Cold Weather Concreting
While we were researching the Plymouth Building, we found out that it is an early example of successful cold weather concrete construction in the US. The daily log recorded during the construction of the building revealed that mixing and pouring of concrete began on February 7, 1910. As is typical for winter in Minnesota, temperatures recorded in the daily log reveal that the temperature was well below freezing for the first month of pouring, with the lowest temperature recorded as 2 degrees Fahrenheit. Temperatures this low require additional measures to be taken during construction to ensure proper curing of the concrete.
The temperature of concrete during the curing period is an important factor for the rate at which it hardens and increases in strength. Furthermore, if the concrete freezes before it has set, the strength of the concrete can be adversely affected. Early concrete construction was limited to warmer months when temperatures were above freezing. While working in warm weather is a practical solution, the impact on the use of concrete was to increase the cost of concrete construction due to labor demands in warmer months, thus delaying national acceptance of the material. Early articles on cold weather concreting in publications such as Engineering News and Engineering Record promoted the use of salts in the concrete mix to prevent freezing of the water during curing. However, it is well recognized today that chloride ions react with the steel reinforcement, which can result in corrosion and ultimately failure of the system. Most current construction projects place strict limits on the addition of salts to the concrete mix. If the Plymouth Building had used salt in the concrete mix, it might not remain today: the salts would likely have corroded the reinforcing steel. The daily construction log, which records work performed and the types and amounts of materials used, makes no mention of salts.
Another method of cold weather concreting is the heating of the concrete materials: aggregate, sand, cement, and water. A Portland Cement Association handbook, Cold Weather Concreting (1916), describes the use of tubes and stoves to heat the concrete materials and then the poured structure during curing. I believe that these “tubes” were used for the construction of the Plymouth Building. On February 10, 1910, the daily log describes the use of “tubes”, and the irritating smoke that was generated by the heating process: “The smoke caused by fire in the tubes with which we heat the concrete materials, has been leaking out at the edge of the roof, adjoining the [neighbor’s] restaurant and annoying the [neighbor]” (I’ve redacted the name used for the neighbor because it is considered to be a racial slur today).
A review of engineering literature and articles covering cold weather concreting around the beginning of the 20th century reveals that the Plymouth Building was one of the earlier examples of such construction in the US. Around the time of the construction of the Plymouth Building (1909-1910), other examples of cold weather concrete construction were noteworthy enough to devote articles to the topic. “Cold Weather Concrete,” by John S. Nicholl, describes the construction methods used for cold weather concrete work, and provides examples of cold weather concrete construction performed on two buildings and two dams from 1908-1911 in the northeastern US. “Reconstruction of bridge 298, New York Central Railroad – Concreting in Cold Weather,” by Charles E. Andersen, describes the steps taken to construct a railroad bridge through the winter of 1910. The majority of the other articles describing cold weather concreting in the US that I was able to locate were published after 1910, which places the construction of the Plymouth Building early in the timeline of successful cold weather concrete construction in the US.
Advancements and changes in cold weather concrete construction practices continue today. The Minnesota Concrete Council, an organization dedicated to advancing education, technical practice, scientific investigation and research into cast in place concrete construction, is hosting a breakfast meeting on September 20, 2012 about “Cold Weather Concreting and Changes to ACI 306R-10.” ACI 306R-10, created and published by the American Concrete Institute, provides guidelines for cold weather concrete work. The main focus of the presentation will be the changes that have been recently made to ACI 306R, the first in over 20 years.
Charles E. Andersen, “Reconstruction of bridge 298, New York Central Railroad – Concreting in Cold Weather,” Engineering and Contracting 36 (Dec 6 1911): 616-618.
Portland Cement Association, Concreting in Cold Weather, (Chicago: Author, 1916).
John S. Nicholl, “Cold Weather Concrete Work,” Cement Age 14 (Feb. 1912): 81-85.