BRICKWORK
Learning Outcomes ď‚—
Explain the definition,classifications,types and process of bricks.
ď‚—
Identify the various types of brickworks bonding, dampness.
DEFINITION
Bricks ,stones,concrete blocks are known as masonry units.
Mason is a person who stacks pieces of masonry unit a top one another to make walls and also known as bricklayer.
Masonry is the building technique
Brickwork is the exterior of most houses and is not only a structural component but also protects against weather and decorates.
Common- as attractive appearance
Engineering- is a strong bricks and have a strength characteristics
Facing- brick free from surface defect or blemishes and facing wall without any surface treatment
Advantages
Disadvantages
Economical
Time consuming construction
Bricks have greater fire resistance
Cannot be used in high seismic zone
Enables easy handling and placement
Absorb water easily
Easily adapted to small scale and large scale
Have a rough surface
Enhances good sound absorption Low maintenance cost
QUALITIES OF BRICKS Internal – suitable for internal use Ordinary – less durable compare to the special quality. But normal durable in the external face of the building Special – durable to extreme exposure. For example for retaining wall, sewage plants or paving.
TYPES OF BRICK SOLID BRICK it is a solid brick without hole A high thermal mass construction mostly used for internal walls
PERFORATED BRICK These bricks are light in weight Require less quantity of clay for their preparation. The drying and burning of these bricks are also easy. The perforated bricks are used in the construction of brick panels for light weight structures and multi-storeyed framed structures.
HOLLOW BRICK They are prepared from special homogeneous clay. They are light in weight about one-third the weight of the ordinary brick of the same size. These bricks can be laid almost about four times as fast as the ordinary bricks . The use of such bricks leads to speedy construction. They are used in the construction of brick partitioning.
CELLULAR BRICKS ï‚— means a brick which holes are closed at one end and exceed 20 percent of its gross cross-sectional area.
SPECIAL BRICKS The special bricks consists of special shape and size. For example: curved wall
Clay bricks Clay bricks are produced by mixing The materials used the clay with water, for making clay moulding,extrusion brick from clay and or pressure into shale. the desired shape, dry and burn
The shape must be in original shape without shrinkage, warping or cracking when the bricks are dried and fired.
MANUFACTURE OF CLAY BRICKS https://www.youtube.com/watch?v=4OJycua56go • Semi dry process • involves placing clay with a moisture content in the range 17-20% in a press and applying hydraulic pressure to produce the required shape.
• Stiff plastic process • involves grinding and mixing clay to produce material with a moisture content of 10-15%.
• Plastic process • Contains a large proportion of moisture • This type of process is used for making wire cut and hand made bricks. • The bricks must be carefully dried before being burnt in the kiln
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MOULDING – pressure process Steam or electric power Hand mould • The rotary press or belt driven press • The prepared plastic clay is to stand or as machine with number of moulds are brought ageing for a period varying from one day to in turn under the plunger. several weeks in cool chamber. • Where the prepared clay will be discharged • This process is to increase the plasticity and and consolidated under great pressure. workability paste and prevent the cracks, • After that, bricks are removed either by an blisters. upward movement of the base or by dropping of the sides.
Intermittent kiln • For firing special bricks • Intermittent kilns (clamp, Scotch, down-draught) are now only used where special colour effects are required.
Continuous kiln • Suitable for large and regular bricks. • In a continuous tunnel kiln, the green bricks are loaded onto steel trucks or kiln cars • These pass into a long chamber, which has a firing zone in the middle of its length. • The trucks slowly pass through the kiln, warming as they reach the firing zone prior to being burnt and then cooling prior to emerging from the kiln.
Tunnel kiln • The stacked bricks will be carry on trucks on track using hydraulic ram and fires stay still. • The bricks will be passes along a tunnel through preheating, firing and cooling zone. • The firing zone and cooling zone are lined with firebricks. • The temperature and speed track are being controlled. • https://www.youtube.com/w atch?v=kwezp0OL1kU
PROPERTIES OF CLAY BRICKS BS 3921: 1985 : Specifies certain requirements for clay brick for use in walling o o o o o
Dimensions Compressive strength Water absorption Efflorescence Sampling
1.
DIMENSIONAL DEVIATION The individual size not exceed 225 x 112.5 x 75 mm BS 3921:1985 maximum of 5235 x 2505 x 1605mm minimum of 5085 x 2415 x 1515mm
2.
COMPRESSIVE STRENGTH Compressive strengths (7 to more than 100 N/mm2) The strength varies depend on the clay composition and the firing
3.WATER ABSORPTION Mode of rain penetration
Bonding of the brick to the mortar in the joint
Result in poor bond and cause leakage
Depends on the composition and temperature of firing
4.
