Concrete Technology ZR (Code : BTCVC603) Semester VI - Civil Engineering (Dr. Babasaheb Ambedkar Technological University) tA Swapnil B. Gorade Nishant A. Upadhye Ph.D. Pursuing, M.E. (Conservative Management), LMICI, BE. Civil), Assistant Professor, ‘Lecturer in Bharati Vidyapeeth’s, Department of Civil Engineering, Jawaharlal Nehru Institute of Technology, Pune. Pimpri Chinchwad College of Engineering, Maharashtra, India. ‘igs, Pune -411044, ‘Maharashtra, India. A 7 BTERMA Price @400/- YF Nitieortons UT (Book Coie: BTEMA)Preface Dear Students, We are extremely happy to present the book on “Concrete Technology” for you. We have divided the subject into small chapters so that the topics can be arranged and understood properly. The topics within the chapters have been arranged in a proper sequence to ensure smooth flow of the subject. We present this book in the loving memory of Late Shri Pradeepji Lunawat, our source of inspiration and a strong foundation of “TechKnowledge Publications”. He will always be remembered in our heart and motivate us to achieve our new milestone. We are thankful to Mr. Shital Bhandari, Shri. Arunoday Kumar and Shri. Chandroday Kumar for the encouragement and support that they have extended. We are also thankful to staff members of ‘TechKnowledge Publications for their efforts to make this book as good as it is. We have jointly made every possible effort to eliminate all the errors in this book. However if you find any, please let us know, because that will help us to improve further. We are also thankful to our family members and friends for patience and encouragement. ~ Authors goa (Gook Code: BTES4A)Syllabus Course Code Course Name Credits BICVC603 Concrete Technology 2 Outcomes : On completion of the course, the students will be able to 1. Understand the various types and properties of ingredients of concrete. 2. Understand effect of admixtures on the behavior of the fresh and hardened concrete. 3. Formulate concrete design mix for various grades of concrete. Course Contents Module 1 : Materials for Concrete : Cement, Manufacturing Process, Physical Properties, Hydration of Cement, hydration products, Chemical Compounds in Cement, Types of Cement, Aggregates : Classification of aggregates, Physical Properties, Bulking of Sand, Mechanical Properties, Water: Specifications of Water to be used For Concrete (Refer Chapter 1) Module 2: Properties of Fresh Concrete : Types of Batching, Mixing, Transportation, Placing Including Pumping and Compaction Techniques for Good Quality Concrete, Workability, Factors affecting workability, Methods of Measuring Workabilty, Segregation and Bleeding, setting time, Curing of Concrete, Types of curing, ‘Temperature Effects on Fresh Concrete. (Refer Chapter 2) Module 3: ‘Admixtures In Concrete : Types, Plasticizers and Super-plasticizers and their Effects On Workabilty, Air Entraining Agents,, Accelerators, Retarders, Pozzolanic Admixtures, Green concrete, Bonding Admixtures, Damp-Proofing Admixtures, Construction Chemicals. (Refer Chapter 3) Module 4: Desired Properties of Concrete; Strength, Durability and Im-permeability, Characteristic Strength, Compressive, Tensile and Flexure of Concrete, Bond Strength, Tests on Concrete, Modulus of Elasticity, Effect of WIC Ratio and admixtures on Strength, Types of concrete, High Strength and High Performance Conerete. (Refer Chapter 4) ‘(Book Code: BTES4A)Module 5 : Creep and Shrinkage of Concrete, Significance, Types of Shrinkage and Their Control, Factors Affecting Creep. Durability of Concrete : Minimum and Maximum Cement Content, Strength and Durability Relationship, Exposure to Different Conditions, Factors Contributing to Cracks in Concrete, Sulphate ‘Attack, Alkali Aggregate Reaction (AAR), factors affecting on AAR, Deteriorating effects of AAR, Chioride Attack, Corrosion of Stee! (Chloride Induced) (Refer Chapter 5) Module 6: Concrete Mix Design, Nominal Mix Concrete, Factors Governing Mix Design, Methods Of Expressing Proportions, Trial Mixes, Acceptance Criteria, Factors Causing Variations, Field Control, Statistical Quality Control, Quality Measurement in Concrete Construction., Non-destructive Testing of Concrete (Refer Chapter 6) gua ‘(Book Code : BTES4A)WF _concrote Technology (BATU) Table of Content Chapter 1: Introduction to Concrete and Various Ingredients of Concrete 4-1 101-28 Syllabus : (@) Materials for concrete : Cement, Manufacturing process, } Physical properties. Hydration of cement, Hydration products, ‘Chemical compounds in cement, Types of coment. ‘Aggregata: Ciassication of aggregates, Physical Properties, Biking of sand, Mecharicl properties Water : Speciation of water to be used foe concrete 1a 12 13 134 132 133 14 tat 142 143 144 145 15 154 152 153 18 161 162 ww ara 172 ‘Manutacturing Process. “The Basic Raw Matera. Gonoral Manufacturing Process of Cement. Consistoncy Test. Sotting Time (1S 4081 Part 5) .on.nn ‘Sounchess Test (I$ 4031, Part 3) Compressive Strength Tast (IS 4031 Part 6)... Hydration of Cement. Definition, ‘Chemical Compounds in Cement... or) Bogue's Compound. 140 Basic Propertios of Bogue’s Compound. ene 10 Types of Cement. 11 Ordinary Portiand Cement ((8:260, 6112 and 12269)... Rapid Hardening Portland Cement (IS 8041) 173 174 175 178 177 178 179 1.710 18 184 182 1821 1.822 1923 184 185 196 187 19 1944 1912 192 193 194 195 195.1 1952 Low Heat Portand Cement (IS 12600)... ‘Suiphate Resisting Cement (IS12330) Quick Set Coment enn Pozzolana Portiand Camont (1S 1489) Blast Fumace Siag Cement (IS 445). White Cement (1S 8042). ‘Air Entraining Cement... ‘According to Surface Textura CO Physical Properties of Aggrogatos... Bung of Sand enon Impurities in San Coa Aggro an Mochanical Propet of Agregstes, ‘Shape Test of Coarse Aggregate Flakinass Tost of Coarse Aggregate: tongation Test of Coarie Aggrogato. Dolterious Materials... ‘Soundnoss of Agaregato. Porosity of AGGFE GRID nnn ‘Siove Analysis — Fineness and Gradation Test. Determination of Fineness Modulus. Grading of Aggregate¥ Concrete Technology (BATU 1.9.6 Artifical and Rocyclod Aggrogato 125 19.61 Atal Aggregate. 128 1.9.6.2 Recycted Aggregate . 127 140 Water. 127 1401 Quality of Water for Mixing and Cun nen 27 1902 Test on Wal een 128 Module Xt, Chapter 2: Production and Properties of Fresh Concrete 241 to 246 Syflabue : (4) Properties of fresh concrete : Typos of batching, Mixing, ‘Transportation, Placing including pumping and compaction techniques for good quality concrete, Workabitty, Factors affecting workability, Methods of messuring workabilly ‘Segregation and Bleeding, Setting tine, Curing of concrete, Types of curing, Temperature effects on fresh concrete. 