What is Concrete?
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What's Concrete? Concrete is made of :
History of Cement: The invention of cement has been credited to Joseph Aspdin, an English mason. Aspdin patented his product in 1824 and called it "Portland Cement" because it resembled the color of natural limestone found on the Isle of Portland, a peninsular in the English Channel. Portland Cement was first manufactured in the United States in 1872. Today, concrete is the most used material in construction. Roads, bridges, schools, foundations of buildings, driveways and large office buildings are made of concrete. Some boats and ships are even made from concrete. It would seem we are only limited by our imagination as to what we can make with concrete. Making Concrete: Whenever we mix cement, sand and water, it is extremely important that the mix contains the correct amounts of each. The basic rules of concrete are: the more cement in the mix design, the higher the strength ; the more the water in the mix, the lower the strength. A typical mix design used in sidewalks, driveways, and floors will have about twice as much cement by weight as it does water. ( You should know that a little water goes a long way and it should be added a little at a time.) Concrete does not gain strength by drying. There is a chemical reaction between cement and water that causes the concrete to set or harden. For this reason, fresh concrete should be covered, so that the cement can continue to react with the water. To obtain the best strength, the concrete should be covered for several day Ancient Concrete
Concrete is a kind of man-made stone. You make it by mixing lime and clay and sand and gravel and water. Lime is basically the ashes of limestone; it's what you get The Egyptians, Mesopotamians, and Greeks knew how to make concrete but they didn't use it very much. The Romans began to use a lot of concrete in their buildings about the time of the Emperor Nero, 60 , and they used it more and more from then on, usually with a brick facing to cover it and make it look prettier. Basilica of Maxentius and Constantine, Rome (312 AD) You can make reinforced concrete by putting metal rods inside the concrete. This makes it a lot stronger. Most concrete buildings today are reinforced with steel. The Romans were the first to use reinforced concrete, mainly in aqueducts. After the fall of Rome, neither the Islamic Empire nor the European kingdoms used as much concrete as the Romans had. They preferred to build in stone. Encyclopedia - Reinforced concrete is plain steel rods or bars ("Parisian gardener named Monier in about the year 1900. compressive[?]tensile[?] will cause rupture and consequent failure. For this reason, plain concrete cannot be used for any structural member subject to bending or direct tensile action. However, if steel bars are incorporated in such a way as to carry the tensile stresses, then reinforced concrete can be used in these roles. There are two physical characteristics which are responsible for the success of reinforced concrete. Firstly, the columns. Continuous beams in buildings generally require some compressive steel at the columns, but beams and slabs usually have reinforcing steel only on the tension side. In the case of continuous girders where the tensile stress alternates between top and bottom of the member, the steel is bent accordingly into a zig-zag shape within the beam. The amount of steel required for adequate reinforcement is usually quite small, varying from 1% for most beams and slabs to 6% for some columns. The percentage is usually based on the area in a right cross section of the member. Reinforcing bars are round and vary by eighths of an inch from 0.25" to 1" in diameter. All concrete must be cured, by exposing it to water, to reach its best strength. Reinforced concrete structures sometimes have provisions (such as ventilated hollow cores) to control their moisture. Corrosion and frost damage reinforced concrete. When rebar rusts, it expands, cracking the concrete and unbonding the rebar from the concrete. Frost damage occurs when water penetrates the surface and freezes. The expansion of freezing water in microscopic cracks widens the cracks, causing flaking,a nd eventual structural failure. In wet and freezing climates, many building codes for public works require Concrete Canoes?
Cement and water chemically act to form a "glue" that binds the aggregates together. Cement by itself is a finely ground powder that is finer than flour. By itself, cement has no strength. When cement is mixed with water and aggregates, it becomes concrete. Thus, do not say a "cement sidewalk," as it is a "concrete sidewalk." |
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