Bricks And Blocks - Mortar

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Learning text part 05Brick and block productionContentspageIntroduction1History of brick making1Clay bricks1Raw materials1Firing2Properties3Calcium silicate bricks3Concrete bricks3Concrete blocks4Autoclaved aerated masonry units5HSE guidance6Glossary of terms6Bibliography7Self-assessment questions8Answers to self-assessment questions9Health and safetyAll mortar mixtures, both wet and dry, are abrasive and alkaline. Whenworking with wet mortar, waterproof or other suitable protective clothingshould be worn. Guidance on the use of these materials can be found inMIA data sheet No. 20.mia mortar industry associationMineral Products Association

Introductioncompounds give rise to red and bluecolouration. Minor constituents suchas sodium and potassium assist in thevitrification process. The manufacturer has tocontrol the content of some minerals, whichmay affect the characteristics of the finishedbrick, eg, calcium sulfate, coal, lignite andcalcium carbonate.This learning text looks at the manufactureof bricks and blocks beginning with thehistorical development before moving ontocurrent production methods of each of themasonry types. A glossary of terminology anda bibliography are included, along with selfassessment questions and answers.The majority of residential building in the UKuses masonry cavity wallconstruction. This involves building theexternal walls of a house as a double layer ofmasonry with a cavity in between. Theexternal leaf is generally built of facing brick,but can also utilize concrete blocks which arethen usually covered with cladding, render,tiles or other material. The inner leaf willusually be constructed with blocks, and thenplastered or dry lined.History of brickmakingFigure 1: The city of Babylon where brickswere used some 6,000 years agoBricks are among the most durable ofbuilding materials. Their use is mentioned inthe bible and the Romans introduced theiruse to the UK but it was not until the 14thcentury that their use spread as they werereintroduced by Flemish refugees into EastAnglia and gradually the sight of yellow“stocks” became common in London. Thegreat fire of London in 1666 encouragedthe introduction of brick partition walls indomestic construction and the use of bricksbecame more widespread although until the18th century, most UK houses were still builtfrom stone, wood or clay.Figure 2 Harvington Hall in Worcestershire,a fine example of Elizabethan Brickwork.The bricks were, it is believed, fired in twonearby fields.Historically bricks were made individuallyby hand in wooden moulds and left todry in the sun. Makers then discoveredthat harder, more durable bricks could bemade by firing the bricks in clamps or kilns,something discussed later in this learningtext. The industrial revolution introducedmechanisation into brickmaking and whiletoday most bricks are made by machine inlarge factories, some are still made by hand.Clay BricksRaw materialsApproximately 96% of bricks in the UnitedKingdom are manufactured from clay.Geologically, brickmaking clays are composedof quartz and clay minerals, the type of claydepending on the locality of the brickworks.In the Midlands, Etruria or Keuper Marl areused, Weald clay or clay from the ReadingBeds is employed in the South East ofEngland, while in the South West, DevonianShale or clay from the Culm Measures isselected.Mineral compounds within the clay areresponsible for the brick’s colour, eg, ironRaw materials for brick making are extractedfrom quarries or pits and then processedand mixed with water. Most manufacturersstockpile clay to minimise the need forextraction in wet weather when themovement of trucks on the clay material isdifficult. Stockpiles may contain sufficient rawmaterials for a year’s production. Stockpilingensures better intermixing of the extractedmaterial and minimises segregation as wellas weathering the raw material. Rainwaterwashes out some of the soluble salts, whichmight later cause efflorescence - whitepatches - on the face of brickwork. Analternative weathering method is to wash theclay thoroughly in a wash mill and store it inan open area traditionally called a ‘clay back’.When clay is removed from the stockpile,a full vertical cut is made so as to producea consistent material for the next stage ofthe brickmaking process. A flow diagramillustrating the clay brick manufacturingprocess is shown in Figure 3. other captions for fig 3!Clay processing involves grinding andworking the material to obtain plasticity anduniform workability. Fineness of the clayinfluences not only the external appearanceof the finished brick but also physicalcharacteristics such as compressive strengthand water absorption. The mixing stageFigure 3: Clay brick productionExcavationof clayWeathering(a) Bystockpilingin the openin wintermonths(b) By passingthrough awash mill andstacking claybricksProcessingMoulding(a) By hand(b) BymachineDrying(a) By storingin the open indrying areas(b) In dryingchambersFiring(a) In clamps(b) Incontinuouskilns(c) Inintermittentkilns1

