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IRC: STANDARD SPECIFICATIONS AND CODE OF PRACTICE FOR ROAD BRIDGES SECTION: III CEMENT CONCRETE (PLAIN. Shitola Sharan NOTATIONS IRC: Es = modulus of Elasticity of steel Ec IRC and revised in and in in the light of their recommendations. IRC: STANDARD SPECIFICATIONS AND CODE OF irc road bridges section iii plain cement concrete Documents STANDARD SPECIFICATIONS AND CODE OF PRACTICE Part-I)pdf c.


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IRC Road Bridges Section III Plain Cement Concrete - Download as PDF File .pdf), Text File .txt) or read online. March, August, September, IRC MEMBERS OF THE .. Committees of the IRC and revised in and in in the light of their. IRC Road Bridges Section III Plain Cement Concrete.,ii. -*r*hL*.: o. al. EE9. o. ;t. a. o. 'tt. 3. FI. z. E. o. z. ayofoto.info a. gE! G,X. € =;{ d. H6.

Shear strength of members under axial compression: The maximum stresses in concrete and steel shall then be found according to the recognised theory of cracked section. The test strength of the sample shall be the average of the strength of three specimens. In plain concrete structures, tension upto limits specified in Table 11 may be permitted. The preferred nominal size of aggregate is 20 mm for reinforced concrete and prestressed concrete. The pitch of transverse reinforcement shall not exceed mm or the lesser of the following two dimensions: Table 9.

Coarse aggregate Coarse aggregates shall consist of clean, hard, strong, dense, non-porous and durable pieces of crushed stone, crushed gravel, natural gravel or a suitable combination thereof or other approved inert material. The maximum size of the coarse aggregate may be as large as possible within the limits specified, but in ho case greater than one quarter of the minimum thickness of member or 10 mm less than the minimum lateral clear distance between individual reinforcements or 10 mm less than the minimum clear cover to any reinforcement.

The preferred nominal size of aggregate is 20 mm for reinforced concrete and prestressed concrete. However, larger sizes upto 40 mm may be permitted in special cases when there is no restriction to flow of concrete in a section. For plain concrete, preferred nominal sizes may be between 20 mm and 40 mm. However, larger sizes may be permitted only in special cases, subject to supplemental specifications and precautions.

Fine aggregates: Fine aggregates shall consist of hard, strong, durable clean particles of natural sand, crushed IRC: They shall not contain dust, lumps, soft or flaky particles, mica and other deleterious materials in such quantities as would reduce the strength or durability of concrete or attack the reinforcement. Grading of aggregates shall be such as to produce a dense concrete of the specified strength, which can be worked readily into position without segregation and without the use of excessive water content.

Water Water used for mixing and curing shall be clean and free from injurious amounts of oils, acids, alkalis, salts, sugar, organic materials or other substances that may be deleterious to concrete or steel. In case of doubt regarding development of strength, the suitability of water for making concrete shall be ascertained by the compressive strength and initial setting time tests specified in The sample of water taken for testing shall represent the water proposed to be used for concreting, due account being paid to seasonal variation.

The sample shall not receive any treatment before testing other than that envisaged in the regular supply of water proposed for use in concrete. The sample shall be stored in a clean container previously rinsed out with similar water.

Average 28 days compressive strength of at least three mm concrete cubes prepared with water proposed to be used shall not be less than 90 per cent of the average of strength of three similar concrete cubes prepared with distilled water. The cubes shall be prepared, cured and IRC: The initial setting time of test block made with the appropriate cement and the water proposed to be used shall not be less than 30 minutes and shall not be more than 30 minutes from the initial setting time of control test block prepared with the same cement and distilled water.

The test blocks shall be prepared and tested in accordance with the requirements of IS: S The pH value of water shall not be less than 6. Potable water is generally considered satisfactory for mixing concrete. As a guide the following concentrations represent the maximum permissible values: The details of test are given in 8. The details of test shall be as given in Clause 8 of IS: Table 2. Permissible Limit for Solids Tested as per Permissible limit max.

Organic IS: Inorganic IS: Sulphates as S0 3 IS: Cholorides as Cl IS: Mixing or curing of concrete with sea water is not permitted because of presence of harmful salts in sea water.

Water found satisfactory for mixing is also suitable for curing concrete. However, water used for curing should not produce any objectionable stain or unsightly deposit on the concrete surface. The presence of tannic acid or iron compounds is objectionable. Wire fabrics conforming to IS: Concrete Concrete grade: The concrete shall be in grades designated in Table 4, where the characteristic strength is defined as the strength of material below which not more than 5 per cent of test results are expected to fall: Minimum concrete grade, minimum cement content and maximum water cement ratio for structural members under different conditions of exposure are given in Table 5.

