Saturday, April 14, 2018

What Was Nephite Cement? – Part I

We learn in Helaman, “And there being but little timber upon the face of the land, nevertheless the people who went forth became exceedingly expert in the working of cement; therefore they did build houses of cement, in the which they did dwell. And the people who were in the land northward did dwell in tents, and in houses of cement…the people in the land northward that they might build many cities, both of wood and of cement” (Helaman 3:7,9,11, emphasis added).
    Now “houses of cement” are unusual in North America and northern Europe; however, they are quite common even today in Mexico, Latin America, and the Middle East. Still, one might wonder what the word “cement” meant in ancient Israel and America.
   First of all, the word “cement” comes from the Old French ciment, but it’s ultimately from the Latin caementum, a contraction of caedimentum (rough cut stone). These are derived from the Latin verb caedere (to cut). from Latin caementum (“quarry stone”). It is the Latin ancestor of our English word “concrete” from concretus, from the verb concrescere (to grow together). Originally, from the Latin verb “to cut” and had reference to stone cutting.
   The first citation is from an 1834 issue of London’s Architecture Magazine: “Making an artificial foundation of concrete (which has lately been done in many places).” The next citation was from an 1836 entry in the Transactions of the Institute of British Architects, suggests that the term concrete came into general use “probably not longer than 15 or 20 years ago.”
   Finally, the word “cement” entered English sometime before 1300, more than 500 years before “concrete” showed up. And in the 1828 American Dictionary of English Language, “cement” is defined as “Any glutinous or other substance capable of uniting bodies in close cohesion, as mortar, glue, soder, etc. In building, cement denotes a stronger kind of mortar than that which is ordinarily used.” At the same time, “concrete” was not listed, suggesting it was not a word in use in 1828 New England America.
Example of Roman cement, or opus caementicium, on a tomb on the ancient Appian Way in Rome

Roman concrete (also called opus caementicium) was invented as early as 250 B.C. By 150 B.C. it was in widespread and customary use (Axel Boëthius, Roger Ling, and Tom Rasmussen, Etruscan and Early Roman Architecture, Yale/Pelican history of art, 1978, Yale University Press, 1978, pp128-129). Marcus Vitruvius Pollio, a Roman author, architect, civil engineer and military engineer during the 1st century BC, known for his multi-volume work entitled De architectura, published as Ten Books on Architecture, wrote around 25 B.C. and dedicated to his patron, the emperor Caesar Augustus, as a guide for building projects about the distinguished types of aggregate that were appropriate for the preparation of lime mortars (Hanno-Walter Kruft, A History of Architectural Theory from Vitruvius to the Present, Princeton Architectural Press, New York, 1994; Heather Lechtman and Linn Hobbs "Roman Concrete and the Roman Architectural Revolution," Ceramics and Civilization Volume 3, American Ceramics Society and Vitruvius, 1986).
    For rebuilding Rome after the devastating fire in 64 A.D., which destroyed large portions of the city, Emperor Nero’s new building code largely called for brick-faced concrete. In fact, exterior Roman concrete was normally faced with stone or brick, while the interiors might further be decorated with stucco or fresco paintings, or thin slabs of fancy colored marbles.
    Gypsum and quicklime or burnt lime (Calcium oxide), a chemical compound, were used as binders. Once set, Roman concrete exhibited little plasticity, although it retained some resistance to tensile stresses.
    It should be noted that tensile strengths, that is the resistance of a material to breaking under elongated tension (being pulled apart), varied substantially since Roman cement had little plasticity, and many old Roman buildings have cracked—especially their domes. However, Roman concrete was far more durable than modern Portland cement, in its reaction to seawater because it had a mixture of volcanic ash (pozzolana) instead of the modern coal fly ash (pulverized fuel ash). Roman cement was a hydraulic cement-based concrete, made from mixing lime and volcanic rock to form a mortar, and could be set underwater. In fact, usable examples of Roman concrete exposed to harsh marine environments have been found to be 2000 years old with little or no wear.
Roman cement contained as much as 85% volcanic ash which created a crystal structure that prevented tiny cracks from spreading

At the same time, Roman cement was rarely used singularly, but was a mixture of lime mortar, aggregate, pozzolana, water, and stones, and was stronger than previously-used concretes. The ancient builders placed these ingredients in wooden frames where they hardened and bonded to a facing of stones or bricks.
    In pre-Roman times, slaked lime mortars were the most common cements, a combination of lime and sand. The Egyptians were the first to use lime mortars, around 3000 B.C., which they used to plaster the pyramids at Giza.
Lime mortar grout application on an old stonework wall. Three steps are visible here: On the right, the wall before applying the mortar. On the center, lime cement was applied with a trowel. On the left, the cement was grated with a metallic brush to obtain its final appearance

It is important to keep in mind, that despite the extensive use of cement in ancient Rome, beginning around 350 years after Lehi left Jerusalem, that it was never used alone, but always as a process of facing with stone or brick, with the mortared concrete adhering the stone or brick to the outer surface.
     In Lehi’s time, slaked-lime mortar was used (before the Roman cement), which was probably invented by the Egyptians,which they used as a facing for stone (on the pyramids). This lime was obtained from limestone naturally containing a sufficient percentage of silica and/or alumina. Artificial hydraulic lime is produced by introducing specific types and quantities of additives to the source of lime during the burning process, or adding a pozzolana to non-hydraulic lime. This lime is produced from a high purity source of calcium carbonate such as chalk, limestone or oyster shells. The slaking process involved in creating a lime putty is an exothermic reaction which initially creates a liquid of a creamy consistency, and matured for two to three months to allow time for it to condense and mature into a lime putty.
    It is slaked through mixture, causing hydration by being thoroughly mixed with enough water to form a slurry (lime putty), or with less water to produce dry powder. This hydrated lime (calcium hydroxide) naturally turns back into calcium carbonate by reacting with carbon dioxide in the air, the entire process being called the lime cycle. 
    This slaked lime (cement) mixed with sand and water makes mortar which is used to stick stone or bricks together, or face the cement for a better appearance and finished look. 
    It should also be kept in mind that solid masonry cement walls that are not reinforced with some type of rebar, were heavily susceptible to earthquake destruction. Where wood construction bends and sways in an earthquake, cement breaks and falls. Today, of course, cinder (cement) block with reinforced concrete is used—but in Nephite times, using rebar to reinforce cement would have been unknown.
(See the next post, “What Was Nephite Cement? – Part II,” for more on what Nephite cement was and how it worked, and how it was made)

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