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i� ' C. Transport from to final deposit concrete mixer place of as rapidly as practicable by methods which prevent separation of ingredients and displacement of reinforcement, and which avoid re- handling. Partially hardened concrete is not to be used. D. Cold joints are to be avoided, but if they occur, are to be treated as bonded construction joints. E. At construction joints the surfaces of the concrete already placed, including vertical and inclined surfaces, shall be thoroughly cleaned of foreign materials and laitance, and weak concrete and roughened with suitable tools to expose a fresh face. At least two hours before and again shortly before the new concrete is deposited, the joints shall be saturated with water. After glistening water disappears, the joints shall be given a thorough coating of neat cement slurry mixed to the consistency of very heavy paste. The surfaces shall receive a coating at least 1/8 -inch thick, well scrubbed -in by means of stiff bristle brushes whenever possible. New concrete shall be deposited before the neat cement dries. ' F. Deposit concrete to maintain, until the completion of the unit, a horizontal plastic surface. Vertical lifts shall not exceed 24- inches and preferably l 8- inches. ' G. Chutes for conveying concrete shall be of U- shaped designed and sized to insure a continuous flow of concrete. Flat (coal) chutes shall not be employed. Chutes be shall metal or metal -lined and each section shall have approximately the same slope. The slope shall not be less than 25 nor more than 45 degrees from the horizontal and shall be such as to prevent the segregation of the ingredients. The discharge end of the chute shall be provided with a baffle plate or spout to prevent segregation. If the discharge end of the chute is more than 5 feet above the surface of the concrete in the forms, a spout shall be used, and the lower end maintained as near the surface of deposit as practicable. When the operation is intermittent, the chute shall discharge into a hopper. Chutes shall be thoroughly cleaned before and after each run, and the debris and any water shall be discharged outside the forms. Concrete shall not be allowed to flow horizontally over distances exceeding 5 feet. H. In thin sections of considerable height, concrete shall be placed using suitable hoppers, spouts with restricted outlets, or otherwise, as required or approved. I. Concrete during and immediately after depositing shall be thoroughly compacted by means of suitable tools. Internal type mechanical vibrators shall be employed to produce required quality of finish. Vibration shall be done by experienced operators under close supervision and shall be carried on long enough to produce homogeneity and optimum consolidation without permitting segregation of the solid constituents of "pumping" or migration of air. All vibrators shall be supplemented by proper wooden spade puddling adjacent to forms to removed included bubbles and honeycomb. This is essential for the top lifts of walls. All vibrators shall travel at least 10,000 rpm and be of adequate capacity. At least one vibrator ' shall be used for every 10 cubic yards of concrete placed per hours. In addition, one spare vibrator in operating condition shall be on the site. J. Concrete slabs on the ground shall be well- tamped into place and foundation material shall be well - tamped, and rolled until thoroughly compacted prior to placing concrete. K. Concrete shall be deposited continuously in layers of such thickness that no concrete will be deposited on concrete which has hardened sufficiently to cause the formation of seams and planes of weakness within the section. If a section cannot be placed continuously, construction joints may be located at points as provided for in the Drawings or approved by the Engineer. 06/05 03300 -9 03- 4138.B