Foundations
Content
Foundations
Foundation of a structure is like the roots of a tree without which the tree cannot stand. The construction of any structure, be it a residence or a skyscraper; starts with the laying of foundations. Before designing the foundation, the type of soil is determined. Depending on whether the soil is hard soil or soft soil, a specific type of foundation is adopted.
Shallow Foundations versus Deep Foundations Foundations are made in various Foundations various materials materials… … They could be reinforced reinforced cement concrete foundations or brick foundations or stone rubble masonry foundations etc. The choice of material to be used in the construction of foundations also depends on the weight of the structure on the ground. The bearing capacity of soil plays a major role in deciding the type of foundation. The safe bearing capacity of soil should be 180N/mm2 to 200N/mm2. Foundations are broadly classified into shallow foundations and deep foundations. The depth of the foundati foundation on means the differenc differencee of level between between the ground surface surface and the base of the foundation. If the depth of the foundation is greater than its width the foundation is classified as a deep foundation. Shallow foundations are commonly used in smaller structures such as residences and small buildings whose floor height is limited to 10m whereas Deep Foundations are used in Skys Skyscr crap aper ers… s….. Pi Pile less ar aree the the most most co comm mmon only ly us used ed Deep Deep Foun Founda dati tion onss us used ed in skyscrapers… Types of Shallow foundations Footings
Footings are structural members used to support columns and walls and to transmit their load to the underlying soils. Mats or rafts Combined footings, strap and strip footings
Column Footing
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In this type of foundation the base of the column is sufficiently enlarged to act as the individual support. The widened base not only provides stability but is useful in distributing the load on sufficient area of the soil. Column footings are usually used in the foundations of residences and buildings where the soil is hard enough has has sufficient bearing capacity.
Pressure distribution Under a Foundation •
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The law The law of dist distri ribu buti tion on of pres pressu sure re un unde derr a fo foun unda dati tion on de depe pend ndss on th thee ho homo moge gene neit ity y of the the soil soil an and d flex flexib ibil ilit ity y of th thee ba base se.. If re real ally ly th thee soil soil is homogeneous and the base of the foundation is flexible, the pressure distribution under the foundation will be uniform. On the contrary if the foundation base is absolutely absol utely rigid, rigid, the pressure distributio distribution n will not be uniform but may follow such pattern. In our designs it is usual to assume a flexible base and hence to regard the pressure distribution to be uniform. This can be achieved by gradually decreasing the thickness of the base towards the edges so that the base is only as much thick as it is regarded to resist the induced moments and shears.
General rules of Foundation Design While designing a foundation the following points must be borne in mind. •
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When a soil is yielding soil, a certain amount of settlement must be reduced as much as possible by bringing down the pressure intensities. It is necessary that a foundation shall be designed so that if at all a settlement should occur, it will be uniform. In other words, the settlement of all the footings must be more or less the same. This is a very important point in reinforced concrete structures due to the rigid connection between the different components of the structure.
In our next article, we will discuss the procedure of designing an isolated foundation and also justify the foundation Potentiometric Potentiometr ic method
In this method the concentration of the total fluoride ion in saturated solutions of EuF3 was measured using the ORION ionalyzer and their fluoride specific ion electrode. Europium trifluoride was precipitated from inactive EuCI3 and NaF solutions and the precipitate purified and dried as described before. Saturated solutions were prepared at 25 ~ At the end of equilibration 10 ml of the supernate was centrifuged for about 15 minutes and 5 ml of the clear solution was used for
