This document provides an overview of concrete, including its definition, composition, properties, speciality types, famous structures made of concrete, and world records. Concrete is composed of coarse aggregate bonded together with a cement that hardens over time. It discusses the main ingredients of concrete including aggregates, cement, water, and reinforcement. Specialty concretes described include nanoconcrete, microbial concrete, and polymer concrete. Famous concrete structures highlighted are the Three Gorges Dam, Petronas Towers, and Burj Khalifa. World records listed include the largest single concrete pour for the Three Gorges Dam and records for concrete pumping and underwater placement.
3. CONTENTS
Definition of concrete and its prehistory - 4-5
Composition - 6-10
Properties - 11-13
Speciality Concretes - 14-16
Some famous concrete structures - 17-20
World records - 21-25
Bibliography - 26
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4. INTRODUCTION
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Concrete is a composite material composed of
coarse aggregate bonded together with a fluid cement that hardens
over time. Most concretes used are lime-based concretes such
as Portland cement concrete or concretes made with other hydraulic
cements, such as ciment fondu. However, asphalt concrete, which is
frequently used for road surfaces, is also a type of concrete, where
the cement material is bitumen, and polymer concretes are
sometimes used where the cementing material is a polymer.
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
chemical and thermal resistance are variables.
5. What is Concrete ?
Concrete is a composite material composed of
coarse aggregate bonded together with a fluid cement
that hardens over time.
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6. PREHISTORY
Perhaps the earliest known occurrence of cement was twelve million years
ago. A deposit of cement was formed after an occurrence of oil shale
located adjacent to a bed of limestone burned due to natural causes. These
ancient deposits were investigated in the 1960s and 1970s.
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14. Water
To produce concrete from most cements (excluding asphalt), water 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
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15. Reinforcement
Reinforcement is often included in concrete. Concrete can be
formulated with high compressive strength, but always has
lower tensile strength. For this reason it is usually reinforced
with materials that are strong in tension, typically steel rebar
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16. Specialty concretes
Nanoconcrete
Nanoconcrete is created by high-energy mixing (HEM) of cement, sand
and water. To ensure the mixing is thorough enough to create nano-
concrete, the mixer must apply a total mixing power to the mixture of 30 -
600 watts per kilogram of the mix
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17. Microbial concrete
Bacteria such as Bacillus pasteurii, Bacillus pseudofirmus,
Bacillus cohnii, Sporosarcina pasteuri, and Arthrobacter
crystallopoietes increase the compression strength of concrete
through their biomass.
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18. Polymer concrete
Polymer concretes are mixtures of aggregate and any of various
polymers and may be reinforced. The cement is more costly than
lime-based cements, but polymer concretes nevertheless have
advantages, they have significant tensile strength even without
reinforcement, and they are largely impervious to water
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20. The elasticity of concrete is relatively constant at low stress
levels but starts decreasing at higher stress levels as matrix
cracking develops
Elasticity
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21. Low coefficient of thermal expansion
and shrinks as it matures.
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23. World Records
The world record for the largest concrete pour in a single
project is the Three Gorges Dam in Hubei Province, China
by the Three Gorges Corporation.
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24. The world record for concrete pumping was set on 7
August 2009 during the construction of
the Parbati Hydroelectric Project
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25. The record for the largest continuously placed underwater
concrete pour was completed 18 October 2010, in New
Orleans, Louisiana by contractor C. J. Mahan Construction
Company, LLC of Grove City, Ohio.
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27. ACKNOWLEDGEMENT
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We would like to extend thanks to the many people,
who so generously contributed to the work presented
in this thesis.
Special mention goes to Mrs Sharmistha Basu. Our
presentation has been an amazing experience and I
thank my team wholeheartedly, not only for his
tremendous support, but also for giving me so many
wonderful ideas.
