Introduction to masonry and masonry construction

AN Fried

Surrey University.

General information

1. Queries – please contact me by e-mail or knock on the door.

2. Design is to BS 5628 and supporting standards.

3. Information on EC6 will be provided

4. U-Learn is used as a repository for notes, presentations and courseworks.

UNIT 1- IntroductionTotal study time 12 hours

• Considers :• Development of masonry materials• Developments in design and construction.

• Historical Introduction• Consider the historical use of bricks.

– The Hanging Gardens of Babylon– The Great Wall of China– Medieval Castles– Brunelleschi’s Dome in Florence– The Taj Mahal– Victorian sewers under London (1200 miles)

How is masonry used in buildings

• “Primary uses exist :– Load bearing structures – Enclosing structures in framed structures.

History of Bricks• Near East and India - Bricks used for 5000yrs.

– No natural stone– Bricks laid orthogonally. Gaps filled with bitumen, straw, marsh

reeds, and weeds.• Ancient Egyptians & Indus Valley Civilization - Mudbrick

used.– Unit dimensions - 4 : 2 : 1 [Same as today]

• Romans - Fired bricks.– Mobile kilns– Exported brick usage.

• 12th century - Northern Italy - Fired bricks re-introduced.• Renaissance and Baroque periods – Plastered bricks

used.• 18th Century - Visible brick walls again popular

• Transport of bricks costly – locally produced• Stone considered superior to brick. • Brick flourished where stone was scarce.

History of Concrete Masonry

• Concrete - Long history. – Ancient Egyptians.– Oldest concrete - 5600 BC – Modern era 1824

• First concrete house 1835 in Kent. • First concrete blocks - 1850 • Concrete block industry established - 1910, • Major growth - 1918 - 1939

History of Concrete Masonry

• Post world war II• Steel short in supply. Concrete expanded.• 1950 – 1960

– Resumption of house building. Concrete blocks used.– Lightweight aggregate blocks introduced.– High quality facing concrete masonry.– High rise masonry buildings. – Reinforced masonry in seismic areas

• 1960 – Present – Expansion of concrete blocks.

Market share for masonry

Block – Brick comparison

Deliveries of bricks and blocks in the UK since 1955

0

20000

40000

60000

80000

100000

120000

140000

Year

Th

ou

sa

nd

s o

f s

qu

are

me

tre

s

Clay bricks

Sandlime bricks

Concrete bricks

Concrete blocks

Concrete blocks – proportion by type

Relative proportions of block types delivered since 1965

0

10

20

30

40

50

60

1965

1967

1969

1971

1973

1975

1977

1979

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

Year

Ma

rke

t S

ha

re %

Dense

Lightweight

Aircrete

Introduction to Mortar

• Mortar for masonry.– Ancient mortars– Gypsum mortars.– Ash Lime mortar– Lime mortars.– Portland cement mortars– Portland cement mortars including lime.– Masonry cement mortars– Thin Layer mortars.

Ancient mortar.

• Most ancient mortar – 10,000 years old - Galilee, Israel– Constructions in excess of 5000years exist– Much of the mortar in these is still sound.

Gypsum mortar.

• Pyramids – Constructed using gypsum.

• Paris – Much of the old city re-constructed using gypsum. Encourages damp.

• Gypsum render has been used in the past. Attracts water.

• Not a modern alternative

Ash lime mortar

• Ash materials are reactive in the same ways as cement.– Ground brick has the same properties in some

cases.– Old bricks – good ash lime mortar.– New bricks – poor ash mortar {Excellent firing

renders active ingredients in-active}

Lime Mortars• Used for over 2000years.• Can take a long time to harden.

• Quicklime• Raw material for lime mortar. Calcium Oxide

• Hydrated lime• Add water to quick lime = Hydrated lime.• Hardens by carbonation – slow process.

• Hydraulic lime• Hydrated lime + clay impurities = Hydraulic lime. Gains strength at say 90

days. Acceptable.

• Lime mortar is hydraulic lime. This is rare in the UK.

