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TABLE 3 <br />Preliminary Geotechnical Parameters for Post -Tensioned Foundation Design <br />Parameter <br />Value <br />Expansion Classification (Assumed to be confirmed at <br />High Expansion <br />the completion of grading): <br />Thornthwaite Moisture Index From Figure 3.3 : <br />-20 <br />Constant Soil Suction From Figure 3.4 : <br />PF 3.6 <br />Center Lift <br />Edge moisture variation distance (from Figure 3.6), em: <br />Medium <br />Center lift, yr,: <br />9.0 feet <br />0.66 inches <br />Edge Lift <br />Edge moisture variation distance (from Figure 3.6), em: <br />Medium <br />Edge lift, ym: <br />5.0 feet <br />1.6 inches <br />Soluble Sulfate Content for Design of Concrete Mix in <br />Assume Negligible Exposure <br />Contact with Site Soils in Accordance with American <br />(to be confirmed at the completion of <br />Concrete Institute standard 318, Section 4.3: <br />grading) <br />Corrosivity of Earth Materials to Ferrous Metals: <br />Corrosive <br />Modulus of Subgrade Reaction, k (assuming <br />85 pci (high) <br />resaturation as indicated below): <br />Additional Recommendations: <br />1. Presaturate slab subgrade to at least optimum -moisture content or to 1.3 times optimum <br />moisture, to minimum depths of 24 inches below ground surface, respectively for high expansion <br />potentials. <br />2. Install a 15-mil moisture/vapor barrier (or equivalent) moisture/vapor barrier in direct contact <br />with the concrete (unless superseded by the Structural/Post-tension engineer*) with 1 to 2 inches <br />of sand below the moisture/vapor barrier. <br />3. Minimum perimeter foundation embedment below finish grade for moisture cut off should be 24 <br />inches for high expansion potentials. <br />4. Minimum slab thickness should be 5 inches. <br />* The above sand and Visqueen recommendations are traditionally included with geotechnical foundation <br />recommendations although they are generally not a major factor influencing the geotechnical performance of <br />the foundation. The sand and Visqueen requirements are the purview of the foundation engineer/corrosion <br />engineer (in accordance with ACI Publication 302 "Guide for Concrete Floor and Slab Construction") and <br />the homebuilder to ensure that the concrete cures more evenly than it would otherwise, is protected from <br />corrosive environments, and moisture penetration of through the floor is acceptable to future homeowners. <br />Therefore, the above recommendations may be superseded by the requirements of the previously mentioned <br />parties. <br />Project i y 6unci1 18 — 835 1 3 , 2021 <br />