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BASICS CONCRETE TECHNOLOGY

BASICS CONCRETE TECHNOLOGY. REFERANCES. IS 456 : 2000 – Plain & reinforced cement concrete- code of practice (forth revision) Amendments up to 4 CBC : 2014 – Code of practice for plain, reinforced & prestressed concrete for general bridge construction (up to CS 4)

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BASICS CONCRETE TECHNOLOGY

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  1. BASICS CONCRETE TECHNOLOGY

  2. REFERANCES • IS 456 : 2000 – Plain & reinforced cement concrete- code of practice (forth revision) Amendments up to 4 • CBC : 2014 – Code of practice for plain,reinforced & prestressed concrete for general bridge construction (up to CS 4) • USSOR: 2010 - Indian Railway Unified Standard Specifications & schedule of rates–Works & Materials–2010 (with CS no. 1 & 2) Chapter 3 & 26 (Plain Concrete & Mortars) • IS 9103:1999 - Specification for admixtures for concrete (first revision)

  3. References • IS 383:1970 ( Reaffirmed 2002 ) - Specification for coarse and fine aggregates from natural sources for concrete (second revisions) • IS 2386 (Part 3) : 1963 – Method of test for aggregates for concrete : part 3 specific gravity, density, voids, absorption and bulking. • IS 8112:1989 - Specification for 43 grade ordinary Portland cement (first revision) • IS 12269 - Specification for 53 grade ordinary Portland cement

  4. CONCRETE • Concrete :A building material obtained by mixing of Cement, Water, fine & coarse aggregates in suitable proportions and curing this plastic mixture to a hard mass. New Definition : Added by CS-1 to CBC, • A mixture of cementitious material, water, fine and coarse aggregates with or without admixtures. Here:- Cementitious material means cement or cement mixed with mineral admixtures like pozzolanic fly ash (PFA), grounded granulated blast furnace slag (GGBFS), micro silica etc.

  5. Concrete Advantages of concrete • Most commonly used man made construction material. • Except cement, all other ingredients are locally available, Low cost. • Desired properties can be achieved. • Can be given any shape. • Can be used in difficult locations such as under water, narrow spaces etc. • Can be poured, pumped, trasported.

  6. Concrete Developments- Grade from M10 to M100 and above, Nominal mix to Design mix, 3. OPC to Blended cement (Fly ash, micro silica, slag etc) 4. High Performance concrete (HPC) i.e. Ready mix concrete (RMC), Self compacting concrete (SCC) and Vacuum dewatered concrete,

  7. The characteristic strength Defined as the strength of material below which not more than 5 percent of the test results are expected to fall. The characteristic compressive strength (fck) Strength of cube of size 150x150x150 mm obtained after 28 days curing in N/mm2. e.g. M20, M35 In the designation of concrete mix, the letter M refers to the mix and the number to the specified characteristic compressive strength of 150mm cube at 28 days, expressed in N/mm2. Tensile Strength of Concrete fcr = 0.7 √ fck

  8. Concrete • Grades – Concrete shall be in grades as designated as per Table 2 of CBC & Table 2 of IS 456-2000 • Ordinary concrete – M10 to M20 • Standard concrete – M25 to M60 • High strength concrete – M65 to M100 • As per Amendment 4 of IS 456-2000, Classification of Concrete has been changed. • M60 Gr. has been shifted to Standard concrete and from Grades M85 to M100 are added to High strength concretes.

  9. Grades of Concrete

  10. Grades of Concrete As per IS 456-2000 (Amendment no.4)

  11. ENVIRONMENTAL EXPOSURE CONDITIONS(Based on Table 3 of IS 456:2000)

  12. ENVIRONMENTAL EXPOSURE CONDITIONS(As per Table in Para 5.4.1 of Concrete Bridge Code, 1997)

  13. (As perIS 456-2000 (Table 5) Minimum Cement Content, Maximum Water-Cement Ratio and Minimum Grade of Concrete for Different Exposures with Normal Weight Aggregates of 20 mm Nomination maximum Size

