Sunday, April 15, 2018

What Was Nephite Cement? – Part II

Continued from the previous post regarding what Nephite cement was and how it worked, and how it was made.
Cinder block house being built in Mexico

Today, concrete is poured with rebar, meaning a reinforcing steel bar, used as a tension device in reinforced concrete and reinforced masonry structures to strength and hold the concrete in compression; however, this tension strength is only about one-tenth of its compressive strength. As an example, the strength of concrete experiences significant gains (strengthening) over time: gaining 16% strength in one day, 40% in 3 days, 65% in 7 days, 90% in 14 days and 99% strength in 28 days. The rebar holds the cement or concrete together as it strengthens immediately, and keeps it from separating, shrinking (which causes cracks) and deteriorating over time—all of which cause strength loss.
    Thus, reinforced concrete has a high compressive strength compared to other materials used for building, and due to the provided reinforcement, reinforced concrete can also withstand a good amount tensile stress.
    The problem is, and it should be kept in mind when discussing building houses out of cement, such as the Nephites are said to have done in the Land Northward, that cement hardens with age. It starts out as a powder, and when made into workable cement, by adding water and lime, it hardens, and as time passes, the nature of cement is to harden and harden until it becomes brittle. It will start to deteriorate and eventually return back into powder, or decompose. Very few cement houses would last very long, especially because of weathering and especially around salt, such as salt water of seas, etc.
Forms are made and rebar placed within before cement is poured. When finished and set, the forms are removed and the cement left to cure

