1. Magnel Laboratory for Concrete Research, Dept. of Structural Engineering, Faculty of Engineering and Architecture, Ghent Univ., Technologiepark Zwijnaarde 904, B-9052 Ghent, Belgium (corresponding author).
2. Professor, Magnel Laboratory for Concrete Research, Dept. of Structural Engineering, Faculty of Engineering and Architecture, Ghent Univ., Technologiepark Zwijnaarde 904, B-9052 Ghent, Belgium.