involves the addition of water to produce ahomogenous material, the quantity addeddepending on the production method beingused. In some works, other materials such aslime, pulverized fuel ash or crushed clinkermay be added to act as fuel, while pigmentsmay also be incorporated to produce specificcolours.For shaping or forming the brick, the clayfeed must be consistent in content, grading,plasticity and water content and threeprincipal processes are used - soft mudmoulding; extrusion/wirecutting; or semi-drypressing.Soft mud processThe clay used in the soft mud process hasa water content in the range 20-30%, andgets its name because the processed claylooks like sloppy mud. The two variants ofthis process are hand moulding and machinemoulding. In hand moulding, processedclay is thrown into a sand-coated mouldand excess material cut off with a wire. Thecharacteristic folded appearance on the facesof the brick is caused by the dragging of theclay against the mould side as it is thrown.A skilled brickmaker can produce up to 100bricks per hour. Nowadays, most productionis by machine, which imitates the handmoulding process. The majority of bricks havea small frog - depression - formed by a raisedcentral area on the bottom face of the mould.The high water content of these bricksmeans they cannot be handled or stackedimmediately after moulding withoutdeformation. Also because of the highdrying shrinkage of such wet mixes and theplasticity of the unfired brick, the size andshape of such units are fairly variable and theytherefore are not suitable for usein thin mortar beds.Extrusion processThe stiff plastic process - sometimes calledthe extrusion process - involves grindingand mixing clay to produce material with amoisture content of 10-15%. This is extrudedand cut into brick-shaped pieces which areallowed to dry for a short period before beingpressed into a die. The stiff clay retains itsshape when ejected from the die and therelatively low moisture content means thatshrinkage is low and that the size is easier tocontrol. A further advantage of this processis that drying time is relatively short. Thistype of unit will normally have at least oneshallow frog. Engineering bricks, facing bricksand other brick products with very accuratedimensions are normally produced in thisway.Wire cut processThe wire cut process uses clay with a moisturecontent in the range 20-25%. A continuousribbon of clay is extruded from a mixerthrough a rectangular die with a cross sectionthe same as that of the required bricks. Theclay ribbon is then cut by a multiple wirecutter into bricks. Cutting wires are set apart adistance depending on the height of the unitplus an allowance for shrinkage that takesplace during drying and firing. The wire cutis made perpendicular to the face and endsof the brick. This type of production processproduces bricks with no frogs in their bedfaces and also allows perforations along thelength of the product by placing bars withinthe die head. Stains may be applied to theextruded clay to obtain a variety of colours.Semi-dry pressing processThe semi-dry pressing process involvesplacing clay with a moisture content inthe range 17-20% in a press and applyinghydraulic pressure to produce the requiredshape. In the UK only the Lower Oxfords clayis used in this process. This material containsapproximately 7% natural shale oil whichresults in a reduction in firing costs. For thesereasons bricks made using the Fletton process(named after the village in Huntingdon wherethey were first made) are relatively cheap toproduce. The clay is dug and then ground topass either a 2.4mm or a 1.2mm sieve. Thecoarser size is used for common bricks andthe finer for facing bricks. Processed materialis fed into automated presses, which forma deep-frogged, standard size brick. Theexternal appearance of the brick may beenhanced by techniques such as applying asurface layer of sand and firing the unit.Following the moulding stage, the bricksare allowed to dry prior to being fired. Thedrying stage is important for two reasons:excessive shrinkage may cause cracking if notcontrolled and preliminary drying reduces theoverall energy requirement.FiringHistorically bricks were dried in ‘hacks’, stacksabout seven courses high. Today, most bricksare dried either in a drier or in a kiln.Firing enhances the colour and develops thestrength and durability of the bricks. There areseveral types of kiln in use and the particularinstallation at brickworks will depend partlyon the levels of production.During firing the bricks go through a numberof property changes. Initially, at temperaturesup to 150ºC - the drying stage - residualmoisture is driven off. In the next stage dehydration - the temperature rises to 650ºCand clay minerals are broken down, releasingwater. Carbonaceous material which may bepresent in the clay or added as fuel is ignitedat temperatures between 200ºC and 900ºC,which results in a more open, lower densitystructure. The highest temperature rangereached is between 900ºC and 1300ºC and isknown as the vitrification stage. It is at thispoint that the brick colours are formed. Thefinal stage is cooling. At approximately 573ºC,silica undergoes a major volume change andcareful control of temperature is essential.During the firing process bricks generallyshrink by several per cent from their original- green - size and this has to be allowed for inthe process.There are two broad categories of kiln: Intermittent Continuous/semi continuousIntermittent kilns (clamp, Scotch, downdraught) are now only used where specialcolour effects are required.(i) A clamp kiln is constructed on a level floorof burnt bricks, with channels filled with fuel.On top of this layer are three or four layers ofgreen bricks and then a further layer of fuel.Layers of bricks are then stacked to a heightof three or four metres.The outside of the clamp is normally sealedwith a coating of clay. The fuel is ignitedand the clamp allowed to burn out, whichcould take from three to twelve weeksdepending on the number of bricks included.(ii) A Scotch or up-draught kiln was apermanent structure with a number of firingchambers built with burnt bricks and thefloor perforated along its full length. Brickswere stacked on the floor with a small gapfor the hot air to circulate. The top of the kilnwas closed with old burnt bricks to conserve2

