Construction Materials, CENG 2092, Chapter Two, 2024 PDF

Construction Materials CENG 2092 Chapter Two Binders  Contents 1 Introduction 2 Lime 3 Gypsum 4 Portland Cement 5 Mortar  Binders Definition Bituminous Binders:Mineral (Asphalt)...

Construction Materials CENG 2092 Chapter Two Binders  Contents 1 Introduction 2 Lime 3 Gypsum 4 Portland Cement 5 Mortar  Binders Definition Bituminous Binders:Mineral (Asphalt) Synthetic  Are substances that are used to bind inorganic and organic Non-hydraulic Hydraulic particles and fibers to form strong, hard and/or flexible Binders components. Binders  The binding action is generally due to chemical reactions which take place when the binder is heated, mixed with water and/or other materials, or just exposed to air. Groups of binders:  Binders…. Non-hydraulic binders:  Non-hydraulic binders only harden in the presence of air.  Which are either not able to set and harden in water.  The most common non-hydraulic binder is lime(non- hydraulic).  Hardening depends on its combination with carbon dioxide from the air (carbonation), by which it again becomes calcium carbonate (limestone).  Gypsum is also a non-hydraulic binder which occurs naturally as a soft crystalline rock.  Binders…. Hydraulic binders:  Hydraulic binders require water to harden and develop strength.  The most common hydraulic binder is Portland Cement.  Hydraulic binders are usually available in the form of a fine powder.  Lime  Lime is one of the oldest known cementing material  Lime is found in many parts of the world in its natural form as a rock of varying degree of hardness.  Lime is mainly composed of calcium oxide (CaO).  Lime in its pure form associates with CO2 to give white CaCo3.  Lime deposits are generally found mixed with impurities such as CO2, Fe2 O3, and MgCO3.  Depending on the impurities, lime deposits acquire different colors.  Is basically non - hydraulic but can be made hydraulic.  Lime…. Production of Lime:  Lime is produced by burning the raw material limestone CaCO3. CaCo3 + Heat CaO + CO2  Chalk and shell can have CaCO3 content exceeding 98%.  Depending on the amount of heat and the method of slaking, the product is hydraulic or non-hydraulic lime. The burning process takes place in either:  Vertical shaft kiln  Rotary kiln  Lime…. Vertical shaft kiln:  The raw materials fed in at the top & the finished product drawn off through an opening at the bottom.  Lime…. Rotary kiln:  Rotary kilns consist of a rotating cylinder inclined at an angle of 3 to 4 degrees to the horizontal.  Limestone is fed into the upper ‘back end’, and fuel plus combustion air is fired into the lower ‘front end’.  The product is then discharged from the kiln into a cooler.  Lime…. Classification Of Lime: Commercial lime is classified into three groups:  Quick lime (Caustic lime)  Hydrated lime (Slaked lime)  Hydraulic lime A. Quick Lime  Is obtained by calcining (burning) the purest available calcium carbonate.  It is white in color and having a specific gravity of about 3.40.  Lime…. B. Hydrated Lime (Slaked Lime):  Quick lime can never be used as such for construction purposes but must be mixed with water. CaO+H2O Ca (OH) 2 + heat  This process is called slaking and the product (calcium hydroxide) is called slaked lime or hydrated lime. Forms of hydrated lime:  Depending upon the amount of water added during the slaking process, three forms of hydrated lime are commonly produced:  Lime…. a) Dry hydrate: a dry, fine powder, formed by adding just enough water (Dry-Slaking) to slake the lime, which is dried by the heat evolved; b) Milk of lime: made by slaking quicklime with a large excess of water (wet-slaking) and agitating well, forming a milky suspension; c) Lime putty: a viscous mass, which is made by slaking the lime with a slight excess of water.  Lime…. C. Hydraulic Lime  Is prepared by burning impure limestone that contains clay, producing compounds similar to those present in Portland cement.  Hardens to some extent by an internal reaction with water.  It is stronger but less plastic than non-hydraulic lime.  Hydraulic lime is manufactured in the same way as quick lime, although a somewhat higher temperature is required in burning.  