Recycled concrete mixes for slip-form paving of roads and airports

Slip-form paving is gaining consensus in road and airport construction due to high production rates and automation of the process. Concrete slabs are extruded by pulling the forms continuously through and surrounding the plastic concrete mass. The technology uses low-slump cement concrete mixes so that the fresh mass is able to hold its shape once the slip-form paver has passed; besides low-slump, several other parameters should be considered for a proper slip-form concrete mix, especially at the fresh state. To date, recycling is being commonly adopted in concrete mixes to address sustainability in construction of transport infrastructures. Recycled Concrete Aggregates (RCA) are used to reduce the consumption of virgin materials although their increased porosity leads to higher absorption and generally lower mechanical performance. The present study aimed at evaluating the compatibility of 100% recycled concrete mixes with slipform paving; recycled concrete was tested to evaluate the fresh-state properties as well as the hardened strength. Results showed that slip-form effective and high-resistance mixes could be prepared by using high content of RCA.