Another factor to keep in mind is that in order to pour or use cement, forms into which it is poured have to be made—and those forms are made of lumber, Of course, a set of forms, once made, can be used over and over again.
    Generally the steel rods are patterned (not smooth) to form a better bond with the concrete. The most common type of rebar is carbon steel, typically consisting of hot-rolled round bars with deformation patterns.
    In practice, any material with sufficient tensile strength that is materially compatible with concrete could potentially be used to reinforce concrete, for example bamboo might be considered a viable substitution in regions where steel is not available. Steel and concrete have similar coefficients of thermal expansion, so a concrete structural member reinforced with steel will experience minimal stress as the temperature changes. Reinforcing bars in masonry construction have been used since at least the 15th century. However, it was not until the mid-19th century that rebar displayed its greatest strengths with the embedding of steel bars into concrete, thus producing modern reinforced concrete. Several people in Europe and North America developed reinforced concrete in the 1850s.
    In 1824, an Englishman named Joseph Aspdin discovered that by burning finely ground chalk and clay in a kiln until the carbon dioxide was removed, that cement could be made. He named it “Portland“ cement because it resembled the high-quality building stones found in Portland, England. Cement was used by the Greeks and the Romans who used lime made by heating limestone and adding sand to make mortar with coarser tones for concrete. The Egyptians made cement by using calcined gypsum—even today an amount of gypsum is added because it controls the “setting of cement,” and plays a very important role in controlling the rate of hardening of the cement.
    The key to making cement is the conversion of calcium carbonate to calcium oxide (lime) in a process called calcination. This means heat is applied and required to break chemical bonds in the compound undergoing decomposition, thus calcium oxide is usually made by the thermal decomposition temperature at which the substance chemically decomposes. This is achieved by heating the materials, such as limestone or seashells, that contain calcium carbonate (CaCO3; mineral calcite) in a lime kiln to above 1,517°F, a process called calcination or lime-burning, to liberate a molecule of carbon dioxide (CO2), leaving quicklime: CaCO3(s)CaO(s)+CO2(g).
The quicklime is not stable and, when cooled, will spontaneously react with CO2 from the air until, after enough time, it will be completely converted back to calcium carbonate unless slaked with water to set as lime plaster or lime mortar.
    This obviously requires fire, and the Nephite producers of cement in the Land Northward would have needed a lot of flammable material to sustain the cement industry in order to make homes for the thousands that moved into that land.
    One of the critics main issues with cement among the Nephites, other than their lack of understanding that cement was known in the ancient world among the Egyptians who were often associated with the Hebrews, is in the firing of materials needed. In other words, they claim, you make cement because you have a lot of wood. If you don't have a lot of wood, you can't make cement. Yet "Helaman" they point out said they made cement because they had no wood.
    To counter this, Brant Gardner erroneously has suggested that the cement buildings were made before the wood ran out, which of course is the opposite of what the Book of Mormon says is very clear. They used cement because there were no trees. Some have suggested that there must have been other stuff to burn. But what? The critics point out that far as we know they knew nothing of oil. And the people covered the land from sea to sea. That implies thousands of houses, many of them made from cement. You cannot make that much cement without trees. Obviously, this has led some critics to claim the Book of Mormon description of cement houses because there were no trees is just impossible.
    The problem lies in part with the fact that we have so little to go on in the scriptural record, and critics love to take limited information and built it into a major issue. When it is said that the Nephites “became exceedingly expert in the working of cement” (Helaman 3:7), we are not told in what way they worked with cement. After all, there are numerous applications for cement—all the way from building a house completely out of cement, to using cement (mortar) as a facing over stone or brick, or even in “cementing together” brick. “Therefore they did build houses of cement, in the which they did dwell” tells us only that they used cement as a major ingredient or material in the building of houses.
    In addition, it needs to be kept in mind that the scriptural record is a complete record and for those who dwell on one idea instead of the overall information and picture it presents often miss the point. As an example, in the midst of the information about the Nephites in the Land Northward who “did dwell in tents, and in houses of cement,” we also find the statement:
    “And it came to pass as timber was exceedingly scarce in the land northward, they did send forth much by the way of shipping” (Helaman 3:10).
    That is to say, not everyone was living in cement houses, and that timber was being shipped into the Land Northward from the Land Southward. Stated differently, while “there being but little timber upon the face of the land” in the Land Northward, and “they did suffer whatsoever tree should spring up upon the face of the land that it should grow up, that in time they might have timber to build their houses, yea, their cities, and their temples, and their synagogues, and their sanctuaries, and all manner of their buildings.”
    That is, they did have lumber in the land. It was shipped there from the south.
    Thus, “they did enable the people in the land northward that they might build many cities, both of wood and of cement” (Helaman 3:11). How that wood shipped into the Land Northward was used and in what manner it was used to build houses, is not stated. It could have been used to build forms into which the cement was poured, it could have been used to fire kilns, it could have been used for beams in roofs—typically flat or slight pitches as opposed to severe snow country in North America where roofs are steeply pitched for snow runoff—or any number of ways to supplement the building of houses, while the generations waited for the forests to grow as “they did suffer whatsoever tree should spring up upon the face of the land that it should grow up” (Helaman 3:9).
    It might be noted that in Ecuador (Land Northward) the Balsa tree is predominant in the rain forest, and 90% of all Balsa wood lumbered comes from Ecuador. However, balsa wood is very light, soft, and with a coarse grain, and is not used for construction and would not be used in building homes. Rubber trees, also a rain forest tree, is not suitable for construction; nor are the Amazonian rain forest palm trees suitable for construction. All of which, however, could be used to fire kilns and make cement.
    Naturally, cedar, fir, pine, spruce, and oak make the best building materials, even elm, hickory and chestnut can all be used for building construction. On the other hand, people are generally adaptable and have been known to make do with natural materials available to them in their building. Still, with a thousand-year history of building with adobe, brick and stone, or living in tents, the Nephites may have preferred more stable construction like what they were used to and found working with cement to their liking more than using some unknown and undesirable material for homes.
    The point is, we simply do not know and to make issues out of unknown factors that cannot be determined, or to judge the past by current standards, is both unwise and foolhardy. Yet, there are some trees that would not have been usable for building homes, temples and cities out of and those would include Balsa, Hemlock, Eucalyptus, Rubber and Palm trees, most of which would have been found in the rain forests of the ancient world where the Nephites were located.
    In addition, tropical forests do not generally grow trees overly suitable for construction, and the Land Northward may well have been in a more tropical area than that of the Land Southward. Also, there are several tree woods that are used for more specific construction, like furniture, cabinets and paneling that may not have been sturdy enough to build the types of homes the Nephites were looking to build, such as Ash, Beech, Birch, Cheery, Dogwood, Mahogany, Ash, Maple and Walnut.
    To judge an entire book and people on such flimsy and limited information seems unworthy of scholars and historians, who would do better to take all things into consideration than a single thought.

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