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//-->ALTERNATIVES TOPORTLAND CEMENTAN INTRODUCTIONCement, or some form of cementingmaterial is an essential ingredient inmost forms of building construction.Cement is the vital binding agent inconcretes, mortars and renders, and isused for the production of wallingblocks and roofing tiles.Since its invention in the first half ofthe 19th century, Portland cement hasbecome the most widely availablecementitious material. Its dominanceover alternative cements has been inFigure 1: Participants at a workshop in Uganda visiting apart, due to successful, aggressivevery small traditional lime plant ©Practical Action/Simonmarketing. This is despite its clearL'epine Eklesstechnical disadvantages for certainapplications. In addition Portlandcement is relatively expensive toproduce and is often in short supply in many developing countries. Typically, a rural Africanlabourer may need to work for up to two weeks to earn enough money to buy one bag ofcement. In comparison alternative cements can be produced locally, on a small scale and atmuch lower cost.Alternative cements are not capable of replacing Portland cement totally, but they can be used inthe many construction applications where they have advantages. These are as mortars, rendersand non-structural concretes. Alternative cements are not normally considered suitable forstructural applications such as reinforced concrete beams and columns.The most common of these so-called ‘alternative’ binders is lime, to which other materials,known as pozzolanas, can be added to enhance strength and water resistance. Other binderssuch as gypsum, sulphur, bitumen, mud and animal dung have also been used.Binding systems from historyThe simplest, and possibly the earliest, binding material used was wet mud, and there arerecords of its use in ancient Egypt. Another example of a binder from the distant past is the useof naturally occurring bitumen by the Babylonians and Assyrians in their brick and alabaster(gypsum plaster) constructions.Lime was known to the Greeks and was widely used by the Romans. The Roman architect andengineer Vitruvius published the first specification for the use of lime in building in his celebratedwork De Architectura. The Romans also knew how to make a lime-pozzolana cement by addingmaterials such as volcanic ash or powdered bricks, tiles and pottery to lime.That lime is an appropriate and durable binding material, especially when mixed with pozzolana,is well proven. The Pont du Gard at Nimes in France, a Roman aqueduct built in AD 18 withhydraulic lime-based mortar, is still waterproof; the excellence of the mortar is attributed to theselection of the materials and to the time spent tamping the mix into place during construction.Alternatives to Portland cementPractical ActionThe rebuilding of the Eddystone lighthouse in the English Channel by John Smeaton in 1756 is amore recent development in ‘lime technology’. It was achieved through Smeaton recognizing thehydraulic properties of lime that result from the burning of a clayey limestone. To make thehighly water-resistant mortar needed for bonding the courses of stone, he thoroughly mixed thisalready hydraulic lime with an equal proportion of imported Italian pozzolana (so adding extra‘hydraulicity’ to the mortar).Why continue to usealternative cementsMajor advantages of alternativesto Portland cement are that theyare usually cheaper to produce,needing much lower or evennegligible capital inputs to getstarted, and requiring far lessimported technology andequipment. They can also beproduced on a small scale tosupply a local market resulting ingreatly reduced transportationcosts and a much greaterdegree of local accountability inthe supply of building materials.From an environmental angleFigure 2: Medium-scale Portland cement plant, India ©Practicallime-pozzolana cements can beActionproduced with lower energyinput than either lime by itself orPortland cement – giving a halfto one third consumption in usecompared with Portland cement and about one fifth compared with lime by itself. Low energyconsumption is particularly prevalent with naturally occurring pozzolanas, or those from wastematerials, which might need little additional processing other than drying. The use of clay as abinder, of course, results in negligible energy consumption in production.Lower production costs mean lower prices for the consumer, enabling those who could notafford Portland cement to purchase and use a quality binding material.Pozzolanic cements additionally have numerous other technical advantages to the user:•Improved workability•Improved water retention/reduced bleeding•Improved sulphate resistance•Improved resistance to alkali – aggregate reaction•Lower heat of hydrationIn many large civil engineering programmes involving mass concrete works, Portland cement-pozzolana mixes are specified due to these technical advantages as well as to save money.Social advantages of alternative cements to Portland cement include the potential for affordablequality housing and the opportunity for local employment generation.The technical and economic advantages of alternative cements are not lost on architects