CONSTRUCTION MATERIALS OF CIVIL ENGG.pptx

CONSTRUCTION MATERIALS

Construction Materials is a subject in the first semester of course of M.E. / M.Tech . in Construction Planning and Management . The presentation is in question - answer format . It can be treated as a study material .

Why are tests done on concrete at the construction site ? Answer - Tests are done on concrete at the construction site so as to ensure that – 1. Proper materials are used in desired proportion in making the concrete . 2. Correct steps of workmanship are followed in making , placing and consolidating the concrete . ( Answer ends here . )

What are the non destructive tests done on concrete at the construction site ? Answer - There are two types of non destructive tests that can be done on concrete at the construction site - 1. Maturity Test 2. Test by Ultrasonic Pulse Velocity Method ( Answer ends here . )

What is “ Maturity Test ” ? Answer - Following are the details of “ Maturity Test ” – 1. Maturity Test is a test done on concrete at the construction site itself . It is a non - destructive test . ( Answer continues )

3. Maturity Test is used in estimating the strength gain of concrete at early ages , generally up to age of 14 days . 4. The strength of concrete that has been properly placed , consolidated and cured is a function of its age and temperature history , that is why , in “ Maturity Test ” , maturity is calculated as the product of time and temperature . ( Answer continues )

5. In “ Maturity Test ” , it is assumed that two concrete samples having same maturity will have same strength , even though each may been exposed to different temperatures and curing conditions . ( Answer continues )

6. This test is very useful for engineers working in road construction as it allows to assess the strength of concrete road at the site itself . This helps in deciding the appropriate time - a) For sawing joints of road . b) For removing the formwork . c) For allowing public or vehicles to use the road . This saves time and overall cost of construction . ( Answer continues )

7. In “ Maturity Test ” , an instrument known as “ Maturity Meter ” is used in determining the “ Maturity ” of concrete . ( Answer continues ) Maturity Meter

Example of Use of “ Maturity Meter ” in Road Work ( Answer ends here . )

What is “ Ultrasonic Pulse Velocity Test ” ? Answer - Following are the details of “ Ultrasonic Pulse Velocity Test ” – 1. It is a test used to check the quality of concrete at the construction site . It is a non - destructive test . ( Answer continues )

3. In this test , the strength and quality of concrete is assessed by passing a pulse of ultrasonic wave through concrete and measuring the time taken by pulse to get through the structure . ( Answer continues )

4. The procedure of this test is as follows - a) Two holes are drilled in the formwork of the member in which concrete is to be placed and the distance between the holes is noted . After this , concrete is properly placed and consolidated . c) After 4 to 6 hours of placing the concrete in formwork , electro acoustical transducers are connected to the surface of concrete through the holes drilled in the formwork . ( Answer continues )

After this , an ultrasonic pulse is produced from one transducer which is received by the other transducer . e) The time taken by the ultrasonic pulse to cover the known distance between the transducers is noted , which enables to calculate the velocity of the pulse . f) The value of the velocity of the pulse is used as the basis of characterizing the concrete quality and workmanship . ( Answer continues )

g) Higher velocities indicate good quality and continuity of the material, while slower velocities may indicate concrete with many cracks or voids . 5. In India , this test is conducted according to code - IS 13311-1992 . ( Answer continues )

Example of “ Ultrasonic Pulse Velocity Test ” ( Answer continues ) Concrete Block Transducer Transducer

Example of “ Ultrasonic Pulse Velocity Test ” ( Answer ends here . ) Concrete Block Transducer Transducer

What is “ Quality Control ” ? Answer - Quality control are procedures followed at construction site so as to ensure that the construction work is as per the specifications described for the job. It also includes field tests on fresh concrete . Quality control is carried out by contractor . ( Answer ends here . )

What is “ Statistical Quality Control ” ? Answer - Statistical Quality Control is the use of statistical method in the monitoring and maintaining of the quality of concrete . ( Answer continues )

In Statistical Quality Control - 1. Suitable number of concrete cubes as samples are made . 2. These concrete cubes are made from its constituents which are randomly selected from their source . 3. These concrete cubes are made as per the mix proportion specified . ( Answer continues )

4. The length of side of each concrete cube kept is 150 mm . 5. The concrete cubes are then properly cured for 28 days . 6. After this , compressive strength of each concrete cube is tested and noted . ( Answer continues )

7. The data so obtained is used in assessing the variations by calculating following things – a) Mean Compressive Strength b) Range c) Standard Deviation d) Variance e) Coefficient of Variation ( Answer continues )

If n = total number of concrete cubes tested x 1 , x 2 , x 3 ….. , x n are compressive strengths of each concrete cube then calculations can be done in the following manner - ( Answer continues )

a) Mean Compressive Strength , denoted by “ a ” , is calculated as follows - ( Answer continues ) a = ( x 1 + x 2 + x 3 + ………. + x n ) n

b) Range - It is the difference between the largest and the smallest value of compressive strength in a set of concrete cubes tested . ( Answer continues )

c) Standard Deviation , denoted by “ S ” , is calculated as follows - ( Answer continues ) S = ( x 1 - a ) 2 + ( x 2 – a ) 2 + ( x 3 – a ) 2 + ………. + ( x n - a) 2 ( n - 1 ) where “ a ” is mean compressive strength

d) Variance , denoted by “ V ” , is calculated as follows - ( Answer continues ) V = S 2 where “ S ” is Standard Deviation

e) Coefficient of Variation , denoted by “ d ” , is calculated as follows - ( Answer continues ) d = S a X 100 where “ a ” is Mean Compressive Strength where “ S ” is Standard Deviation

8. After this , a histogram is plotted with - X - axis representing compressive strength of concrete cubes with suitable class interval . and Y - axis representing frequency , that is , number of concrete cubes falling in a class interval . ( Answer continues )

9. On plotting a histogram , a bell - shaped curve can be obtained . This curve is known as Normal Distribution Curve . 10. A vertical dotted line then is plotted from the value of mean compressive strength . 11. This normal distribution curve is useful in understanding the variations in compressive strength of test cubes . ( Answer continues )

28 - Day Compressive Strength Frequency Mean Compressive Strength Bell - Shaped Curve Example of a Normal Distribution Curve for a Concrete Mix x - axis y - axis ( Answer continues )

When there is good quality control, the compressive strength test values will tend to cluster near to the mean compressive strength value, that is, normal distribution curve is tall and narrow . 13. When there is poor quality control, the normal distribution curve becomes lower and wider . ( Answer ends here . )

What are the recommendations of Indian Standard for quality control of concrete during construction work ? Answer - IS 456 : 2000 is a Indian Standard Code for “ Plain and Reinforced Concrete ” which recommends following things for quality control of concrete during construction work - ( Answer continues )

1) Code recommends that a Quality Assurance Plan shall be made , which shall include - a) The tasks and responsibilities of all persons involved in the construction process . b) Suitable control and checking procedures for the construction work . ( Answer continues )

2) Code recommends that proper documentation of following things shall be done - a) Test reports and manufacturer’s certificate for materials . b) Design details of concrete mix . c) Pour Cards . d) Record of site inspection of workmanship ( Answer continues )

e) Record of field tests . f) Record of non - conformance reports . g) Record of quality control charts , if the concrete is in continuous production over considerable period. h) Record of statistical analysis . ( Answer continues )

3) Code recommends that on any site , minimum number of different concrete mixes should be used . 4) Code recommends that in batching concrete - - Cement , aggregates and solid admixtures shall be measured by mass . - Liquid admixtures and water shall be measured by volume . ( Answer continues )

5) Code recommends to grade the aggregates in different sizes and to store them in separate stock piles and to blend them in the right proportions when required . ( Answer continues )

6) Code recommends that the accuracy of measuring equipments shall be - - Within ± 2 percent of the quantity of cement being measured . - Within ± 3 percent of the quantity of aggregate , admixtures and water being measured . ( Answer continues )

7) Code recommends that concrete shall be mixed in a mechanical mixer and the mixing time shall be at least 2 minutes . 8) Code recommends that the mixing shall be continued until there is a uniform distribution of the materials and the mass is uniform in colour and consistency . 9) Code recommends that if there is segregation after unloading from the mixer , the concrete should be remixed . ( Answer continues )

10) Code recommends to check the workability of concrete at frequent intervals . 11) Code recommends that dosages of retarders , plasticizers and superplasticizers shall be restricted to 0.5 , 1.0 and 2.0 percent respectively by weight of cementitious materials . 12) Code recommends that after mixing , concrete shall be transported rapidly and placed properly in the formwork so as to prevent segregation . ( Answer continues )

13) Code recommends that concrete shall be compacted thoroughly using mechanical vibrators . 14) Code recommends that , in curing , exposed surfaces of concrete shall be kept continuously in a damp or wet condition by ponding or by covering with a layer of sacking , canvas , hessian or similar materials . ( Answer continues )

15) Code recommends that , from the date of placing the concrete in formwork , the surface should be kept wet – a) Atleast for 7 days if concrete is made from ordinary portland cement . b) Atleast for 10 days if mineral admixtures or blended cements are used . ( Answer continues )

16) Code recommends use of impermeable membranes such as polyethylene sheeting , which would be used in covering the concrete surface so as to provide effective barrier against evaporation . 17) Code recommends constant and strict supervision of all construction activities . ( Answer ends here . )

What are Polymer Concrete Composites ? Answer - Polymer concrete composites are obtained by combining polymeric materials with cement concrete . ( Answer continues )

Different types of Polymer Concrete Composites - 1. Polymer - impregnated Concrete 2. Resin or Polymer Concrete 3. Polymer Modified Concrete ( Answer ends here . )

What is the meaning of the term “ impregnate ” ? Answer - The meaning of “ impregnate” is to soak or saturate something with a substance . ( Answer ends here . )

What is Polymer - impregnated Concrete ? Answer - ( Answer continues ) In polymer - impregnated concrete , low viscosity liquid monomers or prepolymers are impregnated into the pores of hardened cement concrete and are then polymerised .

