Reactive-powder concrete (RPC) also known as Ultra-High Performance Concrete(UHPC), is composed of Portland cement, silica fume, quartz flour, fine silica sand, high-range water reducer, water, and steel or organic fibers. It is characterized by high strength up to 29,000 pounds per square inch (psi) and flexural strengths up to 7,000 psi and very low porosity that gives excellent durability and transport properties, which makes it a suitable material for the storage of nuclear waste.
The features of RPC mix design: (1) eliminating the coarse aggregates: it just uses very fine powders such as sand, crushed quartz, and silica fume, all with particle sizes between 0.02 and 300 µm; (2) optimizing the grain size distribution to densify the mixture; (3) post-set heat-treatment to improve the microstructure; (4) addition of steel and synthetic fibers (about 2% by volume); (5) use of superplasticizers to decrease the water to cement ratio usually to less than 0.2 while improving the rheology of the paste.
RPC has found some applications in pedestrian bridges. Also, the low porosity of RPC gives excellent durability and transport properties, which makes it a suitable material for the storage of nuclear waste. A low-heat type of reactive-powder concrete has been developed to meet needs for mass concrete pours for nuclear reactor foundation mats and underground containment of nuclear wastes.