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II <br />J <br />]i <br />J <br />C <br />11' <br />U. <br />u <br />n <br />k <br />u <br />n <br />u <br />u <br />3. Potable tap water will normally fulfill the above requirements. <br />4. Raw water (groundwater) and canal water shall not be allowed in the mix. <br />E. Admixtures: <br />1. A water reducing agent shall be used in all concrete. The admixture shall <br />conform to ASTM Specification C494. Proportioning and mixing shall be as <br />recommended by the manufacturer. <br />2. Admixtures causing accelerated setting of cement in concrete shall not be <br />used. Air entraining admixtures with demonstrated compatibility with the <br />concrete mix shall be used as required as a moderate addition to the water <br />reducing agent to obtain the specified percent air in the resultant concrete. . <br />PART 3 - EXECUTION <br />3.01 MEASURING MATERIALS <br />A. Materials shall be measured by weighing except as otherwise specified or where <br />other methods are specifically authorized by the Engineer. The apparatus <br />provided for weighing the aggregates and cement shall be suitably designed and <br />constructed for this purpose. Scales shall have been certified by the local Sealer <br />of Weights and Measures within one year of use. Each size of aggregate and the <br />cement shall be weighed separately. The accuracy of all weighing devices shall be <br />such that successive quantities can be measured to within one percent of the <br />desire amount. Cement in standard packages (sacks) need not be weighed, but <br />bulk cement and fractional packages shall be weighed. <br />B. Water shall be measured by volume or by weight. The water - measuring device <br />shall be capable of control to 1/2% accuracy. All measuring devices shall be <br />subject to approval. Admixtures shall be dispensed either manually with use of <br />calibrated containers or measuring tanks, or by means of an approved automatic <br />dispenser designed by the manufacturer of the specified admixture. <br />3.02 MIXING <br />1 06/07 <br />A. Concrete shall be ready -mixed or transit - mixed, as produced by equipment <br />acceptable to the Engineer. No hand - mixing will be permitted. Adding water in <br />controlled amounts during the mixing cycle shall be done only with the express <br />approval of, and under the direction of, the Engineer. <br />B. Ready -mix or transit -mixed concrete shall be transported to the site in watertight <br />agitator or mixer trucks loaded not in excess of rated capacities for the respective <br />conditions as stated on the name plate. Discharge at the site shall be within 1 -1/2 <br />hours and within one hour when ambient.temperature is above 85 degree F after <br />cement was first introduced into the mix. Central mixed concrete shall be <br />plant -mixed a minimum of 1 -1/2 minutes per batch and then shall be truck -mixed <br />or agitated a minimum of 8 minutes. Agitation shall begin immediately after the <br />pre -mixed concrete is placed in the truck and shall continue without interruption <br />until discharge. Transit -mixed concrete shall be mixed at mixing speed for at least <br />10 minutes immediately after charging the truck, followed by agitation without <br />interruption until discharged. <br />C. All central plant and rolling stock equipment and methods shall conform to the <br />latest Truck Mixer and Agitator Standards of the Truck Mixer Manufacturers' <br />03300 -6 03 -4197 <br />