Surface Impregnation - ( Answer continues ) If impregnation is done partially in the pores of concrete then it is known as “ Surface Impregnation ” . Surface Impregnation improves the durability and chemical resistance of concrete .

In - depth Impregnation - ( Answer ends here . ) If impregnation is done fully in the pores of concrete then it is known as “ In - depth Impregnation ” . In - depth Impregnation , greatly improves the structural properties of concrete .

What is the procedure of making Polymer - impregnated Concrete ? Answer - ( Answer continues ) The procedure is as follows - 1. The structural member which is to be impregnated is properly constructed with cement concrete and is moistly cured , so that it can achieve its optimum strength .

( Answer continues ) 2. After this , the member is heated upto the order of 120 o C to 150 o C so as to remove moisture present in it . 3. After this , it is allowed to cool upto 35 o C , so as to avoid flammability . 4. The air present in the voids or pores of dried hardened concrete member is now removed by subjecting it to vaccum .

( Answer continues ) 5. Now , the concrete member is soaked in desired monomer for sufficiently long time so as to achieve its desired depth of penetration . 6. After soaking in monomer , the concrete surface is covered with a plastic sheet so as to prevent evaporation of monomer .

( Answer ends here . ) 7. Polymerization , which is the last step , is done , by - - Keeping the concrete member in infrared heaters or air - ovens for 2 to 6 hours and heating it up to the temperature between 60 o C to 150 o C , depending on the type of monomer impregnated . or - Keeping the concrete member in Gamma - ray radiation .

What are the different monomers used for making Polymer - impregnated Concrete ? Answer - ( Answer continues ) The following are monomers used for making Polymer - impregnated concrete - 1. Styrene 2. Polyester

( Answer ends here . ) 3. Methylmethacrylate 4. Butylacrylate 5. Acrilonitrile 6. Epoxies and their copolymer combinations

What are the uses of “ Polymer - impregnated Concrete ” ? Answer - ( Answer continues ) The following are the uses of Polymer - impregnated concrete - 1. It is used in surface impregnation of bridge decks so as to make it impervious against moisture , de - icing chemicals and chloride ions .

( Answer ends here . ) 2. It can be used in repairing works of dams and other hydraulic structures . 3. It can be used as an excellent construction material for desalination plants and sea - floor structures . 4. It can be used in construction of prestressed concrete beams .

What is “ Resin or Polymer Concrete ” ? Answer - ( Answer continues ) Polymer concrete consists of polymer and aggregate . It does not contain cement and water .

Procedure of making “ Resin or Polymer Concrete ” ( Answer continues ) 1. The desired monomer or pre - polymer and aggregates are mixed . 2. The mixing is done either by hand or machine . 3. The thoroughly mixed material is then placed in the moulds or formwork .

( Answer continues ) 4. After placing the mixture in the moulds or formwork , polymerization is done . 5. Polymerization can be done by three methods – a) Thermal - catalytic reaction b) Catalyst - promoter reaction c) Radiation

( Answer continues ) a) In Thermal – catalytic Reaction method , - Catalyst is added in the mixture . - The mixture is then heated upto a temperature of 90 o C , which decomposes the catalyst and leads to polymerization .

( Answer continues ) The “ Catalysts ” that can be used in Thermal - catalytic reaction are – - Benzoyl Peroxide - Methyl - Ethyl - Ketone Peroxide - Benzensulphonic Acid

( Answer continues ) b) In Catalyst - Promoter Reaction method , - A catalyst and a promoter or accelerator are added in the mixture . - The promoter decomposes the catalyst at room temperature and this leads to polymerization .

( Answer continues ) The “ Promoters ” that can be used in Catalyst - Promoter reaction are – - Cobalt Napthanate - Dimethyl - p - Toludine - Ferric Chloride

( Answer continues ) c) In Radiation method , - Gamma rays are applied on the mixture which initiates polymerization .

( Answer continues ) 6) Polymer systems that are used in making Polymer Concrete are – - Methyl - methacrylate - Polyester - styrene - Epoxy - styrene - Styrene

( Answer continues ) - Furfuryl Acetone - Furane - Acrylic - Urea formaldehyde - Phenol formaldehyde

( Answer ends here . ) Polymer concrete can be reinforced with steel , nylon , polypropylene or glass fibres in a manner similar to cement concrete . Polymer concrete can be used as repair material and as surface coatings . Polymer concrete pipes can be used for transporting a variety of chemicals , effluents and wastewater .

What is “ Polymer Modified Concrete ” ? Answer - ( Answer continues ) Polymer Modified Concrete is made by adding polymeric material into cement concrete during the mixing stage . In this , polymer is added in the form of emulsion , dispersion or latex .

( Answer continues ) After adding polymer , the mixture is casted and cured in the same way as it is done for cement concrete . The hydrated cement and the polymer film formed due to curing of the polymeric material constitute an interpenetrating matrix that binds the aggregate .

Types of “ Polymer Modified Concrete ” - 1. Prepolymer - modified Cement Concrete 2. Latex - modified Cement Concrete ( Answer continues )

Prepolymer - modified Cement Concrete In this type , following prepolymer systems are mixed with concrete - 1. Polyester - styrene based system 2. Epoxy systems 3. Furane systems ( Answer ends here . )

Latex - modified Cement Concrete Latex is white milk like suspension . It consists of very small - sized polymer particles suspended in water . Polymer particles are suspended with the help of emulsifiers and stabilizing agents . It consists of 50 percent of polymer by mass . ( Answer continues )

Latex can be made with – 1. Elastomeric Polymers 2. Glassy Polymers ( Answer continues )

Elastomeric Polymers are characterized by - rubber - like elongation - low - modulus of elasticity at room temperature . ( Answer continues )

Example of Elastomeric Polymers - 1) Natural rubber latex 2) Styrene - butadiene rubber latex 3) Acrilonitrile - butadiene rubber latex 4) Neoprene ( Answer continues )

Glassy Polymers are characterized by - High modulus of elasticity - Higher strength - Brittle type failure ( Answer continues )

Example of Glassy Polymers - 1) Styrene - butadiene copolymer latex 2) Acrylic Polymers ( Answer ends here . )

What is “ Ferrocement ” ? Answer - ( Answer continues ) Ferrocement is reinforced cement mortar . That is , mixture of cement and sand , reinforced with many continuous layers of wire meshes .

( Answer continues ) In Ferrocement Construction - 1) First , a frame is made using steel rods . 2) The diameter of steel rods can be from 3 mm to 8 mm . 3) The frame is made as per the geometry and shape of desired structure .

( Answer continues ) 4) The purpose of making frame is to hold wire meshes in position . 5) The wire meshes are made from galvanized steel wires . 6) Wire meshes can be made by welding , twisting or weaving .

( Answer continues ) 7) The diameter of steel wires used in making wire meshes can be from 0.5 mm to 1.5 mm . 8) The centre - to - centre spacing of wire mesh can be from 6 mm to 20 mm . 9) The shape of wire mesh can be hexagonal or square .

( Answer continues ) 10) For making cement mortar , good quality cement , as suitable can be used . The particle size of sand to be used should be less than 2.36 mm but greater than 1.18 mm .

( Answer continues ) 12) The mix proportion for cement mortar ( by mass ) can be from 1 : 1.5 to 1 : 2.5 . 13) The water - cement ratio ( by mass ) can be from 0.35 to 0.6 . 14) The slump of fresh cement mortar should not exceed 50 mm .

( Answer continues ) 15) The 28 - day compressive strength of moist cured cubes of cement mortar should be around 35 N/mm 2 . 16) Suitable plasticizers and admixtures , as per need can be mixed in cement mortar .

( Answer continues ) Advantages of Ferrocement - As compared to concrete , Ferrocement has - Higher Cracking Resistance - Higher Ductility - Higher Impact and Fatigue Resistance

( Answer continues ) - Ferrocement structures are thin and light . - Ferrocement is suitable for manufacturing the precast units , which can be easily transported . - Ferrocement construction technique is simple and does not require skilled labour .

