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1 <br />429 The Contractor shall furnish awater-measuring device in good working condition, <br />430 mounted on each transit mix truck, for measuring the water added to the mix after the <br />431 truck has left the charging plant. Each measuring device shall be equipped with aneasy- <br />432 to-read gauge. Water shall be measured to the accuracy prescribed in. AASHTO M 157. <br />433 <br />434 (d) Self Contained Mobile Mixer. Proportioning and mixing equipment shall be of the self- <br />435 contained, mobile, continuous mixing type subject to the following: <br />436 <br />437 The mixer shall be self-propelled and be capable of can•ying sufficient unmixed dry, bulk <br />438 cement, fine aggregate, coarse aggregate, admixtures and water to produce on the site not <br />439 less than 6 cubic yards of concrete. The mixer shall have one bin for each size aggregate. <br />440 <br />441 The mixer shall be capable of positive measurement of cement being introduced into the mix. <br />442 A recording meter visible at all times and equipped with a ticket printout shall indicate the <br />443 quantity of total concrete mix. <br />444 <br />445 The mixer shall provide positive control of the flow of water into the mixing chamber. Water <br />446 flow shall be indicated by flow meter and be readily adjustable 1:o provide for minor <br />447 variations in the aggregate moisture. <br />448 <br />449 The mixer shall be capable of being calibrated to automatically proportion and blend all <br />450 components of indicated composition on a continuous or intermittent basis as required by the <br />451 finishing operation, and shall discharge mixed material through a conventional chute directly <br />452 in front of the finishing machine. <br />453 <br />454 The Contractor shall perform calibration tests according to the equipment manufacturer's <br />455 recommendations at the beginning of each project, and when there is a change in the mix <br />456 design proportions or source of materials. The Engineer may require a calibration test or <br />457 yield check whenever a change in the characteristics of the mixture is observed. The <br />458 tolerances in proportioning the various ingredients shall be according to subsection 6.8 of <br />459 AASHTO M 241. <br />460 <br />461 601.08 Air Content Adjustment. When a batch of concrete delivered to the project does not <br />462 confome to tha minimum specified air content, an air entraining admixture conforming to <br />463 subsection 711.02 may be added, one time only for the batch, at the ConUractor's option prior to <br />464 consideration for rejection or price adjustment. After the admixture is added the concrete shall be <br />465 re-mixed for a minimum of 20 revolutions of the mixer drum at mixing speed. The concrete will <br />466 then be re-tested and if found acceptable may be placed in accordance with the specifications. A <br />467 maximum of three batches per day may be adjusted by adding air entraining admixture at the <br />468 delivery site. <br />469 <br />3~0 <br />G\101\00100 02AWepoM1S\I(P~Tedirural Spa~wtians COc <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />February 3, 2006 <br />