CONSTRUCTION MATERIALS

CHAPTER THREE

CONSTRUCTION MATERIALSQUESTION ONE (I)

FIVE PROPERTIES OF ORDINARY PORTLAND CEMENT:(A) STRENGTH: This is the hardening specimen of cement after a specific curing. The strength is tested after removing trapped air in the mortar.(B) SETTING TIME: This the time the cement paste of standard consistency reaches two defined condition stiffness which determined periodically by checking the penetration of needle into it.(C) SOUNDNESS: Unsoundness in a material denotes the presence of impurities which are liable to react chemically with moisture resulting in expansion which can cause cracks, spelling, or disintegration.

(D) CHEMICAL COMPOSITION: This is to ensure that the cement conforms to a reasonable standard of chemical composition and is free of excessive harmful impurities. Chemicals to either increase or slow the setting time.

(E) FINENESS: The fineness of cement is important because of its efforts on the rate of hydration and the need for smooth texture. This is calculated by sieving for 15 minutes on Sieve and the residue should not be more than 10%.The general rules, the finer the cement the more rapid the strength development of the cement.

(II)

EXPLANATION OF THE CLASS OF PLASTERS:(A) CLASS A: This is a true hemihydrates which is obtained by heating crushed gypsum to a temperature not exceeding 1500.It is too quick in setting and can used for general plastering works and making precast moulding.

(B) CLASS B: This is a retarded hemi hydrated obtained by adding a retarder which consist of a kerating decorative or lime with an activator during manufacturing. It can be used for under coating, finishing coating and dual purpose.

(C) CLASS C: This is plaster obtained by gypsum in a kiln at 400oc to reduce or dry off all water. If it is slow in setting, a small amount of an accelerator (aluminium or potassium sulphate) is added before heating to speed up the setting action.It is used for under coat, finishing coating and dual purpose.

(D) CLASS D: This is suitably accelerated and it has a uniform set which continuous to the point of complete set. It gives a hard surface which is not porous so it can be used for undercoat, finishing coat or as dual purpose.

(III)USES OF THE TYPES OF CEMENT AS CONSTRUCTION MATERIA:(A) HYDROPHOBIC CEMENT: This is used in construction of damp and humid condition with deteriorating.(B) SULPHATE RESISTANCE CEMENT: It is use as resistance to chemical attack by sulphate and can cause softening and considerable expansion of cement based material.

(C)HIGH ALUMINA CEMENT: This type of cement has a high resistance to most chemicals except alkali so it can be used as chemical resistance and where greater strength is required because it rapidly gains strength.

(D)WATER REPELLANT CEMENT: It is used in water repellant renderings and in base-coat where the background is of uneven.

(E)RAPID HARDING CEMENT: This used in concrete works where greater strength are required and structures which are subjected to loads.

(IV)SIX PROPETIES OF MORTAR:(i) Adequate cohesion in plastic state to ease handling and reduce droppings.(ii) Sufficient strength when hardening for the work is concerned.(iii) Sufficient durability with regards to the degree of exposure likely and any aggressive chemical agency.

(iv) Good water retentivity.(Mixing water do not bleed out) (v) Adequate adhesion to the bedded both in the plastic and hardening state.

(vi) Good workability in the plastic state but with sufficient early to prevent joint squeezing.

(V)

EIGHT REQUIREMENT OF MORTAR.

(i) Mortar must be free from leaves and sticks which is likely to prevent particles from having adequate bonding.(ii) Mortar should have sufficient strength for the purpose for which they are required.

(iii) It must be safe from efflorescence and should have good bond with bricks or blocks.

(iv) Must be free from impurities.

(v) It must be workable so that a bricklayer can handle it easily.

(vi) Must be free from silt or clay.

(vii) It must be resistance to chemical attack.(viii) Must be evenly graded from fine to course.

QUESTION TWO (I)FOUR ADVANTAGES OF ADDITIVES IN MORTAR.

It makes the mortar more workable (plasticizer).

It reduces cracks.

It also reduces shrinkage.

It increases the effectiveness of the mortar.

(II)TWO FUNCTIONS OF THE COMPONENT OF MORTAR.(A) CEMENT:

(i) It provides a very hard and strong binding medium for the aggregates.(ii) It adds sufficient strength to the mortar.

(B) SAND:

(i) It adds volume to the mortar or concrete.

(ii) It reduces shrinkage and cracks in mortar and improves the durability of mortar.

(C) WATER:

(i) It makes mixing mortar very easier.

(ii) It makes the mix workable and easier to handle.(III)

SIX REASONS FOR EXTENDERS WITH BINDERS.