Example of “ Hexagonal Wire Mesh ” ( Answer continues )

Example of “ Square Wire Mesh ” ( Answer continues )

Example of “ Ferrocement Construction ” ( Answer continues )

Example of “ Ferrocement Construction ” ( Answer continues ) Wire Mesh Cement Mortar

Example of “ Ferrocement Construction ” ( Answer continues )

Example of “ Ferrocement Construction ” ( Answer ends here . )

What are the waste materials that can be used in making concrete ? Answer - ( Answer continues ) Waste materials are of three types - 1. Organic Wastes or Agro - Wastes 2. Inorganic Wastes or Urban - Wastes 3. Industrial Wastes

( Answer continues ) Examples of Organic Wastes or Agro - Wastes 1. Sawdust 2. Coconut Pith 3. Rice Husk 4. Wheat Husk 5. Groundnut Husk

( Answer continues ) Examples of Inorganic Wastes or Urban - Wastes 1. Broken or Recycled Concrete 2. Broken Bricks 3. Crushed Glass

( Answer ends here . ) Examples of Industrial Wastes 1. Blast - furnace Slag 2. Fly Ash or Fuel Ash from Power Stations 3. Red Mud Aggregate 4. Silica - fume

What is “ Rice Husk ” ? Answer - ( Answer continues ) Rice Husks are the hard protecting coverings of grains of rice . It is an agro waste and can be used as a building material .

Example of “ Rice Husks ” ( Answer continues )

( Answer continues ) Use of Rice Husks as Building Material - 1) Rice Husks can be used as an aggregate in making light - weight concrete . The light - weight concrete can be used in making precast blocks and slabs for walls and partitions .

( Answer continues ) 2) Rice Husk can be burnt into ash and powdered into desired fineness . - The powdered ash so obtained contains highly reactive form of silica . - The rice husk ash can be utilized in making - a) Blended Cements b) Bricks

Example of “ Rice Husk Ash ” ( Answer continues )

( Answer continues ) Rice Husk Ash Blended Cement - Rice Husk Ash can be blended with ordinary portland cement . - Concrete made from Rice Husk Ash Cement is more acid resistant than ordinary portland cement concrete .

( Answer continues ) Reason for Increased Acid Resistance - - On hydration of Portland cement , Ca(OH) 2 is produced . - The Ca(OH) 2 so produced quickly combines with highly reactive silica present in rice husk ash to form additional calcium silicates . This increases acid resistance .

( Answer continues ) - Rice Husk Ash Cements are black in colour , therefore , these cements can be used in making glare - free pavements .

( Answer continues ) Rice Husk Ash Bricks - Mixture of Rice Husk Ash , Sand and Lime in suitable proportions can be used in making bricks . - The compressive strength of such bricks is between 5 - 6 N/mm 2 . - The water - absorption of such bricks is between 15 - 20 percent .

Example of “ Rice Husk Ash Bricks ” ( Answer ends here . )

What is “ Broken or Recycled Concrete ” ? Answer - ( Answer continues ) Recycled Concrete is the old concrete that has been obtained from - - Demolition of Buildings and its foundations - Demolition of Pavements It is an inorganic waste .

( Answer continues ) Recycled Concrete is made from old concrete . a) The old concrete should be hard . b) The old concrete should be free from finishing materials , reinforcing bars or any other embedded materials .

( Answer continues ) c) The old concrete should not contain excessive amount of dirt , plaster of paris , gypsum , wood or asphalt . d) The old concrete is crushed to the specified size . Recycled Concrete is used as an aggregate for new cement concrete construction .

( Answer continues ) Properties of Recycled Concrete Aggregates - 1) They are angular in shape 2) They are more coarser as compared to natural aggregate . 3) They are more porous , therefore , water absorption is 5 percent higher as compared to natural aggregate .

( Answer continues ) 4) The concrete produced from recycled concrete aggregates loses its workability more rapidly than concrete made from natural aggregate . Hence it requires - - More mixing water - Air entraining admixtures - Water reducing admixtures

( Answer continues ) 5) The slump of concrete made from recycled cement aggregate shall not exceed 200 mm . 6) As compared to conventional cement concrete made from natural aggregates , recycled cement concrete has lower compressive strength and lower durability .

( Answer continues ) Recycled Concrete Aggregates are used in construction of pavements . Lean Concrete made using recycled concrete aggregates is called econo - crete .

Example of “ Recycled Cement Aggregates ” ( Answer ends here . )

What is “ Broken Brick Aggregate Concrete ” ? Answer - ( Answer continues ) Broken brick is an inorganic waste . It is obtained from rejected overburnt or damaged bricks . These bricks can be crushed and reused as aggregates .

( Answer ends here . ) Broken bricks aggregates can be used in making concrete - 1) For foundations of light buildings . 2) For light - weight reinforced concrete floors . Concrete made from broken brick aggregates have satisfactory structural properties .

What is “ Blast - furnace Slag ” ? Answer - ( Answer continues ) Blast - furnace Slag is an industrial waste . It is obtained as by-product during the production of iron and steel . Blast - furnace Slag can be used as a building material .

( Answer continues ) Blast - furnace Slag can be classified as - 1) Granulated Blast - furnace Slag 2) Foamed Blast - furnace Slag 3) Dense Blast - furnace Slag

( Answer continues ) Granulated Blast - furnace Slag can be used in the manufacture of slag cements . Slag cements have - - Low rate of heat evolution - Increased resistance to chemicals [ “ Granulated ” means “ Powdered ” ]

( Answer continues ) Example of Granulated Blast - furnace Slag

( Answer continues ) Foamed Blast - furnace Slag can be used as a light- weight aggregate in concrete . Dense Blast - furnace Slag can be used as a replacement of natural aggregate in concrete .

( Answer ends here . ) Example of Dense Blast - furnace Slag

How “ Fly Ash or Fuel Ash ” can be used as a building material ? Answer - ( Answer continues ) “ Fly Ash or Fuel Ash ” is an industrial waste . It is the fine dust which is collected in cyclones or wet scrubbers and electrostatic precipitators in coal - fired power stations .

( Answer continues ) Powdered fly ash or fuel ash can be used as a building material . It can be used as a partial replacement of cement in concrete .

( Answer continues ) As compared to concrete made from Portland cement , concrete including fly ash has - 1. Lower rate of heat evolution 2. High resistance to sulphate attack 3. Lower rate of development of strength 4. Increased drying shrinkage and creep strains

( Answer ends here . ) Example of “ Fly Ash ”

What is “ Red Mud Aggregate ” and How it can be used as a building material ? Answer - ( Answer continues ) “ Red Mud ” is an industrial waste . It is red in colour . It is obtained as a by - product from the production of alumina from bauxite by Bayer’s Process .

It can be used as a building material . ( Answer continues ) Concrete made with red mud aggregate has relatively higher compressive , tensile and flexural strengths as compared to concrete made with gravel .

( Answer ends here . ) Example of “ Red Mud ”

What is “ Silica Fume ” and How it can be used as a building material ? Answer - ( Answer continues ) “ Silica Fume ” is an industrial waste . It is obtained as a by - product from the reduction of high purity quartz with coal in electric arc furnaces in the production of ferro - silicon metal .

( Answer continues ) Silica Fume is an ultrafine powder and can be used as a building material . Silica Fume can be used - 1) To conserve cement 2) To produce ultra high strength concrete 3) To control alkali - silica reaction

( Answer continues ) 4) To reduce chloride associated corrosion and sulphate attack 5) To increase early age strength of fly ash / slag concrete

( Answer ends here . ) Examples of “ Silica Fume ”

What is “ Sawdust ” ? Answer - ( Answer continues ) “ Sawdust ” is an agro waste . Sawdust are the powdery particles of wood produced by sawing . Sawdust can be burnt into ash which can be used as a partial replacement of cement in concrete .

( Answer continues ) Example of “ Saw ”

( Answer ends here . ) Example of “ Sawdust ”

What is “ Coconut Pith ” ? Answer - ( Answer continues ) “ Coconut Pith ” is an agro waste . Coconut Pith is the outer shell and its fibres obtained from coconut . It can be used as a building material .

( Answer continues ) Coconut outer shell can be used as a light - weight aggregate in concrete . Coconut fibres burnt into ash can be used as a partial replacement of cement in concrete .

( Answer continues ) Example of “ Coconut Pith or Coir ”

( Answer continues ) Example of “ Coconut Pith ”

( Answer ends here . ) Example of “ Coconut Pith or Shell ”

What is “ Wheat Husk ” ? Answer - ( Answer continues ) Wheat Husks are the hard protecting coverings of grains of wheat . It is an agro waste and can be used as a building material . Wheat husk ash can be used as a partial replacement of cement in concrete .

( Answer ends here . ) Example of “ Wheat Husk ”

What is “ Groundnut Husk ” ? Answer - ( Answer continues ) Groundnut Husks are the hard protecting coverings of grains of groundnut . It is an agro waste and can be used as a building material . Groundnut husk ash can be used as a partial replacement of cement in concrete .

( Answer ends here . ) Example of “ Groundnut Husk ” Groundnut Groundnut Husk

What is “ Fibre - Reinforced Concrete ” ? Answer - ( Answer continues ) Fibre - Reinforced Concrete is the concrete or mortar reinforced with fine fibres .

( Answer continues ) For making Fibre - Reinforced Concrete - a) Ordinary Portland Cement ( OPC ) or Pozzolana Portland Cement ( PPC ) is used . b) Crushed Quartz is used as aggregate . c) Fine Fibres are used .

( Answer continues ) Different types of Fibres can be used in making Fibre - Reinforced Concrete , such as - 1) Steel Fibres 2) Polypropylene Fibres 3) Glass - Fibres 4) Asbestos Fibres 5) Carbon Fibres

( Answer continues ) Generally , - Steel Fibres and Polypropylene Fibres are used in reinforcing of concrete . - Glass - Fibres are used in reinforcing of cement mortar .

