Building Construction 7. Dr Nabil El-Sawalhi Associate professor Engineering Projects Management

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1 Building Construction 7 Dr Nabil El-Sawalhi Associate professor Engineering Projects Management

2 Walls A wall is a continuous, usually vertical structure, which is thin relative to its length and height. The prime function of an external wall is to: Provide shelter against wind, rain and the daily and seasonal variations of outside temperature normal to its location, for reasonable indoor comfort. To provide adequate shelter a wall should have sufficient strength and stability to be self-supporting and also to support roofs and upper floors. Internal walls divide space into smaller areas, rooms and compartments.

3 The type of wall used will generally depend on the availability of materials and labour, economic factors and the design approach. Functional requirements The function of a wall is to enclose and protect a building or to divide space within a building. A wide variety of materials are used to construct walls, ranging from the familiar stone, brick and block, timber, concrete, glass and steel

4 The commonly accepted functional requirements of a wall are: Strength and stability Resistance to weather and ground moisture Durability and freedom from maintenance Fire safety Resistance to the passage of heat Resistance to airborne and impact sound Security Aesthetics

5 Damp-proof courses (dpcs) The function of a dpc is to act as a barrier to the passage of moisture or water between the parts separated by the dpc. The movement of moisture or water may be upwards in the foundation of walls and ground floors.

6 Flexible dpcs Lead Copper Bitumen dpc Polyethylene sheet and thermoplastic polymetric products

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8 Concrete Block Concrete masonry units (CMUs) are manufactured in three basic forms: solid bricks, larger hollow units that are commonly referred to as concrete blocks, and, less commonly, larger solid units.

9 Concrete masonry units are made in a variety of sizes and shapes They are also made with different densities of concrete, some of which use cinders, pumice, blast furnace slag, or expanded lightweight aggregates rather than crushed stone or gravel. Many colors and surface textures are available.

10 Bricks and brickwork The word brick is used to describe a small block of burnt clay of such size that it can be conveniently held in one hand and it is slightly longer than twice its width. The great majority of bricks in use today are made from clay, although bricks can also be made from sand and lime or concrete. Glass bricks and blocks are also widely available

11 Types of brick Clay bricks Clay differs quite widely in composition from place to place and the clay dug from one part of a field may differ from that dug from another part of the same field. Clay is ground in mills, mixed with water to make it plastic and then moulded, either by hand or machine.

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13 Concrete bricks Concrete bricks are manufactured in the same size as clay bricks. They tend to be more consistent in shape, size and colour than clay bricks and come in a variety of colours and finishes. Brick classifications Bricks may be classified in accordance with their uses as commons, facing and engineering bricks, although they should be specified according to performance requirements, i.e. strength, thermal performance, water absorption, and so on.

14 Commons These are bricks that are sufficiently hard to carry the loads normally supported by brickwork safely, but because they have a dull texture or are a poor colour they are used for situations where they will not be exposed to view. Facings This includes any brick that is sufficiently hard burnt to carry normal loads. Manufacturers offer an extensive range of colours and textures from which to choose.

15 Engineering bricks These are bricks that have been made from selected clay and carefully burnt so that the finished brick is very solid and hard and is capable of safely carrying much heavier loads than other types of brick. These bricks are mainly used for walls carrying exceptionally heavy loads, for brick piers and general engineering works, especially for works below ground.

16 Special bricks A range of special bricks are made for specific uses in fairface brickwork. These bricks are made from fine clays to control and reduce shrinkage deformation during firing. Physical properties of bricks Compressive strength The crushing resistance varies from about 3.5N/mm2 for soft facing bricks up to 140N/mm2 for engineering bricks

17 Water absorption and suction Absorption rates vary between 1% and 35%. Thermal and moisture movement All building materials move as a result of the expansion and contraction caused by temperature or moisture changes Control joints should be added to prevent cracks.

