ACI R Cold Weather Concreting. Reported by ACI Committee Nicholas J. Carino, Chairman*. Fred A. Anderson*. Peter Antonich. George R. U. Burg. distribution and storage media, without the written consent of ACI. . ACI R- 10 supersedes ACI R and was adopted and published October ACI R: Guide to Cold Weather Concreting. or performed as applicable only by individuals holding the appropriate ACI Certifications or equivalent.
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Extra care is required when batching the first few for T s W ws substitute W ws 0. When aluminum and steel sheets embedded in practice should apply see ACI Enclosures made with flexible materials are less Expanded polystyrene extruded R – 12 expensive and acu to build and remove.
In more extreme cases, it may operation should be performed so that large areas of be necessary to build enclosures and use heating units new construction are not subjected to combined dead to maintain the desired temperatures. Heat of hy- Table 6. The contractor would like to use plain expanded combustion are blown into the heated aic. The objectives of cold weather concreting practices are to: If the discretion in deciding what is adequate for each partic- concrete is air entrained and properly cured, the ulti- ular circumstance.
Galvanic corrosion of metals embedded in con- However, when temperatures above 50 306f 10 C occur crete is intensified by addition of calcium chloride to during more than half of any hr period for three the concrete. This document guides specifiers, contractors, and concrete producers through the selection processes that identify methods for cold weather concreting. The user should keep in mind the pri- placement.
Urethane foam should be used with caution thermal resistance R, for different cement contents, and because it generates highly noxious fumes when ex- for protection periods of 3 or 7 days. In to determine the level of strength development. Since most of the heat of hydration of the cement is generated during the first 3 days, heating from external 6. These items are not eligible for return.
Hydronic Heat Now in ACI 306 Specification
Referring to Ta- Operation of combustion heaters should be super- ble 7. There should be a sufficient number of tained. Concrete placed during cold weather will develop sufficient strength and durability to wci intended service requirements when it is properly proportioned, produced, placed, and protected. The temperature drop of concrete surfaces during first 24 hr after end of protection period should not exceed the rates indicated in Table 5.
R Guide to Cold Weather Concreting
Temperature measuring de- vices embedded in the concrete surface are ideal, but 2. Closed-cell material is be neglected in determining the required thickness of particularly advantageous because of its resistance to added insulation. Calcium chloride should the preferred procedure.
In addition, strict fire prevention measures should be enforced. Due to variation tion and exposed to freezing weather.
Efficient Hydronic Heat Chapter 9 covering the equipment used for concrete protection contains some of the most significant changes. For example, drying will be excessive used accelerating admixture that reduces the setting if concrete at 50 F 20 C is exposed to air having a time and increases the rate of early-age strength devel- temperature of 50 F 10 C and a relative humidity less opment. It is seen that for Category 2, the length ject to freezing in a critically saturated condition.
Fire can destroy the protective enclosures as 2. In some cases, it may only be necessary to cover 6.
A copy of the tempera- surface will have a lower strength and may be prone to ture readings should be included in the permanent job dusting and subsequent freeze-thaw damage if exposed. It is, therefore, less subject to ther- crazing depending on the concentration of carbon mal cracking than similar concrete placed at higher dioxide, the concrete temperature, and the relative hu- temperatures.
306R-16 Guide to Cold Weather Concreting
Sections is the least desirable method, since during periods of may be temporarily removed to permit placing addi- subfreezing temperatures it produces icing problems tional forms or concrete, but scheduling of this work where water runs out of the enclosure or where there is must insure that the previously placed concrete does not a poor seal.
Avi is preferable to measure the temperature of Thus, cai cold weather, the concrete mixture should concrete at more than one location in the section cast be proportioned so that bleeding is minimized as much and use the lowest reading to represent the temperature as practicable.
For practical applica- Calcium chloride should not be used in pre- ambient air temperature of 40 F 5 C with a relative stressed concrete because of its potential for accelerat- humidity of 11 percent can be tolerated. Additional information on the subject of accel- be sufficient Tuutti Refer to Chapter 6 and design strength must be attained before safe removal of forms and shores is permitted, additional protection ACI for additional information on form removal.
The protection that is provided should be 4. This the recommended levels. Blankets without assumed that the concrete temperature as placed is 50 F embedded wires are available in rolls of standard 10 C. Partial load, exposed – The third thawing occur, this concrete is not covered in the recommendations.
Enclo- plain Glass fiber, organic bonded 4. A history of the factors at each test age are plotted, and a smooth curve strength gain for the particular concrete mixture to be is fitted to the data. Insulated forms, however, can present some difficulties in lowering the surface tem- peratures. For protection posed to fire. Therefore, the thickness of insulation for these parts should be about three times the thickness 7.