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

519.3.2.2. Preparation of base: The base on which the cold mix is to be laid shall be prepared
shaped and graded to the required profile in accordance with Clauses 501 and 902 as
appropriate, and a prime coat if specified in the contract, or required by the Engineer in charge,
shall be applied in accordance with Clause 502, or as directed by the Engineer in charge.
519.3.2.3. Tack coat: A tack coat in accordance with Clause 503 shall be applied over the base
on which the cold mix is to be laid if specified in the Contract or required by the Engineer in
charge.
519.3.2.4. Preparation and transportation of the mixture: Mixing shall be carried out using one
of the following types of mixer, which is provided with equipment for spraying the binder at a
controlled rate, and, if necessary, for heating the binder to a temperature at which it can be
applied uniformly to the aggregate:
(a) Rotary drum type concrete mixer,
(b) Single or twin shaft concrete or macadam mixer,
(c) Batch or continuous type mixer without dryer or screens other than a scalping screen.
A sufficient number of haul trucks with smooth, clean beds should be available to ensure
continuous operation of the mixing plant. The type of truck used for transporting the mixture from
the mixer to the road site must be suited to the chosen laying procedure.
519.3.2.5. Spreading:
(i)The mixed material should be spread immediately after preparation.
(ii)The mixture shall be placed only when the specified density can be obtained.
(iii)The mixture shall not be placed on any wet surface or when weather conditions will otherwise
prevent its proper handling or finishing.
(iv)If spreading by motor grader, the grader must have a blade that is straight and sharp and long
enough to ensure finishing closing straight transverse tolerances and all joints and linkages must
be in good condition.
(v)The grader must be heavy enough to hold the blade firmly and uniformly on the surface while
spreading the mixture. On surface courses, the tyres must be smooth.
(vi)The methodology for spreading shall be approved by the Engineer in charge prior to laying,
and if required a laying trial conducted to prove the laying method satisfactory before approval.
519.3.2.6. Compaction:
(i)Initial compaction of the laid material shall be carried out using a pneumatic-tyred roller of a
weight appropriate to the layer thickness to be compacted with single layer thicknesses being 25-
100mm and all compaction being in accordance with Clause 501.6 and 501.7.
(ii)Smooth tyres shall be used. Final rolling and smoothing of the surface should be completed
using steel wheel rollers.
(iii)The Contractor shall demonstrate at laying trials that his proposed laying and compaction
methods can achieve a satisfactory result.
519.3.3. Opening to traffic:
(i)Traffic shall not be allowed to run on new work until all the water or volatiles in the mixture have
evaporated.
(ii)The rate of evaporation will be influenced by the temperature, humidity and wind conditions.
519.3.4. Surface finish and quality control of work:
(i)The surface finish of construction shall conform to the requirements of Clause 902.
(ii)For control of the quality of materials supplied and the works carried out, the relevant
provisions of clause of 501.8.4.1.
519.3.5. Arrangements for traffic: During the period of construction, arrangements for traffic
shall be made as per direction Engineer in charge.