04-CONCRETE PAVEMENT



CEMENT CONCRETE PAVEMENT

Concrete pavement comes under the classification of rigid pavement. The life of a rigid pavement is much higher than that of a flexible pavement.Even though the cost of rigid pavement is very high, owing to its longer service life, better riding surface and low maintenance cost, rigid pavements are widely used in the present road construction. The details and construction procedure for un- reinforced, dowel jointed plain cement concrete pavement are given under Section 600 of MoRTH Specifications for Road and Bridge works (5th revision).

MATERIALS

  1. Only materials from approved sources shall be allowed to be used in the construction.
  2. Cement used shall be preferably 43 grade or higher.
  3. Admixtures, if used, shall be checked for its performance through laboratory and field trials.
  4. Aggregates shall conform to IS: 383 with maximum Los Angeles Abrasion value of 35%.
  5. The maximum size of coarse aggregate shall be 25 mm for pavement concrete. The water absorption shall not exceed 2%.
  6. The fine aggregate shall conform to IS: 383 with fraction passing 75 micron sieve not exceeding 4%.
  7. Water for mixing shall meet the requirements stipulated in IS: 456.
  8. The dowel bars shall conform to IS: 432 Grade I and tie bars to IS: 1786 and of Fe500 Grade or plain bars conforming to IS: 432 Grade I.

JOINT MATERIALS

  1. Joint filler board to be provided at expansion joints shall comply with the requirement of IS: 1838.
  2. The joint sealing compound shall be of hot poured elastomeric type or cold polysulphide/polyurethane/silicone type as per IRC: 57.

MIX DESIGN

  1. The mix design for pavement concrete shall be prepared as per IS: 10262 -Recommended guidelines for concrete mix design. Guidance in this can also be obtained from IS: SP: 23- Hand book on concrete mixes. The mix design shall be based on flexural strength of the concrete.
  2. The cement content shall not be less than 350 kg per m3 of concrete, but in no case shall exceed 425 kg.
  3. The maximum free water cement ratio shall be 0.50.
  4. The control of workability in the field shall be exercised by slump test as per IS: 1199. A slump of 25 mm ±15 mm is reasonable for paving.

PREPARATION OF SUBBASE
a) The pavement quality concrete shall be placed over a subbase prepared with dry lean concrete.
b) Cracks exceeding 10 mm if found on the subbase concrete layer shall be repaired with fine cement concrete or bituminous concrete.
c) Separation membrane of 125 micron impermeable plastic sheets shall be nailed to the lower layer with concrete nails.

CONSTRUCTION JOINTS
a) Joints shall be cut to full depth using sawing machine after the concrete has hardened.
b) Longitudinal and transverse joints in the subbase shall be staggered so that they are at least 1 m and 0.30 m apart.
c) Contraction joints are mechanical sawn joints grooves 3 mm to 5 mm wide extending to one-fourth to one-third depth of the slab.
d) The expansion joints shall consist of joint filler board and dowel bars.
e) Transverse construction joints are made wherever concreting is after a day’s work or work suspended for more than 30 minutes.

f) Longitudinal joints shall be saw cut at least one-third depth of the slab.
g) The tie bars at longitudinal joints shall be placed correctly.
h) The dowel bars shall be positioned at mid-depth of the slab, aligned parallel to
the surface of the slab and to the centre line of the carriage way, unless
otherwise specified in the Drawing.
i) The dowel bars supported on cradles in assemblies shall be checked for deflection and shall be within limits given under Clause 602.6.5.2 of MoRTH
Specifications mentioned below:

i) All bars in joint shall be within ±2 mm per 300 mm length.

ii) Two-third of the total bars shall be within ±3 mm per 500 mm length.
iii) No bar shall differ in alignment from an adjoining bar by more than 300 mm length of bar in either the horizontal or vertical plane.
iv) Cradles supporting the dowel bar shall not extend across the line of joint.

j) For bars inserted using a dowel bar inserter, the tolerance for alignment may be twice as indicated above.
k) The dowel bars shall be covered by a thin plastic sheath to the specified length.
l) Transverse joints at curves shall be radial in the direction of the radius.

QUALITY CONTROL

    1. The surface levels and regularities shall be checked for compliance with respect to Clause 902.3 and 902.4 of MoRTH Specifications (5th revision).
    2. Density of the paved layer shall be assessed from at least 3 cores drilled from each part of the trial section.
    3. No vehicular traffic is allowed to run on the finished surface of a concrete pavement within a period of 28 days of its construction and until the joints are permanently sealed.

REFERENCES

1. MoRTH-Specifications for Road and Bridge works, 5th Edition 2013 – published by IRC, New Delhi.

2. IRC-SP: 11-Quality control for the construction of roads and runways - published by IRC, New Delhi.

3. IS-SP: 23 -Hand book on concrete mixes – published by Bureau of Indian Standards.

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