Govlawircy1974sp55 0

IRC : 55-1974
RECOMMENDED PRACTICE
FOR
SAND-BITUMEN
BASE COURSES
THE INDUN ROADS CONGRESS

1987
/
IRC : 55-1974
MEMBERS OF THE SPECIFICATIONS & STANDARDS COMMITTEE

1. J.S. Marya
( v» onvcfior
Z. Jx.r.oIKKa
(Member-Secretary)
3. Qazi Mohd. Afzal
4. R.C. Arora
5. Maj. Genl. J.S. Bawa
6. T.N. Bhargava
7. E.G. Chandrasekharan
8. M.K. Chatterjce
9. B.K. Choksi
10. Dr. M.P. Dhir
11. The Director, HRS Madras
12. Dr. R.K. Gosh
13. M.K. Guha
14. Dr. V.N Gunaji
15. I.e. Gupta
16. Brig. Harish Chandra
17. S.A. Hoda
18. C L.N. Iyengar
19. M.B. Jayawant
20. S.L. Kathuria
21. Kewal Krishan
22. D.R. Kohli
23. P.K. Lauria
24. H.C. Malhotra
25. O. Muthachen
26. K.K. Nambiar
27. T.K. Natarajan
28. Parasivamurthy
29. M.D. Patel
30. Satish Prasad
31. A.R. Satyanarayana Rao
32. N. Sen
33. D. Ajitha Simha
34. H.P. Sinha
35. S.N. Sinha
36. Dr. N.S. Srinivasan
37. Dr. Bh. Subbaraju
38. Sujan Singh
39. C.G. Swaminathan
)
IRC : 55-1974
RECOMMENDED PRACTICE
FOR
SAND-BITUMEN
BASE COURSES
Published by
THE INDIAN ROADS CONGRESS

Jamnagar House, Shahjahan Road,
New DelhMlO Oil
1987
Price Rs.60/-
(Plus Packing & Postage
IRC : 55-1974
First Published : July, 1974
Reprinted : February, 1987
{Rights of Publication and of Translation are reserved)
Printed at PRINTAID, New Dclhi-110 020

IRC : 55-1974
RECOMMENDED PRACTICE FOR SAND-

BITUMEN BASE COURSES
1. INTRODUCTION
This recommended practice was prepared by the Bitumi-
nous Pavements Committee (personnel given below) in their
meeting held on the 10th December, 1973 :
Sujan Singh —Convenor

C.G. Swaminathan — Member-Secretary
Members
S. Mumtaz Ali C. B.L. Mathur
H.U. Bijlani K.P. Naif
M.K. Chatterjee T.H. Peshori
L.J. Chauhan Mahabir Prasad
A.Y. Gupte Satish Prasad
S. Islam Brig. Gobinder Singh
M.B. Jayawant R.P. Sikka
S.L. Kathuria S.N. Sinha
Kewal Krishan Lt. Col. S.S. Sundaram
M.R. Malya D. R. Upadhyaya
Later, was approved by the Specifications and Standards

it
Committee meeting held on the 31st January and 1st Feb-

in their
ruary, 1974 and then by the Executive Committee in their meeting
held on the 1st May, 1974. Finally, it was approved by the
Council in their meeting held on the 2nd May, 1974.
2. SCOPE
This recommended practice deals with the basic outlines of
providing one or more layers of base courses of sand stabilised
with bituminous materials like penetration grade bitumens,
cut-back bitumens and other special road oils laid directly over
the sandy subgrade or on a prepared base/sub-base of the
pavement.
The practice is mainly intended for desert areas such as in

Rajasthan or bordering close to it where no other construction
material except sand is economically available. A 10 cm thick
1
IRC : 55-1974
base course with a wearing course of 20 premix carpet has mm

been found to be satisfactory for carrying normal traffic upto about
150 vehicles per day (vehicles exceeding 3 tonnes loaded weight)
and also occasional heavy traffic of upto 1500 vehicles per day.
3. DESIGN CRITERIA
The sand-bitumen mix should be properly designed based on
the Hubbard Field Stability Method and satisfy the requirements
given below:
Requirements of the Mix

