Durability of ultra-high-performance concrete with silica fume and rice husk ash

This study analyzed the behavior of Ultra-high performance concrete (UHPC) with two different pozzolans: silica fume and rice husk ash. The use of UHPC as a structural repair material has become common, making it necessary to evaluate its behavior in these situations. The study was conducted by determining compressive strength, assessing permeability and porosity, and assessing its behavior against sulfate attack and exposure to high temperatures. The compressive strength of the concretes was greater than 130 MPa. Regarding porosity and permeability, the concrete composed of silica fume exhibits approximately 20 % lower water absorption than those molded with rice husk ash. Analyzing sulfate attack, the concrete composed of rice husk ash exhibited approximately 50 % lower sulfate penetration than the silica fume composites. The performance of the materials, when subjected to temperatures of 200 and 300 °C, showed reductions in mechanical strength of approximately 26 and 36 %, respectively. At a temperature of 400 °C, the spalling phenomenon occurred. Therefore, there is potential for the use of such a composite due to its high mechanical strength and good performance in relevant characteristics, related to low permeability and high durability.