Lime…. Setting and Hardening of Lime:  Slaked lime hardens or sets by gradually losing the water through evaporation and absorbing carbon dioxide from the air thus changing back from calcium hydroxide, Ca(OH)2 to calcium carbonate, CaCO3 or limestone. CaCO3 Drying Burning Ca(OH)2 CaO Slaking  Lime…. Uses of Lime: Lime as a construction material  As mortar (lime mortar) mixed with sand  Lime is used in cement mortar to make it more workable  Lime mortar with out addition of cement should never be used in foundations or where exposed to moisture.  As plaster (lime plaster)  As a whitewash, when it gives a sparkling white finished at a very low cost  As lime concrete  As a stabilizer in clay soil.  Gypsum Introduction:  Gypsum is a non-hydraulic binder occurring naturally as a soft crystalline rock..  Soft that it can be scratched by a finger nail.  Gypsum occurs naturally as:  Hydrous sulfate of lime (CaSO42H2O) which is generally 76% CaSO4 and 24% H2O. Pure gypsum is known as alabaster and it is a white translucent crystalline mineral.  Gypsum plasters are used in the arts and in building construction.  Gypsum….  When heated, it gives up water and easily turns into powder.  On adding water to the powder it can easily be shaped and molded, and in a short time it hardens again and becomes similar to what it was in its natural state.  When water is added the gypsum forms interlocking crystals.  Building gypsum is an air-setting binder composed mainly of semi hydrate gypsum and obtained by processing gypsum at temperatures 150°C–160°C.  Gypsum…. Advantage of Gypsum as a construction Material:  Incombustibility  superior surface finish  good fire resistance  resistance to insects  low energy consumption during burning  rapid drying Major shortcomings:  Poor strength in wet state and  High creep under load.  Gypsum….  The water of crystallization in the gypsum (CaSO4. 2H2O) is not held firmly by the mineral.  Gypsum plasters are manufactured by heating the raw material gypsum at either moderate or high temperatures the results being plaster of paris or hard-finish plaster respectively. A. Plaster of Paris:  It is produced by incompletely dehydrating pure finely ground gypsum at a temperature some what lower than 185°C. (CaSO4.2H2O)+Moderate Heat (CaSO4.1/2 H2O) +3/2 H2O  At still higher temperatures (About 200°C), gypsum loses all its water of crystallization and turns out into an hydrate gypsum.  Gypsum….  is a white powder having a specific gravity of 2.57.  is also known as low-temperature gypsum derivative or semi-hydrated plasters (hemi hydrate).  is used for small patching jobs on plaster walls.  excellent material for filling cracks, holes in the plastered surfaces and also on the wooden surfaces before painting/polishing.  When mixed with sufficient water to form a plastic paste it sets very rapidly (Setting time: 5-10 minutes).  Owing to the rapidity of set and difficulty in working, its use in structures is limited to ornamental works.  Being unstable in water it should be used for indoor works only.  Gypsum…. B. Hard Finish Plaster  When gypsum is burnt at considerably high temperature than that for calcining of cement plaster, and treated with certain solutions like alum and Glauber’s salt (Na2SO4), the plasters so produced show slow setting but ultimately become very hard.  Hard-finish plaster is also known as anhydrous plaster or high-temperature gypsum derivative. (CaSO4.2H2O)+High Heat CaSO4 +2H2O  Such plasters may be polished to form a smooth surface and make a very satisfactory finish for interior walls.  Gypsum…. Uses of Gypsum: I. Gypsum Wall Plaster  Gypsum wall plasters gain one-half of their one-month strength in a day.  Plaster and sand mortars of 1:1 proportions may be expected to develop 80 per cent of the neat strength at corresponding ages, while those of 1:2 proportion generally possess one-half to two-third of the neat strength.  The gypsum to sand neat plaster in proportion of 1:3 should set in 2 to 32 hours and in 1.5 to 8 hours when mixed with wood fibres.  Gypsum…. II. Gypsum Plaster Boards  It is a gypsum product of recent origin made of thin layers of card board or wood cemented together with wall plaster, used for lining walls and ceiling of buildings.  