(i) To import some special properties such as fire resistence, thermal insulation and caustic characteristics.

(ii) To reduce material cost.

(iii) To obtain better resistance to wear by abrasion weathering using band abrasion resistance.

(iv) To alter appearance such as colour textures.

(v) To obtain increased or decreased density.

(vi) To offset either drying shrinkage or setting expansion. (IV) FIVE CONSTRUCTIONAL USES OF CONCRETE.

For the construction of dams. For constructing beams and columns.

For the construction of bridges.

For the construction of foundations.

For constructing lintels.

(V)TWO METHODS OF BATCHING.(A)BATCHING BY VOLUME: With this method, a gauge box is used to measure the aggregates and pour into the hoper or drum to offset the mixing process. One disadvantage of this method is that, the water cement ratio can not be properly controlled. It avoids excess water.(B)BATCHING BY WEIGHT: With this method, a dial gauge is attached to the revolving drum to determine the batching and to absolutely control the amount of water needed for the mix.

QUESTION THREE (I)DIFFERENCES BETWEEN LIGHT WIEGHT AND DENSE CONCRETE.

(A)Dense concrete are made highly dense aggregate which consist of particles of natural aggregate of crushing strength. That is crushed stone, crushed gravels and blast which when mixed result in a dense concrete of low permeability.

(B)Light weight concrete is made of low density aggregate formed by reaction or heat natural deposits. This is light weight because the aggregate used are highly porous.

(II)DEFINITION OF TERMS IN REACTION TO CONCRETE.

(A)BULKING: This is when fine aggregate come in contact with water. It increase in volume and provision should be made to cater for the bulking during batching.

(B)READY MIXED CONCRETE: This type of concrete is carried in mobile trucks. The procedure is that, the truck will be loaded with concrete materials and it begins to mix when approaching the site.

(C)SITE MIXED CONCRETE: This is the type of concrete mixed at site by a mixing or team. (III)

SIX FACTORS AFFECTING WORKABILITY OF CONCRETE.(1) Increase in cement aggregate ratio.

(2) Increase in water cement ratio.

(3) Uneven mixing of concrete.

(4) Use of aggregate with round particles or smooth surface.

(5)Use of large size aggregate is being combined with correct graded course of aggregate.

(6) Increase in the richness of concrete while constant water in maintained.

(IV)

CLASSIFICATION OF BRICKSA. ENGINEERING BRICKS: They are highly compression in strength, how water absorption, have high density and are used mainly for the construction of retaining walls, bridges, bricks wall and chimneys shaft. Examples are, Stafford, shine blue and Acering red bricks.B. PURPOSE MADE BRICK (SPECIAL BRICK): These are bricks made to serve a special purpose. For example, fire bricks, soft rubber, glazed bricks and paving bricks. The term is also applied to bricks made to non-standard size or shape and to bricks made from different materials.C. COMMON BRICKS: These are those which can not be classified as engineering or facing bricks. They are for internal and external use where neither high strength nor low absorption is essential appearance is not importance.(V)

FOUR PROPERTIES OF ALLOY. It is ductile. It is corrosion resistance. It is malleable.

It increases in length when cooked with.

QUESTION FOUR (I).DEFINITION OF TERMS.

(A)WORKING THE METAL: This is bringing the extracted metal to the required finish, shape and the product being cast or wrought.

(B)SOILDIFICATION: This is when, melted ion turn into solid mass.

(C)FORGING: This is the heating of metal to make it soft and then hammered.(D)PRESSING: This is processing from sheets.

(E)EXTRUDING: This is forcing hot metal of mass through an orifice which has the required section.(F)DRAWING: This is defined as shaping metal into wire or tubes.

(II).

FOUR REASONS FOR TESTING METALS(a) To standardized the metal

(b) To maintain equality control in production.

(c) To check for deterioration in used part

(d) To check metals compliance with a particular specification to establish its suitability for a given purpose

(III).

FOUR TESTS THAT CAN BE CONDUCT ON METALS(A)TENSILE TEST: This is normally applied to either a cylindrical test piece or flat bar strip out from the metal. The specimen is stretched by it progressively in a testing machine while fracture occurs.

(B)IMPACTING TEST: In this test, a notched specimen is truck by a falling pendulum and energy in breaking the specimen is indicating by height to which the pendulum rise at the other side of its wing.

(C)HARDNESS TEST: The methods commonly used are the Burial Rock and Vickers method which measures the resistance offered by the metal to the penetration of hardening steel ball or diamond into test surface under stander diced washing condition. The result is expressed as a number, obtained by dividing the load applied.

