Cement and Concrete

9 Key excerpts on "Cement and Concrete"

• 

  eBook - PDF

  Materials NQF2 SB

  TVET FIRST

  • Sparrow Consulting(Author)
  • 2013(Publication Date)
  • Macmillan

    (Publisher)

  Topic 5 Cement and Concrete 86 Module 6: Understand Cement and Concrete as construction materials Module 6 Understand Cement and Concrete as construction materials Overview By the end of this section you will be able to: • Define and explain concrete terminology. • Briefly discuss the historical development of concrete. • Explain the hardening and strength gain of concrete. • Explain and demonstrate compacting of concrete and adding of strong stone. • Explain tensile and compressive strength of concrete and the impact of reinforcing steel. • List the dangers of working with Cement and Concrete and describe good working practices. Introduction Through years of development and modern changes in the way construction is done, the two major components of large construction have remained the same: Cement and Concrete. These materials are widely used in buildings because of their high strength and durability. The two materials have a distinct difference, as cement is a primary ingredient to concrete mixes. This module will cover the basics of concrete and cement. Unit 6 .1 Concrete terminology Concrete is basically a mixture of water, cement, lime, sand and aggregate. Each of these ingredients serves a specific purpose in the concrete. The different proportions are specifically prepared for each situation on site. When concrete is still moist after mixing, it is referred to as being a “ green” or “fresh” concrete mix. There are various other materials that can be added to a concrete mix to make it stronger, less expensive to manufacture, or a more durable mixture, for example: cement, binders, additives, extenders and admixtures. All these materials have the sole purpose of making the concrete better in various ways: Extenders – these are cheaper non-concrete materials with adhesive properties that are used to increase the volume of a concrete mix while reducing the cost of making the concrete; they are usually provided in powder form.

  Sign up to read

  Learn more about book
• 

  eBook - ePub

  Concrete Materials and Technology

  A Practical Guide

  • Kambiz Janamian, José Aguiar, José B. Aguiar(Authors)
  • 2023(Publication Date)
  • CRC Press

    (Publisher)

  1 Introduction to Concrete Technology

  DOI: 10.1201/9781003384243-1

  Concrete is the most important construction material with a high amount of usage in the structures, because:

  • It is very simple to find its constituent materials everywhere.
  • Fresh concrete is a flexible material. So, you can shape it with all types of forms.
  • The compressive strength of hardened concrete is very good. We can make a concrete with more than 300 MPa compressive strength nowadays.
  • When we use concrete combined with steel bars or steel fibers, the tensile and flexural strength of the mix will be very good.

  So, it is very important for a civil engineer to know about this magic material. The technique of making and controlling the quality of this material defined as the concrete technology.

  Concrete technology is the technique for the preparation of high-quality constituent materials and mixing them. It seems that it is a simple work. But really it is not. The importance of choosing suitable constituent materials and good proportions is one of the most advanced techniques in civil engineering.

  This chapter is the start for a concrete technologist. You should start with some of the most important expressions and definitions of concrete technology. This fundamental knowledge is necessary to continue the other subjects of the book.

  Every page of this chapter contains many important definitions and concepts that you should learn about the concrete technology. We will use these concepts in the following chapters too many times. So, for beginners, this chapter is the base of other chapters.

  Let’s start our journey with the concrete constituent materials.

  1.1 Concrete Constituent Materials

  Concrete is a mixture of below materials:

  • Portland cement (Figure 1.1 ): It is a kind of powder, which contains calcium silicates and calcium aluminate chemicals. This is the main binder in concrete, which reacts with water to harden. This is also the main material for the smoothness of concrete. We can use about 300–600 kg of Portland cement in 1 m3 of concrete which is about 10%–25% by weight of concrete and about 9%–18% by volume of concrete.
    FIGURE 1.1

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Advanced Concrete Technology

  • Zongjin Li, Xiangming Zhou, Hongyan Ma, Dongshuai Hou(Authors)
  • 2022(Publication Date)
  • Wiley

    (Publisher)