andengineers from developed countries. Increasingly, architects, are becoming aware of thebrittleness associated with Portland cement mortars, for example, and are now specifyingblended lime/Portland cement mortars instead. As well as re-discovering the ‘lost arts’ of using2Alternatives to Portland cementPractical Actionalternative binders, recent research has enabled the properties of alternative binders to bethoroughly investigated and catalogued. A body of experience has built up on the appropriateapplication of traditional binders such as clay, lime and pozzolanas, not only in the repair andconservation of historic buildings, monuments and structures but also in adventurous andinnovative new build applications.In some developing countries traditional binders are still slighted, probably because they mightbe associated with poverty or considered to be low status materials. Their performance andtechnical specifications might, completely unjustifiably, also be considered inferior to Portlandcement, they might not be widely produced or available, or the skills to produce and use themmight well have disappeared. A good case can be made for disseminating the developedcountry experience to the South more widely. This would increase interest and awareness ofalternative binders, allow producers and users to gain skills and confidence and determine therightful place of alternative binders in appropriate building for sustainable development.Types of alternative cementsLimeThere are two forms of lime: quicklime and hydrated lime.Quicklime is produced by heating rock or stone containing calcium carbonate (limestone,marble, chalk, shells, etc.) to a temperature of around 1000°C for several hours in a processknown as ‘calcining’ or sometimes simply ‘burning’. It is an unstable and slightly hazardousproduct and therefore is normally ‘hydrated’ or ‘slaked’, by adding water, becoming not onlymore stable but also easier and safer to handle.To produce dry powdered hydrated lime just sufficient water is added for the quicklime lumps tobreak down to a fine powder. This material would have a ‘shelf life’ of only a number of weeks,depending on storage conditions. ‘Old’ hydrated lime would have partially carbonated andbecome a less effective binder.However, if quicklime is hydrated with a large excess of water and well agitated, it forms a milkysuspension known as milk of lime. Allowing the solids to settle, and drawing off the excesswater, forms a paste-like residue, termed lime putty, which is the form of lime which can be usedin building applications to best effect. This will keep almost indefinitely and, in fact, improves withage. In most countries, though, lime is most widely available as a powder, due to its widespreadutilisation in process and treatment industries rather than in construction. Lime putty, whichneeds a stiff bag or container for transportation, is more rarely produced.Limes with high calcium content, often called ‘fat’ or ‘white’ limes are desirable for mostindustries, although the construction industry can use limes containing impurities. For instance,limestones containing a proportion of clay are often seen as an advantage in building as theyproduce hydraulic limes which will set under water and will produce stronger mortars.In the construction industry, lime, in its hydrated or putty form, is mixed with aggregate and waterto produce concrete or mortar in the usual manner. Lime putties generally produce mortars andrenders of excellent quality and consistency.Plain lime-sand mortars are quite weak; any early adhesive strength results from drying out, andlonger term hardening occurs through the action of the air’s carbon dioxide on the lime.Traditionally lime renders and plasters were often mixed with animal hair to improve cohesion.Today the addition of gypsum or Portland cement and/or pozzolanas to increase durability andgive faster setting times is usual.3Alternatives to Portland cementPractical ActionPozzolanasPozzolanas are materials which, although not cementitious in themselves, will combinechemically with lime in the presence of water to form a strong cementing material. They include:•Volcanic ash•Power station fly ash (usually known as pfa)•Burnt clays•Ash from some burnt plant materials•Silicious earths (such as diatomite)Materials not already in a fine powdered form mustbe ground, and some require calcining at around600–750°C to optimize their pozzolanic properties.Pozzolanas can be mixed with lime and/or Portlandcement and can improve quality and reduce costs ofconcretes made from both materials.In some countries (e.g. India and Kenya), pozzolanasare mixed with Portland cement and sold as blendedcement, which in many respects is similar to Portlandcement. In other countries (e.g. Cuba)lime/pozzolana/Portland cement blends are sold asan alternative to Portland cement. Lime-pozzolanacement by itself can make an excellent cementingmaterial for low-rise construction or mass concreteand in some countries (e.g. Indonesia) is stillproduced extensively.Pozzolanas can also be mixed with lime and/orPortland cement at the construction site but caremust be taken to ensure the pozzolana is of aconsistent quality and that the