(D)COLD BEND TEST: This is a simple test whish gives an-indication of metal ductility from wrong works. The test mainly used metal used metal bars or ships from consist of doubling the piece over the land applied.(IV).

DIFFERENCE BETWEEN THERMOOLASTIC AND THERMOSETTING PLASTICS Thermoplastic plastics can be reoffering, remolded and reshape after heating, its construction use could be for flour files and could serve as damp proof coarse while thermosetting plastic are those which once heated and shape, can be reheated.

(V).

SIX PROPERTIES OF PLASTIC ARE:(A)Not- fragile.

(B)Light weight specimen.

(C)They are non-corrosive materials.

(D)They are easily melted.(E)It is self finished.(F)Resistance to moisture.(V).

FIVE EXAMPLES OF THERMOPLASTIC AND THERMOSETTING PLASTIC:

1.) THERMOPLASTIC PLASTICS.(A) Polythene plastic.

(B) Polyvinyl chloride.(C) Cellulose plastic.(D) Polythene.(E) Casein plastic.

2.) THERMOSETTING PLASTICS

(A) Polyester resins.

(B) Alkyd resins.

(C) Melamine formal .

(D) Epoxy resins.(E) Amino resins plastic.QUESTION FOUR (I).DIFFERENCE BETWEEN HARDWOOD AND SOFTWOOD.

HARDWOOD: It has broad leaves which in most cases shed their leaves at the end of growing season. They also hear fruits in which the seed are to be found, example are and . They are mostly used for joinery works. SOFTWOOD: It is usually evergreen with needle like leaves and are cone bearing. Examples are wawa, pitch pine red wood, space and dangles . They are used for construction of works and carcassing.

(B)TWO METHODS OF SEASONING(A)Air or Natural seasoning.(B)Kiln or artificial seasoning.

AIR OR NATURAL SEASONING: Is the method used where the logs are felled immediately and shacked under cover to allow free circulation of air around them to remove mush of the moistures content stickers are used to separate the boards.KILN OR ARTIFICIAL SEASONING: A kiln which is a dry room with hearting pipes arranged in the floor and ceiling funs to circulate the hot air and just to allow the introduction of steam. The timber is loaded in the kiln and allow for sometime before removed. (III)METHODS OF CALCULATING MOISTURE CONTENT I N TIMBER.MOISTURE CONTENT = ORIGINAL WEIGHT - DRY WEIGHT X 100

DRY WEIGHT

This is the actual amount of moisture expressed as the percentage of the dry weight of the wood. The original moisture content is noted before seasoning and after seasoning. The weight of the timber is noted .The moisture content is determined by the dry weight from the original weight per weight per the dry weight.

(IV)THREE METHODS OF CONVERSION OF TIMBER.(1) QUARTER SAWING: This is the most expensive method of conversion although is produces the best quality timber which is ideal for joinery purpose.

(2) THROUGH AND THROUGH SAWING: This method is also known as stash or stab sawing. It is the simplest and cheapest way to convert timber with very little wastage. The majority of boards produced in this way are prone to large amount of shrinkage and distortion.(3) TANGENTIAL SAWING: This method is used when converting timber for floor joint and beams since it produce strongest timber. It is used for decorative purpose on timber which is distinctive annual rings.(V)THREE POSSIBLE CAUSES OF TIMBER DECAY.

(1) Fungi attack.

(2) Insect attack.

(3) Frost/persistent damp prolong heating. (VI)PREVENTION OF TIMBER DECAY.(1) FUNGI ATTACK: This is prevented by dipping or submerging the timber in preservatives and the longer the period of immersion the better the penetration.

(2) INSECT ATTACK: This is prevented by brushing and spraying the surface of timber with an approved preservation to scare the insect attacking the wood.

FROST/PERSISTENT DUMP OR PROLONG HEATING: It is prevented by replacing timber which has been treated by preservative with surrounding brickwork which may still contain live spore.QUESTION SIX (I)LIFE CYCLE OF THE FURNITURE BEETLEThe furniture beetle (Anobiuma Puntatum)is the very common beetle about 1/8 long which files into timber in the late summer and lays small white eggs in minute, cracks bore into the wood. These develop to about long and continue to bore through the wood for one or two years. They finish near the surface of the wood, pupae and beetle develops to reparts the life cycle.(II)FOUR TYPES OF FURNITURE BEETLE.

(1) Death watch beetle.

(2) House long born beetle.

(3) Powder past beetle.

(4) Common furniture beetle. (III)THREE PRESERVATION OF TIMBER.

(A)WATER SOLUBLE PRESERVATION: Most common of these being are only suitable for interior use.

