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11 4. Raw water (groundwater) and canal water shall not be allowed in the mix. E. Admixtures: 1. A water reducing agent shall be used in all concrete. The admixture shall conform to ASTM Specification C494. Proportioning and mixing shall be as recommended by the manufacturer. 2. Admixtures causing accelerated setting of cement in concrete shall not be used. Air entraining admixtures with demonstrated compatibility with the concrete mix shall be used as required as a moderate addition to the water reducing agent to obtain the specified percent air in the resultant concrete. PART 3 - EXECUTION 3.01 MEASURING MATERIALS A. Materials shall be measured by weighing except as otherwise specified or where other methods are specifically authorized by the Engineer. The apparatus provided for weighing the aggregates and cement shall be suitably designed and constructed for this purpose. Scales shall have been certified by the local Sealer of Weights and Measures within one year of use. Each size of aggregate and the cement shall be weighed separately. The accuracy of all weighing devices shall be such that successive quantities can be measured to within one percent of the desire amount. Cement in standard packages (sacks) need not be weighed, but bulk cement and fractional packages shall be weighed. B. Water shall be measured by volume or by weight. The water- measuring device shall be capable of control to 1/2% accuracy. All measuring devices shall be subject to approval. Admixtures shall be dispensed either manually with use of calibrated containers or measuring tanks, or by means of an approved automatic dispenser designed by the manufacturer of the specified admixture. 3.02 MIXING 1 06/05 A. Concrete shall be ready -mixed or transit- mixed, as produced by equipment acceptable to the Engineer. No hand- mixing will be permitted. Adding water in controlled amounts during the mixing cycle shall be done only with the express approval of, and under the direction of, the Engineer. B. Ready -mix or transit -mixed concrete shall be transported to the site in watertight agitator or mixer trucks loaded not in excess of rated capacities for the respective conditions as stated on the name plate. Discharge at the site shall be within 1 -1/2 hours and within one hour when ambient temperature is above 85 degree F after cement was first introduced into the mix. Central mixed concrete shall be plant -mixed a minimum of 1 -1/2 minutes per batch and then shall be truck -mixed or agitated a minimum of 8 minutes. Agitation shall begin immediately after the pre -mixed concrete is placed in the truck and shall continue without interruption until discharge. Transit -mixed concrete shall be mixed at mixing speed for at least 10 minutes immediately after charging the truck, followed by agitation without interruption until discharged. C. All central plant and rolling stock equipment and methods shall conform to the latest Truck Mixer and Agitator Standards of the Truck Mixer Manufacturers' Bureau of the National Ready -Mixed Concrete Association, as well as ACI Standard 304 and ASTM Specification C94. 03300 -6 034138.B