19Concrete road safety barrier (public domain)#
19.1General#
Clause 19 describes the work to be carried out where public domain concrete road safety barrier is required to be constructed under the Contract.
19.2Material#
19.2.1Concrete#
19.2.1.1General#
Concrete shall conform to the requirements of MRTS70 Concrete.
19.2.1.2Placed concrete#
Concrete placed by conventional means shall be grade S40/20.
19.2.1.3Fibre reinforced concrete#
Extruded barriers shall use fibre reinforced concrete.
Fibre reinforced concrete shall consist of grade S32/20, reinforced with nominal 50 mm virgin polypropylene fibrillated fibres incorporated at the rate of 0.9 kg/m³.
19.2.2Steel reinforcing#
Steel reinforcing shall conform to the requirements of MRTS71 Reinforcing Steel.
19.2.3Prestressing strand#
Prestressing strand shall conform to the requirements of MRTS73 Manufacture of Prestressed Concrete Members and Stressing Units.
19.2.4Cement mortar#
Cement mortar shall consist of one part of Type GP cement and three parts of clean, sharp sand with sufficient water added to form a dry-packing mortar. All materials shall comply with MRTS70 Concrete.
19.2.5Steel plate and sections#
Steel plate shall comply with the requirements of AS/NZS 3678 and shall be a minimum of Grade 250. Rolled steel sections shall comply with the requirements of AS/NZS 3679.1 and shall be a minimum of Grade 300.
19.2.6Bolts, nuts and washers#
Bolts shall conform to the requirements of AS 1111.1, nuts shall conform to the requirements of AS 1112.3 and flat washers shall conform to the requirements of AS 1237.1. Bolts, nuts and washers shall be hot-dipped galvanised in accordance with the requirements of AS/NZS 1214.
19.2.7Electrical conduit and pits#
Electrical conduit and cable pits shall comply with the requirements of MRTS91 Conduits and Pits.
19.2.8Compressible filler#
Compressible filler shall consist of a bitumen-impregnated fibrous material.
Approved products are listed in Clause 10.1 of Annexure MRTS14.1. Alternative products may be submitted to the department for approval.
19.2.9Joint sealant#
Joint sealant shall be a polyurethane, elastomer-based two-component product suitable for application in vertical joints using a dispensing gun.
Approved products are listed in Clause 10.2 of Annexure MRTS14.1. Alternative products may be submitted to the department for approval.
19.2.10Delineators#
Delineators shall comply with the requirements specified in Clause 10.2.4 of this Technical Specification for delineators on rigid road edge guide posts.
19.3Fabrication#
Cover assemblies for light poles and cable pits shall be fabricated to the details shown on Standard Drawing 1469.
Cast-in anchor assemblies shall be fabricated to the details shown on Standard Drawing 1467.
Angle connectors and reinforcing connectors shall be fabricated in accordance with Standard Drawing 1473.
All steel fabrication shall be carried out in accordance with the requirements of MRTS78 Fabrication of Structural Steelwork.
Steelwork shall be hot-dipped galvanised in accordance with the requirements of AS/NZS 4680.
All bolts shall be hot dip galvanised in accordance with the requirements of AS/NZS 1214.
19.4Construction#
19.4.1General#
Concrete road safety barrier shall be constructed in the locations shown on the Drawings and to the details shown on Standard Drawings 1458, 1466 to 1473 inclusive and 1486.
19.4.2Surface preparation#
The surface on which concrete road safety barrier is to be placed shall be prepared by trimming, if required, and sweeping to provide a smooth, even surface for the extrusion machine to travel.
Where dowels are required, a 70 mm diameter hole shall be cored in the existing surface 300 mm long x 24 mm diameter 500N dowel bars shall be installed in the hole and set in cement mortar.
19.4.3Conduits and pits#
Where required, electrical conduit shall be installed longitudinally in the location shown on Standard Drawing 1468. Conduit shall be securely anchored to the existing surface so that it is not displaced during concreting operations.
Where required, cable pits shall be installed in the locations shown in the design documentation.
Conduit and cable pits shall be installed in accordance with the requirements of MRTS91 Conduits and Pits.
19.4.4Formwork#
Formwork shall be provided for barrier terminal end sections, barrier cast against walls and piers and any other location where discrete casting of barrier is required.
Compressible filler shall be placed against existing walls and/or piers against which half-section barrier is to be cast.
Anchor bolts or anchor assemblies for connection of steel beam guardrail to barrier terminal ends shall be held securely in place on the formwork so that they are not displaced during placement and compaction of concrete.
19.4.5Steel reinforcing#
Steel reinforcing shall be installed in the locations shown on Standard Drawings 1468, 1470 (includes Steel Schedules) and 1473.
