Bricks masonry

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Bricks Masonry

Transcript of Bricks masonry

Chapter overview

• Mortar • Mortar ingredients • Mortar mixes types • Mortar Hydration • Brick • Forming methods • Brick sizes • Brick classification • Choosing bricks • Laying bricks • Reinforced brick masonry (RBM) • Sustainability issues

Mortar

• Mortar cushions the masonry units

• Gives them full bearing against one another

• Seals between the units to keep water and air away

• Bonds the units as one monolithic structure

Mortar Ingredients Cement lime mortar • Made of Portland cement, (Wet) hydrated lime, inert

aggregate, sand (not too coarse or too fine), and water • Lime is added to increase workability and smoothness • Lime is produced from burning lime stone or seashells (calcium

carbonate) in a kiln to drive off carbon dioxide and leave quick lime (calcium oxide), then it is slaked

• Slaked : allowing it to absorb water, it releases large quantities of heat

• Water: chemically involved in curing cement and lime, it should be free of acids, alkalis and organic materials.

Mortar Types Blended hydraulic cement Blends of Portland cement with other cementitious materials (like blast furnace slag) that replaces the Portland cements alone in the cement lime mortar mix

Masonry cement and mortar cement prepackage cement do not require lime addition ,they are • convenient • consistent (premixed) • workable

Masonry cement • Masonry Cement Contains Portland cement or blended hydraulic cement,

lime or other plasticizers and other additives to achieve workability equivalent to cement lime mortar.

• It is formulated with air entraining admixtures that results in air content which reduces the bond strength to about half of that of cement lime mortar which yields:

• weaker wall in flexural and shear strength and • walls that are more permeable to water

Mortar Mortar cement • Mortar cement is blends of Portland cement. lime and other

additives. • It limits air entrainment to meet bond strength requirement

as cement lime mortar By controlling the ingredients used, cement can be light gray white or range of darker gray Mortar can have lots of different colors by Adding pigments Purchasing dry mortar mix that is custom colored at factory Mortar forms 20% of the area of a wall

Mortar Mixes Types According to ASTM C270, Mortar is classified into: N: is general purpose mortar (750 psi , 5.2 MPa) Balance of good bonding and workability Recommended for non-load bearing exterior wall, veneers, parapets, chimneys and interior load bearing walls S Higher flexural bond than N (1800 psi , 12.4 MPa) For exterior reinforced masonry, exterior load bearing masonry wall , walls subjected to high wind force or high seismic load. O: Low strength (350 psi , 2.4 MPa) Interior non load bearing wall and historic restoration work

M: High strength, with less workability, than S or N (2500 psi ,17.2 MPa) Recommended for below grade masonry construction Masonry subjected to high lateral or compressive force Masonry exposed to severe frost action

Mortar Mixes Types

• Rule: low strength mortar is more workable than high strength, so the lowest strength meet the requirement should be used

• Majority of work done by S or N Type. Mortar mixes are specified by: • Proportion specification • Property specification

Mortar

Lime mortar: • Mix of lime, sand and water. • Lime is non-hydraulic cement • It cures through reaction with carbon dioxide in

the atmosphere “carbonation”. • Used in restoration of historic structures.

Mortar hydration

• A complex set of chemical reaction take up water and combine it with the constituents of the cement and lime to create a dense strong crystalline structure that binds the sand particles and masonry units together.

• After hardening they become water insoluble

Brick masonry

Brick is special in fire resistance and its human scale yields much more building flexibilities. Molding of bricks: The raw materials is dug from pits, crushed to have small fine consistency then tempered with water to produce plastic clay. Forming bricks methods

Forming Brick methods

• The soft mud process – Moist clay (20-30 %water) is pressed into

simple rectangular models by hand or using molding machine.

– Water struck bricks are produced by dipping the molds into water right before forming bricks, this process produces bricks that are smooth and dense.