Efflorescence or salting o Formation of a whitish deposit. o Commonly found in new brickwork and faces of old external walls which subjected to excessive dampness. o To minimize the risk of efflorescence, design the brickwork so that it remains dry.
CALCIUM SILICATE BRICKS (CSB)
Manufacture of CSB: ◦ Autoclaved calcium silicate-bonded bricks. ◦ The performance characteristic of CSB can be adjusted by varying the autoclaving time and the steam pressure
Moulded CSB are hardened in sealed and steam pressurized autoclaves process
To allow reaction between the sand and lime its takes 7 – 10 hrs.
Strong homogenous brick
PROPERTIES OF CSB ď‚—
BS 187: 1978 specifies certain requirements : o o o o
ď‚—
Dimensions Compressive strength Drying shrinkage Sampling
Classes of brick: oThe higher the number the stronger the brick. oLoadbearing brick, facing brick and common brick.
6 classes of the brick ◦ The higher the number indicate the stronger the brick Loadbearing bricks, facing bricks and common bricks. The appearance of the loadbearing bricks and facing bricks must be free from visible cracks.
Compressive Strength ◦ Depend on the quality of bricks being produced.
◦ General : 14 to 27.5 N/mm²
SAND CEMENT BRICKS (SCB) Portland cement and sand (1:6) ď‚— Manufactured of SCB: ď‚—
Moulding by hand or machine
After remove, the surface are scratched and left to matured on pallet under shade
Remove from pallets after 2 days remove from machine
Allow to matured for 26 days
The brick will be watering (fine spray) to kept wet for 24 hrs after removal from machine
PROPERTIES OF SAND CEMENT BRICKS ï‚—
BS 1180: 1978 Specifies certain requirements: oDimensions oCompressive strength oDrying shrinkage oSampling
CONCRETE BRICK Made from a mixture of inert aggregate and cement Cured in by weathering.
Harder
Difficult to cut
Less pleasant to handle
MORTAR FOR BRICKWORK Mortar work is serves to: oCushion the brick units
oGive full bearing against one another despite their surface irregularities.
Bonds the bricks together
Accommodates small movements within the wall.
PURPOSE OF MORTAR
Seal between the bricks against penetration by air and moisture
Appearance of the finished brick wall.
Mortar mixes 1.
Cement o As bonding agent and provide strength and durability.
2.
Lime o Imparts workability, water retention,elasticity and bonding. o If too much will delay the setting of the mortar and wall may be unstable.
3.
Sand o Purpose :
4.
Act as filler which enhance the strength Reduce shrinkage and prevent from cracks Reduce cost
Water o Mixing agent which adds to workability
MORTAR JOINTS
Mortar joints should be finished at the surface.
Type of mortar joints : ◦ Concave joint,V joint,Weathered joint, Flush joint,recessed joint,Squeezed joint,Beaded joint,Raked joint
1.
Flush joint â—Ś
Used where walls are plastered or where it is desidered to hide joints under paint. Joint must be compressed to be acceptable weather joint.
2. V joint â—Ś â—Ś
Tooling works the mortar tight and provides a good weather joint. Used to emphasize joints and conceal small irregularities in laying and provides a line in the center or mortar joint.
3. Concave joint ◦ Most common known ◦ Best joint for preventing water penetration. ◦ Tooling works the mortar tight into the joints, which produces better weather resistance.
4. Weather joint ◦ ◦
Use to emphasize horizontal joints Acceptable weather joint with proper tooling.
6.
Squeezed joint â—Ś
Provides a rustic, high texture look.Satisfactory indoors and exterior fences. Not recommended for exterior building walls
7. Beaded joint â—Ś Special effect joint. Makes for a poor exterior weather joint because of the exposed ledge.
8.
Raked joint ◦ Strongly emphasizes joints but a poor weather joint. ◦ Not recommended for exterior building walls ◦ Not as water-resistant as other mortar joints because the design incorporates ledges, which will collect water as it runs down the wall.
Terms in Brick and Brickwork
Brickwork Bonding
The brick in a length of wall must be properly bonded in order to distribute vertical and horizontal loads over a larger area and so minimize the possibility of differential movement between bricks.
Bonding is part of the bricklayer’s skill in producing a pleasing appearance, besides ensuring stability of the brickwork.
A bond is usually identified by the appearance of the external face of the wall.
Types of Brickwork Bonding
Header Bond Stretcher Bond English Bond Flemish Bond Garden Wall Bond Dutch Bond
Header Bond It has only headers in each course of a wall. This bond permits better alignment and as such it is used for walls curved on plan. This bond is chiefly used for footings in foundations for better transverse distribution of load.
