Development of Portland Cement in the United States
In the spring of 1866, David O. Saylor, Esias Rehrig, and Adam Woolever started the Coplay Cement Company. The Coplay Cement Company was located along the west side of the Lehigh River and along side of the Lehigh Valley Railroad (L.V.R.R). Early in the 1870ís, Sailor began to experiment with the manufacturing of portland cement from rocks from his own quarry. With this experimentation, Saylor discovered the possibility of making portland cement from raw materials at his disposal. He noticed that the harder burned portions of his Rosendale clinker produced cement that would show a tensile strength equal to that of the best imported portland cement, for a short period of time. However the cement had the problem of crumbling away with time. This problem was do to the raw materials not being properly proportioned.
Up until this experimentation, the trio of men manufactured natural rock cement. There were many other manufacturers of natural rock cement in the United States at this time. The Rosendale cement of New York had been on the market for over thirty years and manufacturers were already in operation on the Potomac, James, and Ohio River Valleys. Natural rock cements were made by driving off the carbonic acid from argillaceous (clay-bearing) limestones. This was done at low temperatures in an ordinary upright kiln from 1,000 to 1,200 degrees Fahrenheit, and produced a soft yellow stone. This yellow stone was then ground into a powder and constituted the finished product. On the other hand, portland cement is an artificial mixture of raw materials, has a calcination at a temperature above 2,000 degrees Fahrenheit, and purer raw materials were used than necessary for natural cements. The raw materials used in the manufacturing of portland cement at this time were cement rock, limestone, shale, and coal. At this period in time, portland cements were not available in the United States, and were imported from England and Germany.
The Lehigh deposits were very much different than those commonly used in Europe, but still were thought to be of suitable and sufficient purity for the manufacturing of portland cement. The deposits in this area were a natural mixture of carbonate of lime and clay in proportions approximating those required for the portland cement mixture. To the southeast of this area, the rocks and limestone were unfit for cement making, and to the northwest there was an abundance of shales and slates. These deposits proved to be suitable, and Saylor turned out the first portland cement in 1875. In 1876, Saylorís brand of cement received a medal for highest quality at the Centennial Exhibition in Philadelphia. The rocks used to produce this cement were taken from a quarry near the plant, and had variations in the composition of the rock at different strata. This meant that frequent changes were required to proportion the mixture correctly. Chemists determined these proportions several times daily.
In 1878, the plant had seven kilns for portland cement, producing 2,500 barrels per month. In 1893 a continuous kiln was built for experimental purposes. This kiln was charged with raw materials at the top, and clinker was drawn from the bottom day and night for months. The only time the fire stopped was for repairs. As of 1900, the Coplay cement plant, using continuous kilns, had a maximum production of 500 barrels of portland cement per day.
Before the raw materials reach the kiln, cement rock and limestone are wetted, crushed, and weighed separately. The cement rock and limestone were then discharged together when the weight proportions were right to produce a thoroughly homogeneous mixture so that chemical action between particles could take place. These two rocks were then mixed together and natural cement added to give the mixture a necessary plasticity. This mixture was then made into lumps or balls suitable for charging in a furnace or kiln. All of these processes took place in the raw materials mill. These balls were then sent to the tunnel dryers where they became free from moisture. These balls were then elevated to the upper or charging floor of the continuous kiln. This dried slurry was then charged through the doors on the top floor. All the while, the kiln was constantly kept full up to this point. The fuel was introduced through the stoke holes on the floor below. The long vertical shaft, the upper part of the kiln, served as a pre-heater for the bricks, or balls. The narrow section in the middle was a combustion chamber, or crucible, and the lower section cooled the clinker and heated the current of air. This draft of air from below was heated by passing over the hot clinker before it reached the combustion chamber. The products of combustion heated the balls to a high temperature before they reached the fire. These kilns used gas coal for fuel and proved to be very economical because all of the heat was utilized. The clinker arrived at the grate below, which was six feet above the lower floor, nearly cold. The burnt clinker is withdrawn form the corners of the kilns at regular intervals into wagons and these contents are weighed. The wagons were drawn up an incline by a cable to the second floor of the cement mill. Here the clinker was stored until it was needed on the first floor where it was ground and packaged.
These vertical kilns of mill B still stand today serving as the David O. Saylor Cement Museum. In 1976, Coplay Cement was aquired by the Essroc Company which still produces Saylorís portland cement today. Many portland cement plants still exists in the Lehigh Valley today including: Essroc I and Essroc III located in Nazareth, Hercules Cement located in Stockertown, Keystone Cement located in Bath, Allentown Cement located in Evansville, and Whitehall Cement located in Cementon.
Information compiled by John Harakal