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<br />OQ24:~4 <br /> <br />Durango Pumoing Plant - Stage I <br /> <br />2. Do not place concrete on surfaces which are not free from frost, ice, water, mud, <br />and debris. <br /> <br />3. Prepare rock surfaces free from oil, objectionable coatings, and loose, <br />semidetached, and unsound fragments. Immediately prior to placement of <br />concrete, wash surfaces of rock with an air-water jet and bring surfaces to a <br />saturated surface-dry condition. Maintain surfaces in a saturated surface-dry <br />condition until covered with concrete. <br /> <br />4. Prepare a damp earth foundation for concrete placed against it, with surfaces <br />which are thoroughly moist but not muddy to a depth of 6 inches, or to <br />impermeable material, whichever is less, and maintain this condition until covered <br />with concrete. <br /> <br />C. Construction Joints <br /> <br />I. Roughen and remove all laitance from all construction joints in preparation for <br />placing adjoining concrete. <br /> <br />2. Roughen surfaces and remove laitance by mechanical abrasion or cutting, <br />sandblasting, or high-pressure water jetting of hardened (not green) concrete. <br /> <br />3. High-pressure water jetting will normally be at pressures of at least 6,000 pounds <br />per square inch, but not more than 10,000 pounds per square inch. <br /> <br />4. Thoroughly clean construction joints of loose and defective concrete, coatings, <br />sand, curing compound, and other foreign material on the surface. Maintain water <br />curing on joint if concrete is still within specified curing period. <br /> <br />5. After initial cleanup and at the last opportunity prior to placing concrete, <br />thoroughly wash concrete surface with water or air-water jets, and bring to a <br />saturated surface-dry condition. <br /> <br />D. Control Joints and Contraction Joints <br /> <br />1. Provide control joints and contraction joints where indicated on the drawings to <br />allow for volwnetric shrinkage of monolithic concrete and for movement between <br />monolithic units. <br /> <br />2. Prior to application of a bond-breaker at control and contraction joints, clean the <br />surfaces of all joints of accretions of concrete or other foreign material by <br />approved methods. <br /> <br />3. Coat the control joints and contraction joints with a wax-base curing compound <br />prior to placement of adjoining concrete. <br /> <br />4. Do not remove curing compound from joints prior to placement of adjoining <br />concrete. <br /> <br />5. Clean waterstops, reinforcing steel, or embedded items of curing compound <br />before placing adjoining concrete. <br /> <br />E. Mass Structural Concrete Placements <br /> <br />Cast-in-Place Concrete <br />03300 - 20 <br />