it is called Zonatile manufactured in the 50s and 60's. Its a light concrete roof plank 18"X36". It was manufactured by W.R. Grace out of Chicago. Heres some literature. http://files.engineering.com/getfile.aspx?folder=28333e5c-6abd-4966-b805-34d9ac105f23&file=zonatile.pdf
thread507-232131
I read this earlier thread and we have just come upon Zonatile that failed in an industrial building. I was wondering if anyone has any info on it