Highway Maintenance - Making the Most of Your Money
Materials Innovations: ‘Hot Rolled Asphalt -The Road
to Innovation Drives us Back to Basics’
Bill Larner Technical Manager - Capita Engineering Laboratory
Specification & Control of Hot Rolled Asphalt Surface Course
with Surface Applied Pre Coated Chippings is important
SOME USEFUL FACTS FROM ASPHALT INDUSTRY ALLIANCE
www.asphaltuk.org
During the early 1990s the emergence of SMA (Stone Mastic Asphalt)
and Thin Surface Course systems developed in Europe, led to much
less use of HRA surfacing materials on the UK road network
Rutting of Recipe Mix HRAs under heavy traffic loads during hot
Summers influenced the move away from HRAs
Hot Rolled Asphalt with surface applied Pre Coated
Chippings was the Local Authority and Highways Agency
material of choice for motorways, primary routes and
many local roads during the 1970s, 1980s and early 1990s
Use of SMAs and Thin Surfacing in the
UK over the last 15 years has led to
concerns from many Engineers
regarding the suitability of some of
these types of materials, largely due to
fretting (loss from surface matrix) and
earlier than anticipated failure.
This in turn has resulted in many
Highway Authorities returning to the
use of HRA having not used the
material for many years.
OLD BRITISH STANDARDS FOR HRA MATERIALS:
BS 594 – Hot Rolled Asphalt
Highways Agency Specification for Highway Works Volume 1, Series 900
CURRENT BS EN STANDARDS FOR HRA MATERIALS:
BS EN 594987 – Asphalt for Roads and other Paved Areas
Specification for transport, laying and compaction and type testing protocols
BS EN 13108 – 4 – Hot Rolled Asphalt
PD 6691 – UK Guidance on the use of BS EN 13108 Bituminous Mixtures
Highways Agency Specification for Highway Works Volume 1, Series 900
THE RECENT RETURN TO USE OF HRA REQUIRES
CONSIDERATION OF ALL OF THE FOLLOWING:
From 1st July 2013, all Asphalt Materials are LEGALLY
required to be CE marked in accordance with the
Construction Products Directive
Evidence of this should be provided by suppliers on request.
LOCAL REQUIREMENTS AND CONSIDERATIONS
Site Conditions
Traffic Loadings (including growth factors)
Inclined sites
Economic considerations
Traffic Disruption
Sufficient room for site plant - Chipping Machine
Design Life Requirement or Assumptions
0 – 2 yrs
5 -10 yrs
Up to 25 yrs
Up to 40 yrs
Resurfacing Inlay of Surface Course
only
Design Life Considerations Approximate
New Road - Full Reconstruction, base
& foundation
Partial Reconstruction new base
Problems with material or workmanship
Local Knowledge and Experience
Use of Proven Local Quarries and Suppliers/Mixtures
Pre Works Surveys/ Core Data
Available Resource for Design, Planning & Supervision of Works
Programming of Works where possible outside of Winter months
Consideration of Appointment of Specialists
Use of UKAS Test House
Audit and As Built Records
PRACTICAL CONSIDERATIONS (In Advance of Works)
Before & During the Works, Consider the following:
Site Conditions, substrate condition & cleanliness
Substrate preparation by application of BBA/HAPAS Bond
Coats (SHW & BS EN 594987 3.1 Note 2 and 5.5)
Correct Use & Rate of Spread of Bond Coats (BS EN 594987
5.5.2 (further guidance in BS434-2)
Bitumen Emulsion Bond Coats to BS EN 13808
Polymer Modified Bond Coats to BS EN 14023
For claimed performance of Bond Coats see BBA Website
www.bbacerts.co.uk
GETTING THE JOB RIGHT FIRST TIME
Edge & Joint Sealing
Edge Preparation by Sealing with Bitumen or approved
sealant (As required by BS EN 594987 6.9)
Joint Preparation including sealing as required by BS EN
594987 6.8
Use of approved accredited Sector Scheme Laying Crews
GETTING THE JOB RIGHT FIRST TIME
GETTING THE JOB RIGHT FIRST TIME
Delivery Details
Check Delivery Tickets of HRA Material on arrival to site
(has the correct material been delivered?)