19.4.6Extruded concrete barriers#
Extruded concrete road safety barrier shall be constructed using a proprietary concrete extruding machine. The machine shall be capable of extruding concrete barrier of the profile shown on Standard Drawing 1468 to the lines and levels shown in the design documentation.
The finished wall surfaces shall be smooth, without surface cracks and other imperfections. Curing of the extruded barrier shall be in accordance with MRTS70 Concrete.
An initial test section of concrete road safety barrier at least five metres long (and preferably the minimum length nominated in the Standard Drawings) shall be constructed. The test section of barrier shall be inspected for conformance to this Technical Specification and, if conformance is established, further extruded barrier may be constructed. Hold Point 6
Subject to satisfying the requirements of the Technical Specification, the test section may be part of the Works.
The concrete barrier shall be terminated and restarted at each road lighting pole location and at each cable pit. The ends of the concrete barrier at such locations shall be perpendicular to the longitudinal grade of the pavement.
19.4.6.1Concrete#
Unless noted otherwise on the drawings, the concrete for extruded concrete road safety barriers shall consist of grade S32/20 concrete compliant with MRTS70 Concrete with the following additional requirements:
- a) reinforced with nominal 50 mm virgin polypropylene fibrillated fibres incorporated at the rate of 0.9 kg/m³
- b) specified slump of 10 mm to 20 mm with an acceptance tolerance of ± 10 mm.
Testing and acceptance of concrete for strength and slump shall be in accordance with MRTS70 Concrete.
19.4.7Placed concrete barriers#
Concrete in barrier terminal end sections, barrier cast against walls and piers and any other location where discrete casting of barrier is required shall be placed and compacted in accordance with the requirements of MRTS70 Concrete.
19.4.7.1Expansion joints#
Expansion joints in extruded concrete road safety barrier shall be provided at maximum intervals of 100 metres of continuous extrusion and at the junction between extruded barrier and terminal end sections. Expansion joints shall generally not be required where light poles are included in the line of the barrier.
Expansion joints shall be installed vertical, using compressible filler and 1 metre long x 16 mm or 24 mm diameter round dowel bar as shown on Standard Drawing 1468. The line of the expansion joint shall be perpendicular to the longitudinal grade of the pavement. The external edge of the joint shall be sealed with joint sealant.
19.4.7.2Contraction joints#
Contraction joints shall be provided at maximum intervals of four metres.
Contraction joints shall be formed by saw cutting to a depth of 50 mm right around the external surface of the barrier. The line of the saw cut shall be perpendicular to the longitudinal grade of the pavement. The time of saw cutting shall be determined so that shrinkage cracking is eliminated but in no case shall be longer than 12 hours after extrusion of the barrier.
19.4.8Cover plate assemblies#
Rolled steel angles for attaching cover plates shall be fixed to the ends of concrete barrier at light pole and cable pit openings using proprietary chemical anchors as shown on Standard Drawing 1469.
The gap between the ends of the barrier and the light pole footing or cable pit shall be filled with cement mortar, formed to the shapes shown on Standard Drawings 1469.
Cover plates shall be installed onto the attaching angles with M12 galvanised button head socket screws.
19.4.9Tolerances#
For insitu construction of concrete road safety barrier (i.e., excluding precast units) the dimensional tolerances provided in AS/NZS 3845 Set shall apply.
For precast units, unless specified elsewhere in the design documentation, the alignment in plan of the completed barrier shall not deviate from the design alignment by more than ± 20 mm at any point and the height shall not deviate from the design height by more than ± 20 mm at any point. The relative displacement of adjoining units shall not exceed 20 mm.
19.4.10Delineator spacing#
Delineators on concrete road safety barriers shall be mounted at the spacings prescribed in Part 2 of the MUTCD. The colour of delineators shall be in accordance with the requirements of the MUTCD.
Delineators shall conform with the requirements of Clause 19.2.10 and shall be affixed to the barrier via a fixing bracket in accordance with Standard Drawing 1466. The fixing bracket shall be attached to the top of the concrete road safety barrier with one 10 mm diameter masonry anchor with a minimum of 30 mm into concrete.
19.4.11Precast concrete#
Precast concrete barriers and/or components shall be manufactured in accordance with the relevant Standard Drawings and with the requirements of MRTS72 Manufacture of Precast Concrete Elements. Precast concrete barriers shall be installed to the line and level shown in the design documentation. Barriers shall be installed to achieve the minimum barrier length as detailed in the design documentation. Individual precast concrete barriers shall be connected together with permanent connectors as specified in the design documentation.