( Answer continues ) Example of Steel Fibres

( Answer continues ) Another Example of Steel Fibres

( Answer continues ) Example of Steel Fibre Reinforced Concrete

( Answer continues ) Example of Polypropylene Fibres

( Answer continues ) Example of Glass Fibres

( Answer continues ) Example of Asbestos Fibres ( Asbestos is hazardous to health . Hence it’s use is discontinued . )

( Answer continues ) Example of Carbon Fibres

( Answer continues ) As compared to Plain Cement Concrete , Fibre Reinforced Concrete has - Superior Tensile Strength , Ductility and Compressive Strength - Superior Cracking and Impact Resistance

( Answer continues ) Aspect Ratio of Fibre If The length of fibre is denoted by “ L ” The diameter of fibre is denoted by “ D ” then Aspect Ratio = L D

( Answer continues ) The structural performance of fibre – reinforced concrete depends on - - Strength Characteristics of Fibres - Volume of Fibre Reinforcement used in mixture - Dispersion and Orientation of Fibres - Shape of Fibres - Aspect Ratio

( Answer continues ) Behaviour of Fibre - Reinforced Concrete under Tensile Load 1) On applying load , Fibre Reinforced Concrete behaves elastically till cracking occurs in it . This means that there is no slippage between the fibres and the concrete mixture .

( Answer continues ) 2) After the initial cracking , as the load is increased , multiple cracking occurs continuously over a wide range of loading and debonding of fibres from concrete matrix starts taking place . 3) Finally , failure occurs at peak load and the failure is in the form of fibre - pull out .

( Answer continues ) Graph - Fibre - Reinforced Concrete under Tensile Load

( Answer continues ) Example of Fibre Reinforced Concrete ( This is failure due to Fibre Pull Out . )

( Answer continues ) Fibre - Reinforced Concrete can be classified as - a) Discrete Fibre Reinforced Concrete b) SIFCON c) SIMCON

( Answer continues ) Discrete Fibre Reinforced Concrete In this type - 1) Short , discontinuous , discrete fine fibres of specific geometry are randomly dispersed in concrete mixture and directly placed in the formwork of structural member . 2) The fibres interlock and entangle around aggregate particles .

( Answer continues ) On addition of Fibres - - The mixture becomes more cohesive . - The mixture is less prone to segregation . - The workability of mixture gets reduced . [ The term “ Discrete ” means individually separate and distinct . ]

( Answer continues ) Slurry Infiltrated Fibre Concrete ( SIFCON ) In this type - 1) A framework of desired structural member is made and fibres are pre - placed in it in a desired manner .

( Answer continues ) 2) After this , cementing slurry is allowed to infiltrate in the framework . 3) The Cement Slurry consists of cement , aggregates and water .

( Answer continues ) 4) As compared to Discrete Fibre Reinforced Concrete , - Higher volume of fibre reinforcement can be achieved in SIFCON . - SIFCON has better structural properties .

( Answer continues ) Example of SIFCON Fibres Cement Slurry

( Answer continues ) Slurry Infiltrated Mat Concrete ( SIMCON ) In this type - 1) A framework of desired structural member is made and mats or sheets made from stainless steel fibres are pre - placed in it in a desired manner .

( Answer continues ) 2) After this , cementing slurry is allowed to infiltrate in the framework . 3) The Cement Slurry consists of cement , aggregates and water .

( Answer continues ) 4) As compared to Discrete Fibre Reinforced Concrete and SIFCON , - SIMCON requires smaller volume of fibre reinforcement . - SIMCON has better structural properties .

( Answer continues ) 5) For SIMCON , the fibre mats or sheets are available in the market in pre - packed rolls . Hence it can be easily cut , handled and installed in the field . This makes construction process simpler .

( Answer continues ) Example of SIMCON Fibre Mat

( Answer continues ) Fibre Reinforced Concrete can be used in new construction work or in repair work of - 1) Hydraulic Structures 2) Airfield and Highway Pavements 3) Bridge Decks

( Answer ends here . ) As compared to Reinforced Cement Concrete , Fibre Reinforced Concrete has inferior structural properties because - In Reinforced Cement Concrete , steel bars are used , which are long and continuous and which can be properly placed in the formwork of desired structural member , as per design . Also , Steel Fibres are more expensive then steel bars .

What is “ Ready mix Concrete ” ? Answer - ( Answer continues ) Ready mix Concrete is the concrete which is manufactured in a factory or concrete plant and delivered to construction site . The concrete is delivered through special type of trucks having concrete mixers mounted on them .

( Answer continues ) In Ready mix Concrete - 1) Concrete can be produced as per the desired design mix under controlled conditions . 2) The raw materials used are consistent in quality . 3) Human error is eliminated or minimized in batching and mixing of concrete and dependency on labour is reduced .

( Answer continues ) 4) Instead of cement bags , bulk cement is used , which reduces wastage and dust pollution . This reduces consumption of cement upto 10 - 12 % . Further reduction of cement consumption is possible if other cementitious materials or mineral admixtures are also used .

( Answer continues ) 5) There is no requirement for managing equipments and storage of materials like cement , water , coarse and fine aggregates and admixtures on construction site . 6) Construction process on site becomes easier speedy and qualitative . 7) Conservation of energy and resources is achieved .

( Answer continues ) 8) The ready mix concrete is transported from concrete plant to the construction site through transit - mix trucks . In ready mix concrete , retarders are added to ensure that the concrete does not become hard on its way in truck but remains fresh and can be easily placed and poured in formwork at construction site .

( Answer continues ) Example of Ready Mix Concrete Plant

( Answer continues ) Example of Transit Mix Truck

( Answer ends here . ) Example of Ready Mix Concrete

What is “ Quartz ” ? Answer - ( Answer continues ) Quartz is a hard mineral consisting of silica . It is found widely in metamorphic and igneous rocks .

( Answer continues ) Quartz , typically occurs in colourless or white hexagonal prisms . But many times coloured quartz is found in nature due to the presence of impurities in it . Quartz can be used as a building material . It can be used as an aggregate in concrete . It is chemically inert .

( Answer continues ) Example of Quartz

( Answer continues ) Example of Quartz Powder

( Answer ends here . ) Example of Quartz as Aggregates

What are “ Admixtures ” ? Answer - ( Answer continues ) Admixtures are chemical compounds other than cement that are added to the concrete .

( Answer continues ) Admixtures are added to the concrete during mixing or immediately before placing of concrete in formwork . These are added to modify one or more specific properties of concrete .

Different Types of Admixtures - ( Answer continues ) 1. Accelerating Admixtures 2. Retarding Admixtures 3. Air - entraining Admixtures 4. Water - reducing Admixtures 5. Gas - forming Admixtures

( Answer continues ) 6. Air - detraining Admixtures 7. Corrosion inhibiting Admixtures 8. Water or Damp proofing Admixtures 9. Colouring Admixtures or Pigments 10. Fungicidal , germicidal and insecticidal Admixtures

What is “ Accelerating Admixture ” ? Answer - ( Answer continues ) Accelerating Admixtures are added to the concrete so that - 1) Concrete can gain strength more rapidly . 2) Concrete can set in formworks more rapidly .

( Answer continues ) Accelerating Admixtures can be used where - 1) Concreting is to be done at low temperatures . 2) Plugging of Pressure leaks is to be done . 3) Sprayed Concreting is to be done .

( Answer continues ) Disadvantages of Accelerating Admixtures - 1) Due to heat evolution , concrete may crack . 2) Corrosion of reinforcement may take place . Example of Accelerating Admixture - Calcium Chloride

( Answer ends here . ) Example of Calcium Chloride

What is “ Retarding Admixture ” ? Answer - ( Answer continues ) Retarding Admixtures are added to the concrete so as to delay its setting .

( Answer continues ) Retarding Admixtures can be used - 1) To maintain the workability of concrete at high temperatures . 2) To reduce the rate of heat evolution . 3) For Ready mix Concrete .

( Answer ends here . ) Disadvantage of Retarding Admixtures - - It may promote bleeding of concrete . Example of Retarding Admixture - Sugar

What is “ Air - entraining Admixture ” ? Answer - ( Answer continues ) Air - entraining Admixtures are used for entrainment of air into concrete . “ Entrainment ” means intentional entrapment of air bubbles into concrete.

( Answer continues ) Air - entraining Admixtures can be used - 1) To improve workability . 2) For better resistance against frost without increasing cement content . 3) To lower permeability in concrete .

( Answer ends here . ) Disadvantage of Air - entraining Admixtures - - It becomes necessary to carefully control the type and grading of aggregate used , water - cement ratio , air content , mixing time and temperature . Example of Air - entraining Admixture - Lignosulphonates

What is “ Damp - proofing Admixture ” ? Answer - ( Answer continues ) Damp - proofing Admixtures are used to prevent water from entering capillaries of concrete .

( Answer continues ) Damp - proofing Admixtures can be used - 1) To reduce permeability in concrete . 2) For better resistance against frost .

( Answer ends here . ) Disadvantages of Damp - proofing Admixtures - 1) It requires low water - cement ratio and full compaction . 2) It is not efficient under high hydrostatic pressure . Example of Damp - proofing Admixture - Potash Soaps

What is “ Water - reducing Admixture ” ? Answer - ( Answer continues ) Water - reducing Admixtures are used to reduce the water content in concrete .