Delivery Temperature and Rolling Temperature may be checked and
recorded
Appearance of Material (check material appears to be evenly
mixed and stone is fully coated ensuring no contamination or
adverse bleeding of bitumen)
Chippings
Chipping of HRA – Requirements are given in BS EN 594987
Section 7
Coated Chippings shall conform to BS EN 13108-4
Chippings shall comply with the Resistance to Polishing and
Abrasion in accordance with EN 13043
GETTING THE JOB RIGHT FIRST TIME
Rate of Spread shall be either:
a) At least 70% of that needed to give shoulder to shoulder cover
b) At least 60% of shoulder to shoulder cover where there is
evidence that the required texture depth can be consistently achieved
Note that a typical RoS target value would be about 11.0 kg/m2
RATE of SPREAD of CHIPPINGS BS EN 594987 Section 7
SHOULDER to SHOULDER TEST (kg/m2)
RATE of SPREAD of CHIPPINGS
INSERT PHOTOS SHOWING TRAYS LAYOUT from BS
598 -1 and site photo of trays
CALBRATION OF CHIPPER – PRIOR TO WORKS
INSERT PHOTOS of FINISHED JOB
RATE OF SPREAD OF
CHIPPINGS ON SITE
RATE OF SPREAD OF CHIPPINGS -
TRAYS BENEATH CHIPPER
ON COMPLETION OF WORKS TEXTURE DEPTH TEST MAY BE REQUIRED
THE TEXTURE DEPTH RESULT MEASURED IN mm
WILL BE A FUNCTION OF THE RATE OF SPREAD OF
CHIPPINGS
ADDITIONAL TESTING
THE TEST REQUIRES 10
POSTIONS SPACED AT
INTERVALS OF 5m ON A
DIAGONAL LINE ACROSS
THE LANE WIDTH
TEXTURE DEPTH
(High Value = Small Patch)
DURING WORKS SAMPLING & TESTING of MATERIAL
TEXTURE DEPTH
by Sand Patch
(Large Patch = Low Value)
TEXTURE DEPTH
THERE HAVE BEEN RECENT CHANGES TO THE MINIMUM & MAXIMUM
TEXTURE DEPTH TO BE ACHIEVED WHERE APPLICABLE
CHECK HA INTERIM ADVICE NOTE IAN 154
ALSO SEE ADEPT/SOILS & MATERIALS GROUP DOCUMENT SELECTION
OF SURFACING GUIDANCE FOR LOCAL AUTHORITIES
SURFACE REGULARITY PROBLEMS
MAY RESULT IN PREMATURE SURFACE FAILURES
THIS CAN BE CHECKED BY USE OF THE ROLLING
STRAIGHT EDGE
SURFACE REGULARITY TESTING (see SHW Series 700)
DURING WORKS MEASUREMENT of HRA TEMPERATURE USING
INFRA RED THERMOMETER (see BS EN 594987)
INSERT PHOTOS Taking TEMPS
Insert photos of Blacktop Lab
MATERIALS TESTING for Correct Binder Content and
Aggregate Grading (PSD)
Most Common Types of HRA Mixtures
Performance (Heavy Traffic Road Type 1 >10 msa): 35/14 F surf des PMB WTR2
Design (Normal Traffic 2.5 to 10 msa): 35/14 F surf des 40/60 WTR1
Recipe (Light Traffic <2.5 msa)
WTR = Wheel Tracking Rate (Test for Resistance to Deformation) (Rutting)
PMB = Polymer Modified Binder
10 msa = 600 cvd approx.
2.5 msa = 220 cvd approx.
TERMINOLOGY
HRA 35/14 F surf des 40/60
This means 35% coarse aggregate of 14mm nominal size in the mixture
“F” represents Fine grading
Surf represents surface course
Des represents design mixture
40/60 represents the penetration grade of binder
HRA Product Quality Data IS Available from Supplier
The Highway Authority has the right to request information from the
HRA Material Supplier in support of the Product CE Mark:
Factory Production Test (FPC) Certificates
Aggregate Data
Binder Quality Data
CE Certificate of Conformity
Test Results & Product Performance Data
Evidence of Compliance with Local Specification
REASONS WHY DEFECTS MAY OCCUR DURING OR IMMEDIATELY AFTER LAYING
CLIMATE CHANGE – HOW WE CAN PROTECT OUR ROADS
By getting the job right first time,
We can help to ensure that our finished road is in the best possible condition to offer optimum protection against Climate Change........
Design, planning, preparation, drainage, pre works surveys, material selection, mixture type, compaction, site plant, Quality Assurance, testing, supervision, weather during works, edge sealing, post works inspections/monitoring.
THESE WOULD BE THE MINIMUM STEPS WE CAN TAKE TO HELP TOWARDS DURABILTY
FLOODING
REMEMBER.....THE SPECIFICATION BS EN 594987 REQUIRES THE
SEALING OF THE KERB FACE
THIS WILL PROTECT AGAINST WATER INGRESS & RISK OF DAMAGE
TO ROAD FOUNDATION
SUMMARY
Ensure you have a robust Specification
Use SHW and BS EN Specifications and apply QA requirements
Consider Local Specification & any available Core Survey data
Share technical information between all parties; Local Authority,
Contractors & Suppliers
Check Site Conditions and preparation of substrate
Ensure use of correct material type
Allocate resource for supervision
Use of QA Laying Crews, Audit Sampling & Testing of Materials
Seal around all gullies , manholes and along kerb edges
Consider drainage aspects
Monitor works during Maintenance Period
APPLY BEST PRACTICE AS STANDARDS CHANGE!
ALL OF THE ABOVE CAN HELP TO AVOID THIS
THANK YOU FOR LISTENING