Tightly together done with tools 41 adapted to this

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Unformatted text preview: nd hammer marks in the surface of the lining shall be avoided. After the lining has been attached to the form, the joints shall be rubbed Where absorptive with a smooth tool to press down any projecting fibres. form lining is in contact with the face of a previous pour, care shall be used in setting and sufficient pressure shall be applied in tightening form anchors to produce continuity and evenness at the face, free from offsets, sand The lining shall be kept dry and shall streaks, and other irregularities. not be reused. 30 IS : 457 - 1957 5.3 Form Ties -The use of metal rods or other similar devices embedded in the concrete for holding forms shall be permitted if the ends of the rods are omitted or subsequently removed to a depth of not less than 5 cm ( or 2 in ) from the surface of the concrete without injury to the concrete, provided that for walls subjected to water pressure on one side and required to be watertight, the rods shall not be taken through the wall. Complete removal of embeddedbds shall not be permissible. Removal of embedded fasteners on the ends of the rods shall be done so as to leave holes of regular shape for reaming. All holes left by the removal of fasteners from the ends of the rods shall be immediately reamed with suitable toothed reamers so as to leave the surfaces of the holes clean and rough and completely filled with dry patching mortar, and the surface U’ire ties shall be pershall be finished to match the adjacent concrete. mitted only where specifically approved, and shall be cut off fhsh with the surface of the concrete after the forms are removed. Wire ties shall not be used where permanently exposed finished surfaces are required. 5.4 Erection of Forms - Before placing concrete, the surfaces of all forms, except those lined with absorptive form lining, shall be oiled with a suitable non-staining oil, and, immediately before concrete is placed, precautions shall be taken to see that all forms are in proper alignment and that all form anchors and ties are thoroughly secure and tight. Special care shall be- taken to oil thoroughly the form strips for narrow grooves so as to prevent swelling of the forms and consequent damage to the concrete prior to or during the removal of forms. Where forms for continuous surfaces are placed in successive units, the forms shall fit tightly uver the completed surface so as to prevent leakage of mortar from the concrete and to maintain accurate alignment of the surface. Care shall be taken to -see that the construction joints formed are smooth, free from sharp deviations, projections, or edges. Particular attention shall be given in setting and tightening the form, so that the construction joint surfaces are plumb and accurately aligned. 5.5 Removal of i!‘wms - Removal of forms shall never be started until the concrete has thoroughly set and has aged to give it sufficient strength to carry twice its own wtiight plus the live load which is likely to come on the structure during...
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