The boards may be strengthened by incorporating fibres as fibrous gypsum plaster boards.  Sisal or coconut fibers are generally used.  The weight of plaster in the later variety is 10 kg/m2 of board and that of fibre is 250 g/m2 of board.  They are very light weight and have high fire resisting properties.  Gypsum…. III. Non-Load Bearing Gypsum Partition Blocks  These can be solid or hollow, rectangular with straight and square edges and true surfaces.  The compressive strength of these partition blocks should not be less than 50 N/m2 on gross area. IV. Pyro-cell  It is finely ground powder containing an admixture, forms a gas on being mixed with water and expands the mixture to 3 or 4 times its volume.  This inflated paste hardens into a light, cellular, fire resistant mass possessing good acoustical and insulating properties. Cement  Concrete  Dates around 7000 BC.  A lime concrete floor found during the construction of a road at Yiftah El in Galilee, Israel.  Portland cement was first patented in 1824.  Named after the natural limestone quarried on the Isle of Portland in the English Channel.  Primary Components of Raw Materials:  Calcium  Silica  Alumina  Iron Calciu Sulfa Iron Silica Alumina m te Alkali Blast- Calcium Aluminu Anhydr waste furnace silicate m-ore ite Aragoni flue Cement refuse Calci te dust rock Bauxite um Calcite Clay Clay Cement sulf Cement- Iron ore Fly ash rock ate kiln Mill Fuller’s Clay Gypsu dust scale earth Copper m Cement Ore Limestone slag rock washing Loess Fly ash Chalk s Fuller’s Marl Clay Pyrite earth Ore Fuller’s cinders Granodi washings earth Shale orite Quartzite Limesto Rice-hull Limesto ne ash ne Marble Sand Loess Quarry  Cement… Methods used in Portland cement production  There are two basic methods used in Portland cement production: I. Dry process  Dry materials are proportioned, ground to a powder, blended and fed into the kiln. II. Wet process  Involves adding water to the proportioned raw materials and completing the grinding and blending operations in slurry form.  The manufacture of Portland cement occurs through a series of steps.  Portland cement… Dry Process: The four main steps in this process are:  Treatment of raw materials  Burning of the dry mix  Grinding of the clinker  Packaging and storage I. Treatment of raw materials  The raw materials are subjected to such processes as: crushing, drying, grinding, proportioning and blending or mixing before they are fed into the kiln for burning. II. Burning of the dry mix  The well-proportioned finely powdered mixture (raw meal) is charged into long steel cylinder, called rotary kiln.  Portland cement… Three reactions are believed to take place during the burning stage: a) Complete dehydration Water is completely driven off at a very initial stage of burning at temperatures as low as 400oC. b) Dissociation of carbonate Carbonates of calcium are completely dissociated at temperature between 800-900oC as per the following reaction: CaCO3 CaO+CO2  Portland cement… C ) Compound formation  3CaO.SiO2 (Tricalcium silicate), abbreviated as C3S  2CaO. SiO2 (Dicalcium silicate), abbreviated as C2S  3CaO.Al2O3 (Tricalcium Aluminate), abbreviated as C3A  4CaO.Al2O3.Fe2O3 (Tetracalcium Aluminoferrite) abbreviated as C4AF III. Grinding of the Clinker The completely burnt or calcined raw materials of cement are converted to lump-shaped product called clinker, which is drawn out from the lower end of the rotary kiln.  Portland cement… IV. Packing and storage of cement  Cement is most commonly stored after its manufacture in specially designed concrete storage tanks called silos where from it is drawn off mechanically for the market. For convenience, the cement comes to the customer in bags.  The difficulty in the control of dry mixing and blending has made this method of production of Portland cement much less popular than the wet process.  Portland cement… Wet process:  Wet process is considered a better and convenient process for the manufacture of cement, specifically where limestone of soft variety is available in abundance. Steps in wet process are:  Preparation of slurry  Burning or calcinations and  Grinding of Clinker  As the lump-shaped clinker comes out from the kiln, it is extremely hot. It is, therefore, passed through cooling rotary cylinders.  