Properties of Strength and Pore Structure of Reactive Powder Concrete Exposed to High Temperature

This paper discusses the properties of strength and pore structure of reactive powder concrete (RPC) with various contents of cement, silica fume, and polypropylene (PP) fiber exposed to high temperatures. A series of fire tests was conducted on various RPC specimens with compressive strengths of 100 to 150 MPa (14,504 to 21,756 psi). The specimens were made with various contents of PP fiber and cement at various silica fume-cement ratios (SF/C) (0.25, 0.30, and 0.40). The explosive spalling and residual mechanical properties of RPC exposed to high temperature and the change of pore structure and hydrate products in the RPC specimens before and after the fire tests were investigated. It was confirmed that the addition of PP fiber was effective in preventing the explosive spalling of the RPC specimens in the fire tests, and that more than 2.0 kg/m(3) (3.38 lb/yd(3)) was required, which was greater than the amount in high-performance concrete. The results also indicated that the RPC specimens were more susceptible to explosive spalling as the cement content and SF/C increased. Increased cement and silica fume contents led to the formation of denser microstructures, and thus the buildup of internal vapor pressure at an elevated temperature. The explosive spalling of the RPC specimens was closely related to the pore-volume proportion (capillary porosity) of 0.1 to 100 mu m (0.395 to 395 x 10(-5) in.) to total pore volume in the matrix; this relationship should therefore be studied further.