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Etymology[ edit ] The word concrete comes from the Latin word "concretus" meaning compact or condensed the perfect passive participle of "concrescere", from "con-" together and "crescere" to grow. Prehistory[ edit ] Small-scale production of concrete-like materials dates to BC, pioneered by the Nabataea traders or Bedouinswho occupied and controlled a series of oases and developed a small empire in the regions of southern Syria and northern Jordan.
They discovered the advantages of hydraulic lime, with some self-cementing properties, by BC.
A. if concrete is unsatisfactory, it will not settle during the slump test B. the sag test checks the amount of aggregate in the cement C. the compression test is very costly if the results are unsatisfactory. Youth and agriculture: Key challenges and concrete solutions Published by the Food and Agriculture Organization of the United Nations (FAO) in collaboration with the Technical Centre for Agricultural. Which one of the following statements is true? 1) The concrete cover over the reinforcing steel is not important. 2) The concrete cover over the reinforcing steel must be at least 5 mm. 3) The concrete cover over the reinforcing steel must be at least equal to the aggregate size used in the concrete.
They built kilns to supply mortar for the construction of rubble-wall houses, concrete floors, and underground waterproof cisterns. They kept the cisterns secret as these enabled the Nabataea to thrive in the desert. German archaeologist Heinrich Schliemann found concrete floors, which were made of lime and pebbles, in the royal palace of TirynsGreece, which dates roughly to — BC.
Its widespread use in many Roman structuresa key event in the history of architecture termed the Roman Architectural Revolutionfreed Roman construction from the restrictions of stone and brick materials. It enabled revolutionary new designs in terms of both structural complexity and dimension.
Laid in the shape of archesvaults and domesit quickly hardened into a rigid mass, free from many of the internal thrusts and strains that troubled the builders of similar structures in stone or brick.
First, its mix consistency is fluid and homogeneous, allowing it to be poured into forms rather than requiring hand-layering together with the placement of aggregate, which, in Roman practice, often consisted of rubble.
Second, integral reinforcing steel gives modern concrete assemblies great strength in tension, whereas Roman concrete could depend only upon the strength of the concrete bonding to resist tension.
The Baths of Caracalla in Rome are just one example.
Many Roman aqueducts and bridges, such as the magnificent Pont du Gard in southern France, have masonry cladding on a concrete core, as does the dome of the Pantheon. Middle Ages[ edit ] After the Roman Empire, the use of burned lime and pozzolana was greatly reduced until the technique was all but forgotten between and the 14th century.
From the 14th century to the midth century, the use of cement gradually returned. The Canal du Midi was built using concrete in This third Eddystone Lighthouse pioneered the use of hydraulic lime in concrete, using pebbles and powdered brick as aggregate. His son William continued developments into the s, earning him recognition for the development of "modern" Portland cement.
The first concrete reinforced bridge was designed and built by Joseph Monier in . Composition[ edit ] Many types of concrete are available, distinguished by the proportions of the main ingredients below.
In this way or by substitution for the cementitious and aggregate phases, the finished product can be tailored to its application. Strength, density, as well as chemical and thermal resistance are variables.
Aggregate consists of large chunks of material in a concrete mix, generally a coarse gravel or crushed rocks such as limestoneor granitealong with finer materials such as sand.
Cementmost commonly Portland cementis associated with the general term "concrete. One of the most familiar of these alternative cements is asphalt concrete. Other cementitious materials, such as fly ash and slag cementare sometimes added as mineral admixtures see below — either pre-blended with the cement or directly as a concrete component — and become a part of the binder for the aggregate.
To produce concrete from most cements excluding asphaltwater is mixed with the dry powder and aggregate, which produces a semi-liquid slurry that can be shaped, typically by pouring it into a form.
The concrete solidifies and hardens through a chemical process called hydration. The water reacts with the cement, which bonds the other components together, creating a robust stone-like material. Chemical admixtures are added to achieve varied properties. These ingredients may accelerate or slow down the rate at which the concrete hardens, and impart many other useful properties including increased tensile strength, entrainment of air and water resistance.
Reinforcement is often included in concrete. Concrete can be formulated with high compressive strengthbut always has lower tensile strength.
For this reason it is usually reinforced with materials that are strong in tension, typically steel rebar. Mineral admixtures have become more popular over recent decades. The use of recycled materials as concrete ingredients has been gaining popularity because of increasingly stringent environmental legislation, and the discovery that such materials often have complementary and valuable properties.
The most conspicuous of these are fly asha by-product of coal-fired power plants ; ground granulated blast furnace slaga byproduct of steelmaking ; and silica fumea byproduct of industrial electric arc furnaces. The use of these materials in concrete reduces the amount of resources required, as the mineral admixtures act as a partial cement replacement.Home Essays Concrete and Following Concrete and Following Statements Which of the following statements regarding fire-retardant treatment of wood is MOST accurate?
A. the fire retardant is intended to occur at temperatures lower than those developed in fires. B. the fire retardant is intended to occur at temperatures higher than those. With additions uploaded frequently this category will include method statements related to the building and construction industries.
These documents are delivered by digital download immediately after payment and are in Microsoft Word ™ Format for easy edits.. Written by a UK Chartered Building Engineer with Corporate Membership of the .
SECTION CONCRETE REPAIR CRACK INJECTION PART 1 – GENERAL REFERENCES A. The following is a list of standards that may be referenced in this. SWMS Library for all industries. Download Work Method Statement from our complete SWMS Template library. When the time comes to install a new driveway, the biggest decision is whether to use concrete or asphalt.
Sure, there are other driveway material choices — gravel at the low end and brick pavers at the high end — but concrete and asphalt are the most common, and each comes with advantages and disadvantages..
Concrete lasts longer, but . A. if concrete is unsatisfactory, it will not settle during the slump test B. the sag test checks the amount of aggregate in the cement C.
the compression test is very costly if the results are unsatisfactory.