2a 224 223 23 2a4 232 24 25 268 27 274 28 281 Propertos of Fresh Coneoto 24 “Types of Batching ~ a Volume Batting er a ee 2A Comparison between Weight Batching and Volume Batching... : 22 Maing of Concrete. Diferont Typ68 Of MIE ene 22 ‘Comparison between Titing and Non-Titing type of Mixer. eeemeeiza “Transportaton of Concrete. 25 Placing of Concrete oon BB ‘Compaction Techniques for Good uty of Cnet. Wirkabity.. 26 Fectors Atlecting Workabity cen BB Motnods of Measuring Workabity ‘Stump Cone Test : 2B2 283 284 285 29 2.10 an 2a2 224 2122 Table of Content Compaction Factor Test ann IO \Vee-Bee Compaction Test... Flow Table Tost eB Marsh COn@ Tet ne AB Segre gAtON ea Bleeding : 7 B13 Sotting Time (1$ 4031 Pat 5). Curing of Concrete. so BAS (Cuting Method. “Temperature Etfect on Fresh Concroto. ule Tir Chapter 3: Concrete Admixtures 3-1 103.09 OO) Syllabus = ‘Admixtures. In Concrete : Types, plasticizers, super- plasticizers and their etlects on workability, air entaining agents, acceleraors,retarders, pozzolanic admixtures, groan concrete, bonding admixtures, damp-prooting admixtures, construction materials. aa 32 aa 3a4 332 333 334 335 336 337 338 339 33.10 Adis. so Function of Adm 34 Types. Admit. Chemical Admini... Plastcizers (water reducing agent). ‘Super Piasticizers, 1 Effecton Workabilty.... ‘ir Entraining Admidures. ‘Accelerators (Accelerating Agont) 8 Footarders(Rotarding Agents)... 34 Mineral or Pozzolanic Admistures an 84 ‘Aatitciat Pozzotana ASMA nner 9S Fly ASh (IS 3812) enn SE ‘Ground Granuiated Blast Fumace Siag (GBS) 28 Por 1S 12009 neces 4S Silica Fume. eeeWF _Concrete Technology (BATU) 38.11 lice Husk Ash (RHA)... 34, Green Concrete... 35 Bonding Admixtures. 36 Damp Proofing Admixtures. 37 Chapter 4: Properties and Test on Harden Concrete ‘Syllabus = Desired properties of concrete, Strength, Durability and Im- ‘permeability, Characteristes strength, Compressive, Tonsio and flexure of concrete, Bond strength, Test on concrete, Maduius of lastcity, Etfect of WIC ratio and admistures on strength, Types cof concrete, High strength and High performance concrete. 45 46 464 482 483 484 485 406 487 468 Table of Content ‘Modulus of Elasticity of Concrete 410 ‘Types of Concrete. 411 Light Weight Concrete. an CColuiar or Foam Light Weight Aerated Concrete... 4-12 Polymer Concrete... aig Fiber Reinforced Coverate (FRC). ata High Density Concrete an Solt Compacting Concrete... ve AAS High strength Concrete en AB High Performance Concrete. Creep, Shrinkage and Durability of 4.1 Introduction to Proportes of Hardon Concrete. 41.1 Durailty of Concrete, 41.2 im-permeabilty 41.3 Compressive Strong. 42 Characteristic Strength of Concrete... 43 Factors Affecting Strength of Concrete.. 431 Effectot Water Cement Rati, 432 — GelSpace Ratio... 43.3 Aggregate - Cement Ratio and Bond Strength. 43.4 Aggregate Size, Shape and Grading, 435. Effectof admixture type and dosage. 438 Effectot Ago, Curing and Temperature of Concrete (Maturity of concrete) 44 Tests on Concrete... 44.1 Compressive Strength Test. 44.1.1 Procedure of Compression Test on Cubes. 442 Tensile Strength nn 4421 Flexural Tensilo Test Procodure 44.23 Indirect Tensile Tost or Spit Tensile Test 44.3 Relation Between Tensile and Compressive Strength nnn 444 Microcracking, Bond Failure and Stress-Strain FRlatonship in Concrete £ & presses Concrete 51 to 5-12 Syllabus : (@) Creep and shiinkage of concrete, Signiicance, Types of shrinkage and their contol, Factors affecting creep. (©) Durability of concrete : Minimum and maximum coment content, Strength and durability Relationship, Exposure to diferent conditions, factors. contributing to cracks in concrete, sulphate attack, alkali aggregate reaction (AAR), Factors affecting on AAR, deteriorating effects of AAR, coride attack, corrosion of steel (chloride induced). 51 Creepin Concrete. A 52 Shrinkage in Concrete... 52 B21 Types of Stnkage oan ennnno 52 53 Minimum and Maximum Coment Content. 54 54 Strength and Dutabilty Relationship nn 5A1 Minimum Grades of Concrete for Different Exposure. 55 Exposure to Dilerent Condition. 56 Factors Contbuting to Cracks in ConcrB10 none 55 57 Sulphate Attack. = : 59 57-1 Sulphate Attack can be Control by Following Ways. 58 Akal Aggregate Fleaction (AAR). 510 5.8.1 Factors Affecting the AAR Reaction 510 82 Deterorating Ettects of AAR... nOConcrete Technology (BATU) 583° Controlof AAR... 510 59 Chloride Attack... sen A 5.40 Corrosion of Reinforcement (Stee). ‘Module VE Chapter 6:_Concrete Mix Design and NDT_ 6-1 to 6-21 ‘Syllabus = ‘Concrete Mix Design : Nominal mix concrete, Factors governing ‘mix design, methods of expressing proportions, Trial mixes, ‘Acceptance ciiteria, Factors causing variations, Field control, Statistical quality control, Qualtly measurement in concrete construction, Non destructive testing of concrete. 61 62 63 631 632 633 eat 642 643 64a 45 64s 65 68 6st 652 653 664 67 7a 672 672 Introduction 64 Objectives of Mix Design... a) Types of Mixes... = Nominal Mix... 64 ‘Standard Mix. 62 Design Mix- Most Conect Approach... ez Factors infuancng the Mix Design Proportion of Concrete... roe 2 Grade of Concrete see 6B “Type of Cement. 6s Maximum Nominal Size of Aggregate. a 68 Grading of Combined Aggregates... reer 8 ‘Maximum WIC Ratio... 63 Workabilty nn 63 Methods of Expressing Proportions... 63 Statistical Quality Control of Concrete. os Mean Strength... es Variance... os ‘Standard Deviation (SD) oe 65 ‘Cootciont of Variance. ~ 65 “rial Mices and Factors Causing Variations 6s “rial Mis in Mic design 6s Factors Causing Variations in Trial Mixes. 6 ‘Acceptance Crteria for Strength 6s 68 ea: saz sas sas 585 6a6 6a7 ese 589 69 6a: 692 610 ent ena ez 612 e121 er21a 1212 e122 e121 61222 e223 e124 6.123 61231 e124 e244 e242 6125 Table of Content Guidelines to Improve Mix 67 Grade Designation. Sey “Type of Coment neem oF ‘Maximum Nominal Size of Aggregate 67 Minimum Cement Content. oe ‘Maximum Water Coment Ratio. 