materials arethoroughly mixed.Gypsum plasterGypsum is a not an uncommon mineral, and needsonly a low temperature, of around 150°C, to convert itinto a very useful binding material, known as hemi-hydrate or plaster of Paris.On its own, plaster of Paris sets very rapidly when mixed with water. To give time for it to beapplied, around 5% of lime and 0.8% of a retarding material (such as the keratin glue-likeextracts from boiling fish bones or animal hoof and horn) are added to the plaster.Retarded plaster of Paris can be used on its own or mixed with up to three parts of clean, sharpsand. Hydrated lime can be added to increase its strength and water resistance. Gypsumplasters can be reinforced with various fibrous materials from reeds to chopped glass fibres.Gypsum plaster is not wholly resistant to moist conditions and so is normally used internally,except in the drier Mediterranean and Middle Eastern countries where it has traditionally beenused as an external render.Other alternative bindersSulphur is used as an alternative binder in the Gulf region, where a million tonnes a year comesfrom natural gas plants in the United Arab Emirates. In some other locations, such as St Lucia,sulphur that accumulates around the vents of volcanic fumaroles is utilized.Figure 3: Hydrating of quicklime using awatering can Chenkumbi Limeworks,Malawi © Practical Action/Dave Mather4Alternatives to Portland cementPractical ActionA mixture of 15–25% molten sulphur, heated to around 130°C with 5% of organic additive, and75–85% sand or other mineral aggregates which have previously been heated to 160–170°C,can be cast and de-moulded in only about five minutes. The additive is mainly used to impartdurability. Sulphur concrete has applications which either exploit its quick curing and corrosionresistance or in situations where Portland cement concrete is expensive, unavailable or, forexample in freezing conditions, impracticable.Earth mixed with water to form mud has been, and continues to be, used over much of the worldas a binding material. It develops quite a strong adhesion to fired clay brick and sun dried mudbrick masonry and is satisfactory provided the mud mortar is protected from rainwater. A usefulpractice is to use mud mortar in the internal parts of the wall and do the external pointing in acement or lime-based mortar. The best soils for building purposes contain both sands and claysand therefore it may be necessary to mix two different soils to obtain good results. Mud mortarshave, traditionally, been improved by the addition of organic matter such as straw and cow dung.A number of other alternative binders have been used in a number of applications, whichgenerally relate to soil stabilisation, waterproofing, or the application of a waterproofing or wearresistant coating to vulnerable earth based constructions. Such binders include tars andbitumens (as by-products from petro-chemical industries), sodium silicate (produced from theheat activated reaction between silica and sodium hydroxide), casein (milk whey), oils and fats,molasses, and certain locally specific plant-based materials such as gum arabic, other specificresins and the sap, latexes and juices from specific trees and other plants.References and further reading•••••••••••••••••Alternatives to Portland Cement: An IntroductionPractical Action Technical BriefHydraulic Lime: An IntroductionPractical Action Technical BriefMethods of Testing Lime in The FieldPractical Action Technical BriefCalculating The Energy Efficiency of Your Lime Burning ProcessPractical ActionTechnical BriefHow to Build a Small Vertical Shaft Lime KilnPractical Action Technical BriefLime Kiln Design: Small & Medium Scale Oil Fired Lime KilnsPractical Action TechnicalBriefA Small Lime Kiln for Batch and Continuous FiringPractical Action Technical BriefPozzolanas: Lime-pozzolana CementsPractical Action Technical BriefPozzolanas: IntroductionPractical Action Technical BriefTesting Methods for PozzolanasPractical Action Technical BriefPozzolanas: Portland-pozzolana Blended CementsPractical Action Technical BriefPozzolanas: Calcined Clays and Shales, and Volcanic AshPractical Action TechnicalBriefPozzolanas: Rice Husk Ash (RHA) and Pulverised Fuel Ash (PFA)Practical ActionTechnical BriefClay as a Binder: IntroductionPractical Action Technical BriefGypsum Plaster: Its Manufacture and Use,A. Coburn, E. Dudley and R.Spence, ITDGPublishing, 1989 (now out of print).Appropriate Building Materials,Roland Stulz and Kiran Mukerji, co-published by ITDGPublishing – UK, SKAT Publications – Switzerland, and GATE – Germany. 1993.Supplementary Cementing Materials for Use in Blended Cements,R.J. Detwiler, J.I.Bhatty, S. Bhattacharja, Research and Development Bulletin RD112T, Portland CementAssociation, Skokie, Illinois, USA, 1996Small-scale Lime Burning: A Practical Introduction,M. Wingate and others, ITDGPublishing, 1985.Small-scale Production of Lime for Building,John Spiropoulos, GATE, Eschborn,Germany. 1985,http://ww2.gtz.de/Basin/publications/books/lime.pdfThe Small-scale Vertical Shaft Lime Kiln: A Practical Guide to Design, Construction andOperation,Kelvin Mason, ITDG Publishing, 1999•••5 [ Pobierz całość w formacie PDF ]