– Sand struck or sand mold bricks: the wet mold is dusted , the brick formed has matte-textured surface

• Dry press process

– Used for clays that shrinks excessively during drying, (10%) water clay is used and pressed into steel molds by a high pressure machine

Forming Brick methods

• Stiff mud process – Most widely used

– 12-15% water clay is vacuumed to remove air pockets

– Extruded through rectangular die

– Texture or thin mixture of colored clay can be applied to the surface

– Automatic cutter cuts and forms bricks

• After using one of the three methods, bricks are dried one to two days in law temperature dryer kiln, then pass through a process called firing or burning

Forming Brick methods

Firing or burning • The process takes 40- 150 hours

• Some amount of distortion might generate.

• The higher the temperature the more the shrinkage and the darker the color

• During firing shrinkage takes place and it is done by two means:

• Periodic kiln: fixed structure loaded with bricks –heated cooled and unloaded

• Tunnel kiln , for more productivity, the bricks are passed in tunnel kiln on rail cars to get out from the other side burned

• The color of the brick depends on chemical composition of the clay, temperature and fire chemistry in kiln

Stages of burning

Stages of burning

• Water smoking and dehydration: drive off the remaining water from the clay

• Oxidation and verification

• Flashing: fire is regulated to create reducing atmosphere in the kiln that develop color variation

• Cooling under controlled conditions to achieve color and avoid thermal cracking

Brick classification Solid Units: Any plane measured along the bearing surface is at least 75% solid Two types: Facing brick (face brick) (ASTM C216) for both structural and non structural use where appearance is important Building brick (ASTM C62) used where appearance does not matter if concealed in finish Solid units may be solid or cored or frogged Cores and frogs permit:

• more drying and firing of bricks • reduce fuel cost for firing • reduce shipping cost • create bricks lighter and easier to handle

Brick classification

Brick classification

Hollow bricks: (ASTM C652) 60% void

• Paving bricks: (ASTM C902) for paving

• Fire bricks: (ASTM C64) for fire places ,clay is special called fireclay

Choosing bricks

• Depends on

• molding process,

• color,

• size,

• durability,

• uniformity of shape and compressive strength

Laying bricks

• Different laying for visual

or structural purposes

bricks Bonds

Running Bond: stretches • Common Bond: (American Bond): stretchers

courses and header course each six rows • English Bond: alternative courses of

headers and stretches • Flemish Bond: alternative header and

stretcher in each course • Monk Bonds: alternative header and two

stretchers in each course

bricks bonds

Running bond

Common bond

English garden wall bond with Flemish header courses

English bond

Flemish bond

Monk bond

The first course of bricks for a lead is bedded in mortar, following a line marked on the foundation

As each lead is built higher, the mason uses a spirit level to make sure that each course is level, straight, plumb, and in the same plane as the rest of the lead. A mason’s rule or a story pole is also used to check the heights of the courses

Wall Building

A mason lays brick to a line stretched between two leads. When laying to a line, there is no need to use a level or rule

A finished lead

Wall Building

Spirit level Line block

Joint Tooling

Reinforced brick masonry (RBM)

• Much stronger than regular brick against vertical load and flexural load

• Procedure: • Two wythes of bricks are constructed apart • Placing steel in the cavity • Filling the cavity with grout (mix of Portland

cement, aggregate & water) • Grouting reinforced bricks • Two methods of grouting • Low lift: 4 feet height wall and Fill grout with

1.5 inch of top then repeat the procedure • High lift: after the whole wall is constructed,

grouting starts.

Sustainability issues

• Material – Mortar is made of abundant material – Clay and shale are plentiful (raw materials for bricks) – Clay brick can include recycled brick dust and post industrial waste

such as fly ash.

• Manufacture – Plants are close to source materials – Unfired clay can be recycled into production process – Fired clay is ground up and recycled into the production process or

used as landscape material – Brick manufacture uses lots of water but it can be reused many times – Its manufacturing embodied energy ranges from 1000 to 4000 BTU per

lb (2.3 to 9.3 Mj/kg) – Firing of clay masonry produces fluorine and chlorine emissions – Most of the products are sold regionally

Sustainability issues

• Construction – Small waste that is used in landfill or buried on site

• Brick masonry building – no indoor air quality problems but, in rare cases,

releasing of radon gas – its thermal mass effect can be useful in fuel saving – little maintenance and high life span – can be used as finishing material without using paint

(source of volatile organic compound VOC) – resistant to moisture damage and mold growth – can be reused by cleaning it from mortar