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The table is a consolidation of the graphs indicating the appropriate length of time required to reach a given rate of water vapor outflow, in pounds of water (8.33 pounds per gallon), per 1,000 square feet, in a twenty four hour period. The table and graphs indicate the minimum relative hydrating times, under laboratory conditions, at 73⁰ F and 50% relative humidity, required for concrete, at the appropriate water to cement ratio, in order for a slab to achieve a minimum water vapor transmission rate of three pounds, per 24 hours, per 1,000 square feet.

All graphs indicate continuous exposure for the entire duration. The first graph indicates relative hydration times for concrete in contact with water vapor and would be typical slab-on-grade exposure conditions. The second graph indicates concrete exposed directly to water, such as a slab placed on a saturated sand/visqueen vapor barrier, exposed to constant wet, rainy weather conditions. The third graph indicates concrete which has been air dried only with no exposure to either water or water vapor, indicating slab exposure to absolutely dry soil conditions. The air dried exposure indicates that even when not exposed to normal water vapor conditions there is substantial water vapor outflow for a given period of time

The Portland Cement Association study indicates water vapor transmission under the given laboratory exposure conditions, however, it does not state whether the water, water vapor or air had been maintained at a constant 54⁰ F, approximately the temperature of most soil conditions under slab-on-grade. Had the exposure environment been maintained at this 54⁰ F temperature a greater vapor pressure would have existed, thus, creating even higher water vapor flow rates for a given period of time, at the appropriate water to cement ratio.

The higher the slump/water to cement ratio, the longer the period of time required for complete hydration of the cement paste and a longer period of time is required before impermeable flooring materials can be installed. The slump requirements of MOXIE 1800 SUPER-ADMIX are that slump may only be increased PROVIDED NO bleed water is present, then make adjustments to the water/cement ratio. Additionally, the presence of bleed water will cause shrinkage cracking.

The absence of bleed water ensures the proper water to cement ratio which will result in a minimum time frame of approximately two to three months for the installation of flooring.

Technical Services

WV = Water Vapor exposure

D = Dried only, no water or water vapor exposure

 * Pounds, by weight of water, per 1,000 square feet, per 24 hours calculated by dividing grains per hour by 7000. Factor as stated in MOISTURE MIGRATION - CONCRETE SLAB ON GROUND CONSTRUCTION, H. W. Brewer, Reprinted form Journal of the PCA Research and Development Laboratories, Vol. 7, No. 2, 2-17 (May, 1965) ã Portland Cement Association, 1965, pg. 4, col. 2, par. 2 . Result is multiplied by 1,000 (square feet) and 24 (hours) to arrive at the pounds per 1,000 square feet, per 24 hours.

Data derived from a reprint, H. W. Brewer, MOISTURE MIGRATION - CONCRETE SLAB ON GROUND CONSTRUCTION, ã Portland Cement Association, 1965, Table 4-MIX DATA AND PHYSICAL PROPERTIES-SERIES 3 CONCRETE, from the Journal of the PCA, Research and Development Laboratories, (May, 1965) ã Portland Cement Association, 1965, Bulletin D89, pg. 15.

Table of Concrete Moisture Migration, ã MOXIE International, Inc., 1996

 Data derived from a reprint, H. W. Brewer, MOISTURE MIGRATION - CONCRETE SLAB ON GROUND CONSTRUCTION, ã Portland Cement Association, 1965, Table 4-MIX DATA AND PHYSICAL PROPERTIES-SERIES 3 CONCRETE, from the Journal of the PCA, Research and Development Laboratories, (May, 1965) ã Portland Cement Association, 1965, Bulletin D89, pg. 15.

Water Vapor Flow Rates - Graph 2, ã MOXIE International, Inc., 1996

 Data derived from a reprint, H. W. Brewer, MOISTURE MIGRATION - CONCRETE SLAB ON GROUND CONSTRUCTION, ã Portland Cement Association, 1965, Table 4-MIX DATA AND PHYSICAL PROPERTIES-SERIES 3 CONCRETE, from the Journal of the PCA, Research and Development Laboratories, (May, 1965) ã Portland Cement Association, 1965, Bulletin D89, pg. 15.

paints, coatings, surface treatments and floor coverings will fail.

WATER VAPOR PRESSURE DIFFERENCE, SUB-GRADE TO ROOM, AT THE ABOVE FIGURES EQUALS .084 PSI, CONTINUOUS.