ARCHIVED REPORTS_2019 SOIL MGMT PLAN (JULY-REVISED)

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Murphy Parkway Warehouse December 19, 2016 Job No. 146-618 Page 9 greased and wrapped in plastic to allow horizontal movement. All reinforcement and dowels should be placed at the middepth of the slab. Underlayment and Moisture Control The floor slab may be supported on the chemically treated building pad prepared as recommended above. In warehouse areas where minor moisture penetration through the slabs can be tolerated, the slab should be underlain by a minimum four-inch thick layer of Caltrans Class 2 aggregate base to serve as a leveling course. The aggregate base should be wetted immediately prior to placement of slab concrete. Moisture sensitive areas such as office areas receiving impervious floor coverings should be underlain by a minimum four-inch thick layer of clean three-quarter inch crushed rock graded such that 100 percent passes a one-inch sieve and none passes a No. 4 sieve, to serve as a capillary moisture break. In such areas the drainage rock should be covered with a plastic membrane at least 10-mils thick as a moisture vapor retarder. One to two inches of clean sand may be spread over the membrane for protection and to aid concrete curing, if desired. Alternatively, the membrane may be placed directly on the building pad beneath the rock. With the use of water-based floor adhesives, impervious floor coverings are extremely sensitive to slab moisture. Under some conditions, the small amount of moisture vapor which bypasses the vapor membrane, or even the excess water remaining in the slab from placement, can be sufficient to cause debonding and discoloration problems. To minimize moisture vapor problems, the capillary break gravel must be present to the minimum recommended thickness and the membrane must be continuous throughout the slab area. Any membrane seams should overlap by at least one foot. The membrane should be cut tight to penetrations. Tears and punctures should be sealed with membrane manufacturer-approved tape, or overlain by a second patching membrane. Slab concrete should be placed at as low a water-cement ratio as practical. The under-slab gravel layer should be protected from precipitation and other moisture; wetting of the sand over the membrane prior to concrete placement should be minimized. The edges of the slab at the building perimeter should be thickened to form a cutoff between the building exterior and under-slab gravel layers. If impervious floor coverings are planned and greater assurance against moisture problems is desired, consideration should be given to waterproofing of slabs with a quality commercial concrete sealant. A sealant or other waterproofing system may be necessary for the satisfactory performance of wood laminates, sheet vinyl, and other impervious flooring. PAVEMENTS Resistance (R) value tests are used to evaluate pavement subgrade properties. Our investigation indicates that the pavement subgrades are likely to consist of very silty sands of fair to good pavement support qualities. R values can range from five for the poorest quality clay subgrades to 70 or higher for high quality sand and gravel subgrades. Resistance value tests performed on samples of the site surface soils resulted in design R values of 64 and 65. We consider these R values to be somewhat high for the range of soils that are likely to be present on pavement subgrades, and therefore have used an R value of 45 in our calculations. The R value of 45, together with the results of unconfined compressive strength tests on soils treated with cement, have been used in the Caltrans Design Method for Flexible Pavements and in Portland Cement Association’s design method to evaluate pavement sections. The Caltrans design method uses traffic indices to account for vehicle loads, frequency, and design life. A design life of 20 years is commonly used for commercial pavements.