  14. MIN. CEMENTITIOUS MATERIAL CONTENT (As per CBC Table 4(c) Clause 5.4.5)

  15. Maximum cement content As per IS-456-2000 (Para 8.2.4.2) Not to exceed 450 kg/cum when OPC is used. (when fly ash and ground granulated blast furnace slag is used, OPC content shall be reduced) As per CBC – 2014 (Clause 5.4.5) Shall be limited to 500kg/m3. High cement content increases • Risk of cracking due to drying shrinkage in thin sections, • Early thermal cracking and • Increased risk of damage due to alkali silica reactions

  16. TABLE 4 (a) : MAXIMUM WATER CEMENT RATIO (Clause 5.4.3 of CBC)

  17. Specifications – Concrete Ingredients of concrete • Cement • Fine Aggregate - Sand • Coarse Aggregate • Admixtures • Water

  18. CEMENT The cement used shall be any of the following and the type selected should be appropriate for the intended use. 1. Ordinary Portland cement (OPC) • 33 grade conforming to IS:269 (b) 43 grade conforming to IS: 8112 (c) 53 grade conforming to IS:12269 2.Rapid hardening Portland cement conforming to IS:8041 3.Portland Slag cement conforming to IS:455

  19. CEMENT 4. Portland pozzolona cement (PPC) (a) Fly ash based conforming to IS:1489 (part 1) (b) Calcined clay based conforming to IS:1489 (part 2) 5. Hydrophobic cement conforming to IS:8043. 6. Low heat Portland cement conforming to IS:12600 7. Sulphate resisting Portland cement conforming to IS:12330.

  20. CEMENT • Portland Pozzolana cement (PPC) shall not be used for PSC works. • The rate of development of strength is slow in case of blended cement i.e. Portland pozzolana cement and Portland slag cement, 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 and supporting form work shall not be removed till concrete attains at least 75% of the design strength.

  21. CEMENT • The 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 only. e.g. concrete in contact with soil or ground water containing excessive amount of sulphate. • The sulphate resisting cement shall not be used under such conditions where concrete is exposed to risk of excessive chlorides and sulphate attack both.

  22. 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. • Higher grade cement should hence be used only where there is the need for it on design considerations.

  23. Field checks on cement • The stitching of bag should be intact and original. • Check the grade of cement. • Check the date of manufacture---w-week, m-month, y- year. it should be fresh & not older than 3 month. Older than 6 month is not to 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.

  24. Field checks on cement • When a handful of cement dropped in water, it should float before sinking. • A small cube made of cement paste when immerse in water and after 24 hours it should gain some strength and its edges should be intact. 8. Average weight of 5 bags of cement should be 50kg.

  25. Tests On Cement Chloride Content In terms of Correction Slip No.1 dated 26.04.2000 to Concrete Bridge Code (Revised 1997), the total Chloride content by weight in Cement shall not exceed the following values. • For Prestressed Concrete works • Under extreme and very severe environment : 0.06% (ii) Under severe, moderate and mild environment : 0.10% (b) For R.C.C. Works : 0.15%

  26. Tests On 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 :

  27. Tests On 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.

  28. Tests On Cement Setting Time Tests: Setting time of cement of any type or any grade when tested by Vicat apparatus method described in IS:4031 shall conform to the following requirement. 1. Initial setting time: 1 mm² needle is used. The needle should be 5-5.50 mm above the bottom of mould. Initial setting time : Not less than 30 minutes 2. 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: Not more than 600 minutes

  29. Tests On 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. a)Vicat’s apparatus is used. Mould of 80 mm dia and 40 mm height and plunger of 10 mm dia and 50 mm height are used. b) The percentage of water by weight of cement which causes the penetration of 33-35 mm is called ‘Standard Consistency’ and designated by ‘P’.

  30. Tests On Cement FOR CONSISTANCY TEST

  31. Tests On Cement Standard Consistency Test:

  32. Tests On Cement Soundness Test: ‘Le Chatelier’ apparatus (split brass cylinder) is used to detect presence of unburntlime in the cement. Limit for SGC (Spl grade cement) is 5 mm. All other cements it is 10 mm. Autoclave Test: (high pressure steam boiler) To determine presence of free lime and magnesia both. The expansion of 25x25 mm2 and 250 mm bar should not be more than 0.5%.