( Answer continues ) Water - reducing Admixtures can be used - - To achieve workability and flowability of concrete at low water content without compromising its strength . - To delay the setting of concrete .

( Answer continues ) Disadvantages of Water - reducing Admixtures - 1) These admixtures do not perform well with sulphate resistant cement . 2) Concrete tends to segregate and flowability is not long lasting . 3) During hot weather , the concrete loses its workability rapidly .

( Answer continues ) Water - reducing Admixtures can be classified as - - Plasticizers - Superplasticizers

( Answer continues ) Plasticizers Plasticizers are water - reducing admixtures in which water content is reduced by 8 - 15 % . Example of Plasticizer - Calcium and Sodium Lignosulphonates

( Answer continues ) Example of Plasticizer - Calcium Lignosulphonate

( Answer continues ) Superplasticizers Superplasticizers are water - reducing admixtures in which water content is reduced by 15 - 30 % . Example of Superplasticizer - Sulphonated Melamine Formaldehyde Resin

( Answer ends here . ) Example of Superplasticizer - Sulphonated Melamine Formaldehyde

What is “ Concrete Colouring Admixture ” ? Answer - ( Answer continues ) Concrete Colouring Admixtures or Pigments are used to produce coloured cements .

( Answer ends here . ) Colours produced by different pigments - Colour Pigment Black Carbon Black Black Colour with Brown Tint Manganese Black Black Colour with Purple Tint Magnetic Ferrous Oxide Blue Barium Manganate Ultramarine Brown Raw Umber Burnt Umber Green Artificially produced Chromium Oxide Chromium Hydroxide Red Red Oxide or Iron Yellow Hydroxides of Iron

“ Fungicidal , Germicidal and Insecticidal Admixture ” ( Answer ends here. ) These are admixtures that produce fungicidal , germicidal and insecticidal properties to the hardened cement pastes , mortars or concretes . Example - Polyhalogenated Phenols

What is “ Corrosion - inhibiting Admixture ” ? Answer - ( Answer continues ) These admixtures are used to slow down corrosion of steel reinforcement in concrete . Example - - Sodium Benzoate - Sodium Nitrate

( Answer ends here . ) Example of Sodium Benzoate

What is “ Gas - Forming Admixture ” ? Answer - ( Answer continues ) Gas - forming admixture can be used in cement mortar or in concrete .

( Answer continues ) On adding Gas - forming Admixture - The admixture reacts with hydroxides present in the cement . This leads to formation of minute bubbles of hydrogen gas . The size of bubbles range from 0.1 mm to 1 mm . The gas bubbles prevent bleeding of concrete .

( Answer continues ) If larger amounts of admixtures are added in concrete then it becomes gas filled , light weight and low strength concrete . Such type of concretes can be used for thermal insulation and are called Foamed Concrete or Aerated Concrete or Cellular Concrete . Example of Gas - forming Admixture - Aluminium Powder

( Answer ends here . ) Example of Aluminium Powder

What is “ Air - Detraining Admixture ” ? Answer - ( Answer ends here . ) This admixture is used to remove the air or gas in a concrete mixture . Example - Tributyl Phosphate

What is “ Pozzolana ” ? Answer - ( Answer continues ) Pozzolana is a term used for finely powdered siliceous materials . They are also known as mineral additives or supplementary cementing materials .

( Answer continues ) Pozzolana are added in concrete in desired proportion so as to enhance its properties . Pozzolana do not possess cementing property in themselves .

( Answer continues ) But , when Pozzolana are added in concrete , they react chemically with calcium hydroxide released from the hydration of Portland Cement . This results in formation of compounds having cementing properties .

List of “ Pozzolana ” Materials - ( Answer continues ) 1. Clay 2. Shales 3. Opaline Cherts 4. Diatomaceous Earth 5. Rocks made from Volcanic Ash

( Answer ends here . ) 6. Fly Ash 7. Blast - Furnace Slag 8. Silica Fume 9. Rice Husk Ash 10. Dehydroxylated China Clay 11. Brick Dust

What is the effect of “ Chemicals ” on Concrete ? Answer - ( Answer continues ) The effect of “ Chemicals ” on concrete is hazardous . Exposure and penetration of chemical liquids and gases damages concrete .

( Answer ends here . ) Different types of Chemical Damage are - 1. Leaching 2. Damage due to Carbon Dioxide 3. Damage due to Chlorides 4. Damage due to Sulphates

What is “ Leaching ” in Concrete ? Answer - ( Answer continues ) Leaching is a chemical process . Leaching takes place when water flows through cracks present in concrete .

( Answer continues ) In this process , calcium hydroxides and other solids present in concrete gets dissolved in water and are transported in concrete itself or are completely removed from concrete . Leaching damages concrete .

( Answer ends here . ) Example of Leaching in Concrete Calcium Carbonate deposited on Concrete Surface

What is the effect of “ Carbon Dioxide ” on Concrete ? Answer - ( Answer continues ) The effect of “ Carbon dioxide ” on concrete can be hazardous .

( Answer continues ) Carbon dioxide present in air reacts with calcium hydroxide present in concrete to form calcium carbonate . This process is known as Carbonatation . This process is slow and continuous . This process starts from outer surface of concrete and progresses inwards .

( Answer continues ) Concrete , which is an alkaline substance , acts as a inert coating on steel and prevents the corrosion of steel . But its alkalinity starts decreasing when carbonatation process takes place . This promotes corrosion of reinforcement . Hence , effect of CO 2 on concrete is hazardous if concrete is not properly compacted .

( Answer ends here . ) Example of Carbonatation in Concrete Corrosion of Steel

What is the effect of “ Chlorides ” on Concrete and Steel Reinforcement ? Answer - ( Answer continues ) The effect of “ Chlorides ” on concrete and steel reinforcement is hazardous .

( Answer continues ) A) Effect of Chlorides on Concrete 1. Penetration of chlorides results in swelling of concrete . 2. The swelling of concrete due to penetration of chloride is 2 to 2.5 times larger than swelling of concrete due to penetration of water .

( Answer continues ) 3. Swelling of concrete results in slight reduction in its strength . ( The term “ Swelling ” means abnormal enlargement . )

( Answer continues ) B) Effect of Chlorides on Steel Reinforcement 1) In R.C.C. , chloride ions present in very small concentration do not corrode the steel . 2) But , as the concentration of chloride ions increases , there comes a point when the corrosion of steel reinforcement starts .

( Answer continues ) 3) The concentration of chloride ions at the point when the corrosion starts is called “ Critical or Threshold Concentration of Chloride Ions ” . 4) The corrosion takes place in the presence of oxygen . 5) As the concentration of chloride ions increases further , the rate of corrosion also increases .

( Answer continues ) But 6) At high concentration of chloride ions , the solubility of oxygen in concrete starts reducing and there is reduction in amount of oxygen necessary for corrosion . This results in lowering of rate of corrosion .

Different Ways of improving “ Chloride Resistance ” of Reinforced Cement Concrete ( R.C.C. )

The following are different ways of improving “ Chloride Resistance ” of R.C.C. - ( Answer continues ) 1. By reducing the permeability of concrete , which can be done - a) By reducing the water - cement ratio of concrete mixture .

( Answer continues ) b) By adding mineral additives having high calcium content . For example - Fly Ash , Blast Furnace Slag . The mineral additives can be blended with cement or can be directly added to concrete at the time of mixing .

( Answer continues ) 2. By using cement containing high amounts of Tricalcium Aluminate ( C 3 A ) . 3. By avoiding the use of Calcium Chloride ( CaCl 2 ) as accelerating admixture . 4. By avoiding the use of aggregates having chloride contents .

( Answer ends here . ) 5. By avoiding saline water in mixing and curing of concrete . 6. By ensuring proper placing and compaction of concrete during construction .

What is the effect of “ Sulphates ” on Hardened Concrete ? Answer - ( Answer continues ) The effect of “ Sulphates ” on hardened concrete is hazardous .

( Answer continues ) 1. Sulphates can be found in - a) Groundwater b) Subsoil c) Sea - Water d) Industrial Wastes

( Answer continues ) 2. Various sulphate compounds are hazardous to concrete . These compounds are - a) Calcium Sulphate b) Sodium Sulphate c) Magnesium Sulphate d) Ammonium Sulphate Increasing Order of Hazard

( Answer continues ) 3. The sulphate compounds penetrate and react with concrete to form compounds which increases the volume of concrete . The chemical reactions are as follows -

( Answer continues ) Chemical Reactions - a) Sulphate ions combine with calcium ions present in concrete to form calcium sulphate . + Ca(OH) 2 Na 2 SO 4 CaSO 4 2 NaOH + Calcium Hydroxide Sodium Sulphate Calcium Sulphate Sodium Hydroxide Calcium Sulphate ( CaSO 4 ) precipitates as Gypsum ( CaSO 4 2H 2 O ) .

( Answer continues ) b) Sulphate ions combine with tricalcium aluminate present in concrete to form calcium sulphoaluminate . + 3CaSO 4 C 3 A C 3 A 3CaSO 4 32H 2 O 32 H 2 O + Calcium Sulphate Tricalcium Aluminate Calcium Sulphoaluminate or Ettringite . .

( Answer ends here . ) 4. The formation of Gypsum and Ettringite increases the volume of concrete . The increase in volume results in cracking of concrete and loss in its strength . Hence Sulphates have hazardous effects on concrete .

