Finely Graded Surface Concrete (FGSC) a Sustainable Solution for Exposed-Aggregate Concrete

As a general feedback of most studies and site experiments, the lower the maximum size of aggregate, the lower the rolling noise for exposed aggregate concrete roads. Yet, a small size of aggregate increases the cement demand, and by the way the unit cost of concrete. This is a supplementary barrier for the use of concrete as a wearing course. In this context, LCPC has developed a new concept of mix-design called Finely Graded Surface Concrete (FGSC). It is a gap-graded 0/20 mm mixture containing an excess of 2/6 mm aggregate and designed in such a way that most coarse aggregate particles sink from the surface during casting. Then a concrete is obtained with the same mechanical properties as a traditional 0/14mm mix, with the same cement content but with a surface texture essentially made of 2/6 mm aggregates. Three sections of CRC were built on a same site: a normal 0/14mm concrete with exposed aggregate or covered with a very thin 0/10 mm asphalt concrete layer, and a 600 m section with the proposed BFGS. Continuous measurements of rolling noise (CPX) were realized on these three sections as well as mechanical characterization. The paper presents the results obtained and the potential interest of the proposed approach to save high quality natural aggregates in exposed aggregate concrete wearing course.