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CONCRETE TECHNOLOGY By (R. N. Gupta) Professor/Track machine

CONCRETE TECHNOLOGY By (R. N. Gupta) Professor/Track machine. Reference Codes. CBC:2014 – Indian Railway Standard Code of Practice for Plain, Reinforced & Prestressed Concrete for General Bridge Construction IRUSS:2010 –

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CONCRETE TECHNOLOGY By (R. N. Gupta) Professor/Track machine

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  1. CONCRETE TECHNOLOGY By (R. N. Gupta) Professor/Track machine

  2. Reference Codes • CBC:2014 – • Indian Railway Standard Code of Practice for Plain,Reinforced & Prestressed Concrete for General Bridge Construction • IRUSS:2010 – • Indian Railway Unified Standard Specifications & schedule of rates–Works & Materials–2010 (Chapter 3 & 26) • IS 456:2000 – • Plain & reinforced cement concrete- code of practice (fourth revision) Amendments up to 4 • IS 9103:1999– • Specification for admixtures for concrete (first revision) • IS 2386 (Part 3) : 1963– • Method of test for aggregates for concrete • IS 383:2016 – • Specification for coarse and fine aggregates from natural sources for concrete (Third revision)

  3. Concrete • Combination of Cementatious Material,Aggregates and water along with Admixtures, if required. • It is denoted by Grade M-X Here, X is the Characteristic Strength of Concrete in N/mm2 tested on 15 cm cube after 28 days

  4. Grade of Concrete • Ordinary Concrete – M-10, M-15, M-20 • Standard Concrete – M-25 to M-60 • High Strength Concrete – Above M-60 IS:456 applicable upto M-100 CBC for M60 only

  5. Ingredients of concrete • Cement • Fine Aggregate - Sand • Coarse Aggregate • Water

  6. Cement • The cement used shall be appropriate for the intended use. • OPC 33 Grade as per IS:269 • OPC 43 Grade as per IS:8112 • OPC 53 Grade as per IS:12269 • Rapid Hardening Portland Cement as per IS:8041 • Portland Pozzolona Cement as per IS:1489 • Portland Slag Cement conforming as per IS:455 • Sulphate Resisting Portland cement as per IS:12330.

  7. Cement • In Blended Cements like Portland pozzolana cement and Portland slag cement, the strength gain is slow as compared to ordinary Portland cement. • Accordingly period of removal of form work and period of curing etc. should be suitably increased. • When Portland Pozzolana cement is used in plain and reinforced concrete, it is to be ensured that proper damp curing of concrete is done for at least for 14 days • Sulphate Resisting Cement conforming to IS:12330 shall be used only in such conditions where the concrete is exposed to the risk of excessive sulphate attack e.g. concrete in contact with soil or ground water containing excessive amount of sulphate.

  8. Cement • Different types of cement shall not be mixed together. • In case more than one type of cement is used in any work, a record shall be kept showing the location and the types of cement used. • In case of Grade 33 cement, the gain in strength will continue beyond 28th day. • In case of Higher Grade cement, heat of hydration is at a much faster rate initially. • Release of heat is the highest In case of Grade 53 cement. • Grade of Cement should be used based on design considerations.

  9. Field Checks for Cement • The stitching of bag should be intact and original. • Check the grade of cement as per requirement. • Check the date of manufacture---w-week, m-month, y- year. it should be fresh & not older than 3 month. Older than 6 month should not be used. • No lumps should be present. • Should feel cool when hand is put in the bag of cement and rubbing between fingers should be silky. • When a handful of cement dropped in water, it should float before sinking. • Average weight of 5 bags of cement should be 50kg.

  10. Tests for Cement Standard Consistency Test: • To ascertain the volume of water which is to be added for other tests like Initial Setting Time, Final Setting Time, Soundness and Strength etc. • Vicat’s apparatus is used. • Test plunger of 10 mm dia and 50 mm height • Mould of 80 mm dia and 40 mm height. • The percentage of water by weight of cement which causes the penetration of 33-35 mm is called ‘Standard Consistency’ and designated by ‘P’.

  11. Tests for Cement

  12. Tests for Cement CompressiveStrength Test: • 200 g (Cement)+ 600 g(Sand)+ (P/4+3)% (Water) of combined wt. are mixed. • 7.06 cm side cube moulds are used. • Strength is tested after 1,3,7 and 28 days. • Average of 3 cubes is taken. P- Water required for standard consistency.