What is Standardization of Materials ?

( Answer continues ) Standardization of materials is the process of developing and establishing - - Level of quality and essential properties a material should possess . - Methods of producing materials . - Methods of using the materials .

( Answer continues ) The process of standardization is carried out with general agreement of different parties that include firms , users , interest groups , standards organizations and governments .

Standardization of Materials is necessary and advantageous because - ( Answer ends here . ) 1. It ensures production of materials of uniform quality . 2. It becomes the basis of competition between producers to provide material of standard quality at lesser cost . 3. It ensures the user that the material used for desired purpose is of standard quality .

As per Indian Standard Code , What are the a) Chemical Requirements b) Physical Requirements of “ Ordinary Portland Cement , 33 Grade ” ? ( Answer continues )

( Answer continues ) Cement is a construction material . It can be of different types and different grades . Example - “ Ordinary Portland Cement , 33 Grade ” Answer -

( Answer continues ) For “ Ordinary Portland Cement , 33 Grade ” , the Indian Standard Code is IS 269 : 2013 . The code is made by Bureau of Indian Standards . IS 269 : 2013 , gives information about chemical requirements and physical requirements , which “ Ordinary Portland Cement , 33 Grade ” should fulfill when being manufactured .

( Answer continues ) A) Chemical Requirements 1) Ratio of percentage of lime to percentages of silica , alumina and iron oxide , when calculated by the formula - should be between 0.66 - 1.02 .

( Answer continues ) 2) Minimum value of ratio of percentage of alumina to that of iron oxide, should be 0.66 . 3) Maximum percentage of insoluble residue , by mass , should be 5 % . 4) Maximum percentage of magnesia , by mass , should be 6 % . 5) Maximum percentage of total sulphur content calculated as sulphur anhydride , by mass , should be 3.5 % .

( Answer continues ) 6) Maximum percentage of loss on ignition , by mass , should be 5 % . 7) Maximum percentage of chloride content , percent by mass , should be 0.1 % . 8) Percentage of alkali content , should be 0.05 .

( Answer continues ) 1) Minimum fineness of cement , should be , 225 m 2 / kg . 2) If Soundness of Cement is tested - a) By Le Chatelier method , then , Maximum soundness , should be , 10 mm . b) By Autoclave Test method , then , Maximum percentage of soundness , should be , 0.1 % . B) Physical Requirements

( Answer continues ) 3) Setting time of Cement Water Paste - a) Minimum Initial Setting Time , should be , 30 minutes . b) Maximum Final Setting Time , should be , 600 minutes or 10 hours .

( Answer ends here . ) 4) Compressive Strength of cubes made from cement mortar of ratio 1 : 3 and having area 5000 mm 2 , should be , as follows - a) After 72 ± 1 hour , the minimum compressive strength , should be , 16 MPa . b) After 168 ± 2 hours , the minimum compressive strength , should be , 22 MPa . c) After 672 ± 4 hours , the minimum compressive strength , should be , 33 MPa and the maximum compressive strength should be 48 MPa .

What is “ Codification of Materials ” ? ( Answer continues ) Answer - The process of assigning codes to materials is called codification of materials . A code can be made using symbols , numbers or alphabets .

( Answer ends here . ) Codification of materials is generally based on the nature and characteristics of materials . Codification of materials is advantageous as - 1. It enables easier and quick identification of materials and its characteristics . 2. The materials having similar characteristics can be easily classified and grouped . 3. It minimizes clerical work .

What is “ Shrinkage ” in Concrete ? ( Answer continues ) Answer - Shrinkage is the contraction in concrete that takes place even when no load is applied on it .

( Answer continues ) The ratio of change in volume of concrete due to shrinkage to the original volume of concrete is called Shrinkage Strain . Shrinkage Strain Change in volume of concrete due to Shrinkage = Original volume of concrete It is a ratio and has no unit .

( Answer continues ) This formula is used in estimating the shrinkage strain in concrete . If h = relative humidity in environment , expressed in decimal form , then Shrinkage Strain = 0.00125 ( 0.90 – h ) Schorer ‘s Formula -

Shrinkage in concrete increases with - ( Answer continues ) 1. Increase in water- cement ratio . 2. Decrease in humidity . 3. Decrease in temperature . ( Humidity is the amount of water vapour in the atmosphere . )

Types of Shrinkage - ( Answer continues ) 1. Plastic Shrinkage 2. Drying Shrinkage 3. Carbonation Shrinkage

Plastic Shrinkage - ( Answer continues ) It is the shrinkage in concrete caused due to hydration of cement . Plastic Shrinkage can result in surface cracking .

Drying Shrinkage - ( Answer continues ) It is the shrinkage in concrete that takes place after the concrete has set and hardened . Most of the drying shrinkage takes place in first few months , after the setting of concrete .

Moisture Movement - ( Answer continues ) It is the increase in volume of shrunken concrete when being immersed in water . This increase is actually the partly recovery from drying shrinkage .

Carbonation Shrinkage - ( Answer continues ) It is the shrinkage in concrete that takes place when carbon dioxide present in atmosphere reacts with calcium hydroxide present in concrete to form calcium carbonate . It is a very slow process .

( Answer continues ) Example of Cracks in Concrete due to Shrinkage

( Answer ends here . ) Example of Cracks in Concrete due to Shrinkage

What is “ Creep ” in Concrete ? ( Answer continues ) Answer - Creep is the deformation in concrete that takes place when it is continuously subjected to load for a long period of time .

Creep Resistance of concrete can be increased by - ( Answer ends here . ) 1. By using lower water- cement ratio . 2. By using aggregates having higher crushing strength . 3. By properly compacting and consolidating concrete and making it impermeable .

What is “ Light - Weight Concrete ” ? ( Answer continues ) Answer - Light - weight concrete is the concrete made with light - weight aggregates . It is a special type of concrete .

( Answer continues ) In light - weight concrete , large quantities of air entrainment is done . This is why it is also called Aerated concrete , Foamed Concrete or Cellular concrete . ( “ Air - Entrainment ” means intentional entrapment of air bubbles into concrete . )

( Answer continues ) 1) Expanded or Bloated - Clay 2) Expanded - Shale 3) Expanded - Slate 4) Exfoliated Vermiculite Different “ Light - weight Aggregates ” used in making light - weight concrete are -

( Answer continues ) 5) Sintered - Pulverized Fuel Ash 6) Foamed - Blast Furnace Slag 7) Pumice 8) Diatomite The term “ Pulverized ” means Powdered . The term “ Sinter ” means converting a powdered material into solid mass by heat and / or pressure .

( Answer continues ) Example of Expanded or Bloated - Clay The term “ Bloated ” means swollen with fluid or gas .

( Answer continues ) Example of Expanded - Shale

( Answer continues ) Example of Expanded - Slate

( Answer continues ) Example of Exfoliated - Vermiculite The term “ exfoliated ” means fragments having layers .

( Answer continues ) Example of Pumice

( Answer continues ) 1) Low Density and High Strength 2) High Thermal Insulation 3) Low Coefficient of Thermal Expansion 4) Excellent Fire Resistance 5) Inferior Sound Insulation As compared to ordinary concrete , Light - Weight Concrete has -

( Answer continues ) By using light - weight concrete , the dead load of the concrete structure can be reduced . This allows the structural designer to reduce the size of columns , footings and other load bearing elements .

( Answer continues ) Light - weight concrete is porous . The steel reinforcement embedded in it is more prone to corrosion as compared to ordinary concrete . Hence , special treatment of steel is required for protection against corrosion .

( Answer continues ) Light - weight concrete products can be easily - - Sawn and cut - Drilled and nailed - Repaired

( Answer continues ) Light - weight concrete can be used in - - Insulation of exterior walls of buildings . - Making precast floor and roof panels . - Making prefabricated concrete blocks . - Partition walls .

( Answer continues ) Example of “ Light - Weight Concrete ” Pores

( Answer continues ) Example of “ Light - Weight Concrete Block ”

( Answer continues ) Example of “ Light - Weight Concrete Blocks ”

( Answer continues ) Example of “ Light - Weight Concrete ”

( Answer ends here . ) Example of “ Light - Weight Concrete ”

What is the meaning of “ Material ” ? ( Answer continues ) Answer - Material can be defined as the matter from which a thing can be made .

Materials can be classified as - ( Answer ends here . ) 1. Metals 2. Polymers 3. Ceramics 4. Composites

What are “ Metals ” ? ( Answer continues ) Answer - Metal are solid materials . They are hard , shiny , malleable , ductile . Metals can be melted , that is , they are fusible . They have good electrical and thermal conductivity .

Metals can be classified as - ( Answer continues ) 1. Ferrous Metals 2. Non - Ferrous Metals

Ferrous Metals are the metals and alloys which contain iron . ( Answer continues ) Examples - Iron , Carbon Steel , Stainless Steel .

Non - Ferrous Metals are the metals and alloys which do not contain iron . ( Answer ends here . ) Examples - Aluminium , Copper , Magnesium , Titanium , Precious Metals .

What are “ Ceramics ” ? ( Answer continues ) Answer - Ceramic materials are inorganic , non - metallic materials made from compounds of a metal and a non metal . They are formed by the action of heat and subsequent cooling .