the heat.(iii) A down-draught kiln is a circularconstruction with a domed roof and fire holesspaced around the base of the wall. There isone opening for access which is sealedduring the burning process. Traditionally coalwas used as fuel but this has nowlargely been replaced by oil. The burningprocess takes about ten days to complete.The Hoffman kiln is a multi-chamber,continuous kiln with damper doors betweenthe chambers. Bricks remain stationary duringthe firing process and the fire is transferredfrom one chamber to another, graduallymoving around the kiln with the area in frontof the fire being heated up, that immediatelybehind the fire gradually cooling down. Brickloading and unloading meanwhile takesplace in other chambers. Bricks remain in thekiln for a number of days depending on thenumber of chambers to complete the cycleof preheating, firing and cooling down. Thisprocess is mainly used for the production ofFlettons and, due to the organic content ofthe raw materials, firing is undertaken underoxidizing conditions.In a continuous tunnel kiln, the green bricksare loaded onto steel trucks or kiln cars,which form a continuous line. These passinto a long chamber, which has a firing zonein the middle of its length. The trucks slowlypass through the kiln, warming as they reachthe firing zone prior to being burnt andthen cooling prior to emerging from thekiln. It takes about four days for a car to passthrough the kiln.PropertiesA are a number of brick properties to betaken into account: Dimensions Compressive strength Durability Water absorptionDimensionsBS EN 771-1 states that the manufacturerof a clay masonry unit shall declare thedimensions for length, width and height interms of the work size.Compressive strengthThe compressive strength measures theresistance to crushing and is used byengineers to assess brickwork strength. Claybricks have a vast range of compressivestrengths ranging from less than 10 N/mm2for a soft mud brick to more than 100 N/mm2for an engineering brick.Table 1 lists typical properties for a number ofbrick types.Table 1: Properties of bricksBrick typeCompressivestrength N/mm2Water absorption %Bulk density Kg/m3Fletton15 - 3015 - 251330London Stock5 - 2522 - 351450Solid wirecut904.12370Perforated wirecut4010 - 201500Durability and water absorptionWater absorption does not necessarilyindicate the behaviour of a brick inweathering. Low absorption ie, less than 7%by mass, usually indicates a high resistance todamage by freezing, although some types ofbrick of much higher absorption may also befrost resistant. Very small quantities of salts,usually sulfates, which may be present in thebricks may produce efflorescence during theperiod when the building is drying out.Perforations in a brick result in a number ofadvantages. Firstly, less material is requiredto produce the unit giving savings in rawmaterial and associated processing costs.Secondly the more open structure results ina reduction in drying time and hence costs.The hardened unit also has slightly enhancedthermal insulation properties. Thirdly thelower masses of these units makes them lesstiring for the bricklayer to lay.The technical standard for clay masonry units(BS EN 771-1) groups units according to thepercentage of voids.Calcium silicatebricksThe production process for calcium silicatebricks was developed in 1866. They aremanufactured from a mixture of calciumlime, siliceous sand or crushed flint, sand andwater. Additionally, pigments may be added.Today, approximately 1% of bricks in the UKare made from these materials and thesetypes of bricks are sometimes referred to assandlime or flintlime bricks depending on thetype of sand used in their manufacture.Constituent materials are proportioned andthen mixed before being moulded undergreat pressure into the required shape.Green bricks are loaded into trucks, whichare moved into curing chambers calledautoclaves, similar to a very large pressurecooker. When the green bricks have beenloaded inside the curing chamber the endsare closed and steam at an approximatetemperature of 175ºC is injected into thesealed chamber. This increases the pressureinside the chamber and results in the limeand sand combining chemically. Bricks remainin the autoclave for seven to ten hours andare then unloaded and allowed to cool. Thecalcium silicate reacts with the atmosphereto form calcium carbonate. Dimensionalchanges from the pressed green to the fullycured brick are negligible.Generally calcium silicate bricks have acomparable weight to that of a clay brick.They have negligible soluble salts contentand are not, therefore, prone to efflorescence.Concrete bricksSome 4% of UK bricks are made fromconcrete. Raw materials used for theirproduction are Portland cement andaggregates, with a pigment generally beingincorporated into the mix. Constituentmaterials are proportioned, mixed, placed inmoulds, vibrated or compacted, de-moulded3

