SPECIFICATION FOR ROAD SAFETY HARDWARE SYSTEMS APPENDIX D: SLIP FORMED CONCRETE BARRIERS

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Thomasina Eaton
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1 SPECIFICATION FOR ROAD SAFETY HARDWARE SYSTEMS APPENDIX D: SLIP FORMED CONCRETE BARRIERS 1 GENERAL All slip formed concrete barrier shall be formed using the F-shape profile detailed in Specification M23 Appendix A. NOTE: This is a working draft release. Minor changes may be made before final release. 2 GEOMETRY Any comments or questions may be sent to julian.chisnall@nzta.govt.nz. 2.1 A minimum 3m long by 250mm deep reinforced concrete anchor footing shall be provided at all barrier terminations and at 60m maximum spacing between barrier terminations. Reinforcing shall be continuous through intermediate anchor footing (no air gap required). 2.2 Anchor footing arrangement as shown in Drawing B8-1 below (Extract from M23 Appendix B, in preparation) is an acceptable solution. Footing length may be increased to facilitate construction is desired. 2.3 Where the barrier height transitions up or down, this must occur over at a rate not exceeding 1V:15H. 2.4 To prevent random shrinkage cracking, contraction joints shall be provided at 3m maximum spacing by saw cutting to a minimum depth of 50mm and shall be cut while the concrete is in the plastic state. 3 SUBSTRATE 3.1 Substrate base material shall be compacted granular material, asphaltic concrete or similar to the Engineers specification. Level of base shall be 50mm minimum/100mm maximum below finished Pavement level on both sides, to allow for embedment of barrier as per Drawing B8-1 below. 4 CONCRETE CONSTRUCTION 4.1 Concrete construction shall comply with NZS 3109 and NZS 3104 except at as modified below: i) Concrete minimum cementitious content shall be 350kg/m 3. ii) Concrete maximum water cement ratio shall be 0.4. iii) A set retarding admixture may be used. iv) Concrete consistency shall be assessed by visual and tactile methods. Up to 12 litres of clean water may be added to each m3 of batched concrete before and during M SPECIFICATION FOR ROAD SAFETY HARDWARE SYSTEMS Page 1 of 5

2 placement. Slump and cylinder tests due to this additional water are not required unless requested by the Engineer. v) Test cylinder samples may be taken at the production plant. Tests for acceptance shall be in accordance with clause of NZS In addition one extra cylinder shall be taken and tested at 7 days. vi) Concrete shall be thoroughly compacted in the mould, such that the barrier extruding at the back of the mould is smooth and tight with no open areas at the surface indicating poor compaction apparent. vii) Barrier cross sectional tolerances shall comply with Figure D1: Slip Formed Concrete Barrier Dimensional Tolerances below. viii) Barrier position shall be within +/-30mm of set out position. ix) End of day joints and any barrier cut-outs shall be within +/-20mm of design position and verticality. 4.2 Surface finish shall be Class U3 in accordance with NZS Surface tolerances and irregularities shall meet the requirements for Class F4 in accordance with NZS The primary longitudinal reinforcement for slip formed barriers shall be 12.7mm low relaxation galvanised prestressing strand. Strand shall be suspended mechanically in the correct position within the mould while placing concrete. All cables/bars/strands shall be held taut during slip forming. 4.5 Longitudinal prestressing strand shall be joined by overlapping strand a minimum of 1m and clamping each lap with four ½ commercial rope grips, clamped tightly. 5 CONCRETE TESTING 5.1 Concrete testing shall be in accordance with NZS 3109 as detailed in Table 1 below. M SPECIFICATION FOR ROAD SAFETY HARDWARE SYSTEMS Page 2 of 5

3 TABLE 1: CONCRETE TESTING Test Test method Slump test NZS 3112: Part 1 Compression test NZS 3112: Part 2 Minimum frequency Comments Acceptance criteria One per batch of concrete and when compression test samples are taken. The greater of; a) One set of test specimens for each day of pouring b) One set of test specimens for every 25m 3 poured. In addition, one set of test specimens shall be taken; c) if water is added to the mix in accordance with clause of NZS3109 or, d) if the concrete mix or concrete manufacturer is changed. Tested in the casting yard prior to pouring A set of test specimens shall comprise three cylinders to be tested at 28 days and 1 cylinder to be tested at 7 days. Test specimens may be taken at the production plant unless water is added to the mix, in which case they shall be taken in the casting yard during pouring. Refer to clause of NZS Rejected concrete shall not be used in the works. Refer to clause of NZS3109. Works made from concrete not meeting the acceptance criteria shall be rejected. Cover Site measure Every bar within every pour Refer to clause of NZS3109. Reinforcement outside of cover tolerance requirements shall be rectified before pouring. Reinforcing steel Clause B6 and B7 of AS/NZS 4671 At commencement of construction and whenever reinforcing bar is sourced from a different manufacturer. * Australasian Certification Authority for Reinforcing and Structural Steels This test is to avoid counterfeit and substandard reinforcing bar. If reinforcing bar is not sourced from, and certified by, an ACRS* accredited supplier the local random verification testing requirements of NZTA TAN shall apply. Testing undertaken by the bar manufacturer is adequate proof for acceptance provided authentic verification of the test results are provided. M SPECIFICATION FOR ROAD SAFETY HARDWARE SYSTEMS Page 3 of 5

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5 Figure D1: Slip Formed Concrete Barrier Dimensional Tolerances M SPECIFICATION FOR ROAD SAFETY HARDWARE SYSTEMS Page 5 of 5

5 Concrete Placement

5 Concrete Placement Testing Entrained Air Slump Strength Water/Cementitious Ratio Mixing Placing Concrete Compressive Test Specimens Curing De-Tensioning Multiple Strand Release Single Strand Release