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� Valata Road 5-Lot Residential Development Decer$�B� - Page 133 <br /> � <br /> �� <br /> potential for moZd growth or other microbial confamination. These studies a�so <br /> concluded that it is preferable to eliminate the sand layer and place the slab in direct <br /> contact wifih the vapor retarder, particularly during wet weather construction. However, <br /> placing the concrete directly on the vapor retarder would require special attention to using <br /> the proper vapor retarder, concrete mix desig�, and finishing and cwring technic�ues. In <br /> this case, the vapor retarder should be underlain by at least 2 inches of c�ean washed pea <br /> gravel or crushed rock. <br /> 7. When concrete s�abs are in direct contact with vapor retarders, t�e concrete water to <br /> cement{w/c) ratio must be correctly specified to conh'ol bleed water and plastic shrin�Cage <br /> and cracking. The concrete w/c ratio for this type of application is typical�y in the range <br /> of 0.45 to 0.5. The concrete should be properly cured to reduce slab curling and glastic <br /> shrinkage cracking. Concrete materials, placement, and curing methods should be <br /> specified by the design professional. <br /> 8. To furYher protect rnoisture-sensit'rve floor coverings, tne perirnEters of the post-t��sioned <br /> slabs or structural mat foundations could be deepened to per�etcate a m.ininnuxn of 3 inches <br /> into the subgrade soii. Alsa, the concrete could be proportioned to reduce its porosity <br /> (and its corresponding potentiai for transmitting moisture) by luniting the wlc ratio �o <br /> 0.48 or less. <br /> 9. The post-tensioned slabs or structurai mat foundations should be constructed a.nd <br /> maintained in accordance with the publication Construction and Maintenance Manual for <br /> Post-Tensroned Slab-on-Ground Foarndations by the Post-Tensioning Tnstitute. Particular <br /> attention should be paid to the "�'roperty Owner Maintenance" and "Landscaping" <br /> sections of the Manual. <br /> Driiveway Consti-uchon <br /> 1. Asphalt- Pave�nent designs for t�affic indexes of 4.0 to 5.5 at 0.5 increments are pra�ided <br /> for yaur use. Tiie State of California Highway Design Manual, ASPHALT CONCRETE <br /> PAVEMENT, Secti�n 7-651, dated December 1, 1981 was used in computing pavernent <br /> sections. Alternate pavernent sections are presented below. <br /> Native soil subgrade areas in the }�roposed asphalt pavement areas should be scarified at <br /> least 8 ir�ches deep, moisture conditioned, and tlien compacted to at least 90 percent <br /> 13 <br />