|Cement Additives From TDA to Polyfon T |
Tuckers Dispersing Aid may sound like snake oil, but in the 1930s, much of the U.S. highway system was built with this material, better known as TDA. Author Nile Strohman describes some of the various aids in addition to TDA that help disperse additives in concrete.
by Nile R. Strohman
The history of cement additives goes back to the 1930s. At that time an attempt was being made to disperse carbon black in concrete. The purpose of this dispersion was to provide a different colored passing (aka, suicide) lane on three-lane highways (see photo) to remind drivers where they were. The results at first were not good as the carbon black rose to the surface with a mottled appearance and wore off very quickly. It also led to reduced strength in the concrete due to the use of too much carbon black.
To remedy this, Dewey and Almy (D&A, now part of W.R. Grace) proposed the use of a dispersing agent, which solved the problem of the mottling and the dispersion of carbon black throughout the concrete. Additionally they found that the strength of the concrete was better than the concrete without any carbon black. They concluded that the dispersing agent not only dispersed the carbon black but the cement as well. By including the chemical triethanolamine to offset the retarding effect of the dispersant, a product called TDA was patented. This name was derived from Tuckers Dispersing Aid, after developer George Tucker.
In July of 1933 this product was taken to the Universal Atlas plant in Hudson New York for the first test in a cement production mill. These tests indicated that this material clearly improved the quality and production rate of cement. TDA then replaced the use of coal, which had a negative affects on the strength and durability of concrete.
The testing of this material at over 30 cement plants also showed that cement could be ground significantly finer, which led to the production of a commercially feasible high early-strength cement.
About this same time, another company, Master Builders, developed and patented a similar product. Later they elected to concentrate their efforts in the concrete industry while D&A elected to concentrate their efforts in the cement industry for the life of the patents.
Because of the wide acceptance of TDA use by the cement industry, ASTM modified its rigid prohibition of the use of additives, other than gypsum and water, and agreed to approve the intergrinding of materials shown not to be harmful by tests prescribed and carried out by Committee C1 on Cement.
The use of grinding aids in cement had an unforeseen and unusual effect on testing in cement plants. During the 1930s the typical test for fineness was 325-mesh sieve fineness. Since the fineness of cement with grinding aids was so different, the use of the Wagner test was instituted by the grinding aid producers to demonstrate the effect on the particle size distribution. This became a standard method of testing in cement plants.
During 1937 and 1938 cements ground with TDA were tested by the then-National Bureau of Standards (now the National Institute of Standards and Technology) as the basis for evaluation by ASTM. At that time 17 pairs of treated and untreated cement were ground at various mills under supervision of National Bureau of Standards personnel and then tested by their specialists. In contrast, today it is necessary to test only five pairs for C 150 cements as well as a blended and a slag to gain approval under ASTM C 465, Specification for Processing Additions for Use in the Manufacture of Hydraulic Cements.
Numerous papers were published during the 1930s and 1940s on the effects of grinding aids on cement such as Kansas State College Professor E.R. Dawleys paper Effect of TDA on the Rate of Grinding Portland Cement, Pit and Quarry, July 1939) and D&As Kennedy and Marduliers Dispersion on Cement Raw Materials Rock Products, August 1941).
In 1949 Airalon was accepted as an air-entraining agent and along with vinsol resin, Darex, and N-TAIR were accepted as approved air entraining agents in cement.
By 1960, TDA from Dewey and Almy, 109-B from Master Builders and Polyfon T from West Virginia Pulp and Paper (now Westvaco) were the only approved grinding aids under ASTM.
During the 1960s a number of new grinding aids were developed and or patented and then approved under the new specification C 465. These included the use of acetic acid patented by Missouri Portland cement with C 465 approval gained by Union Carbide, HEA2 by W. R. Grace, and REAX by Westvaco. Later, various glycols came into use as grinding aids, with products being marketed by numerous companies such as Dow, Union Carbide, Westvaco, and W. R. Grace. Until February of 1960 no uniform method determining flowability existed. At that time, W.R. Grace introduced the packset test to the cement industry. Today, this test method is going through the ASTM balloting process. //
Copyright 2002, ASTM