Enhanced durability of ultra high performance concrete by incorporating supplementary cementitious materials

Author(s): E. Ghafari, H. Costa, E. Júlio, A. Portugal, L. Durães
Paper category: Conference
Book title: 2nd International conference on Microstructural-related Durability of Cementitious Composites
Editor(s): Guang Ye, K. Van Breugel, Wei Sun, Changwen Miao
Print ISBN: 978-2-35158-129-2
e-ISBN: 978-2-35158-123-0
Publisher: RILEM Publications SARL
Pages: 1422- 1430
Total Pages: 8
Language: English

Most aspects of concrete durability are directly related with its porous structure, since capillary pores are responsible for fluids’ migration in the concrete matrix. Ultra high performance concrete (UHPC) not only presents ultra-high compressive strength but also exhibits ultra-high durability, due to its ultra-dense structure and consequently highly reduced porosity. However, high dosages of silica fume, commonly adopted in UHPC, also lead to high autogenous shrinkage. This deformation, occurring at early ages, induces high internal stresses which, in turn, cause microcracking, increasing permeability and, therefore, reduces the durability of concrete structures.

The experimental study herein described was conducted aiming to replace silica fume by another fine supplementary cementitious materials (SCMs), such as fly ash (FA) and ground granulated blast furnace slag (GGBS), in order to reduce the amount of autogenous shrinkage, without changing concrete mechanical properties and porosity. The adopted approach involved partial or complete replacement of silica fume by SCMs. Autogenous shrinkage and compressive strength were assessed. Pores size distribution and pores volume were measured using nitrogen gas adsorption test. Total volume of permeable voids (VPV) of specimens was determined through boiling procedure. Results showed a good correlation between the refinement of UHPC fines pore structure and the reduction of autogenous shrinkage. It was concluded that incorporating GGBS, in either binary or ternary blends, does not change concrete mechanical properties or porosity but reduces autogenous shrinkage due to a refined fine pore structure.

Online publication: 2013
Publication Type: full_text
Public price (Euros): 0.00