Specification Part 3 - Road & Bridge Works - Urban Administration ...

ase, followed by a cover of stone chips rolled in to form a wearing course to the requirements of
these Specifications. For information on the Design of Surface Dressing refer to the Manual for
Construction and Supervision of Bituminous Works.
510.2. Materials
510.2.1. Binder: The binder shall have a kinematics viscosity lying in the range IxlO4 to TxlO5
centistokes at the expected range of road surface temperatures at the construction site during the
period of lying. The type of binder to be used will be stated in the Contract documents and shall
.comply with one of the following:
Paving Bitumen IS: 73
Bitumen Emulsion IS: 8887
510.2.2. Aggregates for surface dressing:
(i)The chips shall conform to the requirements of Clause 504.2.2., except that their water
absorption shall be restricted to a maximum of 1 per cent and they shall have a Polished Stone
value, as measured by the method given in BS812 (Part 114), of not less than 60. (ii)The chips
shall be single sized, clean, hard, durable, of cubical shape, free from dust and soft or friable
matter, organic or other deleterious matter and conforming to one of the grading given in Table
500-21.
510.2.3. Rates of spread of binder and chips for surface dressing: For the purpose of pricing
the Bill of Quantities the rates of spread given in Table 500-20 shall be priced.
TABLE 500-20.
NOMINAL RATES OF SPREAD FOR BINDER AND CHIPPINGS
Chipping Size mm
Binder
(penetration grade bitumen)
kg/m2
Chips
Cum/m2
19 1.2 0.015
13 1.0 0.010
10 0.9 0.008
6 0.75 0.004
Note:
(1) These rates of spread are for pricing purposes - see Clause 510.2.3 and Clause 510.8
(2) For emulsion, these rates of spread are for the residual bitumen and appropriate adjustment
must be made to determine the total quantity.
(3) Refer to Manual for Construction and Supervision of Bituminous Works for the procedure of
determining the rates of spread of binder and chips.
510.2.4. Anti-stripping agent: Where the proposed aggregate fails to pass the stripping test
then an approved adhesion agent may be added to the binder in accordance with the
manufacturer’s instructions. The effectiveness of the proposed anti - stripping agent must be
demonstrated by the Contractor, before approval by the Engineer in charge.
510.2.5. Pre -coated chips: As an alternative to the use of an adhesion agent the chips may be
pre-coated before they are spread except when the sprayed binder film is a bitumen emulsion.
Pre-coating the chips may be carried out in any one of the two methods: -
(1) Mixing them with 0.75 to 1.0 per cent of paving bitumen by us light of chips in a suitable
mixer, the chips being heated to 160°C and the bitumen to its application temperature. The precoated
chips shall be allowed to cure for at least one week or until they become non sticky and
can be spread easily.