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GS-4 <br />The exact amount of clean water specified per sack of <br />cement, and no more, shall be used for each batch of concrete. <br />zhe proper consistency of the concrete shall be <br />obtained by varying the proportions of fine and. coarse aggre- <br />gates, depending upon the character of the aggregate and <br />percentage of voids. The consistency shall be such that the <br />concrete can be puddled readily into-the corners and angles of <br />the forms and around the reinforcement without excessive <br />spading and without undue accumulation of laitance on the <br />surface. <br />The consistency of the concrete shall be controlled by <br />frequent slump tests as standardized by the A. S. T. M., the <br />Contractor providing three.standard truncated cones for the <br />purpose. The maximum slump of the concrete shall be as <br />followse <br />For mass concrete from 1 to 4 inches. <br />For wall thicker than 10 inches, and floors from 3 to <br />6 inches. <br />For walls thinner than 10 inches from 4 to 7 inches. <br />A machine batch-mixer approved by the Lngineer shall be <br />used, and each batch shall be turned 11/2 minutes in the <br />mixer. <br />Concrete from a central plant or mixed-in-transit mixer <br />trucks may be used if it complies with these specifications. <br />The kngineer shall have free access at all times to the <br />hatching and mixing plant for sampling of all materials and <br />inspection of work performed for this project. Concrete shall <br />be delivered in watertight containers which will not permit <br />segregation of the materials. When delivered, the concrete <br />shall be uniform throughout the mass. <br />Concrete must be handled and placed so as.to avoid <br />segregation. It shall not be thrown or dropped from a height <br />of more than 5 ft., but shall be deposited in layers not ex- <br />ceeding 6 inches thick, and shall be worked to fill all voids, <br />and to thoroughly encase the steel. None shall be placed in <br />water. All concrete shall be mechanically vibrated into place <br />and form a homogenous, dense, tight mass. Where the rein- <br />forcement may be too close, batches of mortar shall be used to <br />secure density of that part of the concrete. <br />No concrete or mortar shall be used which shall have <br />been mixed more than one hour. <br />Concrete shall be placed monolithic and continuous <br />where required by the Engineer or where a Joint would be . <br />harmful to the structure. All beams must be poured <br />F <br />