68 Workabilty = 68 Exposure Condo nena Method of Concrete PIACIN nner Degree of Suspension and Type of Aggregate a... 69 Methods of Concrete Mix Design 69 1S Code Mothod of Mix Design... sO ‘Step by Stop Procedure for Concrote Mix by IS. Y0262 «2008. ns) ‘Quality Measurement in Concrete Construction. "Non Destructive Testing Objectives of NOT.. ‘Advantages and Disadvantages of NDT nn 648 Various NDT Tosts. - 616 Rebound Hammer Test 516 ‘Assessment Critora for UPV as per (08 13911 Pa 2) enn 618 Factor Mtecting UPV on 1B Applications of Ultrasonic Pulse Velocity 618 Pullout Tost. 618 ‘Advantages and Disadvantagos of Tost oe 19 Impact Echo Test. e19 PROC U ne er) ‘Advantages and Appicaons wn 8 20 Rebar Locator =Introduction to Concrete and Various Ingredients of Concrete ‘Syllabus : (©) Water : Specification of water to be used foe concrete (@) Materials for concrete : Cement, Manufacturing process, Physical properties, Hydration of cement, Hydration Products, Chemical compounds in coment, Types of cement. (b) Aggregate : Classification of aggregates, Physical properties, Bulking of sand, Mechanical properties 1.1 Introduction = Concrete is the most widely used man made construction material and most utilized substance after ‘water in the world. ~ Concrete is made by mixing coarse aggregate (crushed or uncrushed stone), fine aggregate (natural or crushed sand), cementing material (OPC), water and sometimes admixtures. — Cement and water are active components in concrete and provides binder for aggregates. I is also expensive and efforts need to be minimizing it content. Whereas coarse aggregate, sand are the inactive materials called inert in concrete. — Concrete is multiphase material of aggregate, sand, cement water and air as shown below Table 1.1.1 by volume of concrete Table 1.1.1 “Water. | Sand, '}, “Coarse 71-15% | 14-21% | 24-30% | 31-50% | 0.5-2% ~The terminology of concrete is such that we have to start study from its ingredients, Cement particles. suspended in | Cement + water water = Paste ‘Sand particles suspended in | Paste +sand paste = Mortar Coarse aggregate suspended in | Mortar +CA. mortar = Concrete 1.2 __ Materials for Concrete : Cement — In roman times lime and volcanic ash were used as construction materials. — Although many builders, bricklayers worked on investigation of binding material at that time, Joseph ‘Aspdin was the first who took the patent of “Portland Cement” in 1824. The fancy name was given because the harden cement looked very much like to the natural stone occurring at Portland in England. When this ‘cement mixed with water, it hardens so we call it as hydraulic cement also. ~ After Indian independence, through five years plan the ‘manufacturing of cement increased and now India is the 2"4 largest producer of cement after china. 13 1.3.1. The Basic Raw Materials facturing Process 1. Caleareous material : Containing calcium carbonate (CaCO) obtain from limestone, chalk. Calcareous ‘material are those materials in which calcium or lime (CaCO; > 75%) content is major.W Concrete Technology (BATU) ” 1-2 __ Introduction to Concrete & Various ingredients of Conc. 2. Argillaceous material : Containing silica (SiO,) obtained from clay, sand, shale and alumina (Al,03) obtain from clay, bauxite etc. Argillaceous materials are those materials in which lime or calcium is less (CaCO < 40%) and alumina is ‘major constituent. Hence the basic raw materials of Portland cement mainly consist of lime (CaO), silica (SiO,), alumina (Al,O3) and iron e,0)). o 1.3.2. General Manufacturing Process of Cement (@ Firstly Calcareous and Argillaceous materials aré crushed and then mixed in appropriate proportion. (©) The raw material is fine ground so that it can easily blend with each other. This material then sent to pre-heater to remove moisture. (©) From pre-heater dry raw mix fed into the rotary kiln at higher end as fuel source is at lower end. ‘The temperature at hhigher end of kiln is 450°C and increases step by step to 1500°C as shown in Fig. 1.3.1 Exhaust gases Raw feed Limestone Ita formation Free water 2eomposes C28 Clay ke of tna oration aE zone Gas Temp. 450 800 1200 1950 1850°C Feed Temp. 50 600 1000 1350 4450°¢ Fig. 1.3.1 @ The rotary kiln is long steet cylinder with refractory brick. It is inclined with few degrees to horizontal such that raw ‘material move from higher end to lower end. Now a days, In India we use dry process so the length of kiln is about 30 im. The material inside the kiln then pa ‘material called clinker. ly melted due to high temperature called fusion and converts into granular (©) The clinker is then cooled from temp 1450°C to 500°C and then to room'temperature and stored. The clinker is then ground to very fine powder with addition of 3-5% gypsum (CaSO,) in ball or grinding mill. Gypsum control the flash setting of cement. (©The fine ground powder called ordinary Portland cement (OPC) sent to packing plant.W_Concrete Technology (BATU) 1-3 __{ntroduction to Concrete & Various Ingredients of Cone. Fig. 1.3.2: Cement manufacturing process 1.3.3. The Common Two Processes Used for | [7 Be = eas Manufacturing of Cement Dry Method: ‘Wet Method x A] || 3. | Fuet required for | Fuel requirement is very pau Weemettod! ? kiln burning is one | high for kiln burning to 1. | In this method lime | In this method limestone fourth of wet | remove moisture from ‘stone and clay are | and clay crushed first then process. slurry. ‘ground separately | mixed and again sent to 4 | Equipments ‘Equipment’s like no. of and then mixed | vertical ball mill, at this . | required are less | preheaters are more and together to obtain a | point water is added to and smaller Tine | sizeof kiln also more. fine blend mix. | obtain a blended mix of limited preheater ‘This material sent | very fine material called ‘and kiln size. to preheater to | slurry. 5. | Economical, Less efficient, costly so remove amy i efficient and | now a days this method moisture. environment not preferred. 2. | In this method | In this method length of fiddly 30 now a length of the kiln is | kiln is more, as above 100 days we are using less (30m) as | mas most of the length is diy process, almost all moisture | spent to driven out | |] ~ as apy ae ;. | High output, low | Low output, oe power burning process is ea ete atiee — consumption. blend possible. ¥WB _Concrete Technology (BATU) 1.4 Field Tests and Physical Properties — To. know the quality of cement on construction site following field tests are perform. 1. Colour test : Typical colour of OPC should be greenish gray. 2 Presence of lumps : Open the bag and observe the Jumps due to moisture from atmosphere, cement develops lumps and such cement should be rejected. 3. Feel test : This is performed by feeling the cement with fingers. It should feel smooth when rubbed in between fingers. When hand put inside the bag, it should fee! cool 4. Float test : This test consists of throwing some handful ‘of cement on the surface of water in a bucket. The ‘cement should float for sometime before sinking. 