# Reactive Powder Concrete: Durability and Applications
### Early Works  
Reactive powder concrete was successfully applied in several civil engineering projects due to its excellent mechanical and durable properties. For instance, in Sherbrooke, Canada, the first footbridge made of RPC200 was built in the world [20]. The lower chord was formed with prefabricated twin beams made with RPC200 (10 m \(\times\) 3 m). The use of RPC200 reduced the size and then the weight, increased the mechanical strength, and improved the durability. Consequently, it can resist the deicing salt effect in cold environments. The background of producing very high-performance concrete goes back to the availability of silica fume that was pioneered by Elkem (Norway) and Norwegian researchers. This availability moved [21] [PERSON] from Aalborg Cement, in 1986, to develop a very dense material named compact reinforced composite, CRC, which was a very high-performance steel fiber-reinforced concrete. The fiber content was in the range of 2-6% by volume with a strength ranging between 120 and 160 MPa. This material was developed further [22] and its durability was studied by researchers from the Institute of Construction Sciences of Spain [23]. The original reactive powder concrete was developed a bit further under the use of silica fume as a novel mineral addition, first without fibers, and after adding them due to a Bouygues and Aalborg cement collaboration [1]. This set of BPR concretes provided a basis for the development of several derivative ultra-high-performance fiber reinforced concretes (UHPRRC), e.g., Ductal(r). This is a range of materials developed by BOUYGUES, Lafarge (currently LafargeHolcim) and Rhodia, with new properties [24], and furthered by other companies. The following is worth noting:  
* New, hard, and very fine fillers were used to enhance the compactness. This fact improved both the mechanical strength and durability. * Fibers were treated chemically to enhance the matrix-fiber bonding. * Replacement of part of the sand, by mineral microfibers (e.g., wollastonite) to increase the homogeneity. More than 200 engineering projects were carried out with this type of concrete. A selection of such projects can be found in reference [25]. One good example is the Mars Hill Bridge, which was built in Iowa, USA, by Lafarge Corporation. This project won the Bridge Competition Award held by the Portland Cement Association (PCA) in 2006. Another example of this ultra-high-performance concrete (UHPC) is the rehabilitation of The Pulaski Skyway, which is a steel bridge, built in 1930s between Newark and Jersey City, USA [26]. The Federal Highway Administration (FHWA) used this bridge to assess the technical benefits offered by this concrete. It should not be forgotten that infrastructure rehabilitation in the USA is a major political issue, since it is currently estimated that more than 70,000 bridges are structurally obsolete. The new Nipigion River Bridge in Ontario is a cable-stayed structure that commenced in 2013 (full completion was in 2019). This type of concrete was used for the junction of the longitudinal and transverse joints to the steel girders and beams, and the junction of the precast tower segments [27]. Finally, the Saint-Pierre-la-Cour was the first bridge in France made with this type of concrete. It was built with 10 precast girders, and they were pre-stressed with pre-tensioned strands. All of these elements proved to be very durable with low maintenance requirements [28]. In addition, [PERSON] et al. reported several applications of reactive powder concrete in the bridge engineering [29], and they suggested that it could replace reinforcement steel bars [30]. Xialouzi Bridge is a bridge totally built of reactive powder concrete; the reinforcement steel bars were replaced by RPC [30]. Regarding the use of this ultra-high-performance concrete (UHPC) in architectural applications, a selection of roofing and facades examples built with this type of concrete can be found in reference [31].