analysis. Standard solutions with concentrations of 10-2M, 10-3M and 10-aM were prepared from a standard solution of NaF (0.10M) supplied by the dealers. The diluted standards and the reagent TISAB (total ionic strength adjustment buffer) were used to calibrate the instrument in the desired concentration range 286 Z Radioanal. Z Radioanal. Che~ 63(1981) M. P. MENON: RADIOMETRIC, POTENTIOMETRIC AND CONDUCTOMETRIC using 5 ml of the standard and 1 ml of TISAB. The sample was also processed in the same manner for analysis. a nalysis. The pH of the solution being analyzed ranged from 5.0 to 5.5. The instrument gives a direct reading for the concentration of the fluoride ion both free and complexed unless the stability constant of the complex exceeds that of aluminum or iron fluoride complexes. Measurement of the solubility of EuF3 as a function of pH In a previous study on the effect of pH on the solubility of CeFa, WEAVER and PURDY 7 have observed a decrease in solubility with a decrease in pH up to pH = 2 and then a steady increase with pH. In this work, experiments were conducted to investigate whether or not a similar trend exists for the pH dependence of the solubility of EuF3. Buffer solutions of pH ranging from 0.9 to 5.75 were prepared using appropriate pairs and concentrations of the following chemicals: HCI, KCI, potassium hydrogen phthalate, NaOH, CH3COOH and CH3COONa. Both radiometric and potentiometric methods were employed to measure the solubilities of EuF3 in buffer solutions of different pH. Measurement of the solubility of EuF3 as a function of fluoride concentration In this measurement solutions with a constant ionic strength (1 M/l), a pH of 3.1 + 0.I and the desired fluoride concentration were prepared b by y mixing appropriate amounts of NaClO4, NaF and HC1. Radioactive EuF3 was mixed with 50 ml of these solutions and allowed to equilibrate for 2 to 5 days with intermittent shaking during this period. The concentration con centration of the total europium present in the saturated solutions was measured by the radiometric method. Estimation of the stability constant of europium monofluoride complex In this experiment 5 ml of the diluted *EuCI3 (0.1 ml tracer to 100 ml) was counted to determine its gamma-ray activity. Ten milliliter of this solution was shaken with 0.5mesh) g of purified, equilibrated and dry Dowex-50X4 cation resin (100-200 for 30 minutes. The supernate was centrifuged andexchange 5 ml of the supernate was again counted. From these data Keq, the equilibrium constant for the exchange of free Eu 3+ ion with the exchanger was computed. The experiment was repeated by shaking 10 1 0 ml of the saturated aqueous solution (supemate) of *EuF3 at 25 ~ with 0.5 g of the same exchanger for 30 minutes and counting 5 ml of the centrifuged supemate in a counting tube. J. RadioanaL Chem. 63(1981) 287 M. P. MENON: RADIOMETRIC, POTENTIOMETRIC AND CONDUCTOMETRIC Treatment of data In aqueous solution of the slightly soluble EuF3, the solid-solution equilibrium can be written as EuF3(s) - " Eu3+(aq.) + 3F-(aq.) (4) or if complexation occurs
m EuF3(s) . ~ n Eu3§ + (m - n) EuF 2§ 4- (2m + n) F- (5) provided that only the monofluoride complex is formed. 9 The thermodynamic solubility product, Kso, in the absence of complexation is given by the expression KSO = azu~. a~-= 27 C~t 74 If all europium ions exist as the monofluoride complex Ksl = Kso 31 = aEuF2" a~(6) (7) which is probably not the case in aqueous solution. The mean activity coefficient was calculated from DAVIES' equation. I~ With the use of Van't Hoff's equation: AH~ log Kso - + constant (8) 2.303R T a plot of Kso versus 1/T will yield the value for AH ~ the enthalpy cchange hange for the dissolution process, assuming that A H ~ remains constant within the experimental temperature range. From the value of Kso at 25 ~ AG ~ the standard free energy change for the process can also be calculated using the thermodynamic relation: A G~ -R 298 In Kso (9) Using the values for A H ~ and A G~ the standard entropy change, A S~ for the same process can be computed from the following relation: AH o _ AG O - (lO) 298 288 J. Radioanal. J. Radioanal. Chem. 63(1981) M. P. MENON: RADIOMETRIC, POTENTIOMETRIC AND CONDUCTOMETRIC The formation of europium monofluoride complex may be represented by the following equation: Eu 3§ + F- = EuF 2+ (11) For the measurement of the stability constant of EuF :+, the equilibrium constant, Keq, for the exchange of *Eu 3§ with the cation exchanger was first determined by measuring the gamma-ray activity in 5 ml of the solution before exchange [AsoltB.E.)] and after exchange [Asol(A.E.)] with a known mass of resin (mres). AsoI(B.E. ) -- AsoI(A.E. ) Vsol Keq = (12) AsoI(A.E.) mres The activity of free *Eu 3+ (AEx.Equbm) present after the exchange when the saturated solution of *EuF3 was treated with the resin is given by A'soI(B.E. ) -- Asol(A.E. ) Vsol A Eu~*(Ex.Equbm) = (13) Keq mres Assuming that EuF 2+ does not exchange with the resin particles or adsorbs only weakly, the activity of *EuF 2§ [AEuF2§ involved in the complexation equilibrium can be obtained from the following relation: AEuF2*(Form, Equbm) -= ASoI(A.E.) -- AEu3~(Ex.Equbm) (14)
The activity of free *Eu 3+ involved in the same equilibrium is then given by the relation: AEu3*(Free, Form. Equbm) = ASoI(B.E.) -- AEuFa+(Form.Equbm) (15) These two activities can be converted into concentrations with the knowledge of the specific activity (cpm/mol) of the labelled fluoride. The concentration of free fluoride can also be obtained from the concentration of EuF3 in the saturated solution and the concentration of EuF 2§ as follows: (F)Fre e = (F")Total- (EuF 2+) = 3 Csat(EuF~ ) --(EuF 2+) (16) J. Radioanal. Chem. 63(1981) 289 M. P. MENON: RADIOMETRIC, POTENTIOMETRIC AND CONDUCTOMETRIC The stability constant,/~, of the europium monofluoride complex is estimated using the equation: (EuF 2+) ~, - (17) (Eu a+) (F-) assuming that the activities are more or less equal to the respective concentrations.
