USING RIVER GRAVEL IN RCC PAVEMENTS

By: Matthew W. Singel, PE
​What is the best aggregate to use for roller-compacted concrete pavement construction?  One universal truth arguably impacts construction more than any other factor.  The quality and cost of a project are directly influenced by the quality and availability of construction materials....

One example, when planning to mobilize for a paving project, involves the availability of quality aggregates.  Aggregates are an essential ingredient for pavement construction regardless of pavement type.  The nature of RCC pavement requires significant compactive effort to achieve density while maintaining stiffness to support the roller and meet the required pavement surface elevations.  The introduction of river gravel as the available aggregate can complicate matters if you are not familiar.
It is common for river gravel to be rounded due to the erosive nature of the river beds from which it originates.  River gravel, if not well graded, can be difficult to compact to density as it lacks the stable matrix that angular aggregates more easily create.  When developing an RCC mix design, it is important to provide a uniformly graded aggregate.  This is even more important when using river gravel.  An evenly graded material is more stable under compactive forces.
Another option is to have the river gravel crushed at the quarry to increase its angularity.  While this will increase your aggregate cost somewhat, the savings in handling, placement and compaction (i.e. increased productivity) may very well offset this cost.  Of course, for the best results, it is advised to consult those experienced in RCC mixture designs; communicate with your aggregate supplier prior to construction day; and place a sample of your final mixture with a paver to get familiar with its properties. 
When answering the opening question, “What is the best aggregate to use for roller-compacted concrete pavement construction?”, I would say invest time and money in the mixture design early in the project.  This often allows you to use the most economical (readily available) aggregates while insuring a quality finished product.  Successful construction projects of any kind don’t happen without proper planning.  RCC paving is no exception to this rule.
For more information on RCC aggregates, click on this link:  “Production of Roller-Compacted Concrete”, or contact us.

"This blog was previously posted in the Cement Council of Texas' "Texas Cement and Concrete Blog" (now inactive) and was carried forward to the current blog ("Cementx Pavement Blog") as it contains content that may be of interest to the reader".