  13. Tests for Cement • Compressive Strength Compressive strength requirement of ordinary portland cement of various grades when tested in accordance with IS:4031 (part 6) shall be as under

  14. Tests On Cement Standard Consistency Test:

  15. Tests for Cement Setting Time Tests: • Conducted as per IS:4031 by Vicat apparatus • Initial setting time • 1 mm² needle is used. • The needle should be 5-5.50 mm above the bottom of mould. • Initial setting time should not be less than 30 minutes • Final setting time: • When penetration is just less than 0.5 mm or when the circular cutting edge fails to make impression. • Final setting time should not be more than 600 minutes

  16. Tests for Cement Fineness of cement ( IS 4031) : • By Air Permeability test • Minimum specific surface OPC - 2250 cm2/gm PPC, HSPC - 3200 cm2/gm • Actual sieving - • 100 gm cement is hand sieved for 15 minutes on 90µ sieve. • Limits of residues: OPC < 10%, PPC, HSPC < 5% HSPC-High strength Portland, PPC- Portland Pozzolana) Effects Of Fineness: • Higher fineness results in early gain of strength. • Bleeding reduces • Shrinkage and cracking increase.

  17. Fine Aggregate-Sand • Aggregate most of which passes through 4.75mm IS sieve is known as fine aggregate (Para 3.1 of IS:383). • Fine aggregate shall consist of natural sand, crushed stone sand, crushed gravel sand or mixture of these. • It shall be hard, durable, chemically inert, clean and free from adherent coatings, organic matter etc. • The sum of the percentages of all deleterious material like pyrites, coal, mica, lignite, shale, clay, alkali, sea shells, organic impurities etc shall not exceed 5%.

  18. Fine Aggregate-Sand Grading – • On the basis of particle size, fine aggregate is graded into four zones. (Table-9 of IS:383) • The higher the Grading Zone, the finer the sand, with Grading Zone I – coarsest and Grading Zone IV-Finest. • It is recommended that fine aggregate conforming to Grading Zone IV should not be used in reinforced concrete unless tests have been made to ascertain the suitability of proposed mix proportions. • Marine aggregate shall not be used for Reinforced Concrete and Prestressed Concrete works. • Silt Content - The maximum quantity of silt in sand as determined by the method prescribed in Annexure 26.3 of IRUSS shall not exceed 8%.

  19. Table 26.1of IRUSS & Table 9 of IS:383

  20. Fine Aggregate-Sand Grading – • Coarse sand shall fall within the limits of grading Zone I, II, III of Table 26.1 of IRUSS. • Coarse sand shall have Fineness Modulus not less than 2.5. • Fine sand shall fall within the limits of Grading Zone IV of Table 26.1 of USSOR. • Fine sand shall have Fineness Modulus not less than 1.0. • Use of sea sand shall not be allowed, unless otherwise specified.

  21. Fineness Modulus • FM is an empirical factor obtained by adding cumulative % of aggregates retained on each sieve and dividing by 100. • Larger the factor, coarser the aggregate . • Fine sand FM 2.2 – 2.6 • Medium sand FM 2.6 – 2.9 • Coarse sand FM 2.9 – 3.2 FM more than 3.2 is considered unsuitable for concrete

  22. Fineness Modulus

  23. Fine Aggregate-Sand Bulking Of Sand- • It is the property of sand by virtue of which its apparent volume increases when some water is added to it. • It is due to surface tension. • Fine sand bulks more. • Bulking can be upto 38-40%

  24. Bulking of Sand • Bulking of Sand is to be taken into account when sand is to be dealt by Volume • Table 26.4 of IRUSS gives the relation between moisture content and percentage of bulking for guidance only.

  25. Coarse Aggregate • Aggregate, most of which is retained on 4.75mm IS Sieve and contains only as much fine material as is permitted in IS:383 for various sizes and grading is known as Coarse aggregate. • It shall consist of naturally occurring (uncrushed, crushed or broken) stones or river bed shingle or pit gravel. • It shall be hard, strong, dense, durable and clean.It shall be roughly cubical in shape. Flaky and elongated pieces shall be avoided. • Marine aggregate shall not be used for reinforced concrete and prestressed concrete bridges.

  26. Coarse Aggregate • It shall be either graded or single sized as specified in IS:383. • Nominal size and grading shall be as under : • Nominal sizes of graded stone aggregate or gravel shall be 40, 20, 16, or 12.5 mm as specified. • Nominal sizes of single sized stone aggregate or gravel shall be 63, 40, 20, 16, 12.5 or 10 mm as specified.

