1. Professor, Institute of Building Materials and Structures, Dept. of Civil Engineering, Cracow Univ. of Technology, St. Warszawska 24, Kraków 31-155, Poland.
2. Associate Professor, Institute of Building Materials and Structures, Dept. of Civil Engineering, Cracow Univ. of Technology, St. Warszawska 24, Kraków 31-155, Poland (corresponding author).