Roller compacted concrete finds new popularity and uses

First published at CONEXPO-CON/AGG - March 13, 2020

Cost and speed of placement are two of the factors behind the increasing popularity of roller compacted concrete (RCC), conference attendees at CONEXPO-CON/AGG 2020 were told. However, despite the material’s benefits, users have to work carefully to maximise the material’s benefits, said Wayne Adaska, director, pavements and geotechnical markets, Portland Cement Association.

Speed of laying is one factor behind the material’s renaissance: “When putting down asphalt you’re putting down one to one-and-a-half-inch layers, but with RCC you can use eight to nine-inch layers. And you can get traffic on it within 24 hours … in most cases,” Adaska said.

However, he added, it’s equally important to take into consideration factors such as client expectations, aggregate selection and good compaction. In terms of client expectations, RCC’s pale colouration meant that any imperfections showed up more readily than those in dark asphalt … so it is important that customers are made aware in advance of how it will appear. Mixing in smaller aggregate with a maximum size of a half-inch (c12mm) – compared to traditional three-quarter inch (c18mm) aggregate – can help by giving a tighter surface.

Selection of aggregate is also important for other reasons. It constitutes 75-85% of the mix by volume and if larger aggregate is being used, mixing in a quantity of intermediate stone helps to fill void. Also, determining the optimum moisture content (typically 12%) is also vital.

Finally, compaction is critical. The density compaction of RCC is paramount to ensure strength and it makes sense to build in a safety margin above the strength level specified by the client.

Abdo added that the placement of structures, such as drainage systems, around the edge of the area to be paved was the most efficient way of installing them.