THE MANUFACTURE OF PORTLAND CEMENT Cement is the substance which holds h olds concrete together, which means that it is extremely widely used in our society. It has been manufactured in New Zealand for more than 100 years, and during this century production has increased one hundred-fold. Portland cement (the only type of cement in common use today) is manufactured in a four step process. Step 1 - Quarrying Limestone and a 'cement rock' such as clay or shale are quarried and brought to the cement works. These rocks contain lime (CaCO 3), silica (SiO2), alumina (Al2O3) and ferrous oxide (Fe2O3) - the raw materials of cement manufacture. Step 2 - Raw material preparation To form a consistent product, it is essential that the same mixture of minerals is used every time. For this reason the exact composition of the limestone and clay is determined at this point, and other ingredients added if necessary. The rock is also ground into fine particles to increase the efficiency of the reaction. Step 3 - Clinkering The raw materials are then dried, heated and fed into a rotating kiln. Here the raw materials react at very high temperatures to form 3CaO SiO2 (tricalcium silicate), 2CaO SiO2 (dicalcium silicate), 3CaO Al2O3 (tricalcium aluminate) and 4CaO Al2O3 Fe2O3 (tetracalcium alumino-ferrate). Step 4 - Cement milling The 'clinker' that has now been produced will behave just like cement, but it is in particles •
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up to 3 cm in diameter. These are ground down to a fine powder to turn the clinker into useful cement. Cement production has several quite serious environmental hazards associated with it: dust and CO2 emissions and contaminated run-off water. Both cement works in New Zealand have measures in place to minimise these hazards. INTRODUCTION Concrete is an extremely versatile material, being used in the production of anything from nuclear radiation shields to playground structures and from bridges to yachts. It is able to be used in such a wide variety of applications because it can be poured into any shape, reinforced with steel or glass fibres, precast, coloured, has a variety of finishes and can even set under water. Modern concrete is made by mixing aggregate (sand, stones and shingle) with Portland cement and water and allowing it to set. Of these ingredients, the most important is Portland cement. Cement is a fine grey powder which when reacted with water hardens to form a rigid chemical mineral structure which gives concrete its high strengths. Cement is in effect the glue that holds concrete together. The credit for its discovery is given to the Romans, who mixed lime (CaCO3) with volcanic ash, producing a cement mortar which was used during IX-Materials-B-Cement-2
construction of such impressive structures as the Colosseum. When the Roman empire fell, the information on how to make cement was lost and was not rediscovered until the 16th century. A brief history of Portland cement Cement has been made since Roman times, but over time the recipes used to make cement have been refined. The earliest cements were made from lime and pozzolana (a volcanic ash containing significant quantities of SiO2 and Al2O3) mixed with ground brick and water. This cement was not improved upon until 1758, when Smeaton noticed that using a limestone that was 20 - 25 % clay and heating the mixture resulted in a cement that could harden under water. He called this new cement 'hydraulic lime'. When the mixture was heated, a small quantity of it was sintered1. Normally this was discarded as waste, but in the 1800s Aspdin and Johnson discovered that when the entire batch was sintered and then ground, a superior cement was formed. This substance became designated Portland cement (after the region in which they were working) and is the most common cement in use today.
