SPEC WRITER NOTES: Use following Article only if SELECT SUBBASE is specified. If Subbase is selected, delete the phrase (where required). SELECT SUBBASE (WHERE REQUIRED) Mixing: Proportion select subbase by weight or by volume in quantities so final approved jobmixed formula gradation, liquid limit, and plasticity index requirements will be met after subbase course has been placed and compacted. Add water in approved quantities, measured by weight or volume, to produce uniform blend. Placing: Place mixed material on prepared subgrade in uniform layer to required contour and grades, to maximum 200 mm (8 inches) loose depth that, when compacted, will produce layer of required thickness. When required compacted thickness exceeds 150 mm (6 inches), place subbase material in equal thickness layers. Remove unsatisfactory areas and replace with satisfactory mixture, or mix material in placement area. Adding thin layers of material to top in order to meet grade will not be permitted. When subbase elevation is 13 mm (1/2 inch) or more below grade, excavate top layer and replace with new material to minimum 75 mm (3 inches) compacted thickness. Compaction: Perform compaction with approved hand or mechanical equipment well suited to material being compacted. Moisten or aerate material as required to provide moisture content that will readily facilitate obtaining specified compaction with equipment used. Compact each subbase to minimum 95 percent or 100 percent of maximum density as specified by AASHTO T180 or AASHTO T99, respectively. Tolerances: Test completed subbase for grade and cross section with straight edge. Surface Variation: Maximum 10 mm (3/8 inch) each layer. Variation from Indicated Thickness: Maximum 13 mm (1/2 inch). Protection:
Burlap Mat: Provide minimum two layers kept saturated with water during curing period. Overlap mats minimum 150 mm (6 inches). Impervious Sheeting: Provide waterproof paper, polyethylenecoated burlap, or polyethylene sheeting. Wet exposed concrete surface with fine spray and cover with sheet materials. Overlap sheets minimum 300 mm (12 inches). Securely anchor sheet materials preventing displacement. Liquid Membrane Curing Compound: Protect joints indicated to receive sealants preventing contamination from curing compound. Insert moistened or fiber rope into joint or cover joint with waterproof paper. curing compound before concrete dries. Apply curing compound in two coats at right angles to each other. Application Rate: Maximum 5 sq. m/L (200 sq. ft./gal.), both Immediately reapply curing compound to surfaces damaged during curing period. SPEC WRITER NOTE: When the project is located in an area where winter damage from deicing chemicals and freezethaw cycles pose a serious problem, check the need for a special protective coating of linseed oil mixture. The coating protects only against the action of urea, sodium chloride, and calcium chloride used for deicing purposes. Protection against these chemicals is not required for concrete that will be in place for a cumulative time of six weeks at a continuous minimum temperature of 5 °C (40 °F), excluding the curing time. Otherwise, give concrete protective coating. CONCRETE PROTECTIVE COATING Apply protective coating of linseed oil mixture to exposedtoview concrete surfaces, drainage structures, and features that project through, into, or against concrete exterior improvements to protect the concrete against deicing materials. Complete backfilling and curing operation before applying protective coating. Dry and thoroughly clean concrete before each application.