Total water soluble sulphate S0 3 content of the concrete mix expressed as S0 3 shall not exceed 4 per cent by mass of cement used in the mix.

Total chloride content in concrete expressed as chloride-ion shall not exceed the following values by mass of 8 9 IRC: Type Per cent PSC 0. Requirement for Design Mixes Target mean strength: The target mean strength of specimen shall exceed the specified characteristic strength by at least the current margin: Suitability of proposed mix proportions: Table 7. Proportions for Nominal Mix Concrete Concrete Total quantity of dry Proportion of Maximum quantity Grade aggregate by mass per fine aggregate of water per 50 kg 50 kg of cement to be to coarse of cement taken as the sum of individual masses of aggregate Litres fine and coarse aggregate Kg by mass P.

M15 Generally 1: Trial mixes: Trial mixes shall be prepared using samples of approved materials for all grades of concrete. Sampling and testing procedures shall be in accordance with Clauses The concreting plant and means of transportation employed to make the trial mixes and to transport them to representative distances shall be similar to the corresponding plant and transport to be used in the works. A clean dry mixer shall be used and the first batches shall be discarded.

Test cubes shall be taken for trial mixes as follows. For each mix, set of six cubes shall be made from each of three consecutive batches. Three from each set of six shall be tested at an age of 28 days and three at an earlier age approved by the engineer-in-charge. The cubes shall be made, cured, stored, transported and tested in compression in accordance with the specification. The average strength of the nine cubes at 28 days shall exceed the specified characteristic strength by the current margin minus 3.

Additional trial mixes: Additional trial mixes and tests, shall be carried out during production before substantial changes are made in the material or in the proportions of the materials to be used, except when adjustments to the mix proportions are carried out in accordance with Requirement for Nominal Mix Concrete Unless otherwise specified, the nominal mix concrete shall be as detailed in Table 7.

Production of Concrete Batching and mixing: The quantities of cement, fine aggregate and the various sizes of coarse aggregate 12 13 IRC: A separate weighing machine shall be provided for weighing the cement. Different types of cement shall not be mixed. The quantity of water shall be measured. Any admixture to be added shall be measured and, if solid, shall be measured by weight. The batch weight of aggregate shall be adjusted to allow for moisture content typical of the aggregate being used.

All measuring equipment shall be maintained in a clean and serviceable condition. Its accuracy shall be checked over the range in use when set up at each site, and maintained thereafter. The accuracy of equipment shall fall within the following limits: The mixing time shall be not less than that recommended by the manufacturer, subject to the approval of the trial mixes by the engineer-in-charge.

Concrete mixers that have been out of use for more than 30 minutes shall be thoroughly cleaned before any fresh IRC: Unless otherwise agreed the first batch of concrete through the mixer shall then contain only two-thirds of the normal quantity of coarse aggregate.

Mixing plant shall be thoroughly cleaned before changing from one type of cement to another. Control of strength of designed mixes Adjustment to mix proportions: Adjustment to mix proportions may be made in order to minimise the variability of strength subject to approval of engineer-in-charge and to maintain the target mean strength subject to approval of engineer-in-charge. Such adjustments shall not be taken to imply any change in the current margin. Change of current margin: When required by the engineer-in-charge, the current margin shall be recalculated in accordance with Clause The recalculated value shall be adopted as directed by the engineer-in-charge, and it shall become the current margin of concrete produced subsequently.

Sampling and Testing Samples from fresh concrete shall be taken as per IS: Sampling procedure: A random sampling procedure shall be adopted to ensure that each concrete batch shall have a reasonable chance of being tested, that is, the sampling should be spread over the entire period of concreting and cover all mixing units.

The point and time of sampling shall be at delivery into the construction, unless otherwise agreed to. The minimum frequency of sampling of concrete of each grade shall be in accordance with Table 8. Test specimen and sample strength: Three test specimens shall be made from each sample for testing at 28 days.

Additional cubes may be required for various purposes such as to determine the strength of concrete at 7 days for any other purpose. The test strength of the sample shall be the average of the strength of three specimens. Acceptance Criteria Compressive strength: When both the following conditions are met, the concrete complies with the specified compressive strength: The concrete mix proportions chosen should be such that the concrete is of adequate 16 IRC: Suggested ranges of workability of concrete measured in accordance with IS: Chloride content: Unless otherwise specified and agreed, the method of calculation and test shall be based upon the chloride-ion contents of all constituents and t e composition of the concrete.

