GAIL (India) Limited

203.18.5 Accuracy of BatchingThe accuracy of batching shall be within the following tolerance:1 Cement within + 2% by weight2 Aggregate within + 5% by weight3 Water within + 0.5% by weight.3.19 Mixing of Concrete3.19.1 Machine MixingConcrete shall always be mixed in mechanical mixer. Water shall not, normally, be charged into thedrum of the mixer until all other ingredients are already in the drum and mixed for at least one minute.Mixing shall be continued until there is uniform distribution of materials and the mass is uniform incolour and consistency. The mixing time from the time of adding water shall be in accordance with IS1791, but in no case less than 2 minutes or at least 40 revolutions.3.19.2 Hand MixingWhen hand mixing is permitted by the Engineer, it shall be carried out on a water tight platform andcare shall be taken to ensure that mixing is continued until the mass is uniform in colour andconsistency. In case, of hand mixing, 10% extra cement shall be added to each batch at no extra cost toGAIL (INDIA) LTD.,3.20 Transportation of ConcreteConcrete shall be transported from the place of mixing to the place of placing concrete as rapidly aspracticable by any means, which will prevent the segregation or loss of any of the ingredients andmaintain the required workability. No water shall be mixed with the concrete after it has left the mixer.Where concrete is transported over long distances, the Contractor shall provide suitable means bywhich different grades of concrete are readily identifiable at the place of final deposit.3.21 Preparatory Works/Surface Preparation3.21.1 For Concrete Directly on Earth FoundationEarth foundation on which direct placement of concrete is specified, shall be rammed and consolidatedas directed by the Engineer such that it does not crumble and get mixed with concrete during or afterplacement. If the foundation is quite wet, the same shall be kept dry and then sufficiently consolidated,if necessary, a thin top layer of the wet soil shall be removed and replaced by sand or other suitablematerials as directed by the Engineer without extra cost to GAIL (INDIA) LTD., Care shall also betaken that earth from the sides also does not get mixed with the concrete, during or after placement,before it has sufficiently set and hardened.The earth foundation, over which concrete is to be placed directly, shall not be kept abandon at thespecified level and concrete shall be placed immediately following otherwise suitable measures shall betaken, as directed by the Engineer without extra cost to GAIL (INDIA) LTD.,