and then cured. Performance requirementsfor concrete bricks are given in BS EN 771-3but sizes are not specified. Common sizes aregiven in Table 2.to a storage area. The process may be carriedout on uncovered slabs, but some productionunits have a roof covering. Figure 5 shows an‘egg-layer’ machine.A range of compressive strengths areproduced, typically from 7-40 N/mm2Concrete bricks are typically 30-40% heavierthan clay bricks of similar dimensions.Figure 5: An egg layer block machineCellular blockTable 2: Dimensions of concrete 090901906590Hollow blockConcrete blocksConcrete blocks are also known as concretemasonry units and have become increasinglyimportant as a construction material.Technological developments in themanufacture and utilisation of the units haveaccompanied the increase in their use.Concrete masonry walls, correctly designedand constructed, will satisfy a variety ofbuilding requirements including fireresistance, durability, aesthetics and acoustics.In the UK, concrete blocks have traditionallybeen divided into three types: Solid blocks which have no formed voids orcavities Cellular blocks which have one or moreformed voids or cavities, which do not passright through the block Hollow blocks, which have one or moreformed voids or cavities, which pass rightthrough the block.Figure 4 shows these three types of blockFigure 4: Types of blockSolid blockIn April 2006, the new standard for aggregateconcrete masonry units (BS EN 771-3) wasintroduced. This requires that productsare identified according to the followinggroupings:Group 1 25% voidsGroup 2 25; 60% voidsGroup 3 25; 70% voidsGroup 4 25; 50% voids (horizontal holes)Concrete blocks were first produced in theearly part of the last century by placing freshconcrete into moulds made of steel or wood.The moulds were stripped when the concretehad hardened. The disadvantage of thismethod was that a large quantity of mouldswere required to produce a number of blocks.A development from single moulds wasthe so called ‘egg layer’ machine. Using this,mixed concrete was loaded into a hopper onthe machine, material was fed into moulds,vibrated and left on a slab to cure. Themachine then moved a short distance andrepeated the process. The number of blocksmade in a single operation depended onthe size of the block. Initially, most machinespressed blocks on their longest dimensionbut designs have been developed over thelast thirty years that make blocks on end.The ‘egg-laying system’ is relatively simple. Allthat is required is a concrete mixing plant, avehicle to transport the concrete to the blockmachine, the machine itself and a flat slab onwhich to press the blocks. Generally the freshblocks are left on the slab for two to threedays to gain strength and then transportedMost modern block making plants in the UKare highly automated and the block makingmachine is stationary. Earth-dry concrete isfed to the mould where it is vibro-compactedonto steel, timber or plastic pallets.The blocks are de-moulded immediately andtransported on a pallet by conveyor to thecuring chambers where they may be treatedeither with heated air or steam to acceleratestrength increase. After curing the blocks aretaken from the chambers and automaticallystacked for delivery. To preserve theirappearance, blocks to be used for facing workmay be shrink-wrapped in polythene. Figure 6shows blocks on delivery.Figure 6: A delivery of blocksConcrete blocks can be manufactured fromeither natural or lightweight aggregates.Standard blocks have a more open textureintended for finishing with plaster orplasterboard while paint-quality or closetextured blocks have a superior finish so thatthey can be directly decorated.Blocks generally have a face size of 440mm x215mm and have a thickness (termed widthin BS EN 771-3) ranging from 75 to 215mm.Individual blocks have a mass ranging from5.0kg to 40.0kg and compressive strengths4

