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Students in the materials lab mixed concrete with the following ingredients: 9.7 kg of cement, 18.1 kg of sand, 28.2 kg of gravel, and 6.5 kg of water. The sand has a moisture content of 3.1% and an absorption of 4.2%. The gravel has a moisture content of 3.4% and an absorption of 4.4%. Since water absorbed in the aggregate does not react with the cement or improve the workability of the plastic concrete, what is the water-cement ratio of this mix according to the American Concrete Institute’s weight mix design method? If a water–cement ratio of 0.5 is required using the same materials and ingredients but different amount of mixing water, what is the weight of the mixing water to use?
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