The chloride-ion content of each of the constituent used in the calculation shall be one of t e following: The calculated chloride content of the concrete expressed as the percentage of chloride-ion by mass of cement shall not exceed the value specified in Clause Density of fresh concrete: Where minimum density of fresh concrete is specified, the mean of any four consecutive samples shall not be less than the specified value and any individual sample result shall not be less than Density of hardened concrete: Where minimum density of hardened concrete is specified, the mean of any four consecutive samples shall not less than the specified value and 17 IRC: Storage of Materials All efforts shall be made to store the materials in proper places so as to prevent their deterioration or intrusion by foreign matter and to ensure their satisfactory quality and fitness for the work.

The storage space shall also permit easy inspection, removal and re-storage of the materials.

IRC 21-2000_Concrete - IRC 21-2000 STANDARD SPECIFICATIONS...

All such materials, even though stored in approved storage, shall be subjected to acceptance test prior to their use. The permissible stresses for concrete of different grades shall be as indicated in Table 9.

Table 9. Modulus of elasticity Ec-design value GPa 26 Permissible direct compressive stresses MPa a co , allowable 3. Permissible flexural compressive stresses MPa cr c , allowable. Permissible tensile and compressive stresses in steel reinforcement shall not exceed those given in Table Table The basic permissible tensile stresses in plain concrete elements shall not exceed those given in Table Control of Cracking in Concrete The requirement of crack control at the tensile face of reinforced concrete components under sustained loads shall be deemed to have been satisfied, provided the following detailing criteria are met: In special cases, where the detailing criteria stated in Clause Permissible Stresses under various Combinations of Loads and Forces The permissible stresses given in Clause shall not be exceeded for combination I of Clause The permissible increase for other combinations shall conform to Clause of IRC: General Various stresses that are likely to occur in any plain and reinforced concrete structure, under the worst combination of loads and forces, specified in IRC: The detailing of reinforcement in all components shall be such as to ensure satisfactory placement and good compaction of concrete all around in the components with due consideration being given to the construction techniques adopted.

Basis of Design The strength of a reinforced concrete structural member may be assessed by commonly employed elastic theory and it may be assumed that: In plain concrete structures, tension upto limits specified in Table 11 may be permitted. Cover The minimum clear cover to any reinforcement bar, closest to the concrete surface, shall be 40 mm. Increased minimum cover thickness of 50 mm shall be provided when concrete members are exposed to severe conditions of exposure as mentioned in note 1 of Table 5 except that for the condition of alternate wetting and drying and in case of foundations where the minimum clear cover shall be 75 mm.

The above cover may be reduced by 5 mm for 20 21 IRC: Bar Sizes The maximum size of reinforcement shall be 40 mm diameter or a section of equivalent area, unless a bigger size is permitted by the competent authority. The diameter of any reinforcing bar, including transverse ties, helicals, stirrups and all secondary reinforcement, shall generally be not less than 8 mm. The diameter of longitudinal reinforcing bars in columns shall not be less than 12 mm.

The diameter of reinforcement in slabs shall be limited to one-tenth the depth of slab; and the diameter of shear reinforcement in beam-webs, including cranked bars, if any, shall be limited to one-eighth the thickness of the web.

Distance Between Bars The horizontal distance between two parallel reinforcing bars shall not be less than the greatest of the following three dimensions: In order to comply with the provisions of this sub-clause, the size of the coarse aggregate for the concrete around congested reinforcement may be reduced. This does not preclude the use of large size aggregate where the reinforcement is not congested. Sufficient space shall be left between groups of bars to enable the vibrator to be inserted.

The minimum vertical distance between two horizontal main reinforcing bars shall be 12 mm or the maximum diameter of the coarse aggregate or the maximum size of the bar, whichever is greater. When contact of bars along the lap length cannot be avoided, such bars shall preferably be grouped in the vertical plane.

In no case, however, shall there be more than three bars in contact. The vertical and horizontal distances specified in the Clauses Subject to satisfying crack control criteria as given in Clause All mesh reinforcement shall be of such dimensions as will enable the coarsest material in the concrete to pass easily through the meshes of such reinforcement. Bond, Anchorage, Splice To prevent bond failure, design tension or compression in any reinforcing bar at any section of an element shall be developed on each side of the section by an appropriate anchorage length conforming to provisions given in Clause Provided this is done, local bond stresses may be ignored.

