TECHNICAL NOTE

This technical note is applicable to 2 products:

Type 1 Granular Subbase Material (GSB 1) for reinstatements;
Type 1 Unbound Mixtures for Subbase


Projects
Harbours and Ports - Heavy Duty Pavements;
Pavements - Roads, Car Parks, Airport;
Reinstatement of Openings in Highways

Applications
Base for trench reinstatement;
Subbase for trench reinstatement;
Unbound mixtures for subbase

Materials
The following recycled and secondary aggregates may be used alone or in combination:
  • Blast Furnace & Zinc Slag
  • Burnt colliery spoil
  • China clay sand and Stent
  • Incinerator bottom ash
  • Reclaimed asphalt
  • Recycled aggregate (RA)
  • Recycled Concrete Aggregate (RCA)
  • Recycled glass
  • Slate aggregate
  • Spent oil shale
  • Steel slag
Information source / date
Based on November 2009 Manual of Contract Documents for Highway Works: Volume 1 (MCHW1), Specification for Highway Works, Series 800 Clause 801 and 803. April 2010 Highway Authorities and Utilities Committee Specification for the Reinstatement of Openings in Highways Clause S5.1.2, 3rd Edition (England) and the 2007 Structural Design of Heavy Duty Pavements for Ports and Other Industries.

Compliance references
  • Highway Authorities and Utilities Committee Specification for the Reinstatement of Openings in Highways, Third Edition (England), April 2010
  • Manual of Contract Documents for Highway Works: Volume 1 (MCHW1), Specification for Highway Works, Series 800
Technical references
  • BS 1377-2: 1990 Methods of test for soils for civil engineering purposes. Classification tests
  • BS 812-124: 2009 Testing aggregates Part 124: Method for determination of frost heave
  • BS EN 1097-1: 2011 Tests for mechanical and physical properties of aggregates Part 1: Determination of the resistance to wear (micro-Deval)
  • BS EN 1097-2: 2010 Tests for Mechanical and Physical Properties of Aggregates - Part 2: Methods for the Determination of Resistance to Fragmentation; Supersedes BS 812-110: 1990, BS 812-111: 1990 and BS 812-112: 1990
  • BS EN 1097-6: 2000 Tests for mechanical and physical properties of aggregates - Part 6: Determination of particle density and water absorption - CORR 14306: March 31, 2003; AMD 15908: December 16, 2005
  • BS EN 12457-3: 2002 Characterisation of waste Leaching Compliance test for leaching of granular waste materials and sludges Part 2: One stage batch test at a liquid to solid ratio of 10 l/kg for materials with particle size below 4 mm (without or with size reduction)
  • BS EN 13242: 2002+A1: 2007 Aggregates for unbound and hydraulically bound materials for use in civil engineering work and road construction
  • BS EN 13285: 2010 Unbound Mixtures - Specification
  • BS EN 1367-2: 2009 Tests for Thermal and Weathering Properties of Aggregates - Part 2: Magnesium Sulfate Test - Supersedes BS 812-120: 1989
  • BS EN 1744-1: 2009 Tests for Chemical Properties of Aggregates - Part 1: Chemical Analysis
  • BS EN 1744-3: 2002 Tests for Chemical Properties of Aggregates - Part 3: Preparation of Eluates by Leaching of Aggregates
  • BS EN 933-11: 2009 Tests for geometrical properties of aggregates. Classification test for the constituents of coarse recycled aggregate
  • BS EN 933-5: 1998 Tests for geometrical properties of aggregates. Determination of percentage of crushed and broken surfaces in coarse aggregate particles
  • EA NEN 7375: 2004. Leaching characteristics of solid (earth and stony) building and waste material. Leaching tests. Determination of the availability of inorganic components for leaching. Environment Agency (2005)
  • HD 35/04: DMRB Vol. 7, Section 1 Preamble, Pavement Design and Maintenance, Part 2, Conservation and the Use of Secondary and Recycled Material. Highways Agency, Welsh Assembly Government, Transport Scotland and the Department of the Environment for Northern Ireland.
  • MCHW 1 (Manual of Contract Documents for Highway Works Volume 1), Specification for Highway Works. Highways Agency, Welsh Assembly Government, Transport Scotland and the Department of the Environment for Northern Ireland. The Stationery Office, London.
  • PD 6682-6:2009 Aggregates for unbound and hydraulically bound materials for use in civil engineering works and road construction. Guidance on the use of BS EN 13242
  • SROH (Specification for the Reinstatement of Opening in Highways) 3rd Edition (2010) Highway Authorities and Utilities Committee. The Stationary Office, London.
  • TRL Report 447 (2005).Sulfate specification for structural backfills. Reid, JM, Czerewko, MA and Cripps, JC. TRL Limited Crowthorne, UK.
  • The Structural Design of Heavy Duty Pavements for Ports and Other Industries, 4th Edition (2007) Interpave. The British Precast Concrete Federation Ltd, Leicester.
  • WRAP (2004 and 2005). The quality protocols for the production of aggregates from inert waste in England, Scotland and Northern Ireland.
  • WRAP (2008). Quality protocol for the production of aggregates from inert waste. Guidance notes for Producers' compliance checklist.
  • WRAP (2008). Quality protocol for the production of aggregates from inert waste. Guidance notes to the Purchasers'/Specifiers' compliance checklist.
  • WRAP (2008). Quality protocol for the production of aggregates from inert waste. Producers' compliance checklist.
  • WRAP (2008). Quality protocol for the production of aggregates from inert waste. Purchasers'/Specifiers' compliance checklist.
Composition requirements