There after it is mixed with 3-5 percent of gypsum and ground to a very fine powder as in dry process. The fine cement obtained is stored and packed in paper bags.  Manufacturing of Portland Cement 1. Stone is first reduced to 125 mm size, then to 20 mm , and stored. 2.Raw materials are ground to powder and blended. or 2. Raw materials are ground, mixed with water to form slurry, and blended. 3. Burning changes raw mix chemically into cement clinker. 4. Clinker with gypsum is ground into Portland cement and shipped. Clinker Gypsu m Process of Clinker Production Process of Clinker Production Process of Clinker Production Chemical Compounds of Portland Cement  Portland Cement… Compounds of cement clinker:  3CaO.SiO2 :C3S  2CaO. SiO2 :C2S  3CaO.Al2O3 :C3A  4CaO.Al2O3.Fe2O3 :C4AF The relative amounts of these four chemicals in the final product depend on the desired properties such as:  Rate of hydration( hardening)  Strength - early and ultimate  Rate and amount of heat given off  Resistance to chemical attack  Portland cement… 1.C3S (Tri-calcium Silicate)  The most desirable constituent  It hardens rapidly and accounts for the high early strength (the first 7 days) of the cement.  The proportion of C3S ranges from 25-60% 2.C2S (Di-calcium Silicate)  Hardens slowly  Contributes to strength increase at ages beyond one week  The proportion of C2S ranges from 13-50%.  Portland cement… 3.C3A (Tri-calcium Aluminate)  A large amount of heat, (heat of hydration), during the first few days of hardening  It also contributes to early strength development  If gypsum is added it acts as a retarder, and the heat of evolution is less and the setting occurs more slowly.  This is due to the fact that gypsum when present, results in the formation of calcium sulfoaluminate (3CaO. Al2O3. 3CaSO4) rather than hydrated tricalcium aluminate.  The proportion of C3A ranges from 5-15%  Prone to chemical (sulfate attack)  Portland cement… 4. C4AF (Tetra-calcium Aluminoferrite)  Reduces the clinkering temperature, there by assisting in the manufacture of Portland cement  Contributes very little to strength  The proportion of C4AF ranges from 8-15%  Good in resisting chemical attack  Gives the cement gray color.  Portland Cement Compound Hydration Reactions (Oxide Notation) 2 + 11 H2O = + 3 (CaO H2O) (3CaO SiO2 Water 3CaO 2SiO2 Calcium ) 8H2O hydroxide Tricalcium Calcium silicate silicate hydrate (C-S-H) 2 + 9 H2 O = + CaO H2O (2CaO SiO2 Water 3CaO 2SiO2 Calcium ) 8H2O hydroxide Dicalcium Calcium silicate silicate hydrate (C-S-H) 3CaO Al2O3 +3 + 26 H2O = Tricalcium (CaO SO3 2H2O) Water 6CaO Al2O3 3SO3 aluminate Gypsum 32H2O Ettringite 2 + + 4 H2 O =3  Portland cement… Summary of characteristics of the four compounds of clinker : Reactivity of Cement Compounds SEMs of Hardened Cement Paste Types of Portland Cement ASTM C 150 (AASHTO M 85) I Normal IA Normal, air-entraining II Moderate sulfate resistance IIA Moderate sulfate resistance, air- entraining III High early strength IIIA High early strength, air-entraining IV Low heat of hydration V High sulfate resistance  Portland cement… Type I or Normal Portland cement  Is a general-purpose cement.  Is used when the special properties specified for any other type are not required.  Is used where there would be no severe climate changes.  Is used where there is no severe exposure to sulphate attack from water or soil.  Its uses include reinforced-concrete buildings, bridges, reservoirs, floors, and retaining walls  Company Logo Portland cement… Type II or Moderate Portland cement  Used when moderate sulphate resistance or moderate heat of hydration is desired.  It is used in structures of considerable mass, such as abutments and piers and retaining walls.  Its use also minimizes temperature rise when concrete is placed in warm weather.  Portland cement… Type III or High-Early-Strength Portland cement  Is used when high early strength is desired, usually less than one week.  It is usually used when a structure must be put into service as quickly as possible.  