Portland cement was first produced commercially in New Zealand in 1886 by James Wilson and Co., and has been produced here ever since. There are currently two companies producing cement in New Zealand: Golden Bay Cement Ltd. in Whangarei and Milburn New Zealand Ltd. in Westport. Production has increased from aound 5 000 t/annum in 1900 to in excess of 500 000 t/annum in 1991 and a New Zealand market demand in 1996 in excess of 800 000 t/annum. Portland cement is currently defined as a mixture of argillaceous (i.e. clay-like) and calcaneous (i.e. containing CaCO3 or other insoluble calcium salts) materials mixed with gypsum (CaSO4 2H2O) sintered and then pulverised into a fine powder. The precise definition of Portland cement varies between different countries, and in New Zealand are controlled by New Zealand's Standard Specification (NZS) 3122. Portland cement differs from its precursors primarily in the fact that it is sintered. Uses of Portland cement A summary of the uses of cement in New Zealand is given in Figure 1. Cement is produced here in three main grades: ordinary Portland cement (80% of Milburn's and 95% of Golden Bay's domestic sales), rapid hardening cement and moderate-heat cement. Rapidhardening cement is used in precast concrete, con crete, pipes and tiles. It is finer ground so that it hydrates more quickly and has more gypsum than other cements. Moderate-heat cement is used for the construction of hydro-electric dams, as the heat produced produce d by ordinary cement creates uneven expansion and hence cracking when such a large volume of concrete is used. In addition, a few special cements are manufactured in New Zealand for larger projects or expo export: rt: these include sulphate resisting, flyash blend, blastfurnace slag and Prise Mer cement. ⋅
PROPERTIES AND USES OF METAL In the seabees, Steelworkers are the resident experts on the properties and uses of metal. We lay airfields, erect towers and storage tanks, assemble pontoon causeways, and construct buildings. We use our expertise to repair metal items, resurface worn machinery parts, and fabricate all types of metal objects. To accomplish these tasks proficiently, one must possess a sound working knowledge of various
metals and their properties. As we learn their differentproperties and characteristics, we can then select theright type of metal and use the proper method to complete the job. Steelworkers primarily work withiron and steel; however, we also must become familiarwith the nonferrous metals coming into use more and more each day. As Steelworkers, we must be able toidentify various metals and to associate theirindividual properties with their proper application or use.The primary objective of this chapter is to presenta p resenta detailed explanation of some of the properties of different metals and to provide instruction on using simple tests in establishing their identity. METAL PROPERTIES There is no simple definition of metal; however,any chemical element having “metallic properties” is classed as a metal. “Metallic properties” are defined as luster, good thermal and electrical e lectrical conductivity, andthe capability of being permanently shaped or deformed at room temperature. Chemical elements lacking these properties are classed as nonmetals. A few elements, known as metalloids, sometimes behave like a metal and an d at other times like a nonmetal. Some examples of metalloids are as follows: carbon, phosphorus, silicon, and sulfur. Although Steelworkers seldom work with pure metals, we must be knowledgeable of their properties because the alloys we work with are combinations of pure metals. Some of the pure metals discussed in this chapter are the base metals in these alloys. This is true of iron, aluminum, and magnesium. Other metals discussed are the alloying elements present in small quantities but important in their effect. Among these are chromium, molybdenum, titanium, and manganese. An “alloy” is defined as a substance having metallic properties that is composed of two or more elements. The elements used as alloying substances are usually metals or metalloids. The properties of an alloy differ from the properties of the pure metals or metalloids that make up the alloy and this difference is what creates the usefulness of alloys. By combining metals and metalloids, manufacturers can develop dev elop alloys that have the particular properties required for a given use. Table 1-1 is a list of various elements and their symbols that compose metallic materials. Table 1-1.—Symbols of Base Metals and Alloying Elements 1-1 Figure 1-1.—Stress applied to a materiaI. Very rarely do Steelworkers work with elements in their pure state. We primarily work with alloys and have hav e to understand their characteristics. The characteristics of elements and alloys are explained in terms of physical, chemical, electrical, and mechanical properties. Physical properties relate to color, density, weight, and heat conductivity. Chemical properties involve the behavior of the metal when placed in contact with the atmosphere, salt water, or other substances. Electrical properties encompass the electrical conductivity, resistance, and magnetic qualities of the metal. The mechanical properties
relate to load-carrying ability, wear resistance,
