Another project Herb worked on in 1958 was a request from the New York Department of Transportation. Whether it was the city of New York or New York State he does not remember. They needed a concrete for use in bridge tunnels which had a 28-day strength of 25,000 pounds per square inch (psi). That is ten times stronger than the concrete that is used in sidewalks. In retrospect they needed a high-early-strength concrete. The term “high-early-strength” had not been coined at that time. By working on the gradation of the gravel, he found a way to make the gravel mix denser than most gravel mixes. To develop his model, he pictured a container filled with 4-inch diameter balls. It was easy to calculate the amount of solid material in the balls and the amount of pore space between the balls. He then pictured containers with different sizes of balls and determined that no matter what the diameter of the ball was, the relationship between the solid material and the pore space remained the same.
It is a little more difficult to calculate the distance between the surfaces of those balls, but it was a necessary calculation. He then took that pore space between the 4-inch balls and filled it with 1-inch balls (based on calculations, that diameter worked better than 1.25-inch balls or ¾-inch balls), and calculated the pore space between the 1-inch balls, and filled that with quarter-inch balls. He now knew the ratios he needed to develop the extremely dense gravel mix he believed was needed for a high-strength concrete.
To produce the concrete he could not use balls, he needed to use gravel. For the lab testing, he started with 2-inch gravel and filled the pores with 0.5 inch gravel, and filled the pore spaces with 0.125-inch sand. He kept the process up and finally using finely ground volcanic ash, he filled the space left between particles of Portland cement. The volcanic ash was included to react with the calcium ions which were given off when Portland cement hydrates. All of these calculations were done with a slide rule since inexpensive calculators had not been invented. He had concrete breaking at 18,000 psi, and it had about as much Portland cement as concrete that would break at 2,500 psi (sidewalk-grade concrete). The fractures were occurring in the aggregate. He never got to the 25,000 psi strength because he did not have a good enough aggregate. Obviously, this was another failure.
Herb learned that it is better to define what is needed, rather than to accept what brilliant engineers and scientists say that they need.
Fifty-seven years later he was sitting in the dirt on a construction site in one of the worst slums in Haiti teaching people how to use their existing non-standard sand and gravel to produce quality concrete. When he was finished with his “class,” they helped him to his feet because they did not think he was able to get up by himself. Then the children brushed the dirt off of his clothes. That was only one instance of using what he learned trying to help those New Yorkers who did not know what they needed.