This cement is made by changing the proportions of raw materials, by fine grinding, and by better burning.  Contains less di-calcium silicate and the tri-calcium silicate is greater.  Portland cement… Type IV or Low - Heat of Hydration Portland Cement  Is used when a low heat of hydration is required  Develops strength at a slower rate than does than Type I  It is intended for mass structures such as large gravity dams where the temperature rise on a continuous pour is great.  It has higher C2S and lower C3S and C3A  Portland cement… Type V or Sulfate - Resisting Portland cement  Is used when high sulfate resistance is desired.  It is used when concrete is to be exposed to severe sulfate action by soil or water  Contains less C3A  Portland cement… Types IA, IIA, IIIA  Are used in concrete for improved resistance to freezing and thawing action.  Disintegration due to freezing and thawing is caused by the expansion of the water, as it freezes.  Chemical composition, % Type of portland Al2 Fe2 Na2Oe cement SiO2 O3 O3 CaO MgO SO3 q 20. 5. 2. 0.6 I (mean) 2.6 63.9 3.0 5 4 1 1 II 21. 4. 2. 0.5 3.5 63.8 2.7 (mean) 2 6 1 1 III 20. 4. 2. 2.8 63.4 3.5 0.56 (mean) 6 9 2 IV 22. 4. 5.0 62.5 1.9 2.2 0.36 (mean) 2 6 21. 4. 2. V (mean) 3.9 63.8 2.3 0.48 9 2 2 White 22. 4. 0.3 66.7 0.9 2.7 0.18 (mean) 7 1  Potential compound composition,% Blain Type of e portland finen cement C3 S C 2S C3 A C4AF ess m2/kg I (mean) 54 18 10 8 369 II (mean) 55 19 6 11 377 III 55 17 9 8 548 (mean) IV (mean) 42 32 4 15 340 V (mean) 54 22 4 13 373 White  Other Types of Cement Portland Pozzolana Cement (PPC):  The term pozzolana is used to describe naturally occurring and artificial siliceous materials, which in themselves possess little or no cementations value, but will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementations properties.  Portland pozzolana cement (PPC) is manufactured by blending 20-30% by weight of pozzolanic material with ordinary Portland cement (OPC); either by simple mixing or by inter -grinding with cement clinker.  Other Types of Cement Acid-resistant cement: Acid-resistant cement is composed of the following:  Acid-resistance aggregates such as quartz, quartzites, etc.  Additive such as sodium fluosilicate Na2SiF6  Aqueous solution of sodium silicate or soluble glass.  The addition of additive sodium fluosilicate accelerates the hardening process of soluble glass and it also increases the resistance of cement to acid and water.  Other Types of Cement Blast furnace cement:  For this cement type, the slag as obtained from blast furnace is used. The slag is a waste product in the manufacturing process of pig-iron and it contains the basic elements of cement, namely alumina, lime and silica. The clinkers of cement are ground with about 60 to 65 percent of slag.  The properties of this cement are more or less the same as those of ordinary cement. Its strength in early days is less and hence it requires longer curing period. It proves to be economical as slag, which is a waste product, is used in its manufacture. This cement is durable, but not suitable for use in dry arid zones.  Other Types of Cement Colored cement:  The cement of desired color may be obtained by intimately mixing mineral pigments with ordinary cement. The amount of coloring material may vary from 5 to 10 percent. If this percentage exceeds 10 percent, the strength of cement is affected.  The chromium oxide gives green color. The cobalt imparts blue color. The iron oxide in different proportions gives brown, red or yellow color. The manganese dioxide is used to produce black or brown colored cement.  These types of colored cement are widely used for finishing of floors, external surfaces, artificial marble, window sill slabs, textured panel faces, stair treads, etc.  Other Types of Cement Expanding cement:  This type of cement is produced by adding an expanding medium like sulfo-aluminate and a stabilizing agent to the ordinary cement.  Hence this cement expands whereas other cements shrink.  The expanding cement is used for construction of water retaining structures and also for repairing the damaged concrete surfaces.  