ACI 305.1-06 Specification for Hot Weather Concreting

ACI 305.1-06 Specification for Hot Weather Concreting. 3.4—Concrete production and delivery 3.4.1 Concrete shall be produced at a temperature such that its maximum temperature at discharge will not exceed the specified maximum allowable concrete temperature. Acceptable production methods to reduce the temperature of the concrete include: shading aggregate stockpiles, sprinkling water on coarse aggregate stockpiles; using chilled water for concrete production; substituting chipped or shaved iced for portions of the mixing water; and cooling concrete materials using liquid nitrogen. The submittals for hot weather concreting shall indicate which methods will be used and in what order they will be initiated when multiple methods are to be used. The substitution of other cooling methods will be considered by the Architect/Engineer when requested in the submittal and accompanied by satisfactory supporting data. 3.4.2 Unless otherwise specified, deliver concrete in accordance with ASTM C 94/C 94M, which requires the concrete to be discharged within 1-1/2 hours or before the truck-mixer drum has revolved 300 revolutions, whichever comes first. 3.3.3.1 The proposed concrete mixture shall meet the specified slump range at the end of the laboratory mixing period and meet the required strength at the specified test age. 3.3.4 Field trial batch—Batch the field concrete trial mixture within 2 °C (3 °F) of the proposed maximum allowable concrete temperature in a truck-mixer with a minimum batch size of 3 m 3 (4 yd 3 ). If necessary, move the truck mixer into an enclosed, heated, and ventilated space to achieve a concrete temperature within the specified tolerance of the proposed maximum allowable concrete temperature. The concrete mixture shall be held in the mixer for 90 minutes, unless otherwise specified by the Architect/Engineer. During the entire 90-minute period, agitate the mixer at 1 to 6 rpm. At the end of 90 minutes, mix the concrete mixture at full mixing speed designated by the manufacturer (6 to 18 rpm) for 2 minutes. During mixing and agitation periods, the addi- tion of water, chemical admixture, or both, to adjust slump is permitted provided that the specified concrete mixture w/cm is not exceeded. As needed, check and adjust the slump of the concrete mixture during the middle 1/3 of the 90-minute mixing period. 3.3.4.1 The proposed concrete mixture shall be within the specified slump range at the end of the 90-minute field mixing period and meet the required strength at the specified test age. 3.3.5 Test values obtained...