Anchorage length The values of n are given in Table 12 varying with grade of reinforcement grade of concrete and bonding zone Table Bonding zone I favourable shall apply to bar not located in bonding zone II. Design value l d for bars in tension 1 Bars in tension shall be developed either by a design anchorage length with straight ends or with end hooks of the shape 24 IRC: Bonding zones specified in Fig.

For bars of grade Fe anchorage with straight ends is not permitted. Bend diameter for hooks and bent up down bars 26 IRC: Whichever is greater.

Design value l d for bars in compression: Bars in compression shall be developed by an anchorage length with straight ends, end hooks being deemed not effective and value of l d shall be same as that specified for bars in tension in Clause Anchorage of flexural reinforcement in beams and slabs: The provisions of the clause shall illustrate, supplement and modify the general requirements given in Clause Anchorage of bars over bearings: Anchorage length shall be measured from the inner span face of the support, Fig.

Anchorage over bearings 27 IRC: Anchorage of bars in tension zone: Bars may be curtailed and anchored in the tension zone of a beam or slab when the following conditions are satisfied: Curtailment and anchorage of bars in tension zone Anchorage of bars bent up down: Bars not required for shear resistance shall have an anchorage length Id measured from the point of bending.

Anchorage of bars bent up down Id, in compression zone and 1. The shear stirrups shall be deemed adequately anchored when the requirements illustrated in Fig. Special anchoring device: Shape of stirrups continued beyond the end of the curve for at least eight times the.

Splices Splices of reinforcement shall be formed by 1 laps of bars with straight ends or bars with end hooks 2 welded joints 3 joints with mechanical devices 30 IRC: Lap splices of bars in tension 1 Lap splices of bars in tension shall be longitudinally staggered as far as practicable.

The longitudinal and transverse spacing shall conform to Fig. Longitudinal staggering and transverse distance of reinforcing bars in the region of lap splices dimensions in mm 2 Area of bars spliced at any section shall not exceed the following proportions p in relation to the total area of bars provided at the section: Hooks shall not be considered effective.

Transverse reinforcement at lap splices: Minimum reinforcement in the form of stirrups shall be provided over the length conforming to the requirements shown in Fig. Longitudinal section IRC: Welded joints may be used subject to the following: Oxy- acetylene welding shall not be permissible.

Any other process may be used subject to the approval of the engineer and necessary additional requirements to ensure satisfactory joint performance. Precautions on over heating, choice of electrode, selection of correct current in arc welding etc.

S ingle- V or Double-V butt joints may generally be used. For vertical bars single bevel or double bevel butt joints may be used. Site welding where necessary shall, however, be permitted when the facilities, equipment, process, consumables, operators, welding procedure are adequate to produce and maintain uniform quality at par with that attainable in shop welding to the satisfaction of the engineer. All welders and welding operators to be employed shall have to be qualified by tests prescribed in IS: Inspection of welds shall conform to IS: Joints with 32 33 IRC: The method of welding shall conform to supplemental specifications to the satisfaction of the engineer and shall be subject to suitable qualification tests.

At the welded joints complying with Clause Bars may be joined with mechanical devices e. The effectiveness of such joints shall invariably be proved by static and fatigue strength tests. Patented systems with proven use shall only be permitted to be used on production of test results showing the adequacy of the device to the satisfaction of the competent authority. A mechanical joint including its connecting elements shall develop in tension or compression at least per cent of the characteristic strength f 34 IRC: Shear and Torsion Shear Shear stress The design shear stress i at any cross section of beams or slabs of uniform depth shall be calculated by the equation: For obtaining the maximum shear stress, the section at a distance equal to effective depth from the face of the support shall be checked and the shear reinforcement calculated at the section shall be continued up to the support.

In case of a beams or slabs of varying depth, I the equation shall be modified as: The negative sign in the formula applies when the bending moment M increases numerically in the same direction as the effective depth d increases, and the positive sign when the moment decreases numerically in this direction. Maximum permissible shear stress x When shear reinforcement is provided the shear x in beams sThall not exceed stress x max , given in Table 12 A.

For slabs, x shall not exceed half the value of in Table 12 A. Design shear strength of concrete The permissible shear stress x c in concrete in beams without shear reinfocement is given in Table 12B. For solid slabs the permissible shear in concrete shall be K. Shear strength of members under axial compression: For members subjected to axial compression P, the permissible shear stress in concrete x c given in Table 12B, shall be multiplied by the following factor: Table 12C.

