Kent Design - Technical Appendix - Kent County Council

highways specification and construction
Traffic Category shall be to BS 4987 Category B
All material shall comply with Clause 901 and this Section
Basecourses should wherever possible be laid in conjunction with
roadbases and may be used by traffic. Any damage to the surface
should be made good with basecourse or surfacing material.
Dense Bitumen Macadam develops its strength largely as a
consequence of good compaction whilst the material is adequately
hot. The air voids in dense macadam and hot rolled asphalt shall be
checked using a calibrated nuclear density meter at a rate of 1 test
per 25 linear metres of carriageway.
The mean total air voids in Dense Bitumen Macadam shall comply
with the requirements of Clause 929 except that for routine
purposes a calibrated nuclear density gauge may be used
The mean total in-situ air voids of six consecutive determinations on
Hot Rolled Asphalt shall not exceed 5%, with the air voids in any
individual determination not exceeding 8%. The Air Voids content
shall be calculated to ±0.1% as follows:
Air Voids content = ( 1 - ρ/ρmax ) x 100%
where ρ is the initial dry bulk density determined in accordance with
BS 598 Part 104 and ρmax is the maximum density of the Hot Rolled
Asphalt determined in accordance with BS DD 228:1996.
Where there is uncertainty 150 mm diameter cores shall be taken at
the same frequency as stated above and the Air Voids content
determined. They shall comply with the requirements above.
The satisfactory performance of thin surfacing depends upon a good
bond between the surfacing material and the basecourse. Before the
wearing course is laid all loose material or other material adhering to
the surface shall be removed by mechanical broom and if necessary
water jetting.
The surface texture shall comply with the requirements of Kent County
Council`s Specification for Low texture, initially and retained for 2 years
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Kent
Design
TABLE 17: ROLLED ASPHALT
The surfacing provides the impermeable and skid resistant surface to
the road, it is constantly visible to the public and defines their view of
the quality of construction.
3.4.8 CONSTRUCTION OF ROAD PAVEMENTS - BLOCK PAVED SURFACE
In the case of Local Distributor Roads, Industrial Access Roads, Major
Access Roads and Minor Access Roads block paving shall be laid in
45 O herringbone pattern.
Minor Access Ways and Home-zone block paving may be laid either
in 45 O herringbone pattern or in stretcher bond at 90° to the kerb.
There shall be two stretcher courses adjacent to kerbs and a single
stretcher course round ironwork.
Block paving shall be laid in accordance with BS 7533 Part 3. (Clay
and Concrete pavers: Code of practice for construction of
pavements).
The structural strength of a road with a block paved surface depend
upon the thickness of laying sand not exceeding the permitted
tolerances. Any low areas in the roadbase must be made good with
well rammed hot dense bitumen macadam prior to surfacing taking
place. Significant areas outside the permitted tolerances will require
the roadbase to be removed and reinstated to the correct tolerances.
Block Paving shall have a minimum Polished Paver Value of 45
3.4.9 JUNCTION WITH CONCRETE CARRIAGEWAY
Where flexible construction meets a rigid concrete road, a double
row of granite setts bedded on at least 150mm of ST2 mix concrete
and jointed fully with strong cement mortar, shall be laid across the
full width of the joint.
The full depth of construction shall be maintained beneath the sett
paving.
Clause Material Thickness BS594 Coarse aggregate Binder PEN Remarks
(mm) Table Col Nom % Size (mm)
904 Roadbase 90, 80, 70 2 2/5 60 28 50 Up to 60% recycled asphalt may be
905 Basecourse used in accordance with Clause 902
905 Basecourse 60 2 2/4 60 20 50
905 Basecourse 40 2 2/2 50 14 50
TABLE 18: COATED MACADAM
Clause Material Thickness Mix Coarse aggregate Binder PEN Remarks
(mm) Size Min Max
mm PSV AAV
Notes:
932 Roadbase/ 90, 80, 70 Clause 929 28 n/a n/a 50
934 basecourse
60, 50, 45 Clause 929 20 n/a n/a 50
906 Basecourse 40 BS 4987 Clause 7.3 14 n/a n/a 100
906 Basecourse 25 BS 4987 Clause 7.4 10 n/a n/a 100
Clause 929 material shall have the
approval of the Engineer following an
on-site or off-site approval trial.
Up to 60% recycled asphalt maybe
used in roadbase or basecourse in
accordance with Clause 902
912 Wearing course 35 BS 4987 Clause 7.4 10 50 12 100 Traffic category B
912 Wearing course 20, 15 BS 4987 Clause 7.5 6 45 12 100 Traffic category B
a) Gravel aggregate is not permitted
b) Where it is necessary to use the Hot Rolled Asphalt Basecourse as the
running surface for traffic of any kind for more than 7days, the percentage of
materials passing the 75micron BS sieve shall be not less than 5%
c) The delivery temperature at any point in the load shall be in the range 165 o C to 120 o C
(50Pen) 155 o C to 120 o C (100Pen)