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' 1. Immediately after final screeding a dry cement/sand shake in the proportion of 2 sacks of portland cement to 350 pounds of coarse natural concrete sand shall be sprinkled evenly over the surface at the rate of approximately 500 pounds per 1,000 square feet of floor. Neat, dry cement shall not be sprinkled on the surface. This shake ' shall be thoroughly floated into the surface with an approved disc type power compacting machine weighing at least 200 pounds if a 20 inch disc is used or 300 pounds if a 24 inch disc is used (such as a "Kelly Float" as manufactured by the Weisner -Rapp Corporation of Buffalo, New York). A mechanical blade -type float or trowel is not acceptable for this work. ' a. NOTE: This operation (application of the cement/sand shake) may be eliminated at the discretion of the Engineer if the base slab concrete exhibits adequate fattiness and homogeneity, and the need is not indicated. I 2. In lieu of power steel troweling, small areas shall be compacted by hand steel troweling with the dry cement/sand shake as ordered. 3. The floor or slab shall be compacted to a smooth surface and the floating operation continued until sufficient mortar is brought to the surface to fill all voids. The surfaces shall be tested with a ' straightedge to detect high and low spots which shall be eliminated. 4. Compactions shall be continued only until thorough densification is ' achieved and a small amount of mortar is brought to the surface. Excessive floating shall be avoided. 5. After the surface moisture has disappeared, surface shall be steel - troweled to a smooth, even, impervious finish, free from trowel marks. After cement has set enough to ring the trowel, the surfaces of all slabs except concrete roof slabs and bottom tanks shall be given a second steel - troweling to a burnished finish. 3.03 HARDENER APPLICATION A. Where floor slabs are not be otherwise coated or covered, a hardener shall be applied to the floor slabs with monolithic finish after 28 days, minimum, concrete cure. The floors shall be thoroughly cured, cleaned, and perfectly ' dry with all work above them completed. The hardener shall be applied evenly and freely, using three coats, allowing 24 hours between coats. The first coat of fluorsilicate hardeners shall be 1/3 strength, second coat 1/2 ' strength and third coat 2/3 strength, and each coat shall be applied so as to remain wet on the concrete surface for 15 minutes. Sodium silicate hardener shall be applied in three coats, each at full strength and at the rate r 07/06 03350 -4 05 -5564 r