specifications - FAACO - Federal Aviation Administration Contract ...

FTWIC-2235June, 2009placed shall be taken by the Contracting Officer with a thermometer immediately beforeplacement, with the point of measurement being in the chute or bucket.C. COLD WEATHER:1. If air temperature is at or below 40 degrees F, cold weather concreting shall beperformed in accordance with ACI-306R.2. No concrete shall be mixed or placed when the atmospheric temperature is at orbelow 35 degrees F. The temperature shall be taken in the shade away fromartificial heat.3. In cases where the temperature drops below 40 degrees F after the concretingoperations have been started, the sufficient canvas and framework or other typeof housing shall be furnished to enclose and protect the structure, in accordancewith the requirements of ACI-306R. Sufficient heating apparatus such as stoves,salamanders, or steam equipment and fuel to provide heat shall be supplied. Theconcrete shall be protected when placed under all weather conditions. Shouldconcrete placed under such conditions prove unsatisfactory, remove and replacethe concrete at no cost to the Government.4. When mixing with the air temperature below 40 degrees F, water used for mixingshall be heated to raise the concrete temperature to 70 degrees F. Thetemperature of the mixing water shall not exceed 165 degrees F when enteringthe mixer.5. If heating the mixing water only does not raise the placing temperature of theconcrete to 70 degrees F, the aggregate must also be heated, either by steam ordry heat, to raise the placing temperature of the concrete to the requiredtemperature. In no case shall the aggregate temperature exceed 150 degrees F asit enters the mixer. The heating apparatus shall heat the mass of the aggregateuniformly and preclude the occurrence of hot spots which burn the material.6. Salts, chemicals, or other foreign materials shall not be mixed with the concreteto preventing freezing. Calcium chloride is not permitted.D. HOT WEATHER:1. Hot weather is defined as any combination of high air temperature, low relativehumidity and wind velocity that impairs the quality of the concrete. Hot weatherconcreting shall be in accordance with ACI-305R. Concrete shall be placed inthe forms without the addition of any more water than that required by the design(slump). No excess water shall be added on the concrete surface for finishing.Control of initial set of the concrete and extending the time for finishingoperations may be accomplished with the use of approved water-reducing andset-retarding admixture, as specified.Maximum time intervals between the addition of mixing water and/or cement tothe batch, and the placing of concrete in the forms shall not exceed the following(excluding HRWR admixture use):03300-10