sand component in the concrete mix (9-11%) with prewetted, drained ESCS fines. The absorbed moisture adds to the curing process. This moisture, which does not contribute to the w/cm ratio, is released over time throughout the entire depth of the concrete (as opposed to the top 2-3 mm).
ICC (as mentioned earlier) is not a new, untested technology. From the construction of early 20th century cargo ship hulls made of internally cured (and 100% ESCS aggregate) concrete to today’s modern skyscraper construction using semi-lightweight concrete, the internal curing effects of ESCS have become well known. Now, replacing a portion of the normalweight sand with prewetted fine ESCS provides these benefits in normalweight concrete.
History has proven the case for internally cured concrete using ESCS lightweight aggregate as a cost effective and sustainable alternative to concrete made with all normal weight aggregates. Many state DOTs have already begun implement Concrete’s Awesome Sauce for their transportation projects.
