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• If a truck mixer or agitator is used for transporting concrete to the delivery point, discharge shall be completed <br /> within 1.5 hours or before 250 revolutions of the drum or blades,whichever occurs first,after the introduction of the cement <br /> to the aggregates. Under conditions contributing to quick stiffening of the concrete, or if the temperature of the concrete is <br /> 30°C or above,the time allowed may be less than 1.5 hours. If an admixture is used to retard the set time,the temperature of <br /> the concrete shall not exceed 30°C,the time limit shall be 2 hours,and the revolution limitation shall be 300. <br /> • If nonagitating hauling equipment is used for transporting concrete to the delivery point, discharge shall be <br /> completed within one hour after the addition of the cement to the aggregates. Under conditions contributing to quick <br /> stiffening of the concrete, or when the temperature of the concrete is 30°C or above, the time between the introduction of <br /> cement to the aggregates and discharge shall not exceed 45 minutes. <br /> • Each load of concrete delivered at the job site shall be accompanied by a weighmaster certificate showing the mix <br /> identification number, nonrepeating load number, date and time at which the materials were batched, the total amount of <br /> water added to the load, and for transit-mixed concrete, the reading of the revolution counter at the time the truck mixer is <br /> charged with cement. This weighmaster certificate shall also show the actual scale masses (kilograms) for the ingredients <br /> batched. Theoretical or target batch masses shall not be used as a substitute for actual scale masses. <br /> • Weighmaster certificates shall be provided in printed form, or if approved by the Engineer, the data may be <br /> submitted in electronic media. Electronic media shall be presented in a tab-delimited format on a 90 mm diskette with'a <br /> capacity of at least 1.4 megabytes. Captured data, for the ingredients represented by each batch shall be "line feed, carnage <br /> return"(LFCR)and'one line, separate record"with allowances for sufficient fields to satisfy the amount of data required by <br /> these specifications. <br /> • The Contractor may furnish a weighmaster certificate accompanied by a separate certificate that lists the actual <br /> batch masses or measurements for a load of concrete provided that both certificates are imprinted with the same nonrepeating <br /> load number that is unique to the contract and delivered to the job site with the load. <br /> • Weighmaster certificates furnished by the Contractor shall conform to the provisions in Section 9-1.01, <br /> "Measurement of Quantities." <br /> 90-6.04 TIME OR AMOUNT OF MIXING <br /> • Mixing of concrete in paving or stationary mixers shall continue for the required mixing time after all ingredients, <br /> except water and admixture,if added with the water,are in the mixing compartment of the mixer before any part of the batch <br /> is released. Transfer time in multiple drum mixers shall not be counted as part of the required mixing time. <br /> • The required mixing time, in paving or stationary mixers, of concrete used for concrete structures, except minor <br /> structures,shall be not less than 90 seconds or more than 5 minutes,except that when directed by the Engineer in writing,the <br /> requirements of the following paragraph shall apply. <br /> The required mixing time,in paving or stationary mixers,except as provided in the preceding paragraph,shall be not <br /> less than 50 seconds or more than 5 minutes. <br /> • The minimum required revolutions at the mixing speed for transit-mixed concrete shall not be less than that <br /> recommended by the mixer manufacturer, but in no case shall the number of revolutions be less than that required to <br /> consistently produce concrete conforming to the provisions for uniformity in Section 90-6.01, "General." <br /> • When a high range water-reducing admixture is added to the concrete at the job site,the total number of revolutions <br /> shall not exceed 300. <br /> 90-6.05 HAND-MIXING <br /> Hand-mixed concrete, shall be made in batches of not more than 0.25-m3 and shall be mixed on a watertight, level <br /> platform. The proper amount of coarse aggregate shall be measured in measuring boxes and spread on the platform and the <br /> fine aggregate shall be spread on this layer, the 2 layers being not more than 0.3-meters in total depth. On this mixture shall <br /> be spread the dry cementitious materials and the whole mass turned no fewer than 2 times dry; then sufficient clean water <br /> shall be added, evenly distributed, and the whole mass again turned no fewer than 3 times, not including placing in the <br /> carriers or forms. <br /> 90-6.06 AMOUNT OF WATER AND PENETRATION <br /> • The amount of water used in concrete mixes shall be regulated so that the penetration of the concrete as determined <br /> by California Test 533 or the slump of the concrete as determined by ASTM Designation: C 143 is within the nominal values <br /> shown in the following table. When the penetration or slump of the concrete is found to exceed the nominal values listed,the <br /> mixture of subsequent batches shall be adjusted to reduce the penetration or slump to a value within the nominal range <br /> shown. Batches of concrete with a penetration or slump exceeding the maximum values listed shall not be used in the work. <br /> If Type F or Type G chemical admixtures are added to the mix, the penetration requirements shall not apply and the slump <br /> shall not exceed 225 mm after the chemical admixtures are added. <br /> Contract No. 10-OM7104 <br /> 83 <br />