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//-->ALTERNATIVES TOPORTLAND CEMENTAN INTRODUCTIONCement, or some form of cementingmaterial is an essential ingredient inmost forms of building construction.Cement is the vital binding agent inconcretes, mortars and renders, and isused for the production of wallingblocks and roofing tiles.Since its invention in the first half ofthe 19th century, Portland cement hasbecome the most widely availablecementitious material. Its dominanceover alternative cements has been inFigure 1: Participants at a workshop in Uganda visiting apart, due to successful, aggressivevery small traditional lime plant ©Practical Action/Simonmarketing. This is despite its clearL'epine Eklesstechnical disadvantages for certainapplications. In addition Portlandcement is relatively expensive toproduce and is often in short supply in many developing countries. Typically, a rural Africanlabourer may need to work for up to two weeks to earn enough money to buy one bag ofcement. In comparison alternative cements can be produced locally, on a small scale and atmuch lower cost.Alternative cements are not capable of replacing Portland cement totally, but they can be used inthe many construction applications where they have advantages. These are as mortars, rendersand non-structural concretes. Alternative cements are not normally considered suitable forstructural applications such as reinforced concrete beams and columns.The most common of these so-called ‘alternative’ binders is lime, to which other materials,known as pozzolanas, can be added to enhance strength and water resistance. Other binderssuch as gypsum, sulphur, bitumen, mud and animal dung have also been used.Binding systems from historyThe simplest, and possibly the earliest, binding material used was wet mud, and there arerecords of its use in ancient Egypt. Another example of a binder from the distant past is the useof naturally occurring bitumen by the Babylonians and Assyrians in their brick and alabaster(gypsum plaster) constructions.Lime was known to the Greeks and was widely used by the Romans. The Roman architect andengineer Vitruvius published the first specification for the use of lime in building in his celebratedwork De Architectura. The Romans also knew how to make a lime-pozzolana cement by addingmaterials such as volcanic ash or powdered bricks, tiles and pottery to lime.That lime is an appropriate and durable binding material, especially when mixed with pozzolana,is well proven. The Pont du Gard at Nimes in France, a Roman aqueduct built in AD 18 withhydraulic lime-based mortar, is still waterproof; the excellence of the mortar is attributed to theselection of the materials and to the time spent tamping the mix into place during construction.Alternatives to Portland cementPractical ActionThe rebuilding of the Eddystone lighthouse in the English Channel by John Smeaton in 1756 is amore recent development in ‘lime technology’. It was achieved through Smeaton recognizing thehydraulic properties of lime that result from the burning of a clayey limestone. To make thehighly water-resistant mortar needed for bonding the courses of stone, he thoroughly mixed thisalready hydraulic lime with an equal proportion of imported Italian pozzolana (so adding extra‘hydraulicity’ to the mortar).Why continue to usealternative cementsMajor advantages of alternativesto Portland cement are that theyare usually cheaper to produce,needing much lower or evennegligible capital inputs to getstarted, and requiring far lessimported technology andequipment. They can also beproduced on a small scale tosupply a local market resulting ingreatly reduced transportationcosts and a much greaterdegree of local accountability inthe supply of building materials.From an environmental angleFigure 2: Medium-scale Portland cement plant, India ©Practicallime-pozzolana cements can beActionproduced with lower energyinput than either lime by itself orPortland cement – giving a halfto one third consumption in usecompared with Portland cement and about one fifth compared with lime by itself. Low energyconsumption is particularly prevalent with naturally occurring pozzolanas, or those from wastematerials, which might need little additional processing other than drying. The use of clay as abinder, of course, results in negligible energy consumption in production.Lower production costs mean lower prices for the consumer, enabling those who could notafford Portland cement to purchase and use a quality binding material.Pozzolanic cements additionally have numerous other technical advantages to the user:•Improved workability•Improved water retention/reduced bleeding•Improved sulphate resistance•Improved resistance to alkali – aggregate reaction•Lower heat of hydrationIn many large civil engineering programmes involving mass concrete works, Portland cement-pozzolana mixes are specified due to these technical advantages as well as to save money.Social advantages of alternative cements to Portland cement include the potential for affordablequality housing and the opportunity for local employment generation.The technical and economic advantages of alternative cements are not lost on architects