EGQS2111 Construction Technology 1 PDF

EGQS2111 Construction Technology 1 1.1 Introduction This chapter provides an overview of mankind’s use of materials, comparing the use of materials in various industrial sectors, and making clear the point that construction is the world’s largest consumer of materials. It goes on to examine the imp...

EGQS2111 Construction Technology 1 1.1 Introduction This chapter provides an overview of mankind’s use of materials, comparing the use of materials in various industrial sectors, and making clear the point that construction is the world’s largest consumer of materials. It goes on to examine the importance of material properties in their selection for use and outlines the various types and classes of materials and their importance in construction. The most common materials that have been used from the past to the present and still maintain their place in the architectural and construction industry are wood, cement, metal, brick, and concrete. These materials are widely used in various projects due to their high strength and low cost. In today’s modern world, modern building materials are produced and marketed by artisans who have innumerable advantages and advantages over traditional materials. Each of these materials, depending on their strength and performance, is used in different parts of the building. Due to the great diversity in the usage of buildings and installations and the various processes of production, a great variety of requirements are placed upon building materials calling for a very wide range of their properties: strength at low and high temperatures, resistance to ordinary water and seawater, acids and alkalis, etc. Also, materials for interior decoration of residential and public buildings, gardens, parks, etc. should be, by their very purpose, pleasant to the eye, durable, and strong. Figure 1.1 Commonly used construction materials ENGG_CC_LECTURE NOTES_20Sep2022_V04 Page 8 of 77  EGQS2111 Construction Technology 1 1.1.1 Physical properties of materials Density (ρ): The mass of a unit volume of homogenous material is called density. Specific Gravity (Gs): The specific gravity of a material’s solid particles is the ratio of the weight of a given volume of solids to the weight of an equal volume of water at a temperature of 4°C. Water Absorption: Water absorption refers to a material’s ability to absorb and hold water. It mainly depends on the volume, size, and shape of pores present in the material. Weathering Resistance: Weathering resistance refers to a material’s capacity to withstand alternating wet and dry conditions for an extended length of time without significant deformation or loss of mechanical strength. Permeability of Water: Water permeability refers to a material’s ability to enable water to pass through it under pressure. Glass, steel, and bitumen are impermeable to water. Fire Resistance: The ability of a material to withstand the action of high temperatures without significant deformation or loss of strength is referred to as fire resistance. Chemical Resistance: As the name suggests, chemical resistance describes a material’s ability to withstand acids, alkalis, seawater, and gases. Natural stone materials, such as limestone, marble, and dolomite, are degraded by even weak acids, wood is acid and alkali-resistant, and bitumen disintegrates when exposed to alkali liquors. Durability: It refers to a material’s ability to withstand atmospheric and other factors. 1.1.2 Mechanical properties of materials Strength: Strength refers to a material’s ability to withstand stresses induced by loads, the most typical of which are compression, tension, bending, and impact. Materials like stones and concrete have strong compressive strength but poor tensile, bending, and impact strength. Hardness: The ability of a substance to resist penetration by a harder body is referred to as hardness. The Mohs scale is used to determine material hardness. Elasticity: Elasticity refers to a material’s capacity to regain its original shape and dimensions when a load has been removed. The deformation of solid bodies is proportional to the stress within their elasticity limits. Plasticity: When a material is loaded, it can change shape without cracking, and it can retain that shape after the load has been removed, this behavior of a substance is referred to as plasticity. Steel, copper, and hot bitumen are some examples of plastic materials. ENGG_CC_LECTURE NOTES_20Sep2022_V04 Page 9 of 77  EGQS2111 Construction Technology 1 1.2 Aggregates Aggregates are the materials used as filler with a binding material (cement/lime/fly ash and other materials) to produce