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Cut into to receive a concrete structure is such that

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Unformatted text preview: from the prescribed lines. The surfaces of all forms in contact with the concrete shall be clean, rigid, tight and smooth. Suitable tleviccs shall be used to hold corners, adjacent ends, and edges of nanels or other forms together in accurate alignment. 5.1.1 manently Metal forms or metal-lined forms shall be permitted exposed surfaces only when an entire surface is to 29 for perbe built IS : 457 - 1957 completely with such forms. Curved and special forms shall be of a character that would give smooth concrete surfaces. They shall be so designed and constructed as not to warp or spring during erection or placing concrete. Forms to be used more than once shall be maintained in, serviceable condition, and shall be thoroughly clean and smooth before being Tensed. Where metal sheets are used for lining forms. thr sheets shall be placed and maintained on the forms with the minimum amount of wrinkles, bumps, or other imperfections. The use of sheet m&l tc) correct impcrfections in the lining of timber faced forms for surfaces that arc to bt* permanently exposed to view shall not be permitted. \Vhcre ply\vood is used for form lining, the joints between the sheets shall b(: smooth a11t1 as perfect as practicable, and no patching of the plywood shall be permitted for permanently exposed surfaces. Minor imperfections in the plywood shall be corrected by the use of plastic wood, secured firmly in place and sandpapered smooth after it has hardened. 5.2 Absorptive Form bng - Absorptive form lining, \vhcre directed to be used, shall be of the type and quality approved l”y the engineer-inThe form lining shall be highly absorptive to ai:- and water, and charge. through its absorptive capacity be able to eliminate voids, pits and other common defects from the concrete surface. The lining shall he readily rcmovable from the concrete without damage to the surface. It shall produce a dense co:lcmte surface of uniform and satistactorv texture a:ld The lining itself and any treatment employed in its manufactttre coiour. shall not discolour the concrete nor interfere with the IJormal chemical The backing to which absorptive lining is attached reaction of the cement. shall be sufficiently smooth, even and free from cracks, knot’ holes, and other imperfections tci avoid unevenness in the finished surface. The lining shall be ill sheets of uniform length and kvidth. Location and direction of the joints shall be approved by the tneitlccr-ill-charge. The joints between sheets shall be fitted smoothly and accurately. and patching shall be avoided. Edges shall be brought to light co11tact, t jut shall not be Cutting and trimming shall 1)~ trut: and shall bc pressed tightly together. done with tools ~41 adapted to this work so that sharp, smooth, square edges are produced. Tl~e lining shall be attached to the forms in such a Nails or tacks, manner that it is held securely and smoothly in place. and shall be driven flush. if used, shall be spaced in uniform. pattern, Dents a...
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