andengineers from developed countries. Increasingly, architects, are becoming aware of thebrittleness associated with Portland cement mortars, for example, and are now specifyingblended lime/Portland cement mortars instead. As well as re-discovering the ‘lost arts’ of using2Alternatives to Portland cementPractical Actionalternative binders, recent research has enabled the properties of alternative binders to bethoroughly investigated and catalogued. A body of experience has built up on the appropriateapplication of traditional binders such as clay, lime and pozzolanas, not only in the repair andconservation of historic buildings, monuments and structures but also in adventurous andinnovative new build applications.In some developing countries traditional binders are still slighted, probably because they mightbe associated with poverty or considered to be low status materials. Their performance andtechnical specifications might, completely unjustifiably, also be considered inferior to Portlandcement, they might not be widely produced or available, or the skills to produce and use themmight well have disappeared. A good case can be made for disseminating the developedcountry experience to the South more widely. This would increase interest and awareness ofalternative binders, allow producers and users to gain skills and confidence and determine therightful place of alternative binders in appropriate building for sustainable development.Types of alternative cementsLimeThere are two forms of lime: quicklime and hydrated lime.Quicklime is produced by heating rock or stone containing calcium carbonate (limestone,marble, chalk, shells, etc.) to a temperature of around 1000°C for several hours in a processknown as ‘calcining’ or sometimes simply ‘burning’. It is an unstable and slightly hazardousproduct and therefore is normally ‘hydrated’ or ‘slaked’, by adding water, becoming not onlymore stable but also easier and safer to handle.To produce dry powdered hydrated lime just sufficient water is added for the quicklime lumps tobreak down to a fine powder. This material would have a ‘shelf life’ of only a number of weeks,depending on storage conditions. ‘Old’ hydrated lime would have partially carbonated andbecome a less effective binder.However, if quicklime is hydrated with a large excess of water and well agitated, it forms a milkysuspension known as milk of lime. Allowing the solids to settle, and drawing off the excesswater, forms a paste-like residue, termed lime putty, which is the form of lime which can be usedin building applications to best effect. This will keep almost indefinitely and, in fact, improves withage. In most countries, though, lime is most widely available as a powder, due to its widespreadutilisation in process and treatment industries rather than in construction. Lime putty, whichneeds a stiff bag or container for transportation, is more rarely produced.Limes with high calcium content, often called ‘fat’ or ‘white’ limes are desirable for mostindustries, although the construction industry can use limes containing impurities. For instance,limestones containing a proportion of clay are often seen as an advantage in building as theyproduce hydraulic limes which will set under water and will produce stronger mortars.In the construction industry, lime, in its hydrated or putty form, is mixed with aggregate and waterto produce concrete or mortar in the usual manner. Lime putties generally produce mortars andrenders of excellent quality and consistency.Plain lime-sand mortars are quite weak; any early adhesive strength results from drying out, andlonger term hardening occurs through the action of the air’s carbon dioxide on the lime.Traditionally lime renders and plasters were often mixed with animal hair to improve cohesion.Today the addition of gypsum or Portland cement and/or pozzolanas to increase durability andgive faster setting times is usual.3Alternatives to Portland cementPractical ActionPozzolanasPozzolanas are materials which, although not cementitious in themselves, will combinechemically with lime in the presence of water to form a strong cementing material. They include:•Volcanic ash•Power station fly ash (usually known as pfa)•Burnt clays•Ash from some burnt plant materials•Silicious earths (such as diatomite)Materials not already in a fine powdered form mustbe ground, and some require calcining at around600–750°C to optimize their pozzolanic properties.Pozzolanas can be mixed with lime and/or Portlandcement and can improve quality and reduce costs ofconcretes made from both materials.In some countries (e.g. India and Kenya), pozzolanasare mixed with Portland cement and sold as blendedcement, which in many respects is similar to Portlandcement. In other countries (e.g. Cuba)lime/pozzolana/Portland cement blends are sold asan alternative to Portland cement. Lime-pozzolanacement by itself can make an excellent cementingmaterial for low-rise construction or mass concreteand in some countries (e.g. Indonesia) is stillproduced extensively.Pozzolanas can also be mixed with lime and/orPortland cement at the construction site but caremust be taken to ensure the pozzolana is of aconsistent quality and that the