CIVIL ENGINEERING CONSTRUCTION – DDA2132
Chapter 6 BRICKS CONSTRUCTION By
Dr. Mohamad Syazli Fathi
Introduction A brick is defined in BS 3921 as a walling unit with size of 225 mm length, 112.5 mm width and 75 mm height has an actual dimensions of 215 x 102 x 65 mm. Brickwork is used primarily in the construction of walls by the bedding and pointing of bricks into bonding arrangements. The term also covers the hollow and other lightweight concrete blocks that conform to BS 3921.
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Masonry Construction Terminology 1. 2.
3. 4. 5. 6. 7. 8.
Arris : The edges formed by the inter-section of plane surfaces of a brick. Frog : The depression provided in the face of a brick during its manufacturing. Frogs are provided in bricks to form a key of mortar in between any two adjacent courses or layers of brickwork so as to i increase the th lateral l t l strength t th off the th structure, t t tto reduce d th the weight i ht of bricks so that they can be laid with convenience, and to provide a place for putting impression of trademark or the year of manufacture of the bricks. A stretcher is when bricks are laid with their side surfaces in elevation. It provides longitudinal strength to the wall. A header is when bricks are laid with their end surfaces or widths in elevation. It provides transverse strength to the wall. Cross jjoints : The joints j other than bed joints j normal to the surface of the wall. Perpends : The vertical joints between bricks either in longitudinal or cross directions. The perpends of the alternate courses should be in the same vertical lines. Bed joint : The horizontal mortar joints, between any two consecutive courses of brickwork. Quoins : The external corners of walls. Mohamad Syazli Fathi © 2004
Masonry Construction Terminology Arch: An opening made of bricks or one or more stones. Arches can be used to allow much greater opening widths than are possible with lintels.
1) Round arches: were developed by the Romans (basically a semi-circle) 2) Peaked arches: were developed in Islamic architecture, and used also in the gothic context. 3) Flat arches: made form a large stone or stones, or bricks laid obliquely, with a keystone Mohamad Syazli Fathi © 2004
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MANUFACTURE OF CLAY BRICKS Pressed bricks : 2 processes of pressed brick manufacture;; semi-dryy and the stiff plastic method. Wire cut bricks : is extruded as a continuous ribbon and is cut into brick units by tightly stretched wires spaced at the height or depth for the required brick. Soft mud process bricks. Mohamad Syazli Fathi © 2004
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Varieties of brick Common brick ; for general building work Facing brick ; for attractive appearance when used without rendering or plaster. Engineering bricks; dense and strong and conform to defined limits for absorption and strength.
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Types of bricks. Solid : Those in which small holes passing through or nearly through the brick do not exceed 25% of its volume or in which frogs do not exceed 20% of its volume. A small hole is defined as a hole less than 20mm wide or less than 500 mm2 in area. Perforated : Those in which small holes passing through the brick exceed 25% of its volume and the holes are small. Hollow : Those in which the holes passing through the b i k exceed brick d 25% 2 % off its i volume l and d the h holes h l are larger l than the small holes. Cellular : Those in which small holes are closed at one end and exceed 20% of the volume of the brick. Mohamad Syazli Fathi © 2004
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MORTARS FOR BRICKWORK Mortar : a mixture of sand and lime or a mixture of sand and cement with or without lime. It is proportioned by g or volume. The effect of lime is to make the mix weight more workable. It should be used within 2 hours of mixing or be discarded.
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MORTARS FOR BRICKWORK The mortar used in brickwork transfers the tensile, compressive and shear stresses if l between b t dj t bricks b i k to t satisfy ti f the th uniformly adjacent following : 1. 2. 3. 4. 5. 6.
Have adequate strength, but not greater than the required for the design strength. Have good workability. Needs to retain plasticity long enough for the bricks to b laid. be l id Be durable over a long period Bond well to the bricks Be able to be produced at an economic cost. Mohamad Syazli Fathi © 2004
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TYPICAL MIXES (by volume) 1. Cement mortar(cement:sand) 1:3 – suitable for brickwork in exposed conditions such as parapets t and d ffoundations. d ti
2. Lime mortar(lime:sand) 1:3 - for internal use only
3. Gauged mortars(cement:lime:sand) 1:1:6 – suitable for most condition of severe exposure. 1:2:9 – suitable for most conditions except those of severe exposure 1:2:12 – internal use only. Mohamad Syazli Fathi © 2004
DAMPNESS PENETRATION Dampness can penetrate into a building through the brick walls by : The rain penetrating the head of the wall and soaking down into the building below the roof level. This can be overcome by insertion of a suitable damp-proof course in the thickness of the wall. The rain beating against the external wall and soaking through the building. This can be overcome by cement rendering or suitable cladding such as vertical tile hanging or constructing a cavity wall. The ground moisture entering the building above the ground floor level. This can be overcome by insertion of a suitable damp-proof course in the thickness of the wall. Mohamad Syazli Fathi © 2004
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DAMP PROOF COURSES To provide a barrier to the passage of moisture from an external source into the building. 3 types of DPC 1. 2.
