Durability of an Ultra High Performance Fiber Reinforced Concrete (UHPFRC) under progressive aging

We assess the durability of an Ultra High Performance Fiber Reinforced Concrete (UHPFRC) after accelerated aging, i.e. after partial drying, or 105 degrees C oven-drying (dry reference state), 200,300 or 400 degrees C heat-treatment, or progressive splitting (Brazilian test). Our key experimental tool is gas permeability K-gas under varying confinement P-c, coupled to MIP and SEM analysis. UHPFRC properties are compared to standard mortar and ordinary concrete. Whereas usual UHPFRCs involve pozzolanic additions and thermal curing, this UHPFRC does not, and is significantly more porous (by 9-10%). However, 74% of its porosity comprises pores smaller than 4 nm, i.e. located within the C-S-H. Dry reference state UHPFRC lies in the range of very high durable materials, with an average K-gas = 10(-18) m(2). Damage by heat-treatment at 400 degrees C induces limited de-bonding at the fiber/paste interface, which increases K-gas up to 10(-17) m(2) at P-c = 6 MPa. While sustaining more than 300 utm/m tensile strain, K-gas of UHPFRC remains virtually identical. (C) 2013 Elsevier Ltd. All rights reserved.