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6. Where pavement or surfacing is to be placed around or adjacent to manholes or z drainage inlets which will be located within traffic lanes, such structures shall not be 3 constructed to final grade until after the pavement or surfacing has been placed around 4 these locations. 5 8 7. Where a schedule for placing concrete is shown on the plans no deviation will be 7 permitted therefrom unless approved in writing by the Engineer. , 8 9 8. Mixed concrete, after being deposited, shall be consolidated until all voids are filled and 10 free mortar appears on the surface. The concrete shall be placed as nearly as possible >> in its final position and the use of vibrators for extensive shifting of the mass of fresh 12 concrete will not be permitted. Except for concrete used in cast-in-place piles, fresh 13 concrete shall not be permitted to fall from a height greater than 4 feet without the use 14 of adjustable length pipes, tubes or double belting placed to prevent segregation of the , 15 concrete. Double belting shall not be used unless the thickness of the member is less 18 than 16 inches. n 18 9. In vertical sections, concrete shall be deposited continuously in horizontal layers of 24 , 19 inches maximum depth so as to maintain a horizontal plastic surface until the completion 20 of the unit. No concrete shall be deposited on concrete which has hardened sufficiently 21 to cause the formation of seams and planes of weakness within the section. 22 23 10. Concrete for horizontal members or sections shall not be placed until the concrete in the 24 supporting vertical members or sections is no longer plastic and has been in place at 25 least two hours. 28 27 11. In all slabs, concrete shall be deposited in a continuous or monolithic operation to the , 28 full thickness of the slab. Each batch shall be dumped against previously placed 29 concrete and not away from it, and shall not be dumped in separate piles and then 30 worked together. 37 32 12. Concrete shall not be mixed or placed while the atmospheric temperature surrounding 33 the work is at or below 35 degrees F., nor when there is indication that the temperature 34 may drop below 35 degrees F, within 24 hours. , 35 38 13. The concrete in each integral part of the structure shall be placed continuously, and 37 work will not be allowed to commence on any such part unless sufficiently inspected and 38 approved material for the concrete is on hand, and forces and equipment are sufficient ' 39 to complete the part without interruption in the placing of the concrete. 40 41 C. Concrete Vibrating: 42 43 1. With the exception of concrete placed as pipe culvert headwalls and endwalls, slope 44 paving and aprons, and concrete placed under water, all concrete shall be consolidated 45 by means of high frequency internal vibrators within 15 minutes after it is deposited in 48 the forms. The vibrators shall not be attached to or held against the forms or the 47 reinforcing steel. The vibrating shall be done with care and in such manner that 48 displacement of reinforcement, ducts, and embedded items is avoided. 49 50 2. All concrete shall be consolidated by vibration so that the concrete is thoroughly worked 51 around the reinforcement, around embedded items, and into corners of forms, ' 52 eliminating all air or stone pockets which may cause honey-combing, pitting, or planes CONCRETE 042894 03100-8