1. Researcher, School of Civil Engineering, Dept. of Materials Science and Engineering, Univ. of Cantabria, Av/Los Castros 44, 39005 Santander, Spain.
2. Professor, School of Civil Engineering, Dept. of Materials Science and Engineering, Univ. of Cantabria, Av/Los Castros 44, 39005 Santander, Spain (corresponding author).