  33. Tests On Cement FORSOUNDNESS TEST

  34. Tests On Cement Loss On Ignition Test: -1 gm of cement is heated in platinum crucible up to 900-1000°C for 15 min. - Loss of weight should not be more than 5%. Fineness of cement ( IS 4031) : By Air Permeability test or actual sieving - 100 gm cement is hand sieved for 15 minutes on 90µ sieve.

  35. Tests On Cement Fineness of cement: Limits of residues: OPC < 10%, PPC, HSPC and SGC < 5% Minimum specific surface OPC - 2250 cm2/gm PPC, HSPC and SGC - 3200 cm2/gm Effects Of Fineness: Higher fineness results in early gain of strength. Bleeding reduces, Shrinkage and cracking increase. (HSPC-High strength Portland,SGC-Spl grade cement, PPC- Portland Pozzolana)

  36. Fine Aggregate-Sand • 26.1.3.1 General - Aggregate most of which passes through 4.75mm IS sieve is known as fine aggregate. • Fine aggregate shall consist of natural sand, crushed stone sand or crushed gravel sand, stone dust or marble dust, fly ash, Surkhi (crushed brick) or cinder conforming to IS:2686. • 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 shall not exceed 5%.

  37. Fine Aggregate-Sand • Fine aggregate must be checked for organic impurities such as decayed vegetation humus, coal dust etc. in accordance with the procedure prescribed in Annexure 26.2 of USSOR. • In terms of Correction Slip No.1 dated 26.04.2000 to Indian Railways Concrete Bridge Code (Revised 1997), in general, 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 shall not exceed 8%.

  38. Fine Aggregate • Grading - On the basis of particle size, fine aggregate is graded into four zones. • The grading when determined in accordance with the procedure prescribed in Annexure 26.4 shall be within the limits given in Table 26.1 of USSOR below. • 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.

  39. Fine AggregateTable 26.1of USSOR & Table 4 of IS 383

  40. Fine Aggregate • Coarse sand shall be either river sand or pit sand or a combination of the two. Its grading shall fall within the limits of grading Zone I, II, III of Table 26.1 of USSOR. Coarse sand shall have Fineness Modulus not less than 2.5. • Fine sand shall be either river sand or pit sand or a combination of the two. Its grading 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.

  41. FINESS MODULUS (FM) FM is an empirical factor obtained by adding cumulative % ages 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

  42. Fineness Modulus

  43. Fine Aggregate 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%

  44. Fine Aggregate Bulking Of Sand-

  45. Fine Aggregate • Bulking of sand – • In case fine aggregate is damp at the time of proportioning the ingredients for mortar or concrete, its quantity shall be increased suitably to allow for bulkage, which shall be determined by the method prescribed in Annexure 26.5 of USSOR. • Table 26.4 of USSOR gives the relation between moisture content and percentage of bulking for guidance only. • Bulkage % age may be assessed on prorata basis for the different %age of moisture content present at the time of using the fine aggregate or while making payments at the time of measuring the same in case of supply of materials.

  46. Fine Aggregate Bulking of sand (Table 26.4 of USSOR) Relation between moisture content and percentage of bulking for guidance only.

  47. Coarse Aggregate • General : 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. • Coarse aggregate shall be stone aggregate, gravel or brick aggregate and it shall be obtained from approved / authorized sources. • 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.

  48. Coarse Aggregate • It shall be roughly cubical in shape; Flaky and elongated pieces shall be avoided. It shall conform to IS:383 unless otherwise specified. • Where required by the Engineer, test shall be done in accordance with IS 2386 (Parts I to VIII) with the cost fully borne by the Contractor except where otherwise stipulated in the Contract. • Marine aggregate shall not be used for reinforced concrete and prestressed concrete bridges.

  49. Coarse Aggregate Size and Grading of Stone aggregate and gravel • It shall be either graded or single sized as specified. • Nominal size and grading shall be as under : (a) Nominal sizes of graded stone aggregate or gravel shall be 40, 20, 16, or 12.5 mm as specified. (b) Nominal sizes of single sized stone aggregate or gravel shall be 63, 40, 20, 16, 12.5 or 10 mm as specified. For any of the nominal size, the proportion of other sizes as determined by the method prescribed in Annexure 3.1 shall be in accordance with Table.3.1 & Table.3.2 of USSOR.

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