The Effect Of Concrete In Environment

Description

ABSTRACT

This project is carried out to know the effects concrete in environment. Concrete is an artificial engineering material made from a mixture of Portland cement, water, fine and course aggregates, and a small amount of air. It is the most widely used construction material in the world.

The cement and concrete industries are huge. What does this mean in terms of the environment? Concrete and other cementitious materials have both environmental advantages and disadvantages. This paper takes a look at how these materials are made, and then reviews a number of environmental considerations relating to their production and use

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

ABBREVIATION

CHAPTER ONE

1.0      INTRODUCTION

1.1      BACKGROUND OF THE STUDY

• OBJECTIVE OF THE STUDY
• SCOPE OF THE STUDY
• ADVANTAGES OF CONCRETE
• DISADVANTAGES OF CONCRETE

CHAPTER TWO

LITERATURE REVIEW

• REVIEW OF THE STUDY
• DEFINITION OF CONCRETE
• CONCRETE IN PRACTICE
• TYPES OF CONCRETE
• TYPE OF ADMIXTURES
• SELECTED AGENT
• MATERIALS FOR CONCRETE

CHAPTER THREE

3.1     RAW MATERIALS USED

CHAPTER FOUR

4.1    CONSTITUENT OF CONCRETE

CHAPTER FIVE

• CONCLUSION
• REFERENCES

CHAPTER ONE

1.0                                                     INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

Concrete is a material used in building construction, consisting of a hard, chemically inert particular substance, known as an aggregate (usually made from different types of sand and gravel), that is bonded together by cement and water.

Countries like Assyria and Babylon used clay as the bonding substance or cement. The Egyptians used lime and gypsum cement. In 1756, British engineer, John Smeaton, made the first modern concrete (hydraulic cement) by adding pebbles as a coarse aggregate and mixing powered brick into the cement. In 1824, English inventor, Joseph Aspdin, invented Portland Cement, which has remained the dominant cement used in concrete production. Joseph Aspdin created the first true artificial cement by burning ground limestone and clay together. The burning process changed the chemical properties of the materials and Joseph Aspdin created a stronger cement than that which uses plain crushed limestone would produce.

Cement production requires a source of calcium (usually limestone) and a source of silicon (such as clay or sand). Small amounts of bauxite and iron ore are added to provide specific properties. These raw materials are finely ground and mixed, then fell into a rotary cement kiln, which is the largest piece of moving industrial equipment in the world. The kiln is a long, sloping cylinder with zones that get progressively hotter up to about 1,480°C. The kiln rotates slowly to mix the contents moving through it. In the kiln, the raw materials undergo complex chemical and physical changes required to make them able to react together through hydration. The most common type of cement kiln today is a dry process kiln, in which the ingredients are mixed dry. Many older kilns use the wet process.

The first important reaction to occur is the calcining of limestone (calcium carbonate) into lime (calcium oxide) and carbon dioxide, which occurs in the lower-temperature portions of the kiln-up to about 900°C. The second reaction is the bonding of calcium oxide and silicates to form dicalcium and tricalcium silicates. Small amounts of tricalcium aluminate and tetracalcium aluminoferrite are also formed. The relative proportions of these four principal compounds determine the key properties of the resultant Portland cement and the type classification (Type I, Type II, etc.). These reactions occur at very high temperatures with the ingredients in molten form. As the new compounds cool, they solidify into solid pellet form called clinker. The clinker is then grounded to a fine powder, a small amount of gypsum is added, and the finished cement is bagged or shipped bulk to ready mix concrete plants.

Concrete is produced by mixing cement with fine aggregate (sand), coarse aggregate (gravel or crushed stone), water, and small amounts of various chemicals called admixtures that control such properties as setting time and plasticity. The process of hardening or setting is actually a chemical reaction called hydration. When water is added to the cement, it forms a slurry or gel that coats the surfaces of the aggregate and fills the voids to form the solid concrete. The properties of concrete are determined by the type of cement used, the additives, and the overall proportions of cement, aggregate, and water.

1.2                                  OBJECTIVES OF STUDY

The main objective of the study is to know the effect of concrete on our environment.

1.3                                      SCOPE OF THE STUDY

Construction activity is one of the main elements that considerably disturb the environment. The scope of the present work is to study the effects of cement on environment. The consequences of construction activities in contamination of surroundings have been observed through collection of data from the management of various construction companies concerning the measures. The analysis of data reveals that open crushing and grading of aggregates, use of health hazard chemicals and improper deployment of natural resources in construction result into environmental degradation. The construction planners are advised to implement standard and safe policies to ensure environmental protection.

1.4                                 ADVANTAGES OF CONCRETE

Under normal conditions, concrete grows stronger as it grows older. It is the most widely used material (construction) in the world, because it is the only major building material that can be delivered to the job site in a plastic state.

Concrete can be molded into different form or shape due to its unique quality. Other qualities of concrete as a building material are its strength, durability, and economy, depending on the mixture of material used.

Concrete provides a wide latitude in surface texture and colours and can be used to construct a wide variety of structures, such as highways and street bridges, dams, large buildings, airport runways, irrigation structures, breakwaters, piers and docks, sidewalks, silos and farm buildings, home and even barges and ships.

1.5                              DISADVANTAGES OF CONCRETE

• Ordinary concrete are much weaker in tension, than in compression.
• Concrete is a bottle material and presses very low tensile strength, limiting ductility and little resistance to cracking
• Internal micro cracks as inherent present in the concrete and its poor tensile strength propagates such micro cracks and eventually leading to bottle failure of concrete.
• Concrete containing micro silica is vulnerable to plastic shrinkage, cracking and therefore, sheet or mat curing should be considered.