# Reactive Powder Concrete: Durability and Applications
## 4 Discussion  
Ultra-high-performance material reactive powder concrete origins, durable performance, and the main applications are presented and analyzed in this paper. Incorporation of very fine materials, such as silica fume or quartz powder into the concrete matrix to achieve  
Figure 4: Carbonation rate of four high strength concretes cured at four different conditions: (**a**) carbonation rate; (**b**) Carbonation rate versus compressive strength relationship. Figure 5: Nyquist diagram of the reactive powder concrete (RPC200). a high level of compactness, combined with the utilization of additives to reduce the water/binder ratio, led to the development of a new generation of high strength/performance concretes. However, not all show the same durability. Pore volume measured by means of mercury intrusion porosimetry (MIP) was much lower in reactive powder concrete (RPC200) than in high-performance concrete, C80, and normal concrete, C30. The porosity of RPC200 was concentrated around 0.01 \(\upmu\)m, which is four times lower than the concentration of the pores in the high-performance concrete, C80. A similar trend was also observed in normal concrete, C30. In this case, porosity around 0.01 \(\upmu\)m was seven times higher than that of RPC200. These findings show the great compactness of RPC200. Because mercury intrusion porosimetry (MIP) measures the connection from the concrete surface to the pore, this technique fails to measure the internal pore size. Accordingly, the air permeability coefficient was about 50 times lower in RPC200 than in C80, and the effective chloride coefficient was about 30 times lower. In addition, the carbonation depth in RPC200 after two years of natural exposure was almost nil. Regarding the corrosion parameters, similar results were found, i.e., the corrosion rate was much lower (25 times) in RPC200 than in C80. Furthermore, its resistivity was about half of the value found in C80. The excellent mechanical and durable properties of this material makes it a good option for special civil works and buildings because it prolongs their service life in aggressive environments. In addition, it was shown that by optimizing the procedure to reinforce the matrix with fibers, it is possible to achieve an adequate tensile performance to manufacture structural members without reinforcement. Consequently, in some cases, the use of RPC could replace steel reinforcement, leading to a simpler construction procedure. Furthermore, the steel reinforcement corrosion is avoided. Therefore, reactive powder concrete derivative concretes are promising cement-based materials for high durability concrete structures, such as ultra-high-performance fiber reinforced concretes (UHPFRC). In addition, the peculiar properties of reactive powder concrete makes it a suitable material for use in pre-stressed and precast concrete elements. To summarize, experimental measurements of air permeability, porosity, water absorption, carbonation rate, corrosion rate, and resistivity are evidence of the better performance of UHPFRC over HPC. The main barrier for UHPC is its cost--a life cycle cost analysis is seldom made for the selection of the structural material and, consequently, the initial cost. On the other hand, although these materials are now being included in codes for structural calculations, some of the highest strengths are still not well known by numerous designers, meaning these \"high strengths\" are not used in all structural possibilities. However, the durability of these materials is a strong reason for the designer to consider them, particularly when taking into account the whole life cycle. For UHPCs of the future, new mixes are being developed that will improve their characteristics. Different mix designs were reported in the literature [34; 35; 36; 37]. For instance, [PERSON] et al. [38] mixed Portland cement with silica fume, ground granulated blast-furnace slag, and limestone, with a water/binder ratio of 0.16, and steam curing. They reached a compressive strength of 176 MPa.