(1) Hubbard Field Stability at 60° C
for paving grade bitumen Minimum 360 kg
(2) Modified Hubbard Field Stability
at 25°C for cut-back bitumens Minimum 540 kg
(3) Per cent voids Maximum 20 per cent
Note : (a) It is preferable to keep per cent voids on the lower side than the
maximum limit as far as possible.
(b) For mixes in which Kankar is incorporated. Modified Hubbard

Field Stability Method may be used as a guide with appropriate
modification in stability values as desired by the Engineer-in
charge.
4. MATERIALS
4. 1 . Aggregates
Sand
4.1.1. The sand should be clean dune or pit sand free
:
from organic and other deleterious materials. No particular

gradation is specified except that the percentage passing 75 microns
sieve shall be not more than 10 per cent by weight. A typical
grading of sand as obtained in Rajasthan is given in the footnote.
4.1.2. Coarse aggregates for stabilization To impart greater :
stability to the stabilized sand mix, wherever possible and available,

coarse aggregates can be incorporated in the mix, up to a
Footnote :
1. Typical Gradings
J.S. Sieve Size Per cent passing
600 Microns 100
300 Microns 98-100
150 Microns 60-65
75 Microns 4-5
2. Single sized sands are not normally recommended.
2
IRC; 55-1974
maximum of 25 per cent by weight of the mix. The coarse

aggregates should be either gravel or kankar, clean and free
from fines and clayey matter, and the size be such that the
whole of it should retain on I.S. 4.75 mm
sieve with the maximum
size not being more than 1/3 the compacted thickness of the layer
to be laid.
4.2. Binder
The binder shall be paving bitumen of suitable penetration

grade or cut-back bitumen conforming to I.S. 73-1961 *Taving Bitu-
men "(Revised)" or I.S. 217-1961 "Cutback Bitumen (Revised)".
5. DESIGN OF MIX
5.1. Selection of Type of Bitumen

The selection for the type of bitumen shall depend upon the
type of sand available and atmospheric conditions prevailing at the
time of execution of the work.
5.2. Proportion of Bitumen
The proportion of bitumen in the mix shall be designed so as

to satisfy the requirements of the mix given in para 3.
6. CONSTRUCTION
6.1. Formation
The formation shall be prepared well ahead of laying the mix

in the usual manner, to get approximately the required cross slope
or superelevation and shall be compacted dry/wet as may be possi-
ble. The final finishing of the berms as well as providing the pro-
per cross slope or superelevation shall be done after the sand-bitu-
men work has been completed. In the case of sandy subgrades,
the carriageway shall be marked with planks of depth equal to the
proposed loose thickness of the sand-bitumen layer. The subgrade
shall have the required camber or superelevation of the finished
road surface, and it shall then be sprinkled with water and lightly
rolled with suitable rollers until it is well compacted.
6.2. Edge Key

Grooves 8 cm wide and 5 cm deep shall be dug at the edges on
3
IRC : 55-1974
either side so as to give a thickened edge. This is essential to give

additional strength to the edge.
6.3. Heating of the Materials

6.3.1. Whenever necessary, the binder shall be warmed or
heated as the case may be to that temperature pertaining to the
grade of bitumen used and as specified. Normally the temperature
shall be that at which the viscosity of the binder is 150-300 centi-
stokes for which the normal heating temperature for penetration
grade binder is between 150°-165®C and for cutbacks between
80°-120°C.
6.3.2. Sand shall be dry. If necessary and stipulated, the

sand and aggregates shall also be warmed and heated to the requi-
site temperature as specified, such as 135°-163°C when penetration
grade bitumen is employed. At least tilting drum type of drier is
recommended for this purpose.
6.4. Mixing
The mixing of sand, aggregates and binder shall be done by
using a twin shaft paddle type of mixer using the appropriate quan-
tities of aggregates and the binder as per design. The mixing time
shall be determined based on a few initial trials. Normally it will
be between 1 to 2 minutes. The mix shall be laid immediately
thereafter.
6.5. Laying of Mix

