1. Professor, Univ. of South Brittany, Laboratoire d’Ingénierie des Matériaux de Bretagne, Centre de Recherche, Rue de Saint Maudé, BP92116 56321 Lorient cedex, France (corresponding author).
2. Dept. of Civil and Environmental Engineering, National Univ. of Singapore, Kent Ridge Crescent, Singapore 119260, Singapore.
3. Professor, Dept. of Civil and Environmental Engineering, National Univ. of Singapore, Kent Ridge Crescent, Singapore 119260, Singapore.