5. Setting test : Thick paste is prepared by adding little quantity of water and pat a cake on glass plate. Put this cake under water for 24 hours. The cake should not Joss its shape and attain some strength 6. Packing date : The cement should be used before 90 days from the date of packed. Physical properties of cement construction point of view are as follows important from (@ Fineness (b) Standard consistency (©) Initial and Final setting times (@ Compressive strength and (©) Soundness. 1.4.1 Fineness of Cement Fineness It is a measure of the size of the cement particles. It is expressed in term of sieve size and also as specific surface (in cm*/gm, m/kg) (A) Sieve Test - (1S : 4031) 1. Weight 100 gm of cement and take it on standard 1S, sieve no. 9 (sieve size of 90 microns). 14 Introduction to Concrete & Various Ingredients of Cone. 2. Break down the lumps in the sample with finger. 3. Sieve the sample for 15 minutes giving circular and vertical motion. If possible use mechanical sieve shaker. 4. Weight the residue left on the sieve, and calculate the percentage residue retain on sieve. 5. ‘The residue for cement sample on 90 micron IS sieve after sieving should not exceed following percentage — (2) Ordinary Portiand Cement = 10% (b) Rapid Hardening Cement = 54% (© Low Heat Cement = 5% (®) Air Permeability Test (of specific surface) ('S 4031 part 2) = Method used to measure fineness of cement and based (on the principle of passage of air through a bed of ‘cement, The time is measured and is related to the fineness of cement in terms of specific surface area. 1. Knowing the density of cement the weight required to make a cement bed of porosity of 0.475 can be calculated, This quantity of cement is placed in the permeability cell as shown. Fig. 1.4.1 : Blain ir permeability apparatusW_Concrete Technology (BATU) 15 Introduction to Concrete & Various Ingredients of Conc. 3 Slowly pass dry air through the cement best at a constant velocity. Read the difference in manometer limbs (hy). Read difference in flow meter limbs (h,). Repeat the readings till steady state achieved. Spee sures as => [PE Where — S,= Sp. Surface in em’/gm thy, hy are in em, K = Constant of equipment. ‘As per IS the specific surface should not be less than. (@) Onlinary Portland Cement’ - not less than 2250 emP/gm. (b)_ Rapid Hardening Cement - 3250 om"/gm. (©) Low Heat Cement - 3200 cm"/gm. More the fine cement, more is the Sp. Surface area and Jess residue on 90 um sieve, which is more reactive with Initial set need ‘1mm square water. For More rapid strength development fine cement required. Coarser cement causes less strength and durability. 1.42 Consistency Test — Consistency is a measure of the workability of the coment paste, how easy or difficult it is to work with paste. - Standard consistency is that percentage of water (by weight of cement) required to produce a paste of certain predetermined consistency. Standard consistency is defined as that consistency which will allow Vicat plunger having 10mm diameter and 50 mm length to penetrate to a depth of 33 to 35 mm from top (or 5 to 7 mm from bottom of mould) ‘of the mould when tested. <5 mm: Final soting necdio ‘10mm Plunger for measuring ‘normal consistency Fig. 1.4.2: Vieat apparatus for consistency and setting timeW__Concrote Technology (BATU)- Standard consistency test procedure 1. Take 400 gm of cement and prepare a paste with mown weight of water (say about 25% by weight of cement). 2. Fill the paste in Vicat mould within 3 t0 5 minutes, and level the top surface. 3. Shake the mould to expel the air bubbles from cement paste. 4, Attach the plunger at bottom of the sliding rod. Adjust the plunger just touches the top surface of paste and release it to penetrate in the paste. 5. Measure the penetration on scale it should be 33 to 35 mm from top to mould. If it is less increase the water percentage to make fresh paste and repeat the same, till it shows 33 to 35 mm reading and record it as, ‘a standard consistency (P) of the given cement. 1.4.3 Setting Time (IS 4031 Part 5) ~ Setting time refers to gradual hardening of cement paste, , ~ Cement having two setting time ~ Initial and Final. — Initial setting Time ~ It isthe time elapsed between the ‘moment when water is added to the cement, tothe time ‘when paste starts losing its plasticity. Final setting Time ~ It is the time elapsed between the moment when water is added to thie cement, to the moment when the paste has completely lost its plasticity. — As per IS code the setting time of cement by Vicat apparatus method shall confirm to (@) Initial setting time should not less than 30 minutes. (©) Final setting time not more than 600 minutes ~ Detail procedure to find out setting time is discussed in unit 2 1.4.4 Soundness Test (IS 4031, Part 3) _Itis essential that cement in concrete shall not undergo any volume change after setting, = When cement content excess free lime, or is 1-6 __ Introduction to Concrete & Various ingredients of Conc. insufficiently burnt during manufacture, it is remain luncombined and be over burt in kiln, Mortar prepared from such cement is liable to expand after setting. = Other than excess free lime, crystalline magnesia, sulphates in cement also causes change in volume ‘known as unsoundness of cement. = Such cements may develop cracks and will cause disruption of harden concrete. The soundness test ensure that the cement does not show excessive thermal expansion and if shows, it can be rejected. = LcChatelier’s apparatus consists of brass mould, cut along its height with two pointers welded along each side of cut as shown in Fig. 14.3 used for soundness Fig.1.4.3: LeChatelier’s Appratus Procedure L. Take 100 gm of cement, mixed with water (0.78 times, Of standard consistancy) and prepare a paste for about 3 min. 2. Fill the paste in Le-Chatelier’s mould and kept glass plates at top and bottom in water at 27°C for 24 hours ‘with small weight on top glass plate. 3. Measure the distance between two pointer and mould is, submerged in boiling water for 3 hours. 4. Remove the mould after 3 hrs and allow to cool and again measure the distance between two pointers. 5. The difference between the two distances should not be more than 10 mm for OPC, Rapid hardening and low heat cement, then the cement is said to be unsound. +WB _Concrete Technology (BATU) 1-7___Introduction to Concrete & Various Ingredients of Conc. 1.45 Compressive Strength Test (IS 4031 | Tabie. 