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, <br /> , <br /> � � , , � <br /> P.acin� �_�ncrete :n Forms. Depvsit concrete in forms in horizontal layecs �ot �eeoer <br /> than ?4" and in a manner to avoid inc!ined construction joints. Where placement ccnsists <br /> of several layers, place each layer while preceding layer is still plastic to avoid cold � <br /> joints. <br /> Consolidate placed concrete by mechanical vibrating equipment supplemented hy hand- <br /> spading, codding or tamping. Use equipment and procedures for consolidation of ' <br /> concrete in acco�dance with ACI 309. <br /> Do not use vibrators to transport concrete inside forms. Insert and withdraw vibrators , , <br /> vertically at uniformly spaced locations not farther than visible effectiveness of <br /> machine. Place vibrators to rapidly penetrate laced la er and at least 6 ut � `� <br /> P Y " �. t����'�i�;� . •�• , <br /> layer. Do not insert vibrators into lower layers of concrete that have begutti�o se`E.:'�s/�•��, �' .;'.� <br /> each insertion limit duration of vibration to time necessary to consolidate cdnc��fe and � <br /> complete embedment of reinforcement and other embedded items without causin� , <br /> segregation of mix. ,�;�;�:�:� =. <br /> �. , ' , � <br /> Placin� Concrete Slabs: Deposit and consolidate concrete slabs in a �ontiriuous <br /> operation, within limits of construction joints, until the placing of a panel or section is <br /> completed. � ' <br /> Consolidate concrete during placing operations w that concrete is thoroughly worked <br /> around reinforcement and other embedded items and into corners. <br /> Brin� slab surfaces to correct level with straightedge and strikeoif. Use bull floats or � <br /> darbies to smooth surface, free of humps or hollows. Do not disturb slab surfaces prior <br /> to beginning finishing operations. � <br /> Maintain reinforcinR in proper position during concrete placement operations. <br /> Cold Weather Placintt: Protect concrete work from physica! damage oc reduCed strength � <br /> which could be caused by frost, freezing actions, oc low temperatures, in compliance <br /> with ACI 306 and as herein specified. <br /> When air temperature has fallen to or is expected to fall below 40 degrees F (4 degrees , <br /> C), uniformly heat water and aggregates befoce mixin� to obtain a concrete mixture <br /> temperature of not less than SO degrees F (10 de�r�es C), and not more than 80 degrees � <br /> P !27 degrees C) at point of placement. — --______ <br /> Do not use frozen materials oc materials containing ice oc snow. Do not place concrete <br /> on frozen subgrade or on subgrade containinR frozen materials. , <br /> Do not use calcium chloride, salt and other materials containing antifreeze aAents or <br /> chemical accelerators, unless otherwise accepted in mix desiRns. ' <br /> Hot �Veather Placin�: When hot weather conditions exist that would seriously impair <br /> . quality and strength of concrete, place concrete in compliance with ACI 303 and as <br /> herein specified. � <br /> CONCRETE WORK 03310 -8 � <br /> 1 <br />