mortar and concrete. They are derived from igneous, sedimentary, and metamorphic rocks or manufactured from blast furnace slag, etc. Aggregates form the body of the concrete, reduce the shrinkage and affect the economy. They occupy 70-80 percent of the volume and have considerable influence on the properties of the concrete. They should be clean, hard, strong, durable, and graded in size to achieve the utmost economy from the paste. & 1.2.1 Classification of aggregates i) Classification of aggregates based on shape: The following are the types of aggregates classified according to their shape,  Rounded Aggregate: The rounded aggregates are completely shaped by attrition (the resistance of a granular material to wear) and are available in the form of seashore gravel. Rounded aggregates give more workability, and they require a lesser amount of water-cement ratio.  Irregular Aggregates: The irregular or partly rounded aggregates are partly shaped by attrition, and these are available in the form of pit sands and gravel. These will give lesser workability when compared to rounded aggregates.  Angular Aggregates: The angular aggregates consist of well-defined edges formed at the intersection of roughly planar surfaces and these are obtained by crushing the rocks. They give 10-20% more compressive strength due to the development of stronger aggregate-mortar bonds. So, these are useful in high-strength concrete manufacturing.  Flaky Aggregates: When the aggregate thickness is small when compared with the width and length of that aggregate it is said to be flaky aggregate.  Elongated Aggregates: When the length of aggregate is larger than the other two dimensions then it is called elongated aggregate.  Flaky and Elongated Aggregates: When the aggregate length is larger than its width and width is larger than its thickness then it is said to be flaky and elongated aggregates. The above 3 types of aggregates are not suitable for concrete mixing. ENGG_CC_LECTURE NOTES_20Sep2022_V04 Page 10 of 77  EGQS2111 Construction Technology 1 a) Rounded aggregates b) Irregular aggregates c) Angular aggregates d) Flaky aggregates e) Elongated aggregates f) Flaky and Elongated aggregates Figure 1.2 Classification of aggregates based on shapes ii) Classification of aggregates based on size: Aggregates are available in nature in different sizes. The size of aggregate used may be related to the mix proportions, type of work, etc. The size distribution of aggregates is called the grading of aggregates. Following are the classification of aggregates based on size: ENGG_CC_LECTURE NOTES_20Sep2022_V04 Page 11 of 77  EGQS2111 Construction Technology 1 Figure 1.3 Classification of aggregates based on Size Figure 1.4 Sieve analysis test on aggregates  Fine Aggregate: When the aggregate is sieved through a 4.75mm sieve, the aggregate passed through it is called fine aggregate. Natural sand is generally used as fine aggregate, and silt and clay also come under this category. The purpose of the fine aggregate is to fill the voids in the coarse aggregate and to act as a workability agent. Fine aggregates Size variation (mm) Coarse Sand 2.0mm – 0.5mm Medium sand 0.5mm – 0.25mm Fine sand 0.25mm – 0.06mm Silt 0.06mm – 0.002mm Clay 256mm Table 1.2 Sizes of coarse aggregates 1.2.2 Characteristics of aggregates  A good aggregate must be clean & free from coatings of clay and silt.  It should not contain any organic matter and should be free from hygroscopic salt.  It must be strong and durable.  It should be angular or cubical. ENGG_CC_LECTURE NOTES_20Sep2022_V04 Page 12 of 77  EGQS2111 Construction Technology 1 1.2.3 Tests on aggregates  Toughness: It is defined as the resistance of aggregate to failure by impact.  Hardness: It is defined as the resistance to wear by abrasion, and the aggregate abrasion value is defined as the percentage loss in weight on abrasion.  Specific Gravity and Water Absorption: The specific gravity of a substance is the ratio of the weight of a unit volume of the substance to the unit volume of water at the stated temperature. Usually, the specific gravity of most aggregates varies between 2.6 and 2.8.  Bulking of Sand: The moisture present in fine aggregate causes an increase in its volume, known as bulking of sand. 1.3 Cement Cement is a binder, a substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement mixed with fine aggregate produces mortar for masonry, or with fine aggregate and coarse aggregate, produces concrete. 1.3.1 Chemical composition of raw materials The raw materials used for the manufacture of cement consist mainly of lime, silica, alumina, and iron - - - - oxide. These oxides interact with one another in the kiln at high temperatures to form more complex portalizad Spc-cement - a compounds. Composition db Oxide ordinary UK Function (%) 100 site Controls strength and soundness. Its deficiency reduces CaO 60-65 SiO2 y 17-25 strength and setting time > Initial - setting time Gives strength. Excess of it causes slow setting final setting 28-30 ↳ min : 350 min : : 5 alimeyalAl2O3 3-8 Responsible for quick setting, if it is excess, it lowers the Iron Fe2O3 a 0.5-6 strength Gives color and helps in the fusion of different ingredients Imparts color and hardness. If in excess, causes cracks in magnationMgO 0.1-4 mortar and concrete & more Alkalies These are residues, and if in excess cause efflorescence and 0.4-1.3 & -s , is (K2O, Na2O) cracking - SO3 1.3-3 Makes cement sound sulphate Table 1.3 Chemical composition of materials - ) Bogue’s compounds: : - ENGG_CC_LECTURE NOTES_20Sep2022_V04 Page 13 of 77  & EGQS2111 Construction Technology 1 I The compounds formed in the burning process (clinkering) have the properties of setting and hardening in the presence of water. They are known as Bogue compounds after the name of Bogue who identified - them. Le-Chatelier and Tornebohm have referred to these compounds as Alite (C3S), Belite (C2S), - => Celite (C3A), and Felite (C4AF). - - 6 The principal mineral Formula Name Symbol compounds in Portland cement 3 Tricalcium silicate = => 3CaO.SiO2 Alite - C3S 2 Dicalcium silicate 2CaO.SiO2 = Belite C2S - - 3 Tricalcium aluminate 3CaO.Al2O3 Celite C3A - Tetracalcium alumino ferrite 4CaO.Al2O3.Fe2O3 Felite C4AF e => - - Table 1.4 Bogue’s compounds 1.3.2 Hydration of cement The chemical reaction between cement and water is known as the hydration of cement. The process is & exothermic, and it liberates a considerable quantity of heat, which is called heat of hydration. 1.3.3 Manufacturing of cement cilica - The raw materials required for the manufacture of Portland cement are calcareous materials, such as ⑰ limestone or chalk, and argillaceous materials such as shale or clay. The process of manufacturing cement consists of grinding the raw materials, mixing them intimately in certain proportions depending - upon their purity and composition, and burning them in a kiln at a temperature of about 1300 to 1500°C, - > -- at which temperature, the material sinters and partially fuses to form nodular shaped clinker. The clinker J is cooled and ground to a fine powder with the addition of about 3 to 5% of gypsum. - There are two processes known as “wet” and “dry” processes depending upon whether the mixing and grinding of raw materials are done in wet or dry conditions. - ENGG_CC_LECTURE NOTES_20Sep2022_V04 Page 14 of 77  ~ EGQS2111 Construction Technology 1 wash ime & lime O S * F : 1450 -setting = sale palls & - wash Figure 1.5 Manufacturing of cement by Wet process - X pureeash -S Figure 1.6 Manufacturing of cement by Dry process - ENGG_CC_LECTURE NOTES_20Sep2022_V04 Page 15 of 77  EGQS2111 Construction Technology 1 1.3.4 Types of cement Many types of cement are available in markets with different compositions and for use in different environmental conditions and specialized applications. A list of some commonly used cement is described in this section. used   Ordinary Portland cement (OPC) ~ Portland Pozzolana cement (PPC) L commonly forts colorf  Rapid Hardening cement > - Red (like  Quick setting cement  Low Heat cement 3  Sulfate resisting cement - resist and manage , &  Blast Furnace Slag cement -  High Alumina cement  White cement  Colored cement  Air Entraining cement  Hydrographic cement. 1.3.5 Testing of cement Two types of tests are undertaken for assessing the quality of cement.  Field Testing: The following are the field tests:  Open the bag and take a good look at the cement. There should not be any visible lumps. The color of the cement should normally be greenish grey.  Thrust your hand into the cement bag. It must give you a cool feeling. There should not be any lump inside.  Take a pinch of cement and feel it between the fingers. It should give a smooth and not gritty feeling.  Take a handful of cement and throw it on a bucket full of water, the particles should float for some time before they sink.  Laboratory testing: The following are the tests conducted in the laboratory: Fineness: This test is carried out to check the proper grinding of cement and the fineness of cement particles is determined either by a sieve test or permeability apparatus test. ENGG_CC_LECTURE NOTES_20Sep2022_V04 Page 16 of 77  EGQS2111 Construction Technology 1 Setting time: The test is performed to find out the initial setting time and final setting time.  Initial setting time =