Stretcher Bond All the bricks are laid as stretchers. The overlap, which is usually of half brick. Commonly adopted in the construction of half brick thick leaves of cavity walls,partition walls,etc. Since there are no headers, suitable reinforcement should be used for structural bond.
English Bond This is the oldest form of brick bonding, consisting of alternate rows of headers and stretchers. In this bonding, every alternate header in a course sits centrally over the joint between two stretchers in the joint, except at certain stopped end. Comparatively lack of straight joints therefore it gave this bond as the strongest of all bonds. Use particularly in civil engineering work.
Flemish Bond It comprises of alternate headers and stretchers in each course. There are two kinds of Flemish bond :
Double Flemish bond - both external and internal faces of the wall have the characteristic appearance of Flemish. Single Flemish bond - it has a facing of Flemish bond with a backing of English bond. It has a large number of short continuous vertical joints which occur in the longitudinal joints.
Single Flemish Bond
Double Flemish Bond
Garden Wall Bond
Suitable for garden and division.
Two forms of garden wall bond English garden wall bond Flemish garden wall bond.
English garden wall bond
It has three or five courses of stretchers to one course of headers. A queen closer is introduced next to quoin header in the heading course. A header is placed at the quoin of each middle (or alternate) course of stretchers to give a necessary lap and face appearance of the stretching bond.
Flemish garden wall bond It has one header to every three or five stretchers in each course. ď‚— A three-quarter bat is placed next to quoin in every alternate course, and a header is laid over the middle of each central stretcher. ď‚—
Dutch Bond Consists of alternate courses of headers and stretchers. But each stretching course begins at the quoin with a three-quarter bat. Every alternate stretching course have a header placed next to the quoin three-quarter bat.
Dampness There are many ways that dampness can penetrate into a building through the brick wall By the rain beating against the external walls and absorbed the water to show dampness on the internal walls.
Moisture rising up the Moisture penetrates walls at or near to down into the head the base by capillary of the wall and action and moves up moving down into the the wall and enter the building below the building above the roof level. ground floor level.
Dampness Protection Can be overcome by placing a suitable damp-proof course in the thickness of the wall. Damp- Proof Course
It is an impervious material place horizontally or vertically to provide a barrier to the passage of moisture from part of the structure to another. Damp-proof course (dpc) is normally placed at a distance of 150mm to 300mm above the ground level .
Damp-Proof Course Continue….
The materials to be used as d.p.c should satisfy the criteria as stipulated in BS 743, and they are :should be completely impervious. should be durable and long lasting. should be of thin membrane or sheets so as to prevent disfiguration of the wall. should be strong to support load imposed on it without exuding out from the wall. should be of flexible material and able to deflect accordingly with any settlement without fracturing.
Materials Used for Damp-Proof Course
Lead Copper Bitumen MasticAsphalt Slate Bricks Polythene
Lead • It is very costly but effective damp-proof course. It is very durable and flexible material and available in rolls of thin sheets with varying widths, therefore large irregular shapes with few joints can be produced.
Copper • It is also a very excellent damp-proof course and should have a minimum thickness of 0.25mm.Available in rolls of thin sheets, lapped and jointed as described for lead.
Mastic Asphalt • An excellent damp-proof course and it is applied in situ in two layers with a total thickness of 25mm and it is joint less. • This damp-proof course is impervious, indestructible and does not fracture if on account of unequal settlement or cracks in the brickwork.
Bitumen • It comes in the form of felt or rolls usually to brick widths and can be laid quickly with min. number of joints.Should be lapped 75mm where joints occur and lapped full width at all crossings and angles.
Polythene • It is of low density black polythene sheet of single thickness not less than 0.5mm thick. It is easily laid, however care should be taken when lay as it is easily torn and punctured.
Bricks • Effective damp-proof course and are built in two courses in cement mortar.
Slate • It is very efficient damp-proof course. • It is laid in two courses set breaking the joint embedded in cement mortar with a minimum length of 230mm long and thickness not less than 4mm thick.
Metal Anchors For Brickwork
Metal anchors are positioned in the brick walls to provide structural integrity of the walls.
It will attach a wall to its supports, either to another wall, floor,beam, column or other structural support.
Ties are one of the examples of a metal anchor which used to hold a brick walls together, whilst fasteners attach other building elements to walls.
Ties must be strong for it purpose, be non-corrodible (copper or galvanized wrought iron) and normally shape so that water from the outer leaf of the wall will not pass along them to the inner leaf.
Twisted cavity ties
https://www.youtube.com/watch?v=kBXXDK9ooyI
Fixed unit ties
Adjustable brick ties
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