The sand-bitumen mix
shall be laid directly over the subgrade
upto 15 cm so as to be compacted to a 10 cm
to a loose thickness of
thickness. The material shall be spread uniformly and rolled to
the required density. It is to be ensured that uniform density is
obtained throughout the depth of the compacted layer.
6.6. Curing
Where cut-back bitumenis used, the mix, after laying should
be allowed curing till such time that initial rolling could be

for
started. The curing period may vary from 1 to 7 days depending
upon the type of cut-back used and the prevailing weather condi-
tions at the time of construction. The curing time should be reck-
oned from the time of preparing the mix to the period when by
periodically making a ball out of the aerated mix and applying a
light pressure with fingers, the ball crumbles. The smell of the
solvent in the cut-back also gives a good indication. Properly
cured mix should not give the small of the solvent except in traces.
4
IRC : 55-1974
6.7. Rolling
Where penetration grade bitumens are used, rolling should

start as soon as the hot mix is spread and levelled on the sub-base.
In the case of cut-backs, initial rolling shall be done at least after
twenty four hours after laying. In all cases, the initial rolling shall
be done where possible by light pneumatic tyred road roller. The
final rolling shall again be done with 8 to 10 tonnes smooth wheel
roller and continued till the desired density is achieved, which may
be a week where cut-back bitumens are used.
6.8. Opening to Traffic
Traffic may be allowed after 24 hours of completing the final

rolling operation. Only light pneumatic tyred vehicles may be
permitted initially. Normal traffic may be allowed only after a
month. But the final wearing surface should be laid within 3
months.
7. LAYING OF WEARING SURFACE

To provide a running surface and to protect the base from
abrasive action of traffic, a wearing course such as a 20 thick mm
premix carpet should be laid over the sand bitumen base, as per
IRC: 14-1977 "Recommended Practice for 2 cm Thick Bitumen
and Tar Carpets*'. The ruts and undulations that might be formed
during the initial use of the sand-bitumen base course should be
made good with premix aggregate before laying the wearing
surface.
8. CONTROLS
Adequate quality control at every stage of the work is essen-
tial and as such a field laboratory must be set up to ensure the
following controls :
(1) In no case shall the difference in temperature between the sand/

aggregate and binder exceed \4°C,
(2) Density : less of compacted surface,

For every 500 square metres or
one be conducted. This density shall not be less
field density test is to
than 95 per cent of the laboratory designed density.
(3) Tests on the mix At least one sample for every 50 m* of mix or a
:
minimum of two samples per shift should be collected and tested for
stability, voids and determination of the binder content.
(4) The finished surface shall be tested with a 3 m straight edge and any
irregularities greater than 6 mm rectified.

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IRC : 55-1974

THE INDUN ROADS CONGRESS

MEMBERS OF THE SPECIFICATIONS & STANDARDS COMMITTEE

THE INDIAN ROADS CONGRESS

First Published : July, 1974

Reprinted : February, 1987

{Rights of Publication and of Translation are reserved)

Printed at PRINTAID, New Dclhi-110 020

RECOMMENDED PRACTICE FOR SAND-

Sujan Singh —Convenor

Later, was approved by the Specifications and Standards

Committee meeting held on the 31st January and 1st Feb-

The practice is mainly intended for desert areas such as in

base course with a wearing course of 20 premix carpet has mm

Requirements of the Mix

(b) For mixes in which Kankar is incorporated. Modified Hubbard

from organic and other deleterious materials. No particular

4.1.2. Coarse aggregates for stabilization To impart greater :

stability to the stabilized sand mix, wherever possible and available,

2. Single sized sands are not normally recommended.

maximum of 25 per cent by weight of the mix. The coarse

The binder shall be paving bitumen of suitable penetration

5.1. Selection of Type of Bitumen

5.2. Proportion of Bitumen

The proportion of bitumen in the mix shall be designed so as

The formation shall be prepared well ahead of laying the mix

6.2. Edge Key

either side so as to give a thickened edge. This is essential to give

6.3. Heating of the Materials

6.3.2. Sand shall be dry. If necessary and stipulated, the

6.5. Laying of Mix

be allowed curing till such time that initial rolling could be

Where penetration grade bitumens are used, rolling should

6.8. Opening to Traffic

Traffic may be allowed after 24 hours of completing the final

7. LAYING OF WEARING SURFACE

(1) In no case shall the difference in temperature between the sand/

(2) Density : less of compacted surface,

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