( Answer ends here . ) Ceramic materials are hard , heat - resistant , corrosion - resistant and brittle . Examples - Pottery , Bricks , Tiles , Glass , Cements .

What is “ Refractory ” ? ( Answer ends here . ) Answer - Refractory is a substance that is resistant to heat . Oxides of aluminium , silicon and magnesium are used in making refractory materials .

What is “ Composite Material ” ? ( Answer continues ) Answer - Composite is a material made from two or more constituent materials with significantly different physical or chemical properties . Composites have different characteristics from its constituents .

( Answer ends here . ) In composite materials , the individual constituents remain separate and distinct within the finished structure . Example - Concrete , Wood , Reinforced Cement Concrete , Fibre - reinforced Concrete .

What is “ Polymer ” ? ( Answer continues ) Answer - Polymer is a chemical compound that is made up of small molecules . These small molecules are arranged in a simple repeating structure to form a larger molecule .

Polymers can be classified as - ( Answer continues ) 1. Thermosetting Polymers 2. Thermoplastic Polymers

Thermosetting Polymer - ( Answer continues ) It is a polymer which can be heated and shaped only once . Example - Vulcanized Rubber

Thermoplastic Polymer - ( Answer ends here . ) It is a polymer which can be heated and shaped over and over again . Example - Nylon

As per Indian Standard Code , what is the standard test for concrete ? ( Answer continues ) Answer - The Indian Standard Code for Plain and Reinforced Concrete is IS 456 - 20 00 . According to this code , the standard test for concrete is Core Test .

Concrete Core Test - ( Answer continues ) Concrete Core Test is a destructive test . In this test , samples are taken out from concrete member by drilling and cutting .

Concrete Core Test Procedure - ( Answer continues ) This test requires minimum three samples from concrete member . 2. The samples are called cores and are cylindrical in shape . 3. The points from where cores are to be taken from concrete member is decided by engineer .

( Answer continues ) 4. The diameter of cores should be at least three times of the nominal maximum size of the aggregates used in making concrete . Generally , the diameter kept is 100 mm .

( Answer continues ) 5. The ratio of length of core and its diameter is kept 2 . This helps in calculating the depth up to which the drilling is to be done in concrete member so as to get required length of core .

( Answer continues ) 6. The cores in concrete member is usually cut by using an equipment . 7. The equipment consists of rotary cutting tool with diamond bits . 8. During the cutting process , the cutter in the equipment is lubricated with water .

( Answer continues ) 9. The holes formed due to removal of cores from concrete member is filled with dry , low shrinkage concrete and is properly rammed and compacted .

( Answer continues ) 10. The cores obtained from concrete member are trimmed and capped so as to obtain proper cylindrical shape . 11. The capping of cores is done by applying thin layer of mortar made with high alumina cement around the ends of cores .

( Answer continues ) 12. After this , the cores are immersed in water for at least 2 days . 13. After removal from water , the length of each core is measured and their mean diameter is calculated . 14. The mean diameter of core is calculated by measuring diameter at quarters and at midpoint along the core length and then taking average of it .

( Answer continues ) 15. After this , the compression test is done on cores by using suitable testing machine . 16. The rate of compression should be within the range 12 - 24 MPa /min . ( The cores should be tested within 7 days after they have been taken out from concrete member . )

( Answer continues ) 17. After obtaining the compressive strength of cores from testing , the equivalent cube strength of cores is calculated by using the following formula - Equivalent Cube Strength of Core = 1.25 x Compressive Strength of Core Obtained from Testing

( Answer continues ) 18. After this , average of equivalent cube strength of cores is calculated . 19. According to IS : 456 - 2000 , Concrete in the member ( from which cores are taken ) will be considered acceptable if it satisfies following two points -

( Answer continues ) a) The average equivalent cube strength of cores should be at least 85 % of compressive strength of cube made with same grade of concrete as used in making the member and of same age as that of cores . ( The Size of Cube should be 15 cm x 15 cm x 15 cm . )

( Answer continues ) b) The equivalent cube strength of individual core should be at least 75 % of compressive strength of cube made with same grade of concrete as was used in making the member and of same age as that of cores . ( The Size of Cube should be 15 cm x 15 cm x 15 cm . )

( Answer continues ) Equipment to extract “ Concrete Core ”

( Answer continues ) Example of “ Concrete Core ” Core

( Answer continues ) Example of “ Concrete Core ”

( Answer continues ) Example of “ Concrete Cores ”

( Answer continues ) “ Concrete Cores ” immersed in Water before Testing

( Answer ends here . ) Example of “ Compression Test on Concrete Core ”

What is “ Fresh Concrete ” ? ( Answer ends here . ) Answer - Fresh Concrete is the state of concrete from the time it is mixed to the time it sets .

What is “ Workability ” ? ( Answer continues ) Workability is the property of fresh concrete . Workability is the ease with which concrete can be worked . Answer -

Workability of Fresh Concrete means that - ( Answer continues ) 1. Concrete can be easily mixed . 2. It can be easily placed in forms or moulds . 3. It can be easily compacted and finished . Concrete mixture remains uniform and cohesive while mixing , placing , compacting and finishing .

( Answer continues ) For different types of placing conditions , there can be different types of workability of fresh concrete . These are as follows - 1. High Workability - This means fresh concrete has fluidity . 2. Medium Workability - This means fresh concrete is plastic .

( Answer continues ) 3. Low Workability - This means fresh concrete is stiff plastic . 4. Very Low Workability - This means fresh concrete is stiff .

( Answer continues ) 5. Extremely Low Workability - This means fresh concrete is very stiff . ( The term “ Stiff ” means “ rigid ” . ) ( The term “ Plastic ” means “ easy to be shaped or moulded ” . )

( Answer continues ) Workability of Fresh Concrete depends on - 1. Type of cement used in concrete . 2. Fineness of sand used in concrete. 3. Size and shape of coarse aggregates used in concrete .

( Answer continues ) 4. Proportion in which cement , sand and coarse aggregates are mixed . 5. Amount of water added in concrete . 6. Temperature at which concreting is to be done .

( Answer ends here . ) 7. Admixtures used in concrete . 8. Time ( Fresh Concrete loses its workability with passage of time and starts hardening . Hence , workability is time dependent . )

Properties of “ Hardened Concrete ”

( Answer continues ) The properties of “ Hardened Concrete ” are as follows - 1. Compressive Strength 2. Flexural Strength 3. Tensile Strength

( Answer continues ) 4. Shrinkage 5. Creep Resistance 6. Resistance against Chemicals 7. Impermeability 8. Fire resistance

( Answer ends here . ) 9. Thermal Conductivity 10. Thermal Diffusivity 11. Specific Heat 12. Coefficient of Thermal Expansion

What is the importance of properties of fresh and hardened concrete ? ( Answer continues ) There are various important properties of fresh and hardened concrete . For example - Workability , Compressive Strength , Permeability , Fire Resistance . Answer -

( Answer continues ) 1. Concrete is used in construction of various buildings , structures and pavements . 2. For different types of construction works and different types of placing conditions , it is necessary to use concrete having characteristics and strength suitable to those conditions .

( Answer continues ) 3. To assess whether the concrete is suitable for a particular construction work or not and to assess whether it will give desired performance or not , it is necessary to test concrete . 4. There are many tests which can be done on concrete before , during and after construction works .

( Answer continues ) 5. Since , various tests are based on one or the other properties of concrete , it is necessary and important to have knowledge of them . 6. Knowledge of properties and their tests not only helps in assessing concrete but also helps in deciding corrective measures required to achieve concrete of desired characteristics and strength .

( Answer continues ) For example - a. Compressive strength test on hardened concrete cubes is done to assess whether a particular proportion of concrete mixture is giving desired compressive strength or not . Compressive strength is an important property of hardened concrete .

( Answer continues ) For example - b. Flexural strength test on hardened concrete cubes is done when it is required to use concrete in construction of pavement slabs and air - field runways . Flexural strength is one of the properties of hardened concrete .

( Answer ends here . ) c. For concreting of shallow sections with vibrations , concrete needs to be stiff whereas for concreting of heavily reinforced sections with compaction by hand , concrete needs to be flowing . To assess whether fresh concrete is stiff or flowing for different placing conditions , workability tests are performed . Workability is the property of fresh concrete . For example -

What is “ Building Material ” ? ( Answer ends here. ) Building material is any material which is used for construction purposes . Answer -

List of Building Materials

Following are building materials - 1. Bricks 2. Cement 3. Sand 4. Stones , Grit , Kapachi 5. Water ( Answer continues )

6. Steel bars and steel meshes 7. Steel sections like I - sections , sheets , channel sections , angle sections 8. Wood and wood products 9. Industrial waste products like fly ash , blast furnace slag , silica fumes , red - mud aggregates ( Answer continues )

10. Agro - waste products like rice husk ash , groundnut husk ash , coconut pith , saw - dust ash , thatch , cow-dung Fibres like steel fibres , glass fibres , polypropylene fibres , carbon fibres , jute 12. Glass ( Answer continues )

13. Chemical admixtures like sugar , aluminium powder , calcium chloride , calcium lignosulphonates and others 14. Polymers products like polyvinyl chloride pipes , bakelite wires and switches 15. Aluminium products like doors , windows , street lighting poles ( Answer continues )

16. Light weight aggregates like pumice , bloated clay aggregates , expanded shale 17. Lime , gypsum , Plaster of Paris and products like Plaster of Paris boards 18. Putty , paints , varnishes , linseed oil , mineral turpentine , sandpapers , adhesives , resins like shellac ( Answer continues )

19. Tiles like vitrified tiles , marble tiles , Mangalore tiles 20. Cast - Iron pipes and fittings 21. Sanitation fixtures like Toilets , Bath - Tubs 22. Recycled concrete aggregates , Brick - dust ( Answer continues )

23. Asphalt 24. Acids like sulphuric acid 25. Mud 26. Gunny Bags 27. Ropes and cables ( Answer ends here. )

What is “ Fire Rating of Concrete ” ? ( Answer ends here . ) It is the time during which concrete continues to perform satisfactorily , when it is under the exposure of fire . Answer -

What is “ Fire Resistance ” of concrete ? ( Answer continues ) Fire resistance is an important property of concrete . Concrete is a fire - resistant material and is non - combustible . Answer -

( Answer continues ) As compared to ordinary concrete , Light - weight concrete made with aggregates such as - - Broken bricks - Limestone - Blast furnace slag has relatively higher fire - resistance .

