1. Assistant Professor, Dept. of Civil Engineering, Assiut Univ., Assiut 71515, Egypt.
2. Associate Professor, Polymer Nanocomposite Center, Egyptian Petroleum Research Institute, Nasr City 11727, Cairo, Egypt.
3. Professor and Chair, Dept. of Civil Engineering, Univ. of New Mexico, Albuquerque, NM 87131-0001 (corresponding author).