hardness, and elasticity. When selecting stock for a job, your main concern is the mechanical properties of the metal. The various properties of metals and alloys were determined in the laboratories of manufacturers and by various societies interested in metallurgical development. Charts presenting the properties of a particular metal or alloy are available in many commercially published reference books. The charts provide information on the melting point, tensile strength, electrical conductivity, magnetic properties, and other properties of a particular metal or alloy. Simple tests can be conducted to determine some of the properties of a metal; however, ho wever, we normally use a metal test only as an aid for identifying apiece of stock. Some of these methods of testing are discussed later in this chapter. MECHANICAL PROPERTIES Strength, hardness, toughness, elasticity, plasticity, brittleness, and ductility and malleability are mechanical properties used as measurements of how h ow metals behave under a load. These properties are described in terms of the types of force or stress that the metal must withstand and how these are resisted. Common types of stress are compression, tension, shear, torsion, impact, 1-2 or a combination of these stresses, such as fatigue. (See fig. 1-1.) Compression stresses develop within a material when forces compress or crush the material. A column that supports an overhead beam is in compression, and the internal stresses that develop within the column are compression. Tension (or tensile) stresses develop when a material is subject to a pulling load; for example, ex ample, when using a wire rope to lift a load or when using it as a guy to anchor an antenna. an tenna. “Tensile strength” is defined as resistance to longitudinal stress or pull and can be measured in pounds per square inch of cross section. Shearing stresses occur within a material when external forces are applied along parallel lines in opposite directions. Shearing forces can separate material by sliding part of it in one direction and an d the rest in the opposite direction. Some materials are equally strong in compression, tension, and shear. However, many materials show marked differences; for example, cured concrete has a
maximum strength of 2,000 psi in compression, but only 400 psi in tension. Carbon steel has a maximum strength of 56,000 psi in tension and compression but a maximum shear strength of only 42,000 psi; therefore, when dealing with maximum strength, you should always state the type of loading. A material that is stressed repeatedly usually fails at a point considerably below its maximum strength in tension, compression, or shear. For example, a thin steel rod can be broken by hand by bending it back and forth several times in the same place; however, if the same force is applied in a steady motion (not bent back and forth), the rod cannot be broken. The tendency of a material to fail after repeated bending at the same point is known as fatigue. 1-2 Table 1-2.—Mechanical Properties of Metals/Alloys Strength Rockwell “C” number. On nonferrous metals, that are Strength is the property that enables a metal to resist deformation under load. The ultimate u ltimate strength is the maximum strain a material can withstand. Tensile strength is a measurement of the resistance to being pulled apart when placed in a tension load. Fatigue strength is the ability of material to resist various kinds of rapidly changing stresses and is expressed by the magnitude of alternating stress for a specified number of cycles. Impact strength is the ability of a metal to resist suddenly applied loads and is measured in foot-pounds of force. Hardness Hardness is the property of a material to resist permanent indentation. Because there are several methods of measuring hardness, the hardness of a material is always specified in terms of the particular test that was used to measure this property. Rockwell, Vickers, or Brinell are some of the methods of testing. Of these tests, Rockwell is the one most frequently used. The basic principle used in the Rockwell testis that a hard material can penetrate a softer one. We then measure the amount of penetration and compare it to a scale. For ferrous metals, which are usually harder than nonferrous metals, a diamond tip is used and the hardness is indicated by a softer, a metal ball is used and the hardness is indicated by a Rockwell “B” number. To get an idea of the property of hardness, compare lead and steel. Lead can
be scratched with a pointed wooden stick but steel cannot because it is harder than lead. A full explanation of the various methods used to determine the hardness of a material is available in commercial books or books located in your base library. Toughness Toughness is the property that enables a material to withstand shock and to be deformed without rupturing. Toughness may be considered as a combination of strength and plasticity. Table 1-2 shows the order of o f some of the more common materials for toughness as well as other properties. Elasticity When a material has a load applied to it, the load causes the material to deform. Elasticity is the ability of a material to return to its original shape after the load is removed. Theoretically, the elastic limit of a material is the limit to which a material can be loaded and still recover its original shape after the load is removed. 1-3 Plasticity Plasticity is the ability of a material to deform permanently without breaking or rupturing. This property is the opposite of strength. By careful alloying of metals, the combination of plasticity and strength is used to manufacture large structural members. For example, should a member of a bridge structure become overloaded, plasticity allows the overloaded member to flow allowing the distribution of the load to other parts of the bridge structure. Brittleness Brittleness is the opposite of o f the property of plasticity. A brittle metal is one that breaks or shatters before it deforms. White cast iron and glass are good examples of brittle material. Generally, brittle metals are high in compressive strength but low in tensile strength. As an example, you would not choose cast iron for fabricating support beams in a bridge. Ductility and Malleability Ductility is the property that enables a material to stretch, bend, or twist without cracking or breaking. This property makes it possible for a material to be drawn d rawn out into a thin wire. In comparison, malleability is the property that enables a material to deform by compressive forces without developing defects. A malleable material is one that can be stamped, hammered, forged,