  27. GRADED STONE AGGREGATE Table 3.1 of USSOR & Table 7 of IS:383

  28. SINGLE SIZED(UNGRADED) AGGREGATE Table 3.2 of USSOR & Table 7 of IS:383

  29. Coarse Aggregate Size of Coarse aggregate • The nominal maximum size of coarse aggregate should be as large as possible within limits specified but in no case greater than- • One fourth of the minimum thickness of the members, provided that the concrete can be placed without difficulty to fill all corners of the form and to surround all reinforcement. • For reinforced concrete work and prestressed concrete work, aggregates having a nominal size of 20mm are generally considered satisfactory.

  30. Coarse Aggregate • In special cases larger size may be specifically permitted by the Engineer but in no case the nominal maximum size in such RC/ PSC structures shall be more than 40mm. • For heavily reinforced concrete members, the nominal maximum size of aggregate should be • 5mm less than the minimum clear distance between the main bars OR • 5mm less than the minimum cover to reinforcement whichever is smaller.

  31. PHYSICAL PROPERTIES OF AGGREGATEIS:2386 (Part IV)-1963

  32. Water • Water used for mixing and curing shall be clean and free from injurious quantities of alkalies, acids, oils, salts, sugar, organic materials, vegetable growth or other substances that may be deleterious to bricks, stone, concrete or steel. • Potable water is generally considered satisfactory for mixing. • PH value should be between 6 to 8. The pH value of water shall be not less than 6. PH value less than 6 is acidic in nature and causes corrosion. • Sea water shall not be used for mixing or curing. Sea water contains salinity of 3.5% and causes corrosion and reduction in strength of about 10-15%.

  33. Water • Frequency of Testing for Quality - Water from each source shall be tested before commencement of the work and thereafter once in every three months till completion of the work or when ordered. • Compressive strength and initial setting time tests should be carried out in case of doubt regarding development of strength. • Average 28 days compressive strength of at least three 15cm concrete cubes prepared with water proposed to be used shall not be less than 90 percent of the average of strength of three similar concrete cubes prepared with distilled water. The cubes shall be prepared, cured and tested in accordance with the requirements of IS:516.

  34. Water • Percentage of Solids: Maximum permissible limits of solids when tested in accordance with IS: 3025 shall be as under: • Organic - 200 mg/litre • Inorganic - 3000 mg/litre • Sulphates (as SO4) - 500 mg/litre • Chlorides (as Cl) – • 500 mg/ litre for Prestressed Concrete Work, • 1000 mg/ litre for Reinforced Concrete work and • 2000 mg/ litre for Plain Concrete Work. • Suspended matter - 2000 mg/litre

  35. Durability of Concrete • A durable concrete is one that performs satisfactorily in the working environment in anticipated exposure conditions during its service life. • Concrete structure should- • Maintain its required strength and serviceability, during the specified or expected service life. • Concrete must be able to withstand the processes of anticipated deterioration • Durability does not mean an indefinite life.

  36. Durability of Concrete • The cube strength only indicates the strength of the structure at the time of construction. • Whereas Durability is the long term guarantee of the same strength and serviceability of the structure. • Concrete may have strength initially but may not be durable.

  37. Durability of Concrete • The main factor influencing the Durability of concrete is the ingress of water, oxygen, carbon dioxide, chloride, sulphate and other potentially deleterious substances. • Presence of Voids in concrete increase the deterioration of concrete. • Permeability is the primary reason affecting the Durability • Durability is also affected due to surrounding environmental conditions

  38. Durability of Concrete • Voids reduce the strength of concrete. With every one percent entrapped air, the strength is reduced by about 5% to 6%. Five percent entrapped air mean 30% loss of strength. • Compaction helps in reduction of voids. A well compacted concrete is more durable • More water cement ratio adversely affects durability • Insufficient cover to reinforcement adversely affects durability

  39. Durability of Concrete High cement content increases • Risk of cracking due to drying shrinkage in thin sections • Early thermal cracking • Increased risk of damage due to alkali silica reactions Due to these reasons, maximum cement content has also been restricted. Para 5.4.5 of CBC Maximum cementitious material content shall be limited to 500 kg/m3 Para 8.2.4.2 of IS:456 Cement content not including fly ash and ground granulated blast furnace slag in excess of 450 kg/m3should not be used.

  40. Permeability of Concrete • One of the main factor influencing the durability of any concrete is its permeability. Therefore, tests for permeability shall be carried out. • Permeability tests are mandatory for all RCC/ PSC bridges under severe and extreme environment. • Under moderate environment, permeability tests are mandatory for all major bridges.

  41. Permeability of Concrete • Low permeability can be achieved by • ensuring adequate cement content • low free water cement ratio • ensuring complete compaction • by adequate curing

  42. Thanks

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