  CHAPTER 2 MATERIALS FOR MAKING CONCRETE Concrete is one of the most versatile and widely produced construction materials in the world (Penttala, 1997). Its worldwide annual production exceeds 12 billion metric tons, i.e., more than two metric tons of concrete was produced each year for every person on Earth in 2007. The global ever-increasing population, improving living standards, and economic development lead to an increasing demand for infrastructure development and hence concrete materials. As a composite material, concrete is composed of different graded aggregates or fillers embedded in a hardened matrix of cementitious material. The properties of major constituents of concrete mixtures, such as aggregates, cementitious materials, admixtures, and water, should be understood first to better learn the properties and performance of concrete. 2.1 AGGREGATES FOR CONCRETE Aggregates constitute the skeleton of concrete. Approximately three-quarters of the volume of conventional concrete is filled by aggregate. It is inevitable that a constituent occupying such a large percentage of the mass should contribute important properties to both the fresh and hard- ened product. Aggregate is usually viewed as an inert dispersion in the cement paste. However, strictly speaking, aggregate is not truly inert because physical, thermal, and, sometimes, chemical properties can influence the performance of concrete (Neville and Brooks, 1990). 2.1.1 Effects of Aggregates (a) Aggregate in fresh and plastic concrete: When concrete is freshly mixed, the aggregates are suspended in the cement–water–air bubble paste. The behavior of fresh concrete, such as fluidity, cohesiveness, and rheological behavior, is largely influenced by the amount, type, surface texture, and size gradation of the aggregate. The selection of aggregate has to meet the requirement of the end use, i.e., what type of structure is to be built.

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Binders for Durable and Sustainable Concrete

  • Pierre-Claude Aitcin(Author)
  • 2007(Publication Date)
  • CRC Press

    (Publisher)

  Cements of yesterday and today, concretes of tomorrow 12.1 Introduction Cement is still an essential material in making concrete, but in some modern concretes, it is no longer the most important material because these concretes are in fact composite materials. In a composite material, it is impossible to decide which is the most important material, because by its nature, a composite material has properties that are always much better than the simple addition of each component’s individual properties. In the fable of the blind and the lame, it is impossible to decide who, between the blind and the lame, is the most important character. Modern concrete is more than simply a mixture of cement, water and aggre- gates. More and more frequently, modern concrete contains mineral com- ponents having very specific characteristics that give specific properties to concrete and also chemical admixtures which have even more specific effects. Modern concrete is becoming a very complex chemical material where mineral products and amorphous products, and not just ground clinker and calcium sulphate, interact with organic molecules or polymers. These are specially developed to highlight certain characteristics of concrete or correct certain deficiencies of current cements because current cements can present some deficiencies in some of their applications. It would be pretentious to believe that nothing else will be discovered in the field of concrete. The science of concrete is only beginning to develop and it should be expected that in the years to come, new types of concretes that will better fulfil different socio-economic needs will be developed. The development of different types of concrete will not necessarily result in an increase in the number of cement types to be produced, but it will require that the quality of the cement be much more consistent than at present. In the future, cements will have to fulfil tighter specifications.