pressed, or rolled into thin sheets. CORROSION RESISTANCE Corrosion resistance, although not a mechanical property, is important in the discussion of metals. Corrosion resistance is the property of a metal that gives it the ability to withstand attacks from atmospheric, chemical, or electrochemical conditions. Corrosion, sometimes called oxidation, is illustrated by the rusting of iron. Table 1-2 lists four mechanical properties and the corrosion resistance of various metals or alloys. The first metal or alloy in each column exhibits the best characteristics of that property. The last metal or alloy in each column exhibits the least. In the column labeled “Toughness,” note that iron is not as tough as copper or nickel; however, it is tougher than magnesium, zinc, and aluminum. In the column labeled “Ductility,” iron exhibits a reasonable amount of ductility; however, in the columns labeled “Malleability” and “Brittleness,” it is last. 1-4 METAL TYPES The metals that Steelworkers work with are divided into two general classifications: ferrous and nonferrous. Ferrous metals are those composed primarily of iron and iron alloys. Nonferrous metals are those composed primarily of some element or elements other than iron. Nonferrous metals or alloys sometimes contain a small amount of iron as an alloying element or as an impurity. FERROUS METALS Ferrous metals include all forms of iron and steel alloys. A few examples include wrought iron, cast iron, carbon steels, alloy steels, and tool steels. Ferrous metals are iron-base alloys with small percentages of carbon and other elements added to achieve desirable properties. Normally, ferrous metals are magnetic and nonferrous metals are nonmagnetic. Iron Pure iron rarely exists outside of the laboratory. Iron is produced by reducing iron ore to pig iron through the use of a blast furnace. From pig iron many other types of iron and steel are produced by the addition or deletion of carbon and alloys. The following paragraphs discuss the different types of iron and steel that can be made from iron ore. PIG IRON.— Pig iron is composed of about 93% iron, from 3% to 5% carbon, and various amounts of
other elements. Pig iron is comparatively weak and brittle; therefore, it has a limited use and approximately ninety percent produced is refined to produce steel. Cast-iron pipe and some fittings and valves are manufactured from pig iron. WROUGHT IRON.— Wrought iron is made from pig iron with some slag mixed in during manufacture. Almost pure iron, the presence of slag enables wrought iron to resist corrosion and oxidation. The chemical analyses of wrought iron and mild steel are just about the same. The difference comes from the properties controlled during the manufacturing process. Wrought iron can be gas and arc welded, machined, plated, and easily formed; however, it has a low hardness and a low-fatigue strength. CAST IRON.— Cast iron is any iron containing greater than 2% carbon alloy. Cast iron has a high-compressive strength and good wear resistance; however, it lacks ductility, malleability, and impact strength. Alloying it with nickel, chromium, molybdenum, silicon, or vanadium improves toughness, tensile strength, and hardness. A malleable cast iron is produced through a easily as the low-carbon steels. They are used for crane prolonged annealing process. hooks, axles, shafts, setscrews, and so on. INGOT IRON.— Ingot iron is a commercially pure iron (99.85% iron) that is easily formed and possesses good ductility and corrosion resistance. The chemical analysis and properties of this iron and the lowest carbon steel are practically the same. The lowest carbon steel, known as dead-soft, has about 0.06% more carbon than ingot iron. In iron the carbon content is considered an impurity and in steel it is considered an alloying element. The primary use for ingot iron is for galvanized and enameled sheet. Steel Of all the different metals and materials that we use in our trade, steel is by far the most important. When steel was developed, it revolutionized the American iron industry. With it came skyscrapers, stronger and longer bridges, and railroad tracks that did not n ot collapse. Steel is manufactured from pig iron by decreasing the amount of carbon and other impurities and adding specific amounts of alloying elements. Do not confuse steel with the two general classes of iron: cast iron (greater than 2% carbon) and pure iron (less than 0.15% carbon). In steel manufacturing, controlled
amounts of alloying elements are added during the molten stage to produce the desired composition. The composition of a steel is determined by its application and the specifications that were developed by the following: American Society for Testing and Materials (ASTM), the American Society of Mechanical Engineers (ASME), the Society of Automotive Engineers (SAE), and the American Iron and Steel Institute (AISI). Carbon steel is a term applied to a broad range of steel that falls between the commercially pure ingot iron and the cast irons. This range of carbon steel may be classified into four groups: HIGH-CARBON STEEL/VERY HIGH-CARBON STEEL.— Steel in these classes respond well to heat treatment and can be welded. When welding, special electrodes must be used along with preheating and stress-relieving procedures to prevent cracks in the weld areas. These steels are used for dies, cutting tools, mill tools, railroad car wheels, chisels, knives, and so on. LOW-ALLOY, TEMPERED STRUCTURALHIGH-STRENGTH, STEEL.— A special lowcarbon steel, containing specific small amounts of alloying elements, that is quenched and tempered to get a yield strength of greater than 50,000 50,0 00 psi and tensile strengths of 70,000 to 120,000 psi. Structural members made from these high-strength steels may have smaller cross-sectional areas than common structural steels and still have equal or greater strength. Additionally, these steels are normally more corrosion- and abrasionresistant. High-strength steels are covered by ASTM specifications. NOTE: This type of steel is much tougher than
