SPECIFICATION FOR INSTALLATION OF PRECAST CONCRETE KERBS Published by Interpave The Precast Concrete Paving & Kerb Association 60 Charles Street, Leicester LE1 1FB tel: 0116 253 6161 fax: 0116 251 4568 e-mail:
[email protected] website: www.paving.org.uk Interpave is a Product Association of the British Precast Concrete Federation Ltd. © 2006 BPCF Ltd. Every effort has been made to ensure that the statements made and the opinions expressed in this publication provide a safe and accurate guide; however, no liability or responsibility of any kind (including liability for negligence) can be accepted in this respect by the publishers or the authors. Introduction This document is intended to provide guidance with the specification for installation of precast concrete kerbs, including model specification clauses where appropriate. It is intended only for the use of experienced paving designers with a full understanding of kerb technology. Manual for Highway Works All the requirements of the Manual for Highway Works Series 1100 shall apply except where the requirements of this series of special clauses supercede them. In particular, the following should be noted: Kerbs conforming to BS EN 1340 1 Except where otherwise specified in this Clause, precast concrete kerbs, channels, edgings and quadrants shall conform to BS EN 1340 and their dimensions, type designations and performances and classes shall be as described in this Clause and Appendix 11/1. 2 Precast concrete kerbs shall be laid to the requirements of BS 7533:Part 6. Additional Interpave Clauses and Notes NG1. Precast concrete kerbs 1.1 Precast concrete kerbs shall comply with the requirements of BS EN 1340. All kerbs shall be supplied by members of Interpave, The Association of Paving Block Manufacturers. 1.2 Precast concrete kerbs for the different applications as illustrated in Table 1. Table 1. Guide to physical properties Application Kerb type Characteristic Strength MPa 3.5 Abrasion mm N/A Freeze/thaw kg/m2 N/A Slip/skid Gardens Edging 150, 200 or 250 x 50 Edging 150, 200 or 250 x 50 Small element kerbs Small element kerbs BN, HB3 HB2 HB2 HB2 HB1 CS1, CS2 & CS3 N/A Driveways, paths and patios 3.5 N/A N/A N/A Footways, car parks and lightly trafficked areas residential roads Residential roads, Higher speed roads Industrial Channels 5.0 5.0 5.0 N/A 1.0 N/A N/A 1.0 N/A 5.0 5.0 N/A < 20 1.0 1.0 N/A 45 min Note Dimensional Tolerances, measured in accordance with BS EN 1340: Thickness ± 3% – minimum 3mm not exceeding 5mm Length/Width ± 1% – minimum 4mm not exceeding 10mm Downloaded from http://www.paving.org.uk 2 1.3 The recommended surface regularity of the surface course are: Design alignment Difference in levels at the joints of adjacent kerb units 12mm 3mm NG2. Installation There are three methods of installing kerbs, channels, edging and quadrants, as well as combined drainage and kerbs and linear drainage units: 1. Set on a race of fresh concrete 2. Bedded on a mortar race on top of an edge beam of hardened concrete or onto a mortar bedding on a carriageway base 3. Suitably bedded on a carriageway. Where kerbs are subjected to regular heavy traffic, e.g. on approaches to traffic calming ramps, kerbs should be cut to a length not exceeding 300mm. For curves of radius 15m or less, kerbs of appropriate radius shall be used as per BS EN 1340. 2.1 Laying on a kerb race A foundation of C6/8 or ST1 concrete should be deposited along the line of units, onto which the units are laid directly on fresh mixed concrete and set to line and level. The concrete should extend to a width to fully support the units and the backing concrete to haunch the units. It should have a minimum depth after placing the unit of: Edging units 75mm Small kerb units 100mm Kerb and channels 150mm The units should be laid in the fresh concrete and adjusted to line and level with a pavior’s maul. The units should be haunched monolithic with fresh concrete C6/8 or ST1 backing concrete. The concrete should be well compacted. In areas subject to heavy loading dowel bars should be firmly fixed in the kerb race and extended into the backing haunching to strengthen the haunch against horizontal displacement. Dowel bars may be omitted if the backing is adequately restrained by adjacent material. Where units are laid over or adjacent to a concrete pavement which includes movement joints, they should continue throughout the kerb race, kerb and haunching. The mortar bed may be omitted if units are bedded onto a concrete slab or foundation that is still plastic. 2.2 Laying units on a hardened edge beam or existing carriageway base The concrete edge beam should have a minimum depth of 150mm and sufficient width to accommodate the unit and the backing concrete. On the hardened edge beam or carriageway, the units are bedded down on a 12mm to 40mm thick mortar consisting of 3/1 sand/cement moist mix and immediately backed with a C6/8 or ST1 backing mix. The concrete should be fully compacted to support the units. Downloaded from http://www.paving.org.uk 3 2.3 Laying units bonded to the pavement surface The bonding materials and methods of bonding shall be to the manufacturer’s recommendations for this specific application. Bonded kerbs shall not be less than 100mm in width at the base, their height shall not exceed their width and they shall be bonded over their full width. The clear distance between unsupported pavement edge and back of kerb shall be not less than 100mm. Units shall be installed in accordance with the manufacturer’s instructions. They shall be bonded to the pavement surface with a resilient adhesive compatible with the pavement materials and be capable of withstanding a static push-off load of 10 kN/m applied parallel to the pavement surface at right angles to the kerb. NG3. Joints Joint filling between kerb units is generally unnecessary. The kerb units must not be butt jointed. The gap between kerbs should be a minimum of 2mm. Joints shall be provided in kerbs, channels, edgings and backing, which are laid on or adjacent to a concrete pavement to coincide with the pavement transverse contraction, warping and expansion joints. The joints shall be the same width as the joint sealing grooves of the pavement and shall be caulked and sealed. Concrete foundations to kerbs, channels and edgings laid adjacent to a concrete pavement shall be provided with joint filler board and placed vertically through the full extent of the concrete foundation at positions coinciding with the pavement joints. At expansion joints in bridge decks, the kerb joints shall be as described in Appendix 11/1. Where the Contractor proposes the details of bridge expansion joints such details shall include the intended treatment at kerbs and footways. The surface level of units of kerb, channel, edging and quadrant shall not deviate from the design level ± 6mm, nor shall the longitudinal surface regularity deviate more than 3mm in 3m when checked with a 3m straight edge. NG4. Laying units of precast kerbs, channels, edging and quadrants 4.1 Concrete kerb units should be placed mechanically, on the prepared base. 4.2 A string line should be accurately set out along the carriageway, at the intersection or the channel and the kerb, to the required level of the top of the units using pegs or steel pins. 4.3 The kerb units should be compacted to line and level. Allowances should be made on curves for the setting out of the string line which will have been made up of a series of straight lines approximating the radius of the curves. The final unit alignment should be checked to ensure that it follows a smooth curve both horizontally and vertically. 4.4 Kerbs should be laid so that the water check is 25mm above the surface of the pavement. At vehicular crossings, the upstand should be 25mm above the pavement. At pedestrian crossings, kerbs should be laid 6mm above the channel on the low side and level with the high side of the road. To assist wheelchair users the upstand should be between 0mm and 6mm. Consideration must be given to the removal of surface water at the crossing point by the placing of a drainage outlet. Downloaded from http://www.paving.org.uk 4