Other Types of Cement Quick setting cement:  This cement is produced by adding a small percentage of aluminum sulphate and by finely grinding the cement. The percentage of gypsum or retarder for setting action is also greatly reduced.  The addition of aluminum sulphate and fineness of grinding are responsible for accelerating the setting action of cement. The setting action of cement starts within five minutes after addition of water and it becomes hard like stone in less than 30 minutes or so.  The extreme care is to be taken when this cement is used as mixing and placing of concrete are to be completed in a very short period. This type of cement is used to lay concrete under static water or running water.  Properties Of Portland Cement Physical:  Setting time  Soundness  Fineness  Heat of hydration  Specific gravity Chemical:  Lime Saturation Factor (LSF)  Alumina Ratio  Magnesia  Sulfur trioxide  Loss on ignition  Insoluble residue  Company Logo Physical Properties I. Fineness  The fineness of the cement has an important effect on the rate of hydration  The finer the cement the quicker the rate of hardening and the greater is the heat evolution at early ages.  A finely ground cement is more liable to suffer from shrinkage cracking than a coarser cement (for cement of the same composition)  The fineness of grinding does not affect the total heat evolved but only the rate at which that heat is evolved.  Company Logo Properties……..  Extremely fine size does not improve the ultimate strength of the cement  The fineness of cement can be measured in a number of ways:  The sieve test  Specific surface test by :  Wagner Turbid meter method  Blaine air permeability method  The Ethiopian Standard specifies the fineness of grinding should not be less than 2250 cm2/gm for OPC cement.  Company Logo Properties…….. II. Setting time  Setting is the stiffening of the cement paste.  Broadly speaking, setting refers to a change from a plastic to a rigid stage.  During setting, the paste acquires some strength  Hardening, refers to the gain of strength of a set cement paste  Setting is not an abrupt process, which may complete immediately after its start; it is rather a progressive phenomenon, which has : beginning, full development and an end.  Properties…….. It is on this latter basis, setting is distinguished into:  Initial setting time  Final setting time Initial setting time: is the duration of cement paste of standard consistency related to 25 mm penetration of the Vicat needle into the paste in 30 seconds after it is released. Final setting time: is that related to zero penetration of the Vicat needle into the paste.  Company Logo Properties……..  Ethiopian standard recommends that the initial setting time for cement not be less than 45 minutes and the final setting time not to exceed 10 hours. Vicat apparatus  Company Logo Properties…….. Time required for setting is influenced by:  Temperature: the setting time of cement decreases with a rise in temperature. And at low temperatures setting is retarded.  Water content: less water result in incomplete hydration, extra quantity will bleed out after cement is set.  Fineness of the Cement: the greater the cement fineness the greater the rate of hydration and hence the shorter the setting time.  Chemical Composition: Setting is caused by a selective hydration of cement compounds: the two first to react are C3A and C3S.  Properties…….. False set:  different from initial and final set.  Sometimes occurs within a few minutes of mixing with water.  No heat is evolved in a false set and the concrete can be remixed without adding water. Flash set:  caused by the rapid reaction between C3A with water and liberate heat.  Prevented by the addition of gypsum.  Company Logo Properties……. III. Soundness  It is essential that cement paste, once it has set, does not undergo a large change in volume.  Expansion may take place due to the delayed or slow hydration, or other reaction, of some compounds present in the hardened cement, namely free lime, magnesia, and calcium sulfate.  Cements that exhibit this expansion are described as unsound.  