1. Prin. Res., NDE Lab., Korea Res. Inst. of Standards and Sci., Taejon, 305-600, South Korea.
2. Asst. Prof., School of Civ. Engrg., Purdue Univ., West Lafayette, IN 47907-1284.
3. Walter P. Murphy Prof. and Dir. of the NSF Ctr. for Advanced Cement Based Mat., Northwestern Univ., Evanston, IL 60208-4400.