International Concrete Abstracts Portal

For two centuries the U. S. Army Corps of Engineers (CE) has been developing high-performance concretes. In the 1840s, various Corps of Engineers’ officers, including Robert E. Lee, developed concretes that could be placed underwater for construction of coastal defense facilities. General Q.A. Gillmore, whose device for measuring time of setting of cement paste is still used, published a book in 1863 on hydraulic cement and mortar. In 1871, he published a book on concrete, which introduced concrete technology from France that was significantly higher-performance than that then used in the United States. Contemporary development of high-performance concrete began in 1935 at the CE Concrete Laboratory at Eastport, Maine, in support of the Passamaquoddy Tidal Power project. The objective was to develop concrete able to resist twice daily immersion in sea water and freezing in the winter when the tide went out. That objective was achieved. In 1970, when confronted with the problem of severe abrasion-erosion damage in stilling basins below dams, a solution was found in the development of concretes having strengths greater than 100 MPa. This was done using silica fume and high-range water-reducing admixtures. Similar and higher-strength high-performance concretes have also been developed for defense purposes as part of the protective-structures portion of the U.S. military research and development (R&D) program. When stronger concrete or concrete that must resist a more severe exposure is needed, the Corps of Engineers’ concrete R&D capability has been able to develop it, and I expect it will continue to be able to do so.

Douglas Southall Freeman’s authoritative biography of Robert E. Lee has a chapter on the building of Fort Carroll in the middle of Baltimore Harbor in 1849-1852. In the spring of that year, Lee established that there was a stable hard surface 45 ft below low water and began to work on the construction. These preliminary activities, as recounted by Freeman, included the following: "He experimented in the laying of concrete under water with a tremie." Lee continued with the work until August 1852 when he was sent to be Commandant at West Point. By then some concrete had been placed in Fort Carroll. Lee received information from General Totten on 22 June 1849 on placing concrete with a tremie. Lee replied on 25 June, "I shall make experiments to test the tremie preparatory to laying foundations." These experiments are among the earliest bits of concrete research done in the USA.

In a letter in the September 2000 issue of Concrete International, D. Srinivasan asked, "Will there be a self-curing concrete?" My answer to this is strongly affirmative for three reasons. First, most of the concrete that is produced and placed each year all over the world already does self-cure. Some of it wasn’t intended to have anything done to its exterior surface. But finishing did in fact take place, and yet the concrete’s ability to serve its intended purpose had not been significantly reduced.

This lecture is about concrete - specifically, hydraulic-cement concrete. If one starts with the dry powder that is hydraulic cement - usually the particular class of hydraulic cement known as portland cement - and adds water, what results, depending on the amount of water added, is cement paste or grout. Grout can be poured like gravy. If fine aggregate is added, the result is mortar or sanded grout. If both fine aggregate and coarse aggregate are added, the result is concrete. As the Supreme Court of Pennsylvania once wrote in a decision dealing with cement-manufacturing plants, "cement is to concrete as flour is to fruitcake." My first point is, to get proper concrete, get the terminology right. There is no such thing as a cement mixer. And sand is not a synonym for fine aggregate; sand is a class of fine aggregate produced by nature rather than by rock crushers and grinding mills.

No one could question the appropriateness of "Research on Concrete" as a topic for a Stanton Walker Lecture on the Materials Sciences. Research, according to Webster’s Dictionary, is "critical and exhaustive investigation or experimentation having as its aim the discovery of new facts and their correct interpretation; the revision of accepted conclusions, theories, or laws, in the light of newly discovered facts; or the practical applications of such new or revised conclusions." Dr. Bates noted, in the first of these lectures in 1963,1 that it had recently been said that "concrete is not a material, it is a process." However, in 1967, when the American Concrete Institute finally got around to publishing an official definition of concrete,2 hat definition read: "A composite material which consists essentially of a binding medium within which are embedded particles or fragments of aggregate; in portland cement concrete, the binder is a mixture of portland cement and water."