THE MOST WIDELY USED BUILDING MATERIALS

(Binding Materials, Concrete and Structural steel)

 

The designer must be able to select and adapt such materials of construction that will give the most effective result by the most economical means. In this choice of materials for any work of construction, the civil engineer must consider many factors. These factors include availability, cost physical properties of materials and others.

Timber, steel and concrete all vary, sometimes over considerable ranges in the properties desired by engineer. Ever steel, uniform as it appears to be, varies considerably in its microstructure. Concrete is ever less uniform than many other materials.

Lime, gypsum and cement are the three materials most widely used in building construction for the purpose of binding together masonry units, such as stone, brick and as constituents of wall plaster. Cement is furthermore the most important component of concrete. These materials form very important elements in all masonry structures. As a class they are designed as cementing materials.

The gradual improvement in Portland cement quality from the time of its introduction led to the elaboration of rapid hardening Portland cement, or “high early strength”. Later development include low heat and sulphateresisting cement, also white and colored cements. Another important class of cement is high alumina cement. High alumina cement is a material containing alumina. It has an extremely high rate of strength increase which is, owing to the violence of the chemical reaction, accompanied by a considerable evolution of heat. It is very resistant to chemical attack.

It therefore follows that Portland Cement like other materials can to some extent be modified to suit a particular application. The scope for such purpose-made cement has led to the development of an increasing variety such as high alumina cement, blast-furnace slag and pozzuolanas. Portland blast-furnace cement has greater resistance to some forms of chemicals.

The most important building materials may now be considered to be structural steel and concrete. Concrete may be considered an artificial conglomerate of crushed stone, gravel or similar inert material with a mortar. A mixture of sand, screening or similar inert particles with cement and water which has the capacity of hardening into a rocklike mass is called mortar. The fundamental object in proportioning concrete or mortar mixer is the production of a durable material of requisite strength, water tightness and other essential properties at minimum cost. To attain this careful attention must be given to the selection of cement, aggregate and water.

The most accurate method of measuring proportions is to weigh the required quantities of each material. This may be done whether the proportions are based upon volumes or weights. This method is being extensively used in road construction and in many central mixing in central proportioning plans. It is also widely used in large building construction, but in small building construction the less accurate method of measuring proportion by volumes is frequently used. The chief inaccuracies in volumetric measurement arise from the wide variation in the bulk of the fine aggregate due to small changes in its moisture content and faulty methods of filling measuring devices. It is always for a building engineer to bear in mind than workability and strength tests are the chief control tests made on concrete. To be able to undergo high compressive load is a specific characteristic of this materials.

 

 

EXERCISES

 

1. Find the Ukrainian equivalents of the following English terms.

1. high rate of strength            розчин           

2. resistance to                        гіпс

3. high-alumina cement               заповнювач

4. crushed stone                           вміст вологи

5. mortar                                      навантаження на стиск

6. aggregate                                 цемент з високим вмістом глинозему

7. fine aggregate                     висока міцність

8. workability                         щебінь

9. compressive load               міцність на

10. gypsum                             оброблюваність

11. moisture content               дрібний заповнювач

12. masonry                             кам’яна (цегляна) кладка

 

2. Put the following sentences into groups according to three topics (a, b, c).

A. The choice of materials for any work of construction.

B. The properties of high alumina cement.

C. The composition of concrete.

 

1. Another important class of cement is high alumina cement. 2. Such a material may be considered an artificial conglomerate of crushed stone or gravel with a mortar. 3. The civil engineer must consider many factors when selecting the material for construction. 4. This kind of cement is very resistant to chemical attack. 5. The principal object in proportioning concrete is the production of a durable material of adequate strength and water tightness. 6. The factors that condition the selection of materials for construction include availability, cost and physical properties. 7. This material has an extremely high rate of strength increase. 8. Timber, steel and concrete vary over considerable ranges in the properties desired by the engineer and the latter should take them into consideration in selecting the materials. 9. The most accurate method of measuring proportions for concrete is to weigh the required quantities of each material.

 

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