Values of K for Solid Slabs Overall depth of slab, mm or more or less K 1. Members with shear reinforcement: When x exceeds x c given in Table 12B, shear reinforcement shall be provided in any of the following forms: Where more than one type of shear reinforcement is used to reinforce the same portion of the beam, the total shear resistance shall be computed as the sum of the resistance for the various types separately.

The areas of the stirrups shall not be less than the minimum specified in Minimum shear reinforcement for beams: When t is less than x. Maximum spacing of stirrups shall be limited to one-half the depth of the beam subject to a maximum of mm. Stirrups shall pass round, or otherwise be secured to the appropriate longitudinal tensile reinforcement. The ends of stirrups shall be adequately anchored in the compression zone in accordance with Clause Where for practical purposes it is found necessary to anchor the ends of the stirrups in the tensile zone full anchorage length in accordance with Clause Bent-up bars shall be carried through a depth of at least equal to the lever arm of the resisting moment and adequately anchored in accordance with Clause The I spacing of the bent-up bar measured at the level of neutral axis and in the direction of longitudinal axis of the beam shall not exceed three-quarter the effective depth of the beam.

Torsion In structures where torsion is required to maintain equilibrium, members shall be designed for torsion. However, for such indeterminate structures where torsion can be eliminated by releasing redundant restraints, no specific design for torsion is necessary provided torsional stiffness is neglected in the calculation of internal forces. Adequate control of any torsional cracking is provided by the shear reinforcement as per Clause Torsional reinforcement is not calculated separately for torsion alone.

Instead the total longitudinal reinforcement is determined for a fictitious bending moment which is a function 39 IRC: The design rules shall apply to beams of solid rectangular cross-section.

However, these clauses may also be applied to flanged beams by substituting bw for b, in which case they are generally conservative. Critical section: Sections located less than a distance d, from the face of the support may be designed for the same torsion as computed at a distance d, where d is the effective depth. Equivalent shear Equivalent shear, F, shall be calculated from the formula: The values of t c shall not exceed the values of x given in Table 12 A.

If the equivalent shear stress x c does not exceed x c , given in Table 12B, minimum shear reinforcement shall be provided as specified in Reinforcement in members subjected to torsion Reinforcement for torsion, when required shall consist of longitudinal and transverse reinforcement.

Longitudinal reinforcement: If the numerical value of M t as defined in Transverse reinforcement: Distribution of torsion reinforcement: When a member is designed for torsion, torsion reinforcement shall be provided as below: The diameter of these longitudinal bars shall not be less than the diameter of the stirrups or 12 mm whichever is greater. Moment of Inertia Moment of inertia for calculating relative stiffness: To determine the relative stiffness of members of statically indeterminate structures, the moment of inertia may be calculated by considering: Whichever method is adopted for the beams, the same method should be used for the columns.

Moment of inertia for calculating deflection: Appropriate values of moment of inertia may be used. Temperature and Shrinkage Effects Every simply supported span shall be provided with means to permit both rotation and longitudinal expansion caused by the design loads and forces. For bridges having beam and slab type of super-structure the number of longitudinals shall not be less than 43 IRC: The minimum thickness of the deck slab including that at the tip of the cantilever shall be mm.

However, reduction in the thickness of the slab upto a maximum of 50 mm may be permitted at the cantilever tip subject to satisfactoiy detailing. The thickness of the webs shall not be less than mm. Cross girder monolithic with the deck slab shall be provided at the bearings. Intermediate cross-girders shall be provided depending on design requirements. The thickness of the cross girders shall not be less than the minimum web thickness of the main longitudinal girder. The depth of the cross girders at bearings shall be suitably adjusted to allow access for proper inspection of bearings and to facilitate positioning of jacks for future lifting up of the super-structure.

Effective Span In the case of free supports on line bearings, the effective span lo shall be the distance from the centre to centre of the bearings. In the case of restraint at the support, the effective span may be taken as equal to the clear distance between the faces of the supports.

Effective Depth The effective depth of a beam or slab shall be the depth from edge of the compression section to the centroid of the tension reinforcement. Where haunches are provided, no portion of the haunch lying below a plane which makes a slope of 1.

Portion below Line AB to be ignored for effective depth However, for calculating the moments in a haunched slab or beam, the actual variation of moment of inertia in the span shall be considered. Where member thickness varies, no portion of the member lying below or above a plane which makes a slope of 1: When in a beam, part or all of the main reinforcement is required to resist compression, links or ties atleast one quarter of the size of the largest compression bar should be provided at a maximum spacing of times the size of the smallest compression bar.