1.4.1 : Physical Characteristics of some cements Part 6) z r s — Compressive strength is the most important parametér {to compare one cement with other. — Wenever use only cement paste in construction, which shows shrinkage and subsequent cracking, Hence for standardisation of test we use standard sand with fix standard proportion. ~The compressive strength of cement is determine from cubes of 7.06 x 7.06 Xx 7.06 mm (of face area 50 em?) ‘made with one part of cement and three part of standard sand by weight and prepared, cured and tested after 3 and 7 days. Where P is the standard consistency of the cement. ¢eninimum) 00min | 30 600 FST, (maximum) 3. | Soundness in mm max expansion on 10 10 10 Fig. 1.4.4: Compressive test on mortar cube LeChatelier Standard Test Procedure aia 1, Take 200 gm coment and 600 gm of standard sand and | | 4 | Heat of prepare dy mix (I : 3 proportion). ‘hydration in 6 2. Add water (5) percent of combine dry mix and Calg prepare mortar in 3-4 mins. Cay) 3, Fill the mortar in cube mould of 50 cm? face area. (28days) : E 15 ‘Vibrate the moulds on machine for two minutes. s. | visimom 4, Remove cubes from mould after 24 hrs and kept for Compressive curing. Maintain 27°C + 2°C temperature and 90% a 16 strength in humidity. ‘MPa (1 day) 5. Remove the cubes from water, dry it and test under ‘compression machine after 3 and 7 days. The rate of G days) 21 215 10 loading is 35 MPafmin. (raays) 7 16 6. As per IS the average compressive strength of three ae a (28 days) 33 35 (@ Notless than 16 MPa after 3 days. 6. | Total toss on (©) Notless than 22 MPa after 7 days. ignition 4 5 5 (waximum)W_Concrote Technology (BATU) 4-8 __ Introduction to Concrete & Various Ingredients of Conc. 1.5 Hydration of Cement 1.5.1 Definition ‘When cement mixed with water its chemical compound undergoes series of chemical reactions which causes hardening of cement paste. This chemical reaction between cement and water called as ‘exothermic reaction’. During this process heat is liberate called heat of hydration. This whole process of formation of hydrates is known as hydration of cement. — The series of chemical reaction between. cement ‘compound and water occurs at different time and rate, ‘hich finally hardens the cement and gain strength. = Unhydrated cement means’ no reaction between ‘cement and water which cannot bind aggregates. — During reaction water starts filing spaces between cement particles. As hydration progress, the gels are formed and they occupy the remaining spaces. — Hardened cement paste has porous structure and pores present are called gel pores (smaller size) and capillary pores (large size). = Volume of capillary pore decreases as_hydration Progress. = CxS and CS (70 to 80% in cement) reacts and produces calcium silicate hydrate (C-S-H) gel, which govern the concrete strength. Another product produced is calcium hydroxide Ca(OH). = Doring hydration heat liberated by different compound is different. C3A liberates high heat but its percentage content is less compare to C;S. = GS hydrates and hardens rapidly and responsible for initial set and early age strength, = Cement containing high CaS gives high early age ‘strength. = CaS hydrates and harden slowly and responsible for later age (after Tdays) strength. Heat liberated is also = CyA hydrates and harden very quick and also liberates very high amount of heat at early age, hence gypsum added to retard CsA hydration. = CyAF contribution not yet clear to researcher. = Basic wactions are : 2C)S.+ 7H > CyS;H,(gel) + 3CH (caleium hydroxide) 2C,S + 5H > CySyHy(gel) + CH = _ (CH) increase pH of concrete which helps to protect steel from corrosion attack. 1.5.2 Heat of Hydration ‘The heat of hydration is the heat generated when water and Portland cement react. CS and C3A content in cement ‘mostly affect the generation of heat during hydration. It is also influenced by water-cement ratio, fineness of cement and curing temperature. = Higher the temperature heat of hydration also more but it’s not that much affected by fineness of cement. = In case of mass concrete work the heat of hydration is high at inner part and low at surface. — For OPC 50% of total heat is liberated in first 1 to 3 days 75% in next 7 days and remai — Heat of hydration also depend on type of cement, its chemical composition. 1g in 6 months. = In cold weather concrete heat of hydration reduce freezing of water and hence advantageous. Inia heat burst Heat evolution o 4 8 2 6 20 2 Time in hours, Fig. 1.5.1: Heat of Hydrationconcrete Tochnoiogy (GATY) 1.9 Inverctiono Conrao& Various igrcions of Cone. 1.5.3 Hydration Products a CalSi ratio of approximately 2:1, so excess lime is available to produce CH. Following are the hydration products produced after Ree eee 3. AFm and AFt phases : these are two groups of ‘minerals that occur in cement, and elsewhere. One of the most common AFm phases in hydrated cement is monosulfate and the most common AFt phase is 1. Calcium Silicate Hydrate gel : This is the main reaction product and is the main source of concrete strength. It is abbreviated, as "C-S-H" and no strict ratio of SiO, to CaO is inferred. The Si/Ca ratio is is present as rod-like crystals in the early ‘Somewhat variable but typically approximately 0.45- stages of reaction or sometimes as massive growths 0.50 in hydrated Portland cement but up to about 0.6 if slag or fly ash or microsilica is present, depending on the proportions. 2 Calcium hydroxide (or Portlandite) : Ca(OH)>, often abbreviated as ‘CH.' It is formed mainly from ‘Alite” hydration, Alite has a Ca:Si ratio of 3:1 and C-S-H has filling pores or cracks in mature concrete or mortar ‘Monosuiphate : It occurs in the later stages of hydration, a day after mixing, Both ettringite and ‘monosulfate are: compounds of CsA,CaSO, (anhydrite) and water, in different proportions. 1.6 __ Chemical Compounds in Cement Portland cement is composed of following oxides. Table. 1.6.1 Mojoroxides | content | Minor oxides | contamt Lime | Ca0_| 60-67% | Magnesia Mgo o1-4% Silica | SiO, | 17-25% | Alkais (Soda/Potash) | Na,0 and K,0 | 0.2~1.3% ‘Alumina | ALO; |3~89% | Sulphuric trioxide | SOs 1-3% tron _| Fex03 | 05~6% Lime Ca0 > Silica SiO, > Alumina AO, > Iron Fe,03 ‘The oxides present in raw mix are compound each other when clinker form at very high temperature, due to fusion process of the oxides present the oxide compounds formed. These are as follows : Table, 1.6.2 CaO c 3Ca0 -Si0; Cs ‘High Temp SiO, s 2Ca0-Si0, os 1450°C=> ALOs A 3C20-A1,05 GA Fei03 F ACAO-AL0;Fe0) | CAF ‘These complex oxide compounds also called Bogue’s compound. ©3 _Concrote Technology (BATU) Introduction to Concrete & Various Ingredients of Conc. 1.6.1 Bogue’s Compound: Bogue, one of the early coment chemists who worked a lot on cementations formulation with the production of cement and hydration of cement. ‘Major Bogue’s compound are as follows : “Name ‘Tricalcium Silicate 3C20'Si0, Gs Alite 25-50 Dicalcium Siticate 2C20-Si0, CS _| Betite 20-45 ‘Tricalcium Aluminate 3Ca0-Al,Oy GA Aluminate 8.12 ‘Tetracalcium Aluminofertite | 4Ca-A10;Fe,0; | CAF _| Ferrite o12 ‘These all are very important to understand properties of cement and concrete Minor Compounds of OPC ‘The most important minor compounds ate gypsum (CaSO,) magnesia (MgO) and alkali sulphates. Gypsum added about 3% is very important to avoid flash set of cement. C3A is responsible for fast setting so gypsum control immediate stiffening of cement paste. Alkalies (MgO, Na,O, K,0) can increase pH value up to 13.5 which is good for reinforcing steel protection from corrosion, However, for some aggregates, such high alkaline environment can cause alkali aggregate reaction problem. Also high content of magnesia causes excessive expansion of cement. 