low-carbon steels. Shearing machines for this type of steel must have twice the capacity than that required for low-carbon steels. STAINLESS STEEL.— This type of steel is classified by the American Iron and Steel Institute (AISI) into two general series named the 200-300 series and 400 series. Each series includes several types of steel with different characteristics. The 200-300 series of stainless steel is known as AUSTENITIC. This type of steel is very tough and ductile in the as-welded condition; therefore, it is ideal for welding and requires no annealing under normal atmospheric conditions. The most well-known types of steel in this series are the 302 and 304. They are commonly
called 18-8 because they are composed of 18% chromium and 8% nickel. The chromium nickel steels Low-Carbon Steel . . . . . . . . 0.05% to 0.30% carbon are the most widely used and are normally nonmagnetic. Medium-Carbon Steel . . . . . . 0.30% to 0.45% carbon The 400 series of steel is subdivided according to High-Carbon Steel . . . . . . . . 0.45% 0.45 % to 0.75% carbon their crystalline structure into two general groups. One Very High-Carbon Steel . . . . . 0.75% to 1.70% carbon c arbon group is known as FERRITIC CHROMIUM and the other group as MARTENSITIC CHROMIUM. LOW-CARBON STEEL.— Steel in this classifi- Ferritic Chromium.— This type of steel contains cation is tough and ductile, easily machined, formed, 12% to 27% chromium and 0.08% to 0.20% carbon. and welded. It does not no t respond to any form of heat These alloys are the straight chromium grades of staintreating, except case hardening. less steel since they contain no nickel. They are nonharMEDIUM-CARBON normally used in the STEEL.— These steels are denable by heat treatment and are
strong and hard but cannot be welded or worked as annealed or soft condition. Ferritic steels are magnetic
Introduction .- index
In order to be able to decide what kind of stone to use under given conditions, a knowledge of the different kinds employed in the various types of construction is essential. It is not necessary for an mason to determine the exact composition of a stone to be used in a structure, but his knowledge should be sufficient to help him or her in selecting or specifying the stone best adapted to the type of structure. The properties of a stone that determine its fitness for construction purposes are durability, strength, hardness, density, and appearance. The quality of a stone is ascertained approximately from a study of its origin and chemical ch emical composition and from the results of tests and experiments. 2. Definitions.- index
The term rock is commonly defined as a hard mass of mineral matter having, as a rule, no definite external form. In engineering construction the word stone is applied indiscriminately to all classes of hard rocks. 3. Description of Classes.- index
According to their geological origin, rocks may be classified as igneous, sedimentary, and metamorphic. The igneous rocks, of which granite and trap rocks are ex examples, amples, owe their formation to the solidification of molten materials. Sedimentary rocks are formed by the consolidation of particles deposited in any of the three following ways: (a) by the mechanical destruction and subsequent deposition of other rocks, usually by water, as in the case of sandstone or lime stone; (b) by the action of animals and plants, as in the case of coral; (c) by the chemical precipitation of mineral matter from water, as in the case of gypsum. The metamorphic rocks are formed by the transformation, through the influence of heat or chemical action, of either igneous or sedimentary rocks. To this class belong marble, gneiss, and slate. 4. Rocks - - index
May be classified as stratified and unstratified, depending on their structure. Igneous and metamorphic rocks are unstratified, that is, they are not arranged in any definite form in layers, or strata, but have the constituent parts mingled together. The sedimentary rocks are stratified, or formed in a series of parallel layers, as they are deposited from water. The layers were originally horizontal, but in most cases they are found more or rocks less are inclined and curved on account of the action of disturbing forces. Sedimentary composed of grains bound together by a cementing medium, and their strength and durability depend on the nature of the cementing material. 5. Stones -index
May be further classified as silicious, calcareous, and argillaceous, according to the chemical composition of the earths forming their main ingredients. In silicious stones, silica is the principal earthy constituent; in calcareous stones, carbonate of lime is the predominating material; and in argillaceous stones, alumina is the chief component. IGNEOUS ROCKS 6. Granite.- index
Granite is an igneous rock, ordinarily composed of feldspar, mica, and silica or quartz. It is formed by the cooling and crystallization of matter below the earth's surface under conditions of heat and pressure which do not obtain in the case of lava ejected on the surface in a molten state. It is found in the eastern part of the United States, in Canada, in many sections of the Rocky Mountains, and, as a rule. Wherever the later rock formations have been worn away by the weather, and the igneous rock has been exposed. 7. Planes of Fracture.- index
