2000 TOWER ST ARTS AND SCIENCES BLDG 2018-01-02 MF Import

r 1 If water vapor migration through the slabs is objectionable, the gravel should be covered with a heavy plastic sheet, such as 10-mil plastic sheeting, to act as a vapor retarder. This will be desirable where the slabs will be surfaced with tile or will be carpeted. The contractor should be made responsible for maintaining the integrity of the vapor barrier during construction. A 2-inch-thick layer of sand should be placed over the vapor barrier to protect it during construction and to aid in unifomt curing of the concrete. The structural engineer s.sould be conEulted if the contractor proposes deleting the 2-inch-thick layer of sand. It may also be prudent to apply a scaler to the slab to further retard the migration of moisture Ithrough the floor. PAVEMENT RECOMMENDATIONS Subgrade Preparation We recommend that the subgradc soils in new pavement areas be prepared and evaluated as described in the "Earthwork" section of this report. In cut areas in medium dense to dense native soils, we recommend that the upper 12 inches of the existing site soils be compacted to at least 95 percent of the maximum dry density per ASTM D 1557 prior to placing pavement section materials. If the subgradc soils are loose or soft, it may be necessary to excavate the soils and replace them with structural fill, gavel borrow, or gravel base material. Based on our explorations, the majority of the pavement subgradc soils arc expected to consist of medium dense to dense glacial till. Pavement subgradc conditions should be observed and proof -rolled during construction to evaluate the presence of unsuitable subgradc soils and the need for over -excavation and piacement of a geotextile fabric. New Hot Mix Asphalt (HMA) Pavement In light -duty pavement areas (e.g., automobile parking), we recommend a pavement section consisting of at least a 2-inch thickness of/cinch LIMA (PG 58-22) per WSDOT Sections 5-04 and 9-03, over a 4-inch thickness of densely compacted crushed rock base course per WSDOT Section 9-03.9(3). In heavy-duty pavement areas (e.g., truck traffic areas, materials delivery) around the building, we recommend a pavement section consisting of at least a 3-inch thickness of/. --inch HMA (PG 58-22) over a 6-inch thickness of densely compacted crushed rock base course. The base course should b,! compacted to at least 95 percent of t)te Inaximrtm dry density (ASTM D 1557). We recommend that a proof -roll of the compacted base course be observed by a representative from our firm prior to paving. Soft or yielding areas observed during proof -rolling may require over -excavation and replacement with compacted structural fill. The pavement sections recommended above are based on our experience. Thicker asphalt sections may be needed based on the actual traffic data and intended use. Portland Cement Concrete Pavement Portland cement concrete (PCC) sections should be considered for loading dock aprons, trash duntpster arc' : and where other concentrated heavy loads may occur. We recommend that these pavements consist of at least 6 inches of PCC over 6 inches of crushed surfacing base course. A thicker concrete section may be needed based on the actual tra is data. If the concrete pavement will have M i c u F it g 1 11 c e r 5 16 rile No. 5836.002-00/040204