The Portland cement to be used shall be so ground that ninety two percent (92%) will pass through a standard number 100 sieve having ten thousand (10,000) meshes per square inch. Briquettes made from a mortar composed of one part Portland cement and two (2) parts torpedo sand, exposed to the air for one day and immersed in water for six (6) days, shall develop an ultimate strength of two hundred (200) pounds per square inch. (Ord. 27, 1928)