1.6.2. Basic Properties of Bogue’s Compound Basic properties of Bogue’s compound stated in Tuble 1.6.4. Sr.No. L Rate of reaction and hydration process. 2 Heat of hydration (cal/gm) High Low 3. Barly age strength, High and Good | Slow and Poor at start 4 Later age strength or ultimate strength | High and Good | Very Good and HighBE_concrete Technology (BATU) 14__Introduction to Concrete & Various Ingredients of Conc. — Rate of hydration => CsA > C;8 > CyAF > C,S 1.7.2 Rapid Hardening Portland Cement — Strength of cement => C3$ >C,$ > CsA > CAF (IS 8041) — Heat of hydration => CsA > C,S > C,AF> CS. es Properties Wee ‘No. - 4 s 1.7__ Types of Cement 1. | contain high | Good for prefabricated By modifying composition and physical properties percentage of C3$ and | construction. performance of cement can changed favourably to obtain low percentage of CS. different types of cement as follows : 2. | Fineness is 325 mifkg | Suitable where early 1. Ordinary Portland Cement (ASTM Type 1) which is extra fine, | removal of formwork. 2. Rapid Hardening Portland Cement (ASTM Type II) Rs eer 3. Low Heat Portland Cement (ASTM Type IV) reaction and develops 4, Sulphate Resisting Cement (ASTM Type V) strength earlier. 5. Quick Set Cement 3. |3 days RHC strength | Suitable in cold 6. Pozzolana Portland Cement (PPC) (Type IP) equals to 7 days OPC | weather. 7. Blast Fumace Slag Cement (Type IS) strength, nea 4, | More heat of hydration | Road repair work to ee not good for mass | open traffic quickly. concrete. 10. Hydrophobic Cement 1.7.1. Ordinary Portland Cement (1S:269, 8112 and 12269) 1.7.3 Low Heat Portland Cement (IS 12600) __ Properties: 1, | Ttis classify in three | This type of cement grades as 33, 43 and | generally used for all ‘53 which is 28 days, | types of concrete works cube (707 x 7.07 x | which is free from 1. [in this cement | Due to low heat of percentage of C,S is | hydration, the increase more and percentage of | in internal temperature Sand C;Aisless | of mass concreie is low and which control the 707mm) sulphate attack, cracks in. mass compressive concrete. strength in Némm2, 2. | This cement liberates | Construction of dam, 2. | Fineness is 225 mthkg. 3._| MgO - 5% (max) Tess heat during | retaining structures etc. hydration process Mass concreting. work this cement is useful. 3.__| Fineness - 320 m?/kg1-12 __ Introduction to Concrete & Various Ingredients of Cone. ~ || 1.7.5 Quick Set Cement 4, |7 days heat not more than 65 cal/gm 28 days heat not more than 1, | It sets very early - in 20 | When concrete is to mins. be laid under water, 75 ca/gm ala due to quick setting eas ae pumping time strength slowly during ee early ages and gain same at 28 day strength 2. | Barly setting is achieved | Also useful for of OPC. by adding small percentage | special grouting of aluminium sulphate and | operations. reduce percentage of gypsum which accelerate the setting time. 1.7.4 Sulphate Resisting Cement (IS 12330) ‘magnesium sulphate attack on OPC 1.7.6 Pozzolana Portland Cement (IS 1489) when they are in ‘ee dissolved form. These pus : combine with Calcium 1. | A pozzolanic material is | Mass concrete work. hydroxide and calcium essentially a silicious or aluminate, causing luminous material expansion and disruption possessing no cementations of the concrete called Properties, which reacts sulphate attack, with calcium hydroxide in 2. | This cement contain low | Canal and water croatian an percentage of CyA not | courses lining. Produces more than 5% and low Semerntions comport. percentage of C,AF. At 2. | Fly ash, Slag, Volcanic ash | In areas where more ae etc are examples of | resistance to attack of CS content. pozzolanas. aggressive water. ‘and | || 3: | Finely ground pozzolana | Not suitable for cold blended with cement (15 to | weather but good in 35%) hence low cost. ‘hot weather concrete ‘work. 3. | High percentage of | Foundation silicates used. basement if soil contains sulphates. 4, | Fineness -225 m’/kg | Concrete pipes and concrete for sewage treatment plant. 5. | Low early strength and | Certain areas where moderate heat of | water and soil have hydration costly than | alkaline content and ope. OPC is not good then use this cement. 4._| Fineness -300 m’/kg. 5. | Low heat of hydration and slow strength gaining in early ages. 6. | Reduce micro-cracks in conerete and give long termstrength gain,3F_Concrete Technology (BATU) }3_ Introduction to Concrete & Various Ingredients of Conc. 1.7.9 Air Entraining Cement Properties 7. | Pozzolonic action — is Ca(OH)2 + Pozzolana + e ‘ water C-S - H gel. 1, | It is produced by grinding | Due to air entraining 1.7.7 Blast Furnace Slag Cement (IS 445) ee anne ake a | Pera oeaemoer ae eniraining agent with | mixing, it produce OPC. These are Alkali | tiny, discrete air salts of wood resins, | bubbles which synthetic detergents, | improve _ workability, Calcium —_lignosulphate, | segregation, bleeding Calcium salts of glues. and = frost action resistant. zs - Prog lo. Ones ass 1. | Slag obtained from blast | Mass concrete work. furnace is a waste product in the manufacture of pig iron. 2. | Addition of these agent 2. | Slag is finely ground and | Structures require nie mixed with cement. resistant to sulphate attack, 1.7.10 Hydrophobic Cement (IS 8043) 3. | Slow strength gain in| Useful for marine - ‘early ages and achieve | construction. good strength afier 28 days. 1. [1 i prepered by | Usocument wo prevent Less cosh more grinding OPC. clinker | possibilty of moisture workability, Jow heat of with water repellent film | absorption from hydration, high sulphate forming substance like, | atmosphere. resistant, stearic acid, Oleic cid 1.7.8 White Cement (IS 8042) Se by 0110045). S ; <|| 2 | Due to this cement can ee be sore stely for long period, where in casc of ‘OPC lumps formed. Properties — 1. | Very less percentage of | This is mostly used for iron oxide and magnesium | decorative purpose oxide which gives gray | construction. 