Type 1 unbound mixture shall be made from crushed rock, crushed slag, crushed concrete, recycled aggregate or well burnt non-plastic shale. 

The composition of all Recycled aggregate (RA) and Recycled concrete aggregate (RCA) used in unbound mixtures shall have been tested in accordance with Clause 710 of the Manual of Contract Documents for Highway Works: Volume 1 (MCHW1).  Clause 710 requires that the composition be determined in accordance with BS EN 933-11. Recycled aggregate (RA) and Recycled concrete aggregate (RCA) used in unbound mixtures in accordance with Clause 803 (MCHW1) shall comply with the composition requirements of Table 8/3 of the 800 Series, reproduced below.

Clause 710 requires that recycled aggregates are produced in accordance with the ‘Quality Protocol for the production of aggregates from inert waste’ and the ‘Producers’ compliance checklist’ published by the Waste & Resources Action Programme (WRAP). The results of all quality control checks carried out by the Contractor shall be complied in accordance with the procedure set down in the above document and with those in Clause 710. These shall be delivered promptly to the client on request. For further information refer to the WRAP quality protocols for the production of aggregates from inert waste and the WRAP quality protocol checklists and guidance notes for producers, specifiers and purchasers of sustainable aggregates.

The operation of a Factory Production Control system for the production of unbound mixtures is required by BS EN 13285.

Burnt colliery spoil and spent oil shale are required to be non-plastic.

Volume 7, Section 1, Chapter 2 (HD 35/04) in the Highway’s Agency’s Manual of Contract Documents for Highway Works notes that to 15% by mass of Incinerator bottom ash can be a component of Unbound mixtures for subbases, although more can be used following additional testing.

Volume 7, Section 1, Chapter 2 (HD 35/04) in the Highway’s Agency’s Manual of Contract Documents for Highway Works notes that Recycled glass can be used in Unbound mixtures for subbases, although it is not specifically named in Series 800 of the MCHW1.

The recycled and secondary aggregates listed have a specific or a general provision for use within the Manual of Contract Documents for Highway Works, and may be used as long as these materials meet the required properties for aggregates given above.

The Structural Design of Heavy Duty Pavements for Ports and other Industries suggests the use of Type 1 or Type 2 unbound subbase material, as defined in MCHW1, Series 800.