ranging from 3.6 - 40.0 N/mm2. Cellular blocksare manufactured with a thickness rangingfrom 100 to 215mm with individual blockshaving a mass ranging from 8.0 to 27.0kg anda compressive strength of 3.6 - 22.5 N/mm2.Hollow blocks are produced with a thicknessranging from 100 to 215mm. Compressivestrength is generally 3.6 - 22.5 N/mm2 and theweight of the individual blocks ranges from8.0 to 27.0kg.Concrete blocks are generally very stable anddurable and can be used for a wide range ofapplications including below ground wherethey may come into contact withaggressive soils.Autoclaved aeratedmasonry unitsAerated concrete was originally known ascellular concrete and first produced inScandinavia in 1924. In the UK it is commonlycalled Aircrete. Aerated concrete is unliketraditional concrete as it does not containcoarse aggregates. The normal method ofmanufacture is to incorporate an aeratingagent in the mix, the most common of whichis aluminium powder. This reacts with thealkali derived from the cement and/or thelime present, to form complex hydrates andhydrogen gas. It is this gas which forms thevoids and thus the cellular structure.Powdered zinc (rarely used) may be usedinstead of aluminium powder. The principalconstituent material of aircrete blocks is eitherpulverised fly ash (pfa) or quartz sand, whileother constituent materials may comprisecement, lime, aluminium powder and water.Anhydrous calcium sulfate (CaSO4) is alsoused by some manufacturers.Ground quartz sand or pfa is mixed withwater to form a slurry which is then fed to ahigh-speed mixer. Cement and sometimeslime are then added, followed by aluminiumpowder. The quantities of the constituentmaterials are adjusted depending on thetarget density required in the finishedproduct. Mixed material is poured intomoulds and the mixture, called ‘cake’, isallowed to rise due to the hydrogen evolvingand then partially set prior to de-moulding.The demoulded cake is cut by wires intopredetermined sizes. Profiling and handgripscan be machined at this stage which makesthe blocks easier to handle and transport. Thecut cakes are then placed in an autoclave forhigh pressure steam curing at an approximatetemperature of 190ºC and at a pressure of11-12 bar. Autoclaving may last up to twelvehours during which time the constituentmaterials combine to form calcium silicatehydrates. When the product is removedfrom the autoclave it is fully cured and maybe used as soon as it has cooled. Figure 7shows the flow diagram for aircrete blockproduction.Autoclaved masonry units have good thermalproperties but lower sound insulation thanconcrete masonry units. They also have alower range of compressive strengths andneed to be handled more carefully. However,they are easy to cut and shape.Figure t: The aircrete processRaw material storageMixing Constituent MaterialsCastingRising and SettlingProfiling (not normally done in the UK)Horizontal and Vertical CuttingAutoclavingTable 3: Properties of blocksBlock typeCompressivestrengthN/mm2Weight perblock kgNominal drydensity Kg/m3ThermalconductivityW/m3KDenseaggregate7.3 - 4010.0 - 40.01800 - 21001.25Lightweightaggregate3.6 - 17.55.0 - 3.0.0650 - 15000.47Aerated2.9 - 8.43.0 - 24.0400 - 8000.10 - 0.195