• Hadrian’s wall (Roman) and tower of London (900 years old)

The development and types of modern cement mortars

• In 19th century lime mortars were the norm.• Cement mortars used from 1910 onwards.

Range of cement mortars.• Cement : sand • Cement : lime : sand• Cement : Sand plus plasticiser• Cement : sand Plus air entrainer• Cement : sand plus polymers.

• Cement : ground limestone : sand. (Masonry cements)

Current practice

Factory mortars the norm.Good quality and consistency

– Wet ready to use

– Dry ready to use

– Lime sand for mortar

Construction

Site Practices and Requirements • Preparing and Building Reference Panels• When final visual appearance of masonry

important– Guarantees an objective assessment of visual

appearance throughout the contract.– Construct panels close to work on level firm base. – Use materials across several palettes to construct

the panels. – Use same bond and joint finish as specified in

final contract.

Handling, Storage and Protection of Bricks and Blocks

• Provide clean, firm, level surface for storage.

• Check colour of units against reference panels if appearance important.

• Maintain packaging as long as possible.• Store similar materials together.• Protect from excessive rain and splashing.

Transportation of Mortars

• Wet ready-to-use mortar– Delivered in truckmixers – Needs no further mixing upon arrival on site. – Discharge mortar into purpose-made mortar tubs at central safe

convenient location.

• Dry ready-to-use mortar – Delivered in silos or bulk bags, – Add water and mix on site.– Mortar discharged into mortar tubs for site distribution.

• Mortar tubs.– Do not overfill.– Protect from frost.

Mortar management during construction

• Wet ready-to-use mortar– Contains retarding admixture – useable for 2 -3 days.– Do not exceed recommended retardation.– Keep covered - contaminants / rain / excessive heat.– Never allow mortar to freeze – discard if necessary.– Never top up tubs.– Store on level, dry areas – Saturation caused by rain

• Dry ready-to-use mortar.– Keep silos on firm safe base.– Provide adequate access.– Ensure top up is possible.

Summer Working Laying masonry units• Main concerns

– Evaporation of water from the mortar. – Too little water – bond reduced. – High temperatures less damaging to the performance of the masonry as those of low

temperatures.

• Advantages– Rate of hydration increases– Curing can be excellent in hot weather.

• Masonry units-good practice– Bricks and blocks – Unaffected by hot weather. – Bond may be reduced in hot units. Units absorb water. – Store bricks or blocks in the shade, Docking units , spray units with water.

• Mortar-good practice– Loses its plasticity rapidly - evaporation of the water, increased rate of hydration of the

cement. – Increase water content in a controlled way.– Increase the lime content of the mortar.– Use plasticisers which retain water.– Shade materials and mixing equipment

• Masonry – good practice.– Lay units quickly.– After tooling joints, cover masonry to prevent drying.

Winter Working Laying masonry units

• Introduction– Hydration of mortar occurs above 4°C.– Do not construct masonry at temperatures below 3oC– Mortar should never be allowed to frieze when wet.

• Masonry units-good practice– Protect bricks and blocks by covering against rain, frost and snow. – Saturated units may be damaged on freezing.

• Mortar-good practice– Protect mortar against rain, frost and snow. – Discard frozen mortar.– Never lay mortar on frozen surfaces.– Do not trust anti-freeze admixtures.

• Masonry-good practice• Cover newly constructed masonry

– Protect from rain– Protect from snow.– Protect from frost.

Workmanship

• Basic Laying Techniques

• Use correct mortar mix – Traditionally the mason decides.

• Place units as near to their finished positions possible – avoid too much tapping.

• Use full beds of mortar if possible.• Fill perpends.• Strike joints flush when building. Finish joints later.• If appearance is important avoid getting mortar on brick

face.• Mix units from three packs to ensure colour uniformity.

Jointing

• Well filled and tooled joints enhance : – Appearance – Durability– Weather resistance of walls.

• Mortar joints :– Uniform thickness– 10mm is now accepted as the norm.

• Tooling joints.– Commence when mortar resists an easy thumbprint.– Too early or too late affects bond and durability.

Types of Joint.