All other bars within a compression zone shall be within mm of a restrained bar. When the designed percentage of reinforcement in the compression face of a slab exceeds 1 per cent, links of atleast 6 mm or one quarter the size of the largest compression bar should be provided for a depth of mm through the thickness of the slab.

If the thickness of the slab is insufficient to accommodate then it should be tied with the tension bar. The spacing of these links should not exceed twice the member thickness in either of the two principal directions of the member or mm and in the direction of the compression force not greater than 16 times the bar size. Curtailment of Bars To prevent large changes in the moment of resistance the points at which the bars are curtailed shall be suitably spread.

In simply supported spans, at least 33 per cent of the steel required to resist the maximum bending moment shall be carried over the supports along the tension side of the beam and in the case of slab this shall not be less than 50 per 46 IRC: For a span continuous beyond a support, at least 25 per cent of the steel required to resist the maximum positive bending moment shall be similarly carried over the support both in case of beam or slab. Curved or Sloped Reinforcement Where the alignment of the reinforcement deviates from the normal to the plane of bending, as in the case of a beam with curved or sloped soffit, only the area of the reinforcement effective in the direction normal to the plane of bending shall be considered.

Lateral Support in Beams In flanged beams with length between adequate lateral restraints greater than thirty times the width of the compression flange, the permissible compressive stress in concrete shall be reduced by a factor equal to 1.

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IRC 1. January, I March, I 2 July, I April, I I March, I December, I March, Incorporates Amendment No. I -Nov. I97 I Incorporates Amendments No. I, No. I Incorporates Amendment No.

I Incorporates Amendments No. The Chief Enginccr B V.

IRC 21 Standard Specifications and Code of Practice for Road Bridges Section III Cement Concrete

Chakraborty Managing Director. Consulting Engg. Services I Ltd. Tamhanltar Emeritus Scientist. Structural Engg. Pocket E. Secretary Retd. Nalanda Apartments. Vikaspuri, New Delhi 6. Borkar Technical Adviser to Metropolitan Commr. Susnehi Plot No. Bandra Reclamation.

Mumbai 7. Ministry of Surface Transport Roads Wing. Transport Bhawan. New Dclhi— I! Raheja Chambers, 2l3. Nariman Point. Murnbai- l. Thakkar Professor. Department of Earthquake Engg. University of Roorkec. Roorltee ll.

Bhagwagar Consulting Engineer. Consultants P Ltd. Connaught Place. Bank of India Building. Mumbai—S I3. Rcddi Dy. Managing Director. Gammon India Ltd. Gammon House. Setu Bhavan. Madan Mohan Malviya Marg. Lucknowl Kand Consultant. Bhopal l6. Mahcsh Tandon Managing Director. Tandon Consultants P Ltd. Link Road. New Delhi I8. Subba Rao Chainnan. Construma Consultancy P Ltd. Pinlty Plaza. Mumbai— I9. Lucknow MOST Rctd.

Sector NOIDA Jayadas Chief Engineer. Sccma Sadalt Bhavan. Delhi Cantt. New Dclhi Bhasin Mandakini Enclave, Alkananda. The meeting was presided by Shri Prafulla Kumar. Director General Road Development and Add]. Ministry of Surface Transport. Sarmah S. The Secretary to the Govt.

Elithium - Soluções Inteligentes

Guwabati I Secretary. Maharashtra PWD Rctd. Pranit J. Palkar Marg. Podar Hospital, Worli. Mumbai H. Block No. New Saehivalaya. Gandhinagar D. Srec Rama Murthy.

National Highways. Hyderabad D. Public Works Department.

1987 pdf 21 irc

Calcutta R. Haryana P. Sector B. Chandigarh—ll9 Central Public Works Department. Ninnan Bhawan. New Delhi C.

Bureau of Indian Standards. Manak Bhawan. Bahadurshnh Zafnr Marg. New Delhi-I M. Bhopal U. Secretary to the Govt. Mcrani Dr. Adarsh Nagar. Mumbai Chief Engineer.

Hindustan Construction Co. Vikhroli W. Mumbai Adviser Consultant. Services I Pvt. Nehru Place. New Delhi ii 7. To cater for the technological developments which were taking place in course of time, the Code was examined by the Technical Committees of the IRC and revised in and in in the light of their recommendations.