(B)WOLMAN SALT PRESERVATION: This preservation has the advantage of being practically colorless and has no bad effect upon paint and other finishes unless water gets into the timber behind the paint film.(C)CREOSOTE PRESERVATION: This is a cheap and effective method of preservation which may be brush applied or applied by pressure impregnation in tanks.

(IV)SEVEN TESTS THAT COULD BE CONDUCTED ON TIMBER.

(1) Hardness test.

(2) Static bending test.

(3) Impact bending test.

(4) Sheet parallel to the grain test.

(5) Cleavage test.

(6) Tension parallel to the grain test.

(7) Compression parallel to the grain test.

(V)

THREE CONSTRUCTIONAL USES OF THE FOLLOWING MATERIALS.

(A)POLYVING/ACETATE (PVA)

(1) Can be emulsified in water far use as paint base.

(2) It can be also added to plastering and floor topping to improving their bonding properties.

(3) It can be mixed with concrete to give it resilient properties.

(B) UREA FORMAL DEHYDE (UF).

(1) Used in the manufacturing of plywood.(2) They are immune to micro-organism attack.

(3) Suitable for used under most condition.(C) POLYVING PLASTICS (PVC)

(1) For walls and floor covering in its title and rail form.

(2) Used for roofing sheets rain water goods plumbing .

(3) For water proof member (D.P.C).

(D) EPOXY RESIN.(1) Used as an adhesive.

(2) Used as a binder in rendering and abrasion.

(3) Resistance floor surfacing.

(E)POLY UREA THANES.(1) Used to provide a hard durable finish in plants.

(2) Used as a flexible instincts.

(3) Can be formed to give either a resilient or a rigid light weight material.

QUESTION SEVEN (I)SIX PROPERTIES OF GLASS.

(1) A good conductor of heat.

(2) It has self finish product.

(3) Very clear and free from dirt.

(4) It breaks when heated and exceeds its limit of thermal expansion.

(5) Very transparent and for some opaque.

(6) Very fragile, breakable when it falls.(II)PAINT SYSTERM.

Paint system: This consists of a number of coats applied is sequence to a given surface ie.primary coat and it is the first coat of paint applied on any surface. Under coat is applied to a surface which has been primed and finishing coat provide the final colour glass or texture required as well as protection from the weather.

(III)

THREE REASONS FOR PAINTING SURFACE.

(1) To protect surface from sun, rain chemical etc.

(2) To provide hygienic surfaces.(3) To beautify the surface.

(IV)

PREPARATION ON WOOD SURFACE BEFORE PAINTING.

(1) Ensure that the moisture content of within the wood is low 1526%.(2) Punch nails below surface of wood.

(3) Dry-abrade to clean smooth surface.

(4) Prevent resin staining coating knot and resinous parts with shellac knotting.

(5) Apply preservatives when specified.

(6) Apply the primary coat on the wood (wood primer).

(V)

PREPATION OF CORRODIBLE SURFACE BEFORE PAINTING.

(1) A stream of abrasive particles is directed against the meal at height of velocity to dislodged all and mill sale, leaving a clean white metallic surface.

(2) Dry brush to remove dust and stains.

(3) Prime immediately after preparation, the metal should be primed with a special rust inhibitive primer. Because of efforts of surface tension, and bolts heads should receive two coats.

QUESTION EIGHT (I)

THREE METHODS OF APPLYING PAINT UNTO SURFACES.

(A)BY BRUSH: This is a traditional tool used to apply paint unto wall surfaces. The correct type , zinc and quality of brush such as those recommended in British standard 2992 needs to be selected and used to achieve a first class finish by means of brush it requires a high degree of skills.(B) BY ROLLER: This is simple and in expression method of applying a wide range of a paint to a flat and textured surface It consist of a revolving drum mounted on metal strip with a wooden handle at the end of the metal strip. Rollers are good for painting broad surface.

(C) SPRAY: A mechanical means of spraying paint unto surface. It is a good bending property than brush application since the paint is not evenly distributed unto the surface. (II) DESCRIPTION OF TYPES OF SPRAY GUN.(A)GRAVITY FEED: This is a container placed at the top of the spray gun.

(B)PRESSURE FEED: Is a container detached from the gun.

(C)SUNCTION FEED: Is a container attached to the gun below the nozzle.

(III) FOUR PROPERTIES OF CASEIN GLUE.(A) It resist moisture to a reasonable extends.

(B) When dump they are also liable to attack micro organisms.

(C) It can not withstand prolonged direct exposure to weathering and are unsuitable for unprotected external use.

(D)Some type has staining action and with which they are commonly used but non-staining grades are obtainable.