1.8 Aggregates Sater OFC 1.8.1. Introduction 2. [CAF is low, Kaoline | Fitting the tle joints. together with chalk ‘Aggregates are defined as inert, granular, inorganic limestone used tmaerial and do not chemically react and mixed with binding 3 [Low specific gravity and | Used a a base for|| Metts like cement for preparation of mortar or concrete. strength that of OPC. __| colour cement. — Aggregates are used because (function of aggregate) : For coloured cement some special type of pigients | ~ ABBrezates occupy 65 to 80% of concrete volume, added in Portland cement/white cement. The required | - They are cheaper than cement, put into concrete as pigments are insoluble, not affected by light, filler material. They increase the volume of mortar or chemically inert. concrete mix and reduce the cost.WF _Concrote Technology (BATU) 414 Introduction to Concrete & Various Ingredients of Conc. = They reduce thermal cracking, reduces shrinkage and improve workability. — They used to reduce the heat of hydration. = They gives higher volume stability and better durability than cement paste alone. They imparts unit weight of concrete, = High aggregate to cement ratio is desirable related to cement content. 1.8.2 Classification of Aggregates General classification of aggregates is as follows : 1, According to Source : Natural and artificial. 2, According to Petrology = Igneous, Sedimentary and ‘Metamorphic. 3. According to Grain Size : Fine and coarse. 4, According to Unit weight : Heavy, Normal and light weight. S. According to Shap Flaky and Elongated. 6 According to Surface Texture : Smooth, rough, granular, crystalline, honeycombed and porous. 1.8.24 + Rounded, Imegular, Angular, According to Source (a) Natural Aggregates : Natural deposits without changing their natural state other than washing, crushing and grading such as sand, gravel, crushed rock aggregates. Artificial or manufactured aggregate : ‘They are obtained either as a by-product or by special ‘manufacturing process such as heating. ) ‘These are blast-furnace slag, cinder, fly ash etc. 1.8.2.2 According to Petrology (@) Igneous Rock : They are formed by solidification of molten lava. Example ~ Quartz, granite, basalt. (b) Sedimentary Rock : They are formed by deposition of weathered and transported pre-existing rocks. Example- sandstone, limestone, shale. Metamorphic Rocks : They are formed at higher depth under high heat and pressure alteration of either © igneous and sedimentary rocks. Example- marble, slate, schist. 1.8.2.3 According to Grain Size @ ) A @ ®) © Fine aggregates : The aggregates having size less than 4,75 mm and retain on 75 p sieve. Coarse aggregates : The aggregate having size 4.75 mm and more than that. Silt are the fine particles having size 0.002-0.075 mm. 2.4 According to Unit Weight Heavy weight aggregates than 2.8 and unit weight is greater than 2800 kg/m? to 3000 kg/m?, concrete produced by them also heavy. Example- Hematite, Barte, Limonite, Magnetie, iron slag. ‘Used for radiation shielding. Normal weight aggregate : Whose specific gravity is in between 24 to 2.8 and unit weight of normal weight concrete is 2200 to 2400 kg/m’. Example- Gravel, sand, Light weight aggregate : Whose, sp. gravity is less than 24 and unit weight is 1200 kg/m?. Example- Slag, slate, pumice, voleanie cinder, datomite. nose sp. gravity more ‘They reduce weight of concrete structure. Some demerits like poor workability, low modulus of elasticity and high creep and shrinkage, 1.8.2.5 According to Shape (@) ) © @ ‘Rounded : Completely water work and fully shaped by attrition. eg river gravel, sand. Irregular : Partly shaped by some rounded edges. e.g, land gravel. ‘Angular : It has sharp comers. e.g. Crushed rock. Flaky : Thickness is relatively small with respect to ‘other two dimensions. e-g. laminated rock.WE _Concrete Technology (BATU) 4-15 Introduction to Concrete & Various Ingredients of Conc. (© Elongated : Length is considerably large than other two dimensions ¢.2- 7 fue regular || Angular | % of voids | % voids 35- | % voids 38- | They 321033% | 38% 0% should not be more than 15% A of total aggregate. Require | Require - | Require | Affect less cement | more rmoré cement | strength. paste. cement | paste, paste. Good Interlocking | High bond workability. | more bond, | due to ‘good, poor | interlocking. workability. | Less workability. ‘Angular Elongated Fig. 1.8.1 : Shapes of aggregates 1.8.2.6 According to Surface Texture (@) Glassy : e.g Black flint. (b) Smooth : Due to smooth surface bond between cement paste and aggregate is weak. e.g gravel, marble sate, (©) Rough : Duc to rough surface bond between paste and. aggregate is strong. -g granite, gabbro, gneiss. @ Honeycomb and porous + expanded clay. eg Brick, pumice, 1.8.3 Fine Aggregate — Size : The aggregate passing through the IS 4.75 mm sieve and retain on 75 sieve are called as fine aggregate. =" Shape : Rounded shape sand increased workability and for economy as reflected by use of less cement. The purpose of sand is to fill the voids in the coarse aggregate and produce dence concrete. — They are obtained as river sand or by crushing rocks. ~All important properties explained in test on aggregate section. Requirements of good quality sand are — Surface texture should be smooth. — High crushing strength = Well graded and free from impurities. = Silt content should be less than 2%. = Gives high workability and low permeability when used in concrete water absorption should be less than 5% Be Bees “Manufacture No. | Property “River Sand | sand or erushed : x ‘sana 1. | Shape | Rounded Cubical particle particle 2, | Gradation | Cannot be | Can be control control 3, | Particles | Presence of silt | Presence of dust below 75 shall be less | Particles shall be micron __| than 3% Jess than 159% 4, | Sit and | Present Absent organic impurities 5. | Specific | 23-27 25-29 gravityManufacture sand of crushed [sand 6. | Water | 15-3% 2-4% absorption 7. | Grading | Zone It and MI | Zone It Zone (FM 22-28) | @M26-3.0) 8._| Souncness | Relatively less_| Relatively sound 9, | Ability to | Upto 7% Upto 10% hold surface ‘moisture, 1.8.4 Physical Properties of Aggregates (A) Particle shape and surface texture (B) Water absorption and moisture content (© Bulk density (©) Specific gravity ‘A. Particle shape and surface texture Shape and surface texture of aggregate affects ‘workability and strength. Rounded aggregates with smooth surface increase workability. ‘The aggregate with rounded particles