Requirements of Good Portland Cement

               The requirements of good Portland cement is as follows.
             * Initial setting time should be not less than 30 minutes.
             * Final setting time should not be more than 10 hours.
             * Compression strength after 3 days not less than 16N per square millimetre.
             * Compression strength after 7 days not less than 22N per square millimetre.
             * Tensile strength after 3 days 2 N per square millimetre.
             * Tensile strength after 7 days 2.5 N per square millimetre.
             * By lechatelier method expansion not more than 10 mm.