V. Matte et al., Simulated microstructure and transport properties of ultra-high performance cement-based materials, CEM CONCR R, 30(12), 2000, pp. 1947-1954
Ultra- high performance cement-based materials expected to be used in nucle
ar waste containers were submitted to a leaching test in order to evaluate
their long-term durability. Reactive powder concretes (RPC) were attacked b
y de-ionized water. Previous studies revealed a superficial degradation aft
er leaching with a sound zone underneath an altered porous zone in which an
hydrous silicates C3S and C2S were dissolved. To predict the long-term dura
bility of RPC, the hydration rate of cement minerals, pozzolanic reactivity
of silica fume, pore structure, and mechanisms of chemical reactions were
needed. So first, the microstructure of RPC matrix was simulated using the
NIST microstructural model. Then the transfer of Ca ions through percolatin
g water was estimated using DIFFU-Ca, a model based on the local chemical e
quilibrium. This double modeling validates the damage process related to an
instantaneous dissolution of anhydrous cement silicates at the degradation
front which results in a higher connected pore space, and is in good agree
ment with experimental results. The long-term behavior is expressed as the
depth of the altered zone, the leaching kinetics and the evolution of Ca co
ncentration in the material. (C) 2001 Elsevier Science Ltd. All rights rese
rved.