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904.11 BLANK <br /> 90-5 PROPORTIONING <br /> 90-5.01 STORAGE OF AGGREGATES <br /> • Aggregates shall be stored or stockpiled in such a manner that separation of coarse and fine particles of each size <br /> shall be avoided and the various sizes shall not become intermixed before proportioning. <br /> • Aggregates shall be stored or stockpiled and handled in a manner that prevent contamination by foreign materials. <br /> In addition, storage of aggregates at batching or mixing facilities that are erected subsequent to the award of the contract and <br /> that furnish concrete to the project shall conform to the following: <br /> A. Intermingling of the different sizes of aggregates shall be positively prevented. The Contractor shall take the <br /> necessary measures to prevent intermingling. The preventive measures may include,but are not necessarily limited <br /> to,physical separation of stockpiles or construction of bulkheads of adequate length and height;and <br /> B. Contamination of aggregates by contact with the ground shall be positively prevented. The Contractor shall take the <br /> necessary measures to prevent contamination. The preventive measures shall include,but are not necessarily limited <br /> to,placing aggregates on wooden platforms or on hardened surfaces consisting of portland cement concrete,asphalt <br /> concrete,or cement treated material. <br /> • In placing aggregates in storage or in moving the aggregates from storage to the weigh hopper of the batching plant, <br /> any method that may cause segregation, degradation, or the combining of materials of different gradings that will result in <br /> any size of aggregate at the weigh hopper failing to meet the grading requirements shall be discontinued. Any method of <br /> handling aggregates that results in excessive breakage of particles shall be discontinued. The use of suitable devices to <br /> reduce impact of falling aggregates may be required by the Engineer. <br /> 90-5.02 PROPORTIONING DEVICES <br /> • Weighing, measuring, or metering devices used for proportioning materials shall conform to the requirements in <br /> Section 9-1.01, "Measurement of Quantities," and this Section 90-5.02. In addition, automatic weighing systems shall <br /> comply with the requirements for automatic proportioning devices in Section 90-5.03A, "Proportioning for Pavement." <br /> Automatic devices shall be automatic to the extent that the only manual operation required for proportioning the aggregates, <br /> cement,and supplementary cementitious material for one batch of concrete is a single operation of a switch or starter. <br /> • Proportioning devices shall be tested as frequently as the Engineer may deem necessary to ensure their accuracy. <br /> Weighing equipment shall be insulated against vibration or movement of other operating equipment in the plant. <br /> When the plant is in operation,the mass of each batch of material shall not vary from the mass designated by the Engineer by <br /> more than the tolerances specified herein. <br /> • Equipment for cumulative weighing of aggregate shall have a zero tolerance of f0.5 percent of the designated total <br /> batch mass of the aggregate. For systems with individual weigh hoppers for the various sizes of aggregate,the zero tolerance <br /> shall be f0.5 percent of the individual batch mass designated for each size of aggregate. Equipment for cumulative weighing <br /> of cement and supplementary cementitious material shall have a zero tolerance of f0.5 percent of the designated total batch <br /> mass of the cement and supplementary cementitious material. Equipment for weighing cement or supplementary <br /> cementitious material separately shall have a zero tolerance of t0.5 percent of their designated individual batch masses. <br /> Equipment for measuring water shall have a zero tolerance of f0.5 percent of its designated mass or volume. <br /> • The mass indicated for any batch of material shall not vary from the preselected scale setting by more than the <br /> following: <br /> A. Aggregate weighed cumulatively shall be within 1.0 percent of the designated total batch mass of the aggregate. <br /> Aggregates weighed individually shall be within 1.5 percent of their respective designated batch masses;and <br /> B. Cement shall be 99 to 102 percent of its designated batch mass. When weighed individually, supplementary <br /> cementitious material shall be 99 to 102 percent of its designated batch mass. When supplementary cementitious <br /> material and cement are permitted to be weighed cumulatively,cement shall be weighed first to 99 to 102 percent of <br /> its designated batch mass, and the total for cement and supplementary cementitious material shall be 99 to 102 <br /> percent of the sum of their designated batch masses; and <br /> C. Water shall be within 1.5 percent of its designated mass or volume. <br /> • Each scale graduation shall be approximately 0.001 of the total capacity of the scale. The capacity of scales-for <br /> weighing cement, supplementary cementitious material, or cement plus supplementary cementitious material and aggregates <br /> shall not exceed that of commercially available scales having single graduations indicating a mass not exceeding the <br /> Contract No. 10-OM7104 <br /> 79 <br />