3.
Those below ground level to prevent the entry of moisture from the soil. Those placed just above groung level to prevent moisture creeping up the wall by capillary action called rising damp. Those placed at openings, parapets and similar locations to exclude the entry of the rainwater which falls directly onto the fabric of the structure.
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MATERIALS FOR DPC BS 743: SPECIFICATION FOR MATERIALS FOR DPC Be completely impervious Be durable, longer life than other component in the building and should not need replacing during its lifetime. Comparatively thin sheets so as to prevent disfigurement of the building. Strong enough to support loads placed upon it without exuding from the wall Flexible enough to give any settlement of the building without fracturing.
BS 6398 : Specification for bitumen damp proof courses for masonary BS 6515 : Specification for polythene damp proof courses for masonary. BS 8215 : Code of practice for design and installation do damp proof courses in masonary construction.
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MATERIALS FOR DPC Lead : flexible material , therefore irregular shapes can be formed but expensive and exude under heavy loading. Copper : Thin sheets but expensive. Bitumen : felt form and can be laid quickly. Various bases such as Hessian, fibre, asbestos and lead. Inexpensive but easily torn. Mastic asphalt : applied in 2 layers of total thickness 25 mm, applied is-situ, jointless but expensive in small quantities. Polythene : low density polythene sheets of 0.5 mm thick, easily laid but torn and puncture easily. Slates : Should not be less than 230 mm long and 4 mm thick. Laid in 2 courses. Limited flexibility but impervious and durable. Bricks : BS 3291, laid in 2 courses in cement mortar and can be out of context with the general façade of the building. Mohamad Syazli Fathi © 2004
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Bond. The arrangement of bricks in each layer so as to avoid continuity of vertical joints in any two adjacent courses both on the face and inside of a structure is called bond. This is done by overlapping bricks or stones in the successive courses longitudinally as well as transversely. Necessity of providing bond to achieve the following objects: 1.
2 2. 3. 4.
The primary object is to break the continuity of the vertical joints in the successive courses both in length and thickness of a masonry structure. To ensure longitudinal and lateral strength of the structure. structure To enable the structure to act as a bounded mass and to distribute the load uniformly to its foundation. To provide pleasing appearance by laying bricks symmetrically.
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Types of Bonding 1. Stretcher Bond 2. Header Bond 3 English Bond 3. 4. Flemish Bond Materials for bonding. i. ii.
Mortar : cement : sand = 1: 2 Plastisicer : to be mixed with mortar so that it’s workable. iii. to strengthened brick wall: Used ‘Exmet’ or starter bar every fourth layer, stiffener, brick-pier.
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BRICK JOINTS : JOINTING AND POINTING
1. 2. 3. 4. 5. 6.
Jointing : the finish given to joints when carried out as the work proceeds. Pointing : the finish given to joints by raking out a depth of 20 mm and filling in on surface with a hard setting cement mortar which could have a colour additive. Can be applied to new and old building. Examples of jointing and pointing : pg 120 Flush joint Recessed joint Weathered jjoint Keyed joint Weathered pointing Rake out joint
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The different common mortar joint finished: 1) Flush joint: excess mortar is scraped away with the flat of the trowel, until the mortar is flush with the brick. 2) Raked joint: the tip of the trowel is used until the mortar is set back about ½” from the brick. 3) Stripped joint: wood inserts are used to form a joint similar to raked joint, but flat edged. 4) Weathered joint: mortar is set back from the top brick, and slopes down to meet the bottom brick (this is an expensive procedure). 5) Concave joints: are formed with a special tool, and are like raked jjoints. 6) Struck joint: flat joints set far into the wall, these are only used in interior functions. 7) Combinations of the above can also be used (i.e. different horizontal and vertical joints). Details in page 129 – Brick Joints Mohamad Syazli Fathi © 2004
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Aceh Mosque
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