• Flush: – Suitable for moderate and sheltered exposure.– Joint has an open texture. – Bond between unit and mortar depends upon skill used during the unit laying. – Produce a uniformly coloured and textured appearance.

• Struck or Weathered: – Suitable for every degree of exposure. – Surface of the mortar is closed by ironing and inclined to the lower edge to shed off water. – Ironing produces a good bond between the mortar and units. – Masonry constructed with this joint type requires good workmanship to obtain a uniform colour and texture.

• Bucket Handle: – Suitable for every degree of exposure. – Surface of the mortar is closed by ironing and the curved profile tends to allow water to run from the face. – Ironing produces a good bond between the mortar and units. – Masonry constructed using this joint type requires good workmanship to obtain a uniform colour and texture.

• Recessed: – Only suitable for sheltered, and moderate exposure. – Special tool used to rake joint. – Deep raking should be avoided - Never extend over half way through the unit depth or into perforations.– Produces excellent uniformity of colour and shade.

Protection after construction

• In most temperate conditions adequate curing of masonry occurs naturally.

• If heat is excessive, keep masonry covered and wet.• Do not build masonry in excessive cold or heat if

essential.• Polythene wrapped around masonry is usually

sufficient.

Requirements for Masonry units

• Masonry needs to satisfy a number of varied criteria :

– appearance– performance– ease of use– durability

• Achieving our criteria is done through correct unit selection which obviously depends on how masonry is made.

Concrete Blocks

• Three processes exist in the UK.

– a foaming process in the case of autoclaved aerated concrete

– a mobile machine called an egglayer– a static machine

Autoclaved aerated blocks

• Manufactured under controlled factory conditions. • Materials - Cement and sand (sometimes with pfa) mixed with

foaming agent.• Discharged into large steel moulds. • Foaming proceeds and causes mix to rise like a cake and start to

set• Cakes are cut using wires.• Cut cakes placed in autoclave ovens (High pressure steam curing

oven).• Produced blocks of density 460–750 kg/m3

• Produces blocks of strength up to 7.0N/mm2

• Blocks have excellent thermal insulation properties. • Wires are adjustable – unit size can be altered.• Autoclaves stabilises units dimensionally.

The egglayer• Produces a wide variety of solid dense concrete blocks.• Manufacturing technique :

– Mobile batching plant – Concrete discharged into hopper and then egg pots.– Egg pots compacted and block pressed out onto concrete apron.– Mix has to be such that the blocks are free standing directly from

the mould without .– Blocks covered or cured as appropriate.

• If operation is out of doors, operation is weather dependant.

• Apron needs maintenance to ensure unit dimensions are acceptable.

• Moulds need replacement regularly.

The static machine

Most consistent method of producing good quality dense and lightweight blocks.

• Similar to egg layer except compaction is greater and curing controlled.

• Low shrinkage.• Higher density blocks possible.• Greater dimensional accuracy possible• Greater wear of surfaces.

A variety of concrete blocks

Concrete Bricks

Soli dense concrete blocks

Blocks - specials

Linteland

Bond BeamBlocks

Aircrete and lightweight aggregate blocks and bricks

Solid dense concrete and Aircrete Density difference

Clay bricks

• Manufactured from fired clay. • Properties of bricks determined by the

type of clay, kiln and the method of forming the brick.

• UK - bricks are either moulded or extruded.

• Colouring can be added before firing• Finishes (textures) can be added before

firing.

Manufacture of clay bricks.

• Moulding

Hand

Automated

• Extruding

Hand moulding

Large kiln firing of clay bricks

Extruding clay brick units

Wire cutting clay brick units

Large perforated clay units (European)

Clay bricks – some face bricks

Clay bricks – showing variety

Calcium silicate units

• Manufacture from sand or flint mixed with lime.

• Constituents are pressed and autoclaved.

• Pigments may be added during manufacture.

Calcium silicate units going into an autoclave

Calcium silicate units Clay units

Calcium Silicate units (and some clay units)

Calcium Silicate test walls

Calcium silicate units 1000 x 600 x 100/150/240

Calcium silicate units.Clay brick wallettes