Durability performance of uncracked and cracked nanoadditioned UHPFRCs in a dynamic leaching system

This work aims to analyze the aggressiveness induced by waters rich in sulfate and chloride simulating the water from geothermal power plants with an ultra high performance fiber reinforced concrete (UHPFRC) in cracked and un-cracked states. A dynamic water interaction has been reproduced by a test in which water impacts on the surface of the concrete. The chemical composition of the water leads to a leaching and interaction with the concrete surface, and the movement of the water provokes a mechanical erosion. Ionic composition and pH of the leachates have been evaluated together with mass losses. The self-healing ability of the cracked UHPFRC is evaluated with Non-Destructive Techniques (NDT) and visual inspection.
The plain UHPFRCs exhibit a good response during one year of exposure. No sealing of the crack surface has been observed neither mass losses are detected. The pH of the leachates varies during tests in the range from the initial pH=3 to near-neutral conditions. The ionic data indicate that alkalis (K and Ca) are the main elements released from the concretes. Chloride ions remain in the leachate indicating no entrance in the concrete matrix, while sulfate and sodium ions decrease probably due to the reaction and solid phases precipitation on the concrete surface.