Concrete barriers are distinguished by an extrudable character that facilitates their implementation using slipform machines. The first objective of this study was to formulate an extruded concrete in order to achieve stable road safety barriers with a flat-face. The tests were first carried out at the laboratory; then the most promising ones were tested on site. It was noted that the measure of the slump alone does not ensure the stability of concrete barriers on site. A range of variation of a yield stress (t0) was determined for which the concrete was extrudable and stable. This reduced the number of tests on site and therefore minimised economic costs. The second objective was to utilise local mineral admixtures with the aim of improving concrete properties and reducing environmental impacts and costs. Furthermore, the hardened concrete properties were tested for compressive strength, durability and shrinkage. The results indicated that the mineral admixtures improved the concrete compressive strength and lead to good durability while minimising shrinkage. This increased road user safety by providing high quality and reliable barriers. In conclusion, it is possible to successfully formulate an extrudable concrete in the laboratory from rheological parameters. The inclusion of mineral admixture has proven to be very beneficial.