Company Logo Properties…….. Cement can be unsound due to: I. Insufficient burning II. The presence of excess CaO III. The presence of excess MgO IV. Addition of excess gypsum In order to determine the soundness of cement the Le Chatelie’r test is used.  Properties…….. Iv. Heat of Hydration  Heat of hydration is the quantity of heat in joules/gram generated when cement and water react.  For practical purpose, it is not necessarily the total heat of hydration that matters but the rate of heat evolution. The amount of heat generated depends on: a. The chemical composition  In the early stages of hydration the different compounds hydrate at different rates, the rate of heat evolution, as well as the total heat, depends on the compound composition of the cement  By reducing the proportions of the compounds that hydrate most rapidly (C3A& C3S) the high rate of heat evolution in the early life of concrete can  Properties…….. Iv. Heat of Hydration…. b. The fineness of the cement  The early rate of hydration of each compound in cement is proportional to the surface area of the cement. However, at later stages, the effect of the surface area is negligible and the total amount of heat evolved is not affected by the fineness of cement.  Heats of Hydration of the Pure Compounds of Portland cement  Company Logo Properties…….. V. Compressive strength  The mechanical strength of hardened cement is the property of the material that is perhaps most obviously required for structural use.  Strength tests are not made on a neat cement paste because of difficulties of molding and testing with a consequent large variability of test results.  Strength of cement can be determined by two methods i.e. mortar test and concrete test.  Chemical Properties  Chemical tests are conducted by the manufacturer or in research laboratories in order to check on the quality of Portland cement. But of little importance to the ordinary consumer. The results of chemical tests are reported in terms of oxides. It is also important to know the amounts of:  The four major oxides-(CaO), (SiO2), (Al203) and (Fe2O3)  Free lime , (SO3), and magnesium oxide  Sodium and potassium (Na2O ,K2O) oxides play also importance incase the cement is used in concrete with alkali reactive aggregates.  Quality requirements of Portland cement Lime Saturation Factor (LSF) 0.66 < L.S.F 8 %. An upper limit on S03 is specified in order to avoid unsoundness resulting from the delayed hydration of the sulfate phase.  Mortar Definition: A mortar is a mixture of sand or similar inert particles with a binding agent (generally cement and/or lime), to which water is added in predetermined proportions. Mortar = Binder + Sand + H2O  Company Logo Mortar Uses of Mortar I. Jointing medium in masonry construction The mortar used transfers from block to block the pressure that is produced by the weight of the masonry and the supper imposed load if any. In such cases the compressive stress on the mortar is as large as on the blocks themselves. The jointing mortar must have satisfactory strength if a durable masonry is to be built. Mortar  Mortar II. Wall plaster Plastering is the process of covering various surfaces of structure with a plastic material such as cement mortar, lime mortar or composite mortar, etc. to obtain an even, smooth, regular, clean and durable surface. Plastering conceals inferior quality materials and defective workmanship and also provides a protective coating against atmospheric effects. It further provides a base for receiving other decorative finishes such as painting and whitewashing.  Company Logo Mortar Types of Mortar There is a large number of mortar types used in the construction industry. 1. Mud mortar 2. Lime mortar 3. Cement mortar 4. Compo mortar  Mortar 1. Mud mortar  The most elementary mortar.  Is made from soil mixed with water.  It may be suitable for laying soil blocks  If exposed to the weather will quickly be eroded by rain. 2. Lime mortar  Lime mortar= lime +sand + water  Use of lime results in a relatively workable mixture  slow hardening makes it less attractive than cement mortars  Company Logo Mortar 3. Cement mortar  Cement mortar= Portland cement + sand(inert particles)+water.  