(IV) DEFECTS IN PAINTING WORKS.DEFECTCAUSESREMEDIES

FLAKING (peeling) paint film lifting or lifting from the surfaceLoss of adhesion between paint film and surface the moisture is brought to the surface by heat causing the paint film to lift awayRemove all the paint and start again from a bare surface. All loose paint should be scraped off and the whole area be bound by a good coating of oil primer before rebuilding the subsequent paint system

WRINKLING Small hard pained ridges on the paint surfaceOccurs in varnishes and gloss paint were there is too thick an application of the film to the undercoat. It happens in hot weather where the surface drying is accelerated heaving a comparatively soft under fill to which oxygen cannot penetrateAvoiding by using thin films of paint to cover the surface and not applying the film in a hot day in direct sun light, also by removing the offending layers and repainting

CRAZING fine irregular cracks in the paint filmLoss or elasticity of the whole system resulting from oil age, the application of a film on to an undercoat which has not fully dried or the application of a hard drying film to a soft or oily undercoatStrip the surface and repaint using compatible materials allowing sufficient drying time between the application of each film

SAPONIFICATION Soft sticky or soapy textureAlkaline attacks of the paint plaster and cement surfaces have a high alkali contentAvoiding by the surface being thoroughly dry and coat with alkali resistant primer, also to remove the defective work.

BLOOMING

Misty or hazy appearance on the surfaces of glossThe presence of moisture during the application of the gloss coatRemove with a soft rag or wash down with clean water polish, or rub down with fine glass paper and regloss

BLEEDING

Discolouration of paint film generally brownishBitumen, creosote, nicotine and other surface stains together with resinous deposits exuding from knows in timerStrip off the affected paint and if possible remove the cause of the defect and surface sealed with a suitable sealer before painting

EFFLORESCENE

White crystalline deposits formed on the surface of the paint film in the case of emulsion paintWater soluble salts with in the building fabric brought to the surface as a result of the fabric drying outSalt deposits should be thoroughly brushed from the surface, on attempt should be made to seal them or wash off. Emulsion paint may be applied to the surface

CHALDING

Whitening of the surface of oil paintPowdering of the paint surface caused by external exposure to harmful chemical and a breakdown of paint binderWash with clean water rub down, seal and repaint

STAININGDiscolouration change of colour of surface, either a change of shade or a colour alterationOutside agents reacting with the various paints constituents may cause this, but more commonly it is the result of the natural ageing of the paint filmAvoiding by frequent washing down of the surface using clean water, repainting the existing surface will overcome the problem provided the surface is well rubbed down washed off and dry before application of the system

CAUSES OF DEFECTS IN PAINTINGI. BLEEDING: This is caused by when applying an incorrect paint over another.II. BLOOMING: The presence of moisture during the application of glass coat or a chilling of the surface being glazed.

III. SAPONIFICATION: Alkaline attack of the paint plaster and cement surface has a high alkali content.

IV. EFFLORESENCE: The presence of soluble salt in material evaporates leaving the solid salt behind which tends to accumulate as the solution is drain by capillarity actions.V. CRAZING: The less of elasticity of the whole system result from old age, the application of a film or to an undercoat which has not fully dried or the application of a hard-drying to a soft or only under-coat.

VI. WRINKLING: Occurs in vanishes and glass paint where there is too thick and application of the film to the under-coat. It happens more frequently in hot weather where the surface drying is accelerated, leaving a comparatively soft under film to which oxygen cannot penetrate in order to complete the drying process.

VII. FLAKING: A loss of adhesion between paint and surface idled to blistering where the moisture is brought to the surface by heat, causing the paint film to lift away. (V)THE PRACTICAL APPLICATION OF PAPER HANGING.

QUESTION NINE (I)

DEFECTS IN TIMBERA. HEART SHAKE: This occurs in hardwood when it is left too long after it has been felled for use. It is due to lack of food (sap)B. RING SHAKE: They are called so because they follow the colours so the growth rings. They result from excessive sawing of the tree on high wind about separation of the fiber. C. STAR SHAKE: This defect gives the appearance of a star following the lines of the rays, they are usually fine cracks and can be due to the sun drying up the cellular tissue when the back has been damaged or when the timber has been seasoned too quickly.

(II)FOUR MECHANICL PROPERTIES OF METALS.

(A)HARDNESS: The metal is resistance to surface identification or scratching.

(B)DUCTILTY: A ductile metal is easily drawn into shapes or wires.

(C)TOUGHNESS: The metal is resistance of fracture by dead, live and impact loads.

(D)MALLEABILITY: A malleable metal is one easily hammered into thin sheets. Page 17