The forms is more than 50c or 120f whenever ncccssary

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Unformatted text preview: wnpours, all freshly placed concrete shall hc covrrcd and protected against surface wash. Special precautions shall bc taken to prevent the formation of lean scams or sand streaks. Mortar coats for bonding construction joints as specificd under 4.9.1, and 4.10.5 shall not be placed or left exposed if the rain is tending to increase the water-cement ratio of the mortar. Under no conditions shall concrete bc placed in a pool or a sheet of water. The top of all badly washed or streaked surfaces shall be removed and wasted bpfore depositing the next course. 4.14 Curing and Protection 4.14.1 All concrete shall be finished surfaces of concrete shall be from the sun for at least 72 hours general, be kept continuousiy ( not 14 days. Construction joints shall protected against injury. Eqosed protected against heating and drying Concrete shall, in after placement. periodically) moist for not less than be cured in the same way as other 25 1s : 454 - 1957 concrete and shall also, if practicable, be kept moist for at least 72 hours prior to the placing of additional concrete upon the joint. Horizontal and approximately horizontal surfaces shall be cured by sprinkling or by covering with damp sand, or by the use of wet sacks which satisfactorily retain the required amount of water for curing purposes. Where damp sand or sack cover is used for curing, it shall be completely removed later. Water curing shall be used ‘on all concrete in dams and shall be applied by means of sprays or sprinklers to cover the entire area of the concrete. Forms shall be kept sprinkled until removal. Concrete shall not be disturbed by workmen walking on it or by storing materials on the surface or otherwise for at least 10 hours after placing. 4.14.2 In special cases, such as powerhouses, the use of an approved, properly-applied sealing compound on limited areas shall be permitted. The curing compound shall be of the surface membrance type which shall thoroughly seal the concrete surface. Curing compound shall not be used on joints where bonding is required. The concrete surface shall be thoroughly wetted before applying the compound. All surfaces covered with curing compound shall be protected from trafhc or injury of the sealing coat until expiration of the curing period. All methods used for curing shall leave the concrete free from any discolouration or damage to the concrete. 4.15 Repair of Concrete -Repair of all impcrfcctions of the concrete surfaces necessary to p-~~**pp surfaces that conform to the requirements shalI be completed as soon = practicable’ after removal of forms and whereever possible within 24 hours after tire removal of forms. Fins shall be neatly removed from surfaces for which finishes F2 and F3 ( see 4.16.2 ) are required. Concrete that is damaged from any cause, and concrete that is honey-combed, fractured, or otherwise defective, and concrete, which because of cxccssive surface clepressions, has to be excavated and built up to bring the surf;lce to...
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