has minimum voids, which gives minimum ratio of surface area to ‘volume, thus require minimum cement paste to produce ‘concrete. They also gives high packing density. Interlocking of rounded aggregate is poor and hence bond strength also poor. ‘Angular particles has a maximum percentage of voids, they requires more cement paste to achieve workable concrete. @ ®) © @ Introduction to Concrete & Various ingredients of Conc. Interlocking between angular particles is good and hhence bond strength is good. Due to more surface area of angular particles water ‘demand increases then rounded particles. Rough surface reduce workability but due to more area for bonding with cement paste increase strength. Rounded, smooth texture aggregates not suitable for hhigh strength concrete and pavement instead of that angular aggregate preferred, Flaky and elongated particles reduce workability increase water demand and reduce strength and durability of concrete. Hence they should be limited to 15% by weight of total aggregate. Water absorption and surface moisture ‘The water absorption of aggregate is measured by the percent increase in weight of an over dry sample after immersion in water for 24 hours. Water absorpti in concrete and the concrete will require higher water will decrease the actual water content cement ratio. ‘The water absorption and surface moisture depends on the porosity of aggregate. There are four different moisture conditions. Oven dry : No water present at all and fully absorbent. ‘Air dry : Dry at surface but contain some moisture in pores inside the aggregate. Saturated surface dry (SSD) : Pores of the aggregates are fully filled with water and surface is dry. It neither absorb water nor contribute water to the concrete mix. SSD is obtained by immersion in water for 24 hr and dry surface by cloth. Wet or moist : The pores of the aggregates are fully filled with water and surface of aggregate is covered with film of water.Concrete Technology (BATU) 47. Introduction to Concrete & Various ingredients of Conc. Oven dry ‘ir dry Saturated dry Moist surface dry (SSD) Fig. 1.8.2 Wsso Specific gravity % water absorption Woo * 100 Wssp = Weight of aggregate in SSD Wop =" Weightof oven dry aggregate at 110°C — For water absorption test aggregate require in SSD condition, which achieved by keeping aggregate in water for 24 hours and after removal drying of surface with cloth to remove surface moisture. = Moisture content is the water excess of that SSD state. — At time of concrete mix design aggregate is in a SSD state. C. Bulk density — The ratio of net weight of aggregate in kg to the ‘Volume of aggregate in liter. It is expressed in kgfit. = The volume of metal cylinder required for bulk density is depend on size of particles. For sand particles (below 4.75 mm) 3 lit and 4.75 mm to 40 mm size particles 15 lit eylinder used. Fill the sand or coarse aggregate in 3 layers in respective cylinder and each layer tamped 25 times by tamping rod. = Measure the weight of cylinder with aggregate. Find the weight of aggregate in cylinder by subtracting weight of empty cylinder. Net weight of aggregate: Caleulate bulk density $f = SSeS rosie Cd — Bulk density depends upon (1) grading of aggregate. 2) shape of particles. (3) degree of compaction (4) moisture. Its the ratio of dry weight of aggregate to the weight of equal volume of water. It is very important property required in concrete mix design. To calculate specific gravity of Sand or Fine aggregate pychnometer bottle is used. Mass of empty pychnometer (M;) calculated in gm. Then 400 gm dry aggregate put inside the pychnometer and combine weight (M,) noted. Then fill the pychnometer sand with water and weight taken (Ma), Then fill the pychnometer with water only and weight (M,) noted. May *100 Specific gravity of course aggregate determined with the help of wire basket. The procedure given in IS 2386 part Il. Sp. gravity of CA Apparent sp. gravity 0 ‘Water absorption Where, A. = Weight of saturated aggregate in water (Ay ~ Az) Gm ‘Weight of aggregate and basket in water Weight of empty basket in water Weight of saturated surface dry aggregate in air C= Weight of oven dried aggregate in air. 1.8.5 Bulking of Sand Bulking is a phenomenon duc to which the fine aggregate swells by absorbing moisture from air. Hence the free moisture present in FA increase the ‘volume of sand called bulking of sand,Concrete Technology (BATU) 4-18 — A film of moisture around individual sand particle produces surface tension which keeps the neighbouring sand particles away and increase volume, This make swell and volume appears more. = Due to bulking W/C ratio changes and concrete mix design may go wrong, may produce less workable hharsh mix. If water percentage increases segregation takes place. 0 & Increase in volume percent 8 () Fig. 1.8.3 : Bulking of sand 1.8.6. Impurities in Sand (@) Organic impurities : When the sand is dredged from river bed, then it may contain dead plants, animals humus, clay ete. This organic impurities interferes the hydration process of cement and ultimately affects the strength of cement. Organic impurities determined by colorometic test in which sand is mixed with 3% [NaOH solution and its colour is matched with standard colorometric card, to find organic content. If it is more thon the sand cither rejected or treated before use. Introduction to Concrete & Various Ingredients of Conc. (b) Inorganic impurities - These are obtained from ‘quarries. They are mainly silt, clay. They can. be removed by washing the sand. (©) Presence of salt will affect the setting properties. @ Presence of mica considerably reduces durability and strength. 1.8.7 Coarse Aggregate ~The aggregates retained on the 4.75 mm IS sieve and ‘more than that called as coarse aggregate. ~ They may be of ~ crushed gravel or stone, uncrushed ‘gravel or stone and partially crushed gravel or stone. — The graded CA is described by its nominal size 40 mm, 20mm, 16mm, 12.5 mmete. — According to grading they are classify as well graded, ‘gap graded, uniformly graded, poorly graded. — The physical and mechanical properties of coarse aggregate explained in next section. 1.9 Mechanical Properties of Aggregates ‘Strength of aggregate determined through (A) Crushing value B) Impact value © Abrasion value Following sieve used (passing) to check strength properties. [Test | Stove used Passing) ¢ ‘Crushing | 2.36 mm Impact 2.36 mm Abrasion | —__1.70mm (A) The test procedure of crushing value as follows ('S : 2386) 1, Sample passing 12.5 mm and retained on 10 mm IS sieve. 2, Sample oven direct at 100 - 110°C temp for 3-4 hours.