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20 Bonding bricks Stretcher bond The four faces of a brick, which may be exposed in fairface brickwork, are the two long stretcher faces and the two header faces illustrated in Figure 5.29 (also see Photograph

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22 English and Flemish bond A solid wall, 1B and thicker, is bonded along its length and through its thickness. The two basic ways in which a solid brick wall may be bonded are with every brick showing a header face with each header face lying directly over two header faces below or with header faces centrally over a stretcher face in the course below. The bond in which only header faces show is termed heading or header bond.

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24 Blocks and blockwork Building blocks are wall units, larger in size than a brick, which can be handled by one person. Building blocks are made of concrete or clay. Concrete blocks These are used extensively for both loadbearing and non-loadbearing walls. Lightweight aggregate concrete blocks have good insulating properties against transfer of heat

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26 Concrete blocks are manufactured from cement and either dense or lightweight aggregates as solid, cellular or hollow blocks as illustrated in Figure The thicker blocks are made with cavities or holes to reduce weight and drying shrinkage

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28 The usual compressive strengths for blocks are 2.8, 3.5, 5.0, , 15.0, 20.0 and 35.0N/mm2. Dense aggregate blocks for general use The blocks are made of cement, natural aggregate. The usual mix is one part of cement to six or eight parts of aggregate by volume.

29 These blocks are as heavy per cubic metre as bricks, they are not good thermal insulators and their strength in resisting crushing is less than that of most well-burnt bricks. Lightweight aggregate concrete blocks for general use in building The blocks are made of cement and one of the following lightweight aggregates: granulated blast-furnace slag, foamed blast-furnace slag The usual mix is one part cement to six or eight of aggregate by volume

30 Bonding blocks Blocks are made in various thicknesses to suit most wall requirements and are usually laid in stretcher bond. Thin blocks, used for nonloadbearing partitions, are laid in running stretcher bond with each block centred over and under blocks above and below. At return angles full blocks bond into the return wall in every other course, as illustrated in Figure 5.38.

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32 Concrete block walls of specially produced blocks to be used as a fairface finish are bonded at angles to return walls with specially produced quoin blocks for the sake of appearance, as illustrated in Figure 5.39.

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34 Mortar It is essential that brickwork and blockwork be laid in true horizontal courses, and the only way this can be done with bricks is to lay them on mortar. The basic requirements of a mortar are that it should harden to such an extent that it can carry the weight normally carried by bricks, without crushing, and that it should be sufficiently plastic when laid to take the varying sizes of bricks.

35 Types of mortar Cement mortar When fine cement powder is mixed with water a chemical action between water and cement takes place The usual mix of cement and sand for mortar is from one part cement to three or four parts sand to one part of cement to eight parts of sand by volume, mixed with just sufficient water to render the mixture plastic

36 Lime mortar Lime is manufactured by burning limestone or chalk and the result of this burning is an off-white lumpy material known as quicklime When quicklime is mixed with water a chemical change occurs during which heat is generated, and the lime expands to about three times its former bulk. This change is gradual and takes some days to complete, and the quicklime afterwards is said to be slaked, i.e. it has no more thirst for water

37 Lime for building is delivered to site ready slaked and is termed hydrated lime. When mixed with water, lime combines chemically with carbon dioxide in the air, and in undergoing this change it gradually hardens into a solid mass, which firmly binds the sand. The particular advantage of lime is that it is a cheap, reusable, readily available material that produces a plastic material ideal for bedding bricks

38 Its disadvantages are that it is a messy, laborious material to mix, and it gains strength slower than cement. Because it is to some extent soluble in water it will lose its adhesive property in persistently damp situations, crumble and eventually fall out of joints A lime mortar is usually mixed with one part of lime to three parts of sand by volume

39 Proportions by volume Mortar for general brickwork may be made from a mixture of cement, lime and sand in the proportions set out in Table 5.2.

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41 mortar for brickwork or blockwork as follows: Mix 1: for cills, copings and retaining walls Mix 2: parapets and chimneys Mix 3: walls below dpc Mix 4: walls above dpc Mix 5: internal walls and lightweight block inner leaf of cavity