Microstructure and Properties of Hardened Concrete





Preface

There is a direct relationship between population and urbanization. During the

last 100 years, the world population has grown from 1.5 to 6 billion and nearly

3 billion people now live in and around the cities. Seventeen of the 20 megacities,

each with a population of 10 million or more, happen to be situated in developing

countries where enormous quantities of materials are required for the

construction of housing, factories, commercial buildings, drinking water and sanitation

facilities, dams and canals, roads, bridges, tunnels, and other infrastructure. And

the principal material of construction is portland cement concrete. By volume, the

largest manufactures product in the world today is concrete. Naturally, design and

construction engineers need to know more about concrete than about other materials

of construction.



This book is not intended to be an exhaustive treatise on concrete. Written

primarily for the use of students in civil engineering, it covers a wide spectrum

of topics in modern concrete technology that should be of considerable interest

to practicing engineers. For instance, to reduce the environmental impact of concrete,

roles of pozzolanic and cementitious by-products as well as superplasticizing

admixtures in producing highly durable products are thoroughly covered.

One of the objectives of this book is to present the art and science of concrete

in a simple, clear, and scientific manner. Properties of engineering materials are

governed by their microstructure. Therefore, it is highly desirable that structural

designers and engineers interested in the properties of concrete become

familiar with the microstructure of the material. In spite of apparent simplicity

of the technology of producing concrete, the microstructure of the product is highly complex.

Concrete contains a heterogeneous distribution of many solid compounds as well as

voids of varying shapes and sizes that may be completely or partially filled with alkaline solution.



Compared to other engineering materials like steel, plastics, and ceramics,

the microstructure of concrete is not a static property of the material. This is

because two of the three components of the microstructure, namely, the bulk

cement paste and the interfacial transition zone between aggregate and cement

paste change with time. In fact, the word concrete comes from the Latin term

concretus, which means to grow. The strength of concrete depends on the volume of

the cement hydration products that continue to form for several years, resulting


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