HSE guidanceDryliningLightweight aggregate concrete blockDry-covering to any internal building surfaceLightweight concrete block manufacturedHSE guidance for one person repetitively(usually refers to plasterboard).using lightweight aggregate.handling masonry units is that such unitsEngineering brickshould not exceed 20kg in mass. This rulingBrick sized fired-clay unit that has a denseMasonry uniteffectively only applies to concrete blocksand strong semi-vitreous body that conformsBrick, block or stone.and autoclaved aerated blocks. Units aboveto defined limits for water absorption and20 kg should be handled mechanically, noncompressive strength.Perforated bricksrepetitively or by more than one person.Bricks having formed voids which passFacing unitthrough the unit.Masonry unit specially made or selected togive an attractive appearance without anSandlime unitsAircrete/Aerated concrete unitapplied finish.Calcium silicate unit of which the aggregate isA lightweight concrete masonry unitnatural sand.produced by mixing pulverised fly ash orFBA blockground quartz sand with cement, lime,Lightweight aggregate concrete blockSolid brickwater and aluminium powder and thenusing furnace bottom ash as the baseBrick having no holes, cavities (holes closed atautoclaving the partially set material.aggregate. (The use of the term breezeone end) or frogs.block is deprecated).AutoclaveSpecialsA sealed vessel or chamber in which materialsFlettonMasonry units that are not a standard shapeare heated under pressure. In concreteA brick made from clay found in Bedfordshireor size, but are made to order for variousproduction it is used for accelerated curing.and Huntingdonshire, characteristics aredifferent uses.sharp edges and a deep frog.BarStandard blockA unit of pressure. 1 bar 105 NewtonsFlintlime unitsBlock suitable for general building work,per square metre.Masonry unit formed essentially from aoffering all round performance and normallymixture of lime, crushed flint aggregate andavailable in 440 x 215mm face size.Blockwater, cured in high-pressure steam.Masonry unit exceeding the size of a brick inStock brickany dimension.FrogBrick originally hand made in the SouthDepression formed in one or both of theEast of England, so called from the timberBreeze block (deprecated) largest surfaces of a brick.stock fixed to the bench that forms the frog.See FBA block.Glossary of TermsFrogged brickWire cut brickBrickBrick in which any frogs do not exceed 20% ofBrick without frogs shaped by extruding aMasonry unit that does not exceed 338mm inthe gross volume of the brick.column of clay through a die, the columnlength, 225 in width nor 113mm in height.being subsequently cut to the size of a brickGreen bricksby means of taut wires.Bricks that are waiting to be fired.Work sizeHand made brickSize of a masonry unit specified for itsBrick formed by throwing by hand a clod ofmanufacture, to which the actual sizesoft clay into a mould.conforms within permissible deviations.Cellular unitMasonry unit in which formed voids do notHollow clay blocks (Not common in the UK)Yellow stockspass through the masonry unit.Hollow clay blocks are produced by extrusion,The name generally used for London stockCalcium silicate unitMasonry unit formed essentially from amixture of lime, siliceous aggregate andwater, cured in high-pressure steam.dried in a tunnel or chamber driers and firedClampin zig zag Hoffman kilns. They have texturedA type of kiln.faces and are used for external walls onbricks.factory and farm buildings or as the inner leafCommonof cavity walls in housing.Common brick: a brick with no face, designedto be used out of sight.6