Table 8/3 - 800 Series:

Unbound Mixture Type 1Type 2Type 4 (asphalt arisings)
Component Identified by Clause 710Maximum Permitted Content              (% by mass) 
Asphalt (Class Ra)50500
Glass (Class Rg)25
Other materials (Class X), including wood, plastic and metal 1
 

Grading requirements

The categories used to express the requirements of the mixture are given below:

Unbound mixture (BS EN 13285)

Type 1 Unbound subbase mixture

Mixture requirement category

- Designation (see Note 1)

0/31.5

- Maximum fines category (UF)

UF9

(i.e. < 9% by mass passing the 0.063 mm sieve)

- Oversize category (OC)

OC75

(i.e. 75 to 99% by mass passing D)

Grading requirement category

 

- Overall grading (G)

GP

The aggregate grading shall be within the limits below:

Sieve size (mm)

Percentage by mass passing the sieve size shown

Overall grading range

Supplier declared value grading range

Tolerance on the supplier declared value

63

100

-

-

35.1

75 - 99

-

-

16

43 - 81

54 – 72

± 15

8

23 - 66

33 – 52

± 15

4

12 - 53

21 – 38

± 15

2

6 - 42

14 – 27

± 13

1

3 - 32

9 – 20

± 10

0.063

0 - 9

-

-

Additional requirements for individual batches from a Factory Production Control (FPC) system are given below:


 

Grading of individual batches - differences in values passing selected sieves

Retained sieve size (mm)

Passing sieve size (mm)

Percentage by mass passing the sieve size shown

Not less than

Not more than

8

16

7

30

4

8

7

30

Notes:

1.     Aggregate sizes are expressed as d/D or lower limiting sieve size/upper limiting sieve size.

2.     Annex B of BS EN 13285 contains an explanation of supplier declared grading values.

Physical properties requirements

Aggregates shall comply with the requirements listed in Clause 801 and Table 8/2 of the 800 Series of the Specification for Highway Works. There are volume stability requirements for blastfurnace and steel slag.

Subject to any tolerances given in MCHW table 7/1, material shall not be frost susceptible if used within 450 mm of the designed final surface of a road or paved central reserve area, or 350 mm if the Mean Annual Frost Index (MAFI) of the site is less than 50. Material shall be classified as non frost susceptible if the mean heave is 15 mm or less, when tested in accordance with BS 812-124:2009.

Chemical properties

General requirements for sulfur compounds of materials deposited within 500 mm, or other distances described in Appendix 7/1 of the MCHW, of concrete, cement bound materials, other cementitious materials, stabilised capping or metallic structural elements forming part of the Permanent Works are given in Clause 801.2 and 801.3 of the 800 Series of the Specification for Highway Works (Series 800). The requirements above shall not apply to metallic items protected by concrete and ancillary metallic items such as the tops of chambers and gullies. Further details are given in the Notes for Guidance for the Specification for Highway Works, NG800 Series (Series NG800) and in TRL 447.

No further restrictions on chemical properties are specified. However, in certain circumstances, the Environment Agency in England and Wales, (or their equivalent in Scotland and Northern Ireland) will require that the construction activities will not lead to contamination of ground or surface waters due to leaching or spillages. For this reason you are advised to discuss, as a matter of routine, your intended application with the relevant regulatory authority.

Additional information

Under the Construction Products Regulations, CE marking will be mandatory for aggregates from July 2013. This includes aggregates from primary, recycled and secondary sources.

Maintained by TRL Limited from October 2009.

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revised: 24 Jan 2011

Important warning

The information set out above is only concerned with the technical aspects of construction and is of a general nature only and not intended to be relied upon in specific cases.

It is derived from currently available UK Standards and Specifications applicable at the time of writing. Reference should be made to the relevant Standards and Specifications applicable at the time of writing and you should seek and rely upon expert professional advice on specific issues.

The information does not take account of environmental issues which you should discuss as a matter of routine with the regulatory authorities (the Environment Agency in England and Wales, the Scottish Environment Protection Agency in Scotland and the Department of the Environment in Northern Ireland).

Consequently, the information is provided only on the condition that WRAP and their sub-contractors will not be liable for any loss, expense or damage arising from your use or application of such information. See clause 3 of our Terms and conditions.