The structure of granite is quite uniform, but there are often planes of cleavage caused by stresses produced while the molten material was cooling. The plane along which the rock
can be split most easily is known as rift; it is often nearly horizontal. Rock can also be split along a plane, known as the grain, which is perpendicular to the rift, but this cleavage is not so easy as that along the rift. Sometimes, the stresses are sufficient to cause fractures, called joints, running parallel to the surface. 8. Qualities of Granite.- index
Granite is one of the most valuable stones for construction purposes. Although the quality of granite varies according to the proportions of the constituents and to their method of o f aggregation, this kind of stone is generally durable, strong, and hard. The hardest and most durable granites contain a greater proportion of quartz and a smaller proportion of feldspar and mica. Feldspar makes granite more susceptible to decomposition by the solution potash contained in it, potash po tash feldspar being less durable than lime or soda feldspar. Mica, being easily decomposed, is an element of weakness in granite. An excess of lime or soda in the mica or feldspar hastens disintegration, as does also an excess of iron. Therefore, stones showing large and dark d ark iron stains should be rejected for outside work. Fine-grained granite weathers better than does granite g ranite of coarser grain. Granite has a pearly luster. The color of common granite varies from white through yellow to lighter deep red, and the stone is generally classified as gray and red. Feldspar renders the stone in color. Because of its uniform structure, granite can be quarried in large blocks. The rift, the grain, and the joint planes are advantageous in quarrying, as it is very difficult to cut granite in other places. The uses for which granite is suitable depend on the texture of the stone. Medium-grained stone is best fitted for building construction. Fine-grained stone can be carved and polished, but, on account of its extreme hardness, it cannot be worked readily. Such stone is, therefore, costly when it has to be cut, Coarse-grained granite should be used only for concrete aggregate. 9. Trap Rocks.- index
The term trap is generally applied to a large variety of dark-colored, igneous, unstratified rock~ that occur in large tabular masses rising one above another in successive steps like stairs. These rocks consist chiefly of hornblende, lime, feldspar, and augite, with some magnetic and titanic iron. The predominance of one or the other of these minerals gives rise to many distinctive names, as greenstone, olivine, etc. The color varies, being dark d ark gray, dark green, or nearly black, according to the proportions of the different constituents. The texture is usually so fine and close-grained that the character of the structure cannot be determined by the naked eye. Trap rocks are exceedingly dense, hard, and durable. However, they are not much used for structural purposes because of their somber and unattractive appearance, the great cost of working, and the difficulty of securing large blocks on account o off the numerous joint planes. As they split and break easily, trap rocks are extensively used for paving blocks, for the aggregate in making concrete, and for the construction of macadamized
roads, for which purpose their fine texture especially e specially fits them. They are also used for railroad ballast. 10. Syenite.- index
The stone known as syenite consists of feldspar and hornblende, frequently associated with mica and quartz. It is of a granular texture and closely resembles ordinary granite, but is somewhat darker; it is hard and tough, is fairly coarse-grained, an takes a good polish. Owing to its limited occurrence, it is but little used in building construction. SEDIMENTARY ROCKS 11. Sandstone.- index
Sandstone consists of fragments of other rocks cemented together. It is a stratified rock and belongs to the later geological periods. Most of the grains are quartz, but often feldspar is also present in sandstone. The cementing material may be silica, oxide of iron, clay, or carbonate of lime. If the cementing material ismaterial silica, the is very durable, but difficult to work. IronClay oxide is a good cementing androck gives the stone a reddish or brownish color. is a satisfactory binder, but it readily absorbs water, which may cause destruction of the stone by freezing. Lime renders the stone particularly liable to disintegration when exposed to an atmosphere containing gases, or when used for foundations in a soil that contains acid. 12. Sandstones - index
Are variable in character, some being be ing nearly as valuable as granite and others being practically useless for permanent construction. The best stone is characterized by small grains with a small proportion of cementing material. When broken, it has a bright, clear, sharp fracture. It is usually found in thick beds and an d shows slight evidences of stratification. When quarried, sandstones are usually saturated with quarry water and are very soft; but on exposure to the air, they dry out and become hard. Water can readily penetrate between the layers of this stone; therefore, in foundations it should be laid on its natural bed, that is, in the same position that it occupied in the quarry, so that the penetration of moisture and possible disintegration by freezing may be prevented as much as possible. The colors of sandstone are white, cream, yellow, dark brown, blue, and red. A finegrained blue sandstone is known as bluestone. This variety is widely used for trimmings and for stone sidewalks, as it readily splits into slabs.