In the light of further developments in the field of plain and reinforced concrete, the provisions of the Code were reviewed by the Committee for Reinforced, Prestressed and Composite Concrete B-6 consisting of the following personnel: Ninan Koshi.

Converter A. Sinha Jose Kurien S. Joglekar P. Manjure Dr. Subba Rao A. Prasada Rao M. Mukherjee R. Chaudhary Dr. Tamhankar G. I-laridas Shitala Sharan D. Basa Vinod Kumar T. Tyagi l The draft amendments were discussed and approved by the Council of the Indian Roads Congress at the th Council Meeting held at Madurai on 4th January, It was also decided that the document would be published as a fully revised Code after incorporating all the amendments.

The publication is meant to serve as a guide to both the design engineers and the construction engineers but compliance with the provisions therein does not relieve them in any way of the responsibility for the stability, soundness and safety of the structures designed and erected by them.

The design and construction of road bridges require an extensive and thorough knowledge of science and technique involved and should be entrusted only to specially qualified engineers with adequate experience of bridge engineering, capable, of ensuring careful execution of work.

SCOPE This Code deals with the structural use of plain cement concrete and reinforced cement concrete in road bridges. IRC 2 Reinforced concrete: Concrete containing steel reinforcement non—prestressed conforming to Clause Plain concrete: Core of Helieally Reinforced Column 2 The portion of the concrete enclosed within the outer surface formed by the helical reinforcement.

Maintaining moisture condition to promote continued hydration of cement in the C! Effective Depth of a Beam: A mixture of cement, fine aggregate and water and any admixture that may be permitted by the competent authority. The thickness from the outer surface of the concrete to the nearest surface of the reinforcement.

Cement Any of the following types of cement may be used with prior approval of competent authority. Table 1: I Use of Portland pozzolana cement may be pemiitted only in plain concrete members.

Durability criteria like minimum cement content and water cement ratio, etc. Admixtures To improve workability of concrete, admixtures, conforming to IS: Aggregates All coarse and fine aggregates shall conform to [S: Coarse aggregate Coarse aggregates shall consist of clean, hard, strong, dense, non-porous and durable pieces of crushed stone, crushed gravel, natural gravel or a suitable combination thereof or other approved inert material.

The maximum size of the coarse aggregate may be as large as possible within the limits specified, but in no case greater than one quarter ofthe minimum thickness of member or 10 mm less than the minimum lateral clear distance between individual reinforcements or 10 nun less than the minimum clear cover to any reinforcement. The preferred nominal size of aggregate is 20 mm for reinforced concrete and prestressed concrete.

For plain concrete, preferred nominal sizes may be between 20 mm and 40 mm. Fine aggregates: Fine aggregates shall consist of hard, strong, durable clean particles of natural sand. Water Water used for mixing and curing shall be clean and free from injurious amounts of oils, acids, alkalis, salts, sugar, organic materials or other substances that may be deleterious to i concrete or steel.

In case of doubt regarding development of strength, the suitability of water for making concrete shall be ascertained by the compressive strength and initial setting time tests specified in The sample of water taken for testing shall represent the water proposed to be used for concreting, due account being paid to seasonal variation. The sample shall not receive any treatment before testing other than that envisaged in the regular supply of water proposed for use in concrete.

The sample shall be stored in a clean container previously rinsed out with similar water. Average 28 days compressive strength of at least three mm concrete cubes prepared with water proposed to be used shall not be less than 90 per cent of the average of strength of three similar concrete cubes prepared with distilled water.

The cubes shall be prepared, cured and 6 l The initial setting time of test block made with the appropriate cement and the water proposed to be used shall not be less than 30 minutes and shall not be more than 30 minutes from the initial setting time of control test block prepared with the same cement and distilled water. The test blocks shall be prepared and tested in accordance with the requirements of IS: The pH value of water shall not be less than 6.

Potable water is generally considered satisfactory for mixing concrete. As a guide the following concentrations represent the maximum permissible values: The details of test are given in 8. The details oftest shall be as given in Clause 8 ofIS: Table 2. Permissible Limit for Solids Tested as per Permissible limit max.

Organic IS: Inorganic IS: Sulphates as S0, IS: Cholorides as Cl IS: Mixing or curing of concrete with sea water is not permitted because of presence of harmful salts in sea water. Water found satisfactory for mixing is also suitable for curing concrete. However, water used for curing should not produce any objectionable stain or unsightly deposit on the concrete surface. The presence of tannic acid or iron cornpounds is objectionable. Reinforcement Reinforcement shall consist of the following grades of reinforcing bars, designated by their characteristic strength, where characteristic strength shall be taken as that specified in governing IS Specifications listed in Table 3 as the minimum value of 0.