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Structural Concrete

  Materials; Mix Design; Plain, Reinforced and Prestressed Concrete; Design Tables

  • C. B. Wilby(Author)
  • 2013(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  Chapter 2 Properties of materials and mix design 2.1 Cement Cement is the most important and expensive ingredient of concrete, on a price per tonne of material basis (dependent upon the mix, the aggregates can sometimes cost more than the cement in a cubic metre of concrete). It was patented by J. Aspdin in the U.K. in 1824 and he called his product Portland Cement because the 'artificial stone' (concrete) made with it resembled Portland stone. Portland cement is made by grinding together its principal raw materials, which are (a) argillaceous, for example silicates of alumina in the form of clays and shales, and (b) calcareous, for example calcium carbonate in the form of limestone, chalk, and marl which is a mixture of clay and calcium carbonate. The mixture is then burned in a rotary kiln (shaft kilns are still used for works with small outputs and there is an interest in their installation in developing countries) at a temperature between 1400 and 1500°C; pulverised coal, gas or oil is the fuel. The material partially fuses into a clinker which is taken from the kilns, cooled and then passed on to ball mills where gypsum is added and it is ground to the requisite fineness. The resulting cement is allowed to contain small strictly limited percentages of materials not required, some disadvantageous for some uses, such as iron oxide and sulphur trioxide. A general idea of the composition of cement is indicated by the following oxide composition ranges for Portland cements: lime (CaO) 60-67%, silica (Si0 2 ) 17-25%, alumina (A1 2 0 3 ) 3-8%, iron oxide (Fe 2 0 3 ) 0.5-6%, magnesia (MgO) 0.1-4%, sulphur trioxide (S0 3 ) 1-3%, soda (Na 2 0) and/or potash (K 2 0) 0.5-1.3%. The constituents forming the raw materials used in the manufacture of Portland cement combine to form compounds, sometimes called Bogue 1 compounds, in the finished product.

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Bricklaying & Plastering Theory N1 SB

  TVET FIRST

  • Jowaheer Consulting and Technologies(Author)
  • 2021(Publication Date)
  • Macmillan

    (Publisher)

  8 Module 133 Concrete works TVET FIRST Concrete works Overview of Module 8 By the end of this module, you should be able to discuss the following in relation to normal concrete: • Hand mixing. • Machine mixing. • Transportation. • Setting and hardening. • Protection and curing. • Removal of formwork. • Lightweight concrete. Concrete is the most widely used construction material on Earth. It is used in all types of buildings, from houses to tall offi ce blocks. It is also used in roads, pavements, bridges, dams and water reservoirs. Concrete is relatively inexpensive, but it is strong and durable. It can be made porous or watertight, heavy or light. It is soft and can be shaped without breaking or cracking when freshly mixed. However, it hardens to one of the strongest building materials known. In addition, concrete is fire-resistant and requires little maintenance. Figure 8.1: The Gariep Dam is an example of a large concrete structure Starter activity 1. What is concrete made of? 2. Give examples of where concrete has been used in your college building. 3. Why do you think it is necessary to compact concrete? 134 Module 8 TVET FIRST Unit 8.1: Concrete 8.1.8 What is concrete? Concrete is a composite material, which means that it is made up of more than one type of material. It basically consists of two components: the binder and the filler. Cement paste (cement mixed with water) is the ‘glue’ or binder that holds the filler together to create a stable, strong material. The filler in concrete consists mainly of coarse and fine aggregates. We saw in Module 3 that aggregate is made up of sand, gravel and stones. In addition, admixtures may be added to improve the properties of concrete. 8.1.2 Concrete materials The key to good-quality concrete is to use the right type of ingredients in the correct amounts, and to mix them according to the specifications for the particular application.

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Cement-Based Composites

  Materials, Mechanical Properties and Performance, Second Edition

  • Andrzej M. Brandt(Author)
  • 2005(Publication Date)
  • CRC Press

    (Publisher)

  14 Application and development of cement-based composites 14.1 Introduction The great development of all kinds of cement-based materials was the result of their ability to satisfy new requirements in building and civil engineering structures, among other advantages described in previous chapters of this book. Without entering into historical details, it may be observed that there were periods with steady continuous developments and periods with stepwise development related to outstanding innovations and discoveries. A few of the important steps are listed here: understanding of the influence of • w/c ratio on the strength of concrete; discovery of plasticizers and superplasticizers; • application of various kinds of mineral admixtures, additives and • microfillers; application of dispersed reinforcement; • concept of high performance cement composites. • After 100 years or so, the advanced cement-based composites appeared in the early 1980s and now represent a new generation of various composite materials in building and civil engineering (Brandt and Kucharska 1999). Without doubt their application will be increased in many kinds of structures to comply with new requirements. However, there are still several problems that should be investigated to ensure further development in building materials in general, and in cement-based composites in particular. The most important are: improved quality to satisfy the increasing needs for safe and durable struc-• tures of various kinds (housing, transportation, industrial buildings); requirement of sustainable development (economy of raw materials, • energy and space, limitations on emission of gases and wastes, etc.). Furthermore, the concrete structures should answer the requirements of new challenges due to an increasing population, intensification of natural disasters and the development of terrorism. On the other hand, there are

