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