BibliographyBS EN 771-1: Specification for masonry units. Clay masonry units.BS EN 771-2: Specification for masonry units. Calcium silicatemasonry units.BS EN 771-3: Specification for masonry units. Aggregate concretemasonry units (dense and light-weight aggregates).BS EN 771-4: Specification for masonry units. Autoclaved aeratedmasonry units.BS EN 771-5: Specification for masonry units. Manufactured stonemasonry units.BS 4729: Clay and calcium silicate bricks of special sizes.Recommendations.BS 6073-2: Precast concrete masonry units. Methods forspecifying precast concrete masonry units.BS 6100-5.3: Glossary of Building and civil engineering termsPart 5: Masonry- Section 5.3 Bricks and blocks.Brick Development Association - Data Sheets.Concrete Block Association - Data Sheets.7

Self-assessment questions1 What are the four main quality requirements for clay that is to be fed to the shaping process?A2 What are the five principal stages in the brick making process?A3 What is a Fletton brick?A4 What are the seven important properties of a brick?A5 In what type of brick production is an autoclave used?A6 List the advantages and disadvantages of aircrete blocks compared to other types of concrete blocks.A7 What is an egg layer?A8 What is the difference between a cellular concrete block and a hollow concrete block?A9 What is the face size of a standard concrete block?A10 What is the HSE guidance on the maximum weight of unit that one person should repetitively handle?A8

Answers to self-assessment questions123456Consistent composition, grading, plasticity and water content.Clay extraction, Clay processing, Forming the brick, Drying, Firing.A brick made from clay found in Bedfordshire and Huntingdonshire, characteristics are sharp edges and a deep frog.Voids in the brick, Water absorption, Crushing strength, Durability, Efflorescence, Suction rate, Appearance.The production of calcium silicate bricks.Advantages: (i) Good thermal insulation properties, (ii) Relatively light, (iii) Easy to work with (cut etc).Disadvantages: (i) Lower sound insulation, (ii) Lower compressive strength range, (iii) Needs more careful handling.7 A machine for producing concrete blocks.8 In a cellular concrete block the cavities do not pass right through the unit, in a hollow concrete block the cavities pass right through the unit.9 440 x 215 mm.10 That the mass of the unit should not exceed 20kg.MIA Learning Texts include:12345678910111213Introduction to modern mortarsCementitious materialsAggregatesAdmixtures, additives and waterBrick and block productionProperties of masonry mortarProduction, deleivery and storage of mortarMortar testingSpecificationsQuality assuranceConstructionProperties of rendering mortarBest practice - potential site problemsThe

Clay Bricks Raw materials Approximately 96% of bricks in the United Kingdom are manufactured from clay. Geologically, brickmaking clays are composed of quartz and clay minerals, the type of clay depending on the locality of the brickworks. In the Midlands, Etruria or Keuper Marl are used, Weald clay or clay from the Reading

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Injection system Hilti HIT-RE 500 V4 Annex A1 Product description . Injection mortar / Static mixer / Steel elements / Materials . Product description: Injection mortar and steel elements . Injection mortar Hilti HIT-RE 500 V4: epoxy system with aggregate 330 ml, 500 ml and 1400 ml Marking:

mortar Hilti HIT-HY 200-A are used for rebar connections. The steel element is placed into a drilled hole filled with injection mortar and is anchored via the bond between embedded element, injection mortar and concrete. The product description is given in Annex A. 2 Specification of th

8th Grade Writing and Speaking/Listening Scope and Sequence 1 s t Q u a r te r 2 n d Q u a r te r 3 r d Q u a r te r 4 th Q u a r te r Writing N a rra t i ve I n t ro d u ce ch a ra ct e rs a n d o rg a n i ze a n e ve n t se q u e n ce (W . 8 . 3 a ) U se n a rra t i ve t e ch n i q u e s i n cl u d i n g