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Advanced Civil Infrastructure Materials

  Science, Mechanics and Applications

  • H Wu(Author)
  • 2006(Publication Date)
  • Woodhead Publishing

    (Publisher)

  Finally, in 1824, Joseph Aspdin, a Leeds builder, took out a patent on ‘portland’ cement (so named because of a real or fancied resemblance of the hardened cement to a naturally occurring limestone quarried on the Isle of Portland, which was then a popularly used material in buildings). This cement was prepared by calcining finely ground limestone, mixing this with finely divided clay, calcining the mixture again in a kiln, and then finely grinding the resulting clinker. This patent was followed by work in many countries, leading to improved kiln designs and methods of proportioning the raw materials. However, work on the chemistry of Portland cement really began only late in the 19th century, with the publication in 1887 of the doctoral thesis of Henri Le Chatelier in France. He established that the main cementing phase in the cement was tricalcium silicate (3CaO·SiO 2 ), and identified some of the other phases as well. Subsequent work by many others finally resulted in the high quality Portland cements that we use today. Finally, in the 1930s, a systematic study was begun on the role of chemical admixtures in Portland cement concrete. (This technology was not entirely new; the Romans had used animal fat, blood and milk in some of their concretes, probably to improve the workability.) Air entraining agents, water reducers, superplasticizers, set retarders and accelerators, corrosion inhibitors, and various other admixtures make possible the high performance concretes that can now be produced. Still, to the lay person, concrete is a deceptively simple material: You mix together cement, water and aggregates, and it gets hard – what else is there to know? Indeed, it is this apparent simplicity that has helped to make Advanced concrete for use in civil engineering 3 concrete such a widely used material. The reality, of course, is very different. Modern concretes, despite the popular prejudice to the contrary, are truly ‘high-tech’ materials.

  Sign up to read

  Learn more about book
• 

  eBook - ePub

  Durability of Concrete

  Design and Construction

  • Mark Alexander, Arnon Bentur, Sidney Mindess(Authors)
  • 2017(Publication Date)
  • CRC Press

    (Publisher)

  Chapter 3

  Materials for concretes in relation to durability

  3.1Introduction

  Prior to the early 1930s, concrete was a relatively simple, straightforward material, consisting only of “pure” Portland cement, aggregate, and water. These were combined in varying proportions to produce concretes with a range of compressive strengths and workabilities. In North America, it was only then that the first concrete additives began to come into general use: air-entraining, set-controlling, and water-reducing admixtures, and fly ash as a cement replacement. In Europe, ground-granulated blast-furnace slag (GGBFS) had been used since the beginning of the twentieth century, but the chemical admixtures were still not available until the 1930s. More recently, the numbers and types of materials being added to Portland Cement and Concrete have been growing at an accelerating pace, driven by a combination of economic considerations and a desire to make the Cement and Concrete industries more sustainable. Of course, both durable and non-durable concretes are made using much the same materials. The object is to ensure that the right materials are chosen for any particular project, taking into consideration both the exposure conditions and any special requirements for the concrete. In what follows, the materials found in modern concretes will be examined primarily in terms of their impact on the durability of concrete. This chapter deals only with the concrete-making materials themselves; the corrosion of steel reinforcement is dealt with in Chapters 4 and 8 , and other durability issues are described in greater detail elsewhere in this book.

  3.2Portland cements and other binders

  Of all of the materials used to make concrete, it is the Portland cement-based binder that is the most unstable part of the system, and is responsible for most of the durability problems that may beset concrete. It may be subject to both chemical and physical attack, as shown in Table 3.1 . (A much more detailed list of deterioration mechanisms is provided in Chapter 4 , Table 4.1

  Sign up to read

  Learn more about book