Fe lS: Wire fabrics conforming to lS: Concrete Concrete grade: Minimum concrete grade, minimum cement content and maximum water cement ratio for structural members under different conditions of exposure are given in Table 5. Total water soluble sulphate S0, content of the concrete mix expressed as S0, shall not exceed 4 per cent by mass of cement used in the mix.

Total chloride content in concrete expressed as chloride-ion shall not exceed the following values by mass of L msoz as UUM 3 SM 22 ZOQ Emzmu. IO Type Per cent PSC 0. Requirement for Design Mixes Where there are insufficient data to satisfy the above, the current margin for the initial mix design shall be taken as given in Table 6.

IRC 2 This initial current margin, given in Table 6, shall be used only until sufficient data are available to determine the current margin as per sub-clause i above.

1987 pdf 21 irc

M15 Generally 1: Trial mixes: Trial mixes shall be prepared using samples of approved materials for all grades of concrete. Sampling and testing procedures shall be in accordance with Clauses The concreting plant and means oftransportation employed to make the trial mixes and to transport them to representative distances shall be similar to the corresponding plant and transport to be used in the works.

A clean dry mixer shall be used and the first batches shall be discarded. Test cubes shall be taken for trial mixes as follows. For each mix, set of six cubes shall be made from each of three consecutive batches.

Three from each set of six shall be tested at an age of 28 days and three at an earlier age approved by the engineer-in-charge. The cubes shall be made, cured, stored.

21 1987 pdf irc

The average strength of the nine cubes at 28 days shall exceed the specified characteristic strength by the current margin minus 3. Additional trial mixes: Additional trial mixes and tests, shall be carried out during production before substantial changes are made in the material or in the proportions of the materials to be used, except when adjustments to the mix proportions are carried out in accordance with Production of Concrete Batching and mixing: The quantities of cement, fine aggregate and the various sizes of coarse aggregate l3 A separate weighing machine shall be provided for weighing the cement.

Different types of cement shall not be mixed. The quantity of water shall be measured. Any admixture to be added shall be measured and, if solid, shall be measured by weight. The batch weight of aggregate shall be adjusted to allow for moisture content typical of the aggregate being used.

All measuring equipment shall be maintained in a clean and serviceable condition. Its accuracy shall be checked over the range in use when set up at each site, and maintained thereafter. The accuracy of equipment shall -fall within the following limits: Measurement of cement: The mixing time shall be not less than that recommended by the manufacturer, subject to the approval of the trial mixes by the engineer-in-charge.

Concrete mixers that have been out of use for more than 30 minutes shall be thoroughly cleaned before any fresh 14 Unless otherwise agreed the first batch of concrete through the mixer shall then contain only two-thirds of the normal quantity of coarse aggregate. Mixing plant shall be thoroughly cleaned before changing from one type of cement to another. Control of strength of designed mixes Adjustment to mix proportions: Adjustment to mix proportions may be made in order to minimise the variability of strength subject to approval of engineer-in-charge and to maintain the target mean strength subject to approval of engineer-in-charge.

Such adjustments shall not be taken to imply any change in the current margin. Change of current margin: When required by the engineer-in-charge, the current margin shall be recalculated in accordance with Clause The recalculated value shall be adopted as directed by the engineer-in-charge, and it shall become the current margin of concrete produced subsequently.

Sampling and Testing General 2 Samples from fresh concrete shall be taken as per IS: Sampling procedure: A random sampling procedure shall be adopted to ensure that each concrete batch shall have a reasonable chance of being tested, that is, the sampling should be spread over the entire period of concreting and cover all mixing units.

The point and time of sampling shall be at delivery into the construction, unless otherwise agreed to. The minimum frequency of sampling of concrete of each grade shall be in accordance with Table 8.

Test specimen and sample strength: Three test specimens shall be made from each sample for testing at 28 days. Additional cubes may be required for various purposes such as to determine the strength of concrete at 7 days for any other purpose.

The test strength of the sample shall be the average of the strength of three specimens. The individual variation should not be more than: Acceptance Criteria Compressive strength: When both the following conditions are met, the concrete complies with the specified compressive strength: The concrete mix proportions chosen should be such that the concrete is of adequate l6 Suggested ranges of workability of concrete measured in accordance with IS: Chloride content: The chloride-ion content of each of the constituent used in the calculation shall be one of the following: