CONTENTS

COVERPREFACE....................................................................................................................2CONTENTS....................................................................................................................3CHAPTER I....................................................................................................................4A. Cement ...........................................................................................................4B. Chemical Composition of Cement................................................................... 4C. The Cement Manufacturing Process................................................................ 6D. Types of Cements ...........................................................................................7E. The Physical Properties of Cement ................................................................. 10SOURCES ...........................................................................................................................12

CHAPTER ITHEORY

A. CementA cement is a binder, a substance that sets and hardens as the cement dries and also reacts with carbon dioxide in the air dependently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum, cimentum, cment, and cement.Function of cement : To bind the sand and coarse aggregate together To fill voids in between sand and coarse aggregate particle To form a compact massTypes of cement normally used in building industry are as follows:a) Hydraulic CementHydraulic Cement sets and hardens by action of water. Such as Portland Cement. In other words it means that hydraulic cement are any cements that turns into a solid product in the presence of water (as well as air) resulting in a material that does not disintegrate in water. Most common Hydraulic Cement is Portland Cement. b) Nonhydraulic CementNonhydraulic cement are any cements that does not require water to transform it into a solid product. Two common Nonhydraulic Cement are :a) Lime - derived from limestone / chalkb) Gypsum

B. Chemical Composition of CementIngredient%ageEffect

Lime (CaO)60-65Controls strength and soundness

Sillica (SiO2)20-25Gives strength, excess quantity causes slow setting

Alumina (Al2 O3)4-8Quick setting, excess lowers strength

Iron Oxide (Fe2 O3)2-4Imparts color, helps in fusion of ingredients

Magnesium Oxide (MgO)1-3Color and hardness, excess causes cracking

Na2 O0.1-0.5Controls residues, excess causes cracking

Sulphur Trioxide (SO3)1-2Makes cement sound

Raw materials for cement manufacture The first step in the manufacture of portland cement is to combine a variety of raw ingredients so that the resulting cement will have the desired chemical composition. These ingredients are ground into small particles to make them more reactive, blended together, and then the resulting raw mix is fed into a cement kiln which heats them to extremely high temperatures. Since the final composition and properties of portland cement are specified within rather strict bounds, it might be supposed that the requirements for the raw mix would be similarly strict. As it turns out, this is not the case. While it is important to have the correct proportions of calcium, silicon, aluminum, and iron, the overall chemical composition and structure of the individual raw ingredients can vary considerably. The reason for this is that at the very high temperatures in the kiln, many chemical components in the raw ingredients are burned off and replaced with oxygen from the air. Table 3.3 lists just some of the many possible raw ingredients that can be used to provide each of the main cement elements.Table 3.3: Examples of raw materials for portland cement manufacture (adapted from ref., Table 2.1).CalciumSiliconAluminumIron

LimestoneClayClayClay

MarlMarlShaleIron ore

CalciteSandFly ashMill scale

AragoniteShaleAluminum ore refuseShale

ShaleFly ash Blast furnace dust

Sea ShellsRice hull ash

Cement kiln dustSlag

The ingredients listed above include both naturally occurring materials such as limestone and clay, and industrial byproduct materials such as slag and fly ash. From Table 3.3 it may seem as if just about any material that contains one of the main cement elements can be tossed into the kiln, but this is not quite true. Materials that contain more than minor (or in some cases trace) amounts of metallic elements such as magnesium, sodium, potassium, strontium, and various heavy metals cannot be used, as these will not burn off in the kiln and will negatively affect the cement. Another consideration is the reactivity, which is a function of both the chemical structure and the fineness. Clays are ideal because they are made of fine particles already and thus need little processing prior to use, and are the most common source of silica and alumina. Calcium is most often obtained from quarried rock, particularly limestone (calcium carbonate) which must be crushed and ground before entering the kiln. The most readily abundant source of silica is quartz, but pure quartz is very unreactive even at the maximum kiln temperature and cannot be used. Grinding and blending prior to entering the kiln can be performed with the raw ingredients in the form of a slurry (the wet process) or in dry form (the dry process). The addition of water facilitates grinding. However, the water must then be removed by evaporation as the first step in the burning process, which requires additional energy. The wet process, which was once standard, has now been rendered obsolete by the development of efficient dry grinding equipment, and all modern cement plants use the dry process. When it is ready to enter the kiln, the dry raw mix has 85% of the particles less than 90 gm in size.C. The Cement Manufacturing Process

Portland cement is the basic ingredient of concrete. Concrete is formed with portland cement creates a paste with water that binds with sand and rock to harden. Cement is manufactured through a closely controlled chemical combination of calcium, silicon, aluminum, iron and other ingredients. Common materials used to manufacture cement include limestone, shells, and chalk or marl combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore. These ingredients, when heated at high temperatures form a rock-like substance that is ground into the fine powder that we commonly think of as cement. Bricklayer Joseph Aspdin of Leeds, England first made portland cement early in the 19th century by burning powdered limestone and clay in his kitchen stove. With this crude method, he laid the foundation for an industry that annually processes literally mountains of limestone, clay, cement rock, and other materials into a powder so fine it will pass through a sieve capable of holding water.Cement plant laboratories check each step in the manufacture of portland cement by frequent chemical and physical tests. The labs also analyze and test the finished product to ensure that it complies with all industry specifications. The most common way to manufacture portland cement is through a dry method. The first step is to quarry the principal raw materials, mainly limestone, clay, and other materials. After quarrying the rock is crushed. This involves several stages. The first crushing reduces the rock to a maximum size of about six inches. The rock then goes to secondary crushers or hammer mills for reduction to about three inches or smaller. The crushed rock is combined with other ingredients such as iron ore or fly ash and ground, mixed, and fed to a cement kiln. The cement kiln heats all the ingredients to about 2,700 degrees Fahrenheit in huge cylindrical steel rotary kilns lined with special firebrick. Kilns are frequently as much as 12 feet in diameterlarge enough to accommodate an automobile and longer in many instances than the height of a 40-story building. The large kilns are mounted with the axis inclined slightly from the horizontal. The finely ground raw material or the slurry is fed into the higher end. At the lower end is a roaring blast of flame, produced by precisely controlled burning of powdered coal, oil, alternative fuels, or gas under forced draft. As the material moves through the kiln, certain elements are driven off in the form of gases. The remaining elements unite to form a new substance called clinker. Clinker comes out of the kiln as grey balls, about the size of marbles. Clinker is discharged red-hot from the lower end of the kiln and generally is brought down to handling temperature in various types of coolers. The heated air from the coolers is returned to the kilns, a process that saves fuel and increases burning efficiency. After the clinker is cooled, cement plants grind it and mix it with small amounts of gypsum and limestone. Cement is so fine that one pound of cement contains 150 billion grains. The cement is now ready for transport to ready-mix concrete companies to be used in a variety of construction projects.Although the dry process is the most modern and popular way to manufacture cement, some kilns in the United States use a wet process. The two processes are essentially alike except in the wet process, the raw materials, are grounded with water before being fed into the kiln.

D. Type of Cements

Type of cements divided into five kinds. There are portland cement, water proofed cement, white cement, high alumina cement, and blended cement.

1. Portland cementThe ASTM has designated five types of portland cement, designated Types I-V. Physically and chemically, these cement types differ primarily in their content of C3A and in their fineness. In terms of performance, they differ primarily in the rate of early hydration and in their ability to resist sulfate attack. The general characteristics of these types are listed in Table 3.7.

Table 3.7. General features of the main types of portland cement.

ClassificationCharacteristicApplications

Type I (Ordinary Portland Cement)Fairly high C3S content for good early strength development.General construction (most buildings, bridges, pavements, precast units, etc)

Type II (Moderate sulfate resistance)Low C3A content (