While the use of lime results in a relatively workable mixture, rapid development of strength as well as stronger mortar is most conveniently obtained with Portland cement.  Mortar 4. Compo mortar  Compo mortar= cement + lime +sand + water.  In order to combine the advantages of both lime and cement, mortars are prepared with appropriate proportions of Portland cement, lime and sand, which is known as compo-mortar.  Mortar Properties of mortar Some of the properties of mortar are: 1. Workability 2. Strength 3. Water tightness  Properties…….. 1. Workability  Is an easiness of the mortal mix to transport ; place and finish.  For the same proportions, lime-sand mortar invariably gives better workability than Portland cement-sand mortar  Mortar produced from sand of circular grains results in better workability than those produced from sand of angular grains.  At times admixtures are used in order to improve the workability of cement-sand mortars, especially when they are lean (i.e. containing less amount of cement) mixes.  Properties…….. 2. Strength  Strength of mortar is affected by a number of factors, which include the quality of the ingredients, their proportion, the curing method and age.  For the same proportions, lime-sand mix gives weaker mortar than cement-sand mix.  The compressive, tensile, shear and bending strengths of cement mortar increases with an increase in the cement content.  Properties…….. 3. Water Tightness  When Mortar is used in parts of buildings exposed to dampness or moisture and might be required to be watertight.  To make such type of mortar, Portland cement should be used because of its hydraulic property.  With the cement content, materials, and workability all constant, strength and degree of water-tightness increase with the density of the mix.  Mortar Factors affecting the properties of mortar include:  The amount of mixing water  Properties of the binder used  Cement content; fineness and composition  Characteristics and grading of the sand  Mortar Materials for mortar A. Binder: Cement: Cement used for preparing masonry mortars maybe: OPC,PPC,RHC…etc Lime: If lime mortar is used, lime may be of hydraulic or semi hydraulic category. Prepared lime mortar shall be kept damp and shall never be allowed to go dry. Partly set or dried mortar shall never be retempered for use.  Mortar B.Sand:  should be well graded, that is the particles should not all be fine or all coarse. If the sand is well graded:  The finer particles help to occupy the space(voids) b/n the larger particles.  A dense mortar which permits the most economical use of cement and /or lime can be obtained.  should be clean, free from dust, loam, clay and vegetable matter. These foreign materials prevent the adhesion of the particles ,thereby reduce the strength.  Mortar Silt test (Jar test)  Silt test should be made at the site to determine the silt content of the sand.  fill the jar to a depth of 5cm with representative sample of sand.  Add water until the jar is about three fourth full.  Shake vigorously  Allow the jar to stand for an hour or more during which the silt will be deposited.  If the layer of silt is more than 3mm or 6%,the sand is not suitable for mortar work.  Mortar C. Water  Clean water is important for the same reasons, as is clean sand; any impurities present will affect bond strength between the paste and sand.  Mortar Proportioning of the component materials : In proportioning the component materials the following points must also be considered:  The mixture must be workable so that it can be placed and finished without undue labour.  Since Portland cement is the most costly ingredient in the mixture the proportion used should be as small as its consistent with the attainment of desired properties. (Economical)  It should be strong enough.  Batching and mixing  Materials used for making mortar should be accurately measured.  Cement is usually measured by weight in cement bags whereas sand is measured by volume.  1 bag of cement=50 Kg =35 liters (loose volume)  Sand is measured by using a measuring box to hold quantities in multiples of 35lt.  The convenient size of the box can be 40cm X 35cmX 25cm internally 40cm X 50cmX 18cm internally(Ethiopian) Mortar…. Mortar