Fire Resistance of concrete depends on following factors - ( Answer continues ) 1. Size of concrete member . 2. Type of aggregates used in concrete . 3. Type of reinforcing steel embedded in concrete and its positioning . 4. Cover provided to reinforcement .

Behaviour of Concrete under Fire - ( Answer continues ) 1. Concrete has good resistance against fire . 2. It has low thermal conductivity . 3. It does not emit toxic fumes , when exposed to fire .

( Answer continues ) 4. When concrete is exposed to fire for a long period of time or when the rise in temperature is very high then the moisture present in it gets converted into steam . 5. The steam exerts expansion pressure on concrete member .

( Answer ends here . ) 6. Continuous exposure of fire for long period of time results in loss of strength of concrete , deformation and spalling . ( “ Spalling ” means breaking down of concrete into small pieces . )

What is the meaning of “ Structure ” of solid ? ( Answer ends here . ) The type , amount , size , shape , and distribution of phases present in a solid constitute its structure . Answer -

What is the meaning of “ Microstructure ” of material ? ( Answer ends here . ) Microstructure is the fine structure of a material , which can be made visible and examined with a microscope . The microscope to be used , should be , above 25x magnification . Answer -

How materials are analyzed at micro - structure level ? ( Answer continues ) The microstructure of materials can be analyzed by many instruments , some of them are - 1. Optical Microscope 2. Scanning Electron Microscope Answer -

( Answer continues ) 3. Transmission Electron Microscope 4. Field Ion Microscope 5. Scanning Tunneling Microscope 6. Scanning Probe Microscopy 7. Atomic Force Microscope

( Answer ends here . ) 8. X - ray Diffraction Topography 9. Secondary Ion Mass Spectrometry 10. Mass Spectrometry 11. Terahertz Spectroscopy

Understanding Microstructure of Steel

( Answer continues ) Steel is an alloy of Iron and Carbon . The carbon content in steel may vary from 0.002 % to 2.1 % by weight . Other elements like manganese , nickel , chromium , tungsten , molybdenum , titanium , vanadium , cobalt may also be alloyed into steel , so as to achieve desired properties .

Microstructure of Steel - ( Answer continues ) 1. Ferrite 2. Austenite 3. Cementite 4. Pearlite 5. Martensite Steel consists of following constituents -

Ferrite - ( Answer continues ) 1. It is also known as “ Alpha Iron ” . 2. It is a solid solution with limited amounts of carbon in iron . 3. It has body - centered cubic ( B.C.C. ) crystal structure .

( Answer continues ) 4. The magnetic properties in steel and cast iron is due to the presence of B.C.C. crystal structure of ferrite .

( Answer continues ) Body - centered cubic crystal structure looks like this -

Austenite - ( Answer continues ) 1. It is also known as “ Gamma - Phase Iron ” . 2. Austenite is a solid solution of carbon in a non - magnetic form of iron . 3. It exists at temperature above 912 o C . 4. It has face - centered cubic ( F.C.C. ) crystal structure .

( Answer continues ) 5. As compared to ferrite , austenite can dissolve relatively more amount of carbon . - The process of heating of iron or steel or iron - based metal at high temperature which results in conversion of ferrite into austenite is called Austenitization .

( Answer continues ) Face - centered cubic crystal structure looks like this -

Cementite - ( Answer continues ) 1. It is also known as “ Iron Carbide ” . 2. Chemical Formula is “ Fe 3 C ” . 3. It is hard and brittle material . 4. It has orthorhombic crystal structure .

( Answer continues ) 5. Cementite is formed either - - From austenite during cooling . or - From martensite during tempering . ( The process of destroying martensite by heating steel is termed as tempering . )

Pearlite - ( Answer continues ) 1. It is a two - phased layered structure . 2. It is composed of alternating layers of ferrite and cementite . 3. It is formed when iron- carbon alloy is slowly cooled below 727 o C . 4. Ductility in steel is due to pearlite .

Martensite - ( Answer continues ) 1. Martensite is formed when austenite is rapidly cooled . 2. The process of rapidly cooling is termed as quenching . 3. The cooling is done at such a high rate that carbon atoms do not have time to diffuse out of the crystal structure of austenite in large enough quantities to form cementite .

( Answer ends here . ) 4. It has body - centered tetragonal crystal structure which is supersaturated with carbon . 5. Martensite makes steel very hard .

Understanding Microstructure of Concrete

Microstructure of Concrete - ( Answer continues ) 1. Hydrated Cement Paste 2. Aggregate 3. Transition zone between hydrated cement paste and aggregate Concrete consists of three phases -

Hydrated Cement Paste Phase - ( Answer continues ) 1. This phase consists of following solids in itself - - Calcium Silicate Hydrate - Calcium Hydroxide - Calcium Sulphoaluminates - Unhydrated Cement Particles

( Answer continues ) Calcium Silicate Hydrate - This solid is about 50 % to 60 % of total volume of solids present in hydrated cement paste . - The particles of calcium silicate hydrate are bonded together by Van der Waals forces .

( Answer continues ) Calcium Hydroxide - This solid is about 20 % to 25 % of total volume of solids present in hydrated cement paste . - This solid is soluble in water and may have adverse effects on chemical durability of concrete .

( Answer continues ) Calcium Sulphoaluminates - This solid is about 15 % to 20 % of total volume of solids present in hydrated cement paste .

( Answer continues ) Unhydrated Cement Particles - Some amount of unhydrated cement particles are also found in hydrated cement paste . - The amount of unhydrated cement depends on their particle size .

( Answer continues ) 2. The hydrated cement paste phase consists of following types of voids - - Voids in internal layers of calcium silicate hydrate - Capillary Voids - Air Voids

( Answer continues ) Capillary Voids - Capillary voids are voids which are not filled by the solid components of the hydraulic cement paste . - These are irregular in shape .

( Answer continues ) Air Voids - These are voids occupied by air in hydraulic cement paste . - These are spherical in shape .

Aggregate Phase - ( Answer continues ) 1. The aggregate phase is predominantly responsible for the density , strength , and dimensional stability of concrete . 2. The properties of concrete depend on type of aggregates used , its size , shape , volume and distribution of pores in it .

Transition Zone - ( Answer continues ) 1. It is a interfacial region between the particles of coarse aggregate and hydrated cement paste . 2. It exists as a thin shell or cover around large aggregates . 3. The thickness of thin shell may range from 10 μm to 50 μm .

( Answer continues ) 3. The transition zone is generally weaker than the aggregate phase and the hydrated cement paste phase . 4. It limits the strength of concrete .

Cracks - ( Answer continues ) There can be three types of cracks – 1. Bond Cracks These are formed at the interface of mortar and aggregate . 2. Mortar Cracks These are formed through the mortar .

( Answer continues ) 3. Aggregate Cracks These are formed through aggregates . Lesser the voids and cracks in concrete , higher will be its strength and durability .

( Answer ends here . ) The microstructure of concrete is said to be - - Heterogeneous as it is diverse in its contents . - Dynamic as it changes with temperature , environmental humidity and time .

What are “ Thermal Properties of Concrete ” ? ( Answer ends here . ) The thermal properties of concrete are - - Thermal Conductivity - Specific Heat - Coefficient of Thermal Expansion - Thermal Diffusivity Answer -

What is “ Thermal Conductivity ” ? ( Answer ends here . ) It is the quantity of heat that passes in unit time through unit area of a substance whose thickness is unity , when its opposite faces differ in temperature by one degree. It’s unit is watt per metre per kelvin , W·m -1 ·K -1 . Answer -

What is “ Specific Heat ” ? ( Answer ends here . ) It is the quantity of heat needed to raise the temperature of a unit mass of a material by one degree. It’s unit is Joule per kilogram per kelvin , J / kg·K . Answer -

What is “ Coefficient of Thermal Expansion ” ? ( Answer ends here . ) It is the change in unit length per degree of temperature change . It’s unit is per kelvin , K -1 . Answer -

What is “ Thermal Diffusivity ” ? ( Answer ends here . ) It is calculated by following formula - Answer - Thermal Diffusivity Thermal Conductivity Specific Heat Density = X It’s unit is square metres per second , m 2 /s .

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