materials arethoroughly mixed.Gypsum plasterGypsum is a not an uncommon mineral, and needsonly a low temperature, of around 150°C, to convert itinto a very useful binding material, known as hemi-hydrate or plaster of Paris.On its own, plaster of Paris sets very rapidly when mixed with water. To give time for it to beapplied, around 5% of lime and 0.8% of a retarding material (such as the keratin glue-likeextracts from boiling fish bones or animal hoof and horn) are added to the plaster.Retarded plaster of Paris can be used on its own or mixed with up to three parts of clean, sharpsand. Hydrated lime can be added to increase its strength and water resistance. Gypsumplasters can be reinforced with various fibrous materials from reeds to chopped glass fibres.Gypsum plaster is not wholly resistant to moist conditions and so is normally used internally,except in the drier Mediterranean and Middle Eastern countries where it has traditionally beenused as an external render.Other alternative bindersSulphur is used as an alternative binder in the Gulf region, where a million tonnes a year comesfrom natural gas plants in the United Arab Emirates. In some other locations, such as St Lucia,sulphur that accumulates around the vents of volcanic fumaroles is utilized.Figure 3: Hydrating of quicklime using awatering can Chenkumbi Limeworks,Malawi © Practical Action/Dave Mather4Alternatives to Portland cementPractical ActionA mixture of 15–25% molten sulphur, heated to around 130°C with 5% of organic additive, and75–85% sand or other mineral aggregates which have previously been heated to 160–170°C,can be cast and de-moulded in only about five minutes. The additive is mainly used to impartdurability. Sulphur concrete has applications which either exploit its quick curing and corrosionresistance or in situations where Portland cement concrete is expensive, unavailable or, forexample in freezing conditions, impracticable.Earth mixed with water to form mud has been, and continues to be, used over much of the worldas a binding material. It develops quite a strong adhesion to fired clay brick and sun dried mudbrick masonry and is satisfactory provided the mud mortar is protected from rainwater. A usefulpractice is to use mud mortar in the internal parts of the wall and do the external pointing in acement or lime-based mortar. The best soils for building purposes contain both sands and claysand therefore it may be necessary to mix two different soils to obtain good results. Mud mortarshave, traditionally, been improved by the addition of organic matter such as straw and cow dung.A number of other alternative binders have been used in a number of applications, whichgenerally relate to soil stabilisation, waterproofing, or the application of a waterproofing or wearresistant coating to vulnerable earth based constructions. Such binders include tars andbitumens (as by-products from petro-chemical industries), sodium silicate (produced from theheat activated reaction between silica and sodium hydroxide), casein (milk whey), oils and fats,molasses, and certain locally specific plant-based materials such as gum arabic, other specificresins and the sap, latexes and juices from specific trees and other plants.References and further reading•••••••••••••••••Alternatives to Portland Cement: An IntroductionPractical Action Technical BriefHydraulic Lime: An IntroductionPractical Action Technical BriefMethods of Testing Lime in The FieldPractical Action Technical BriefCalculating The Energy Efficiency of Your Lime Burning ProcessPractical ActionTechnical BriefHow to Build a Small Vertical Shaft Lime KilnPractical Action Technical BriefLime Kiln Design: Small & Medium Scale Oil Fired Lime KilnsPractical Action TechnicalBriefA Small Lime Kiln for Batch and Continuous FiringPractical Action Technical BriefPozzolanas: Lime-pozzolana CementsPractical Action Technical BriefPozzolanas: IntroductionPractical Action Technical BriefTesting Methods for PozzolanasPractical Action Technical BriefPozzolanas: Portland-pozzolana Blended CementsPractical Action Technical BriefPozzolanas: Calcined Clays and Shales, and Volcanic AshPractical Action TechnicalBriefPozzolanas: Rice Husk Ash (RHA) and Pulverised Fuel Ash (PFA)Practical ActionTechnical BriefClay as a Binder: IntroductionPractical Action Technical BriefGypsum Plaster: Its Manufacture and Use,A. Coburn, E. Dudley and R.Spence, ITDGPublishing, 1989 (now out of print).Appropriate Building Materials,Roland Stulz and Kiran Mukerji, co-published by ITDGPublishing – UK, SKAT Publications – Switzerland, and GATE – Germany. 1993.Supplementary Cementing Materials for Use in Blended Cements,R.J. Detwiler, J.I.Bhatty, S. Bhattacharja, Research and Development Bulletin RD112T, Portland CementAssociation, Skokie, Illinois, USA, 1996Small-scale Lime Burning: A Practical Introduction,M. Wingate and others, ITDGPublishing, 1985.Small-scale Production of Lime for Building,John Spiropoulos, GATE, Eschborn,Germany. 1985,http://ww2.gtz.de/Basin/publications/books/lime.pdfThe Small-scale Vertical Shaft Lime Kiln: A Practical Guide to Design, Construction andOperation,Kelvin Mason, ITDG Publishing, 1999•••5 [ Pobierz całość w formacie PDF ]