Specification 49 Stone Mastic Asphalt for Airfields - Ministry of Defence

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Specification 49 Stone Mastic Asphalt for Airfields Appendix C – Guidance on Suitable Temperatures and Wind Speeds for Laying Appendix C – Guidance on Suitable Temperatures and Wind Speeds for Laying C.1 In addition to the requirements in Clause 5.2, Table C.1 gives recommended wind speed and air temperature limits for the laying of SMA with paving grade bitumen. (NOTE 1. When a polymer modified binder when is employed, guidance on laying conditions should be sought from the binder supplier.) TABLE C.1 RECOMMENDED WIND SPEED AND AIR TEMPERATURE LIMITS Bitumen Grade 40/60 70/100 100/150 Thick- Maximum Wind ness Speed (km/h) (mm) 2 m 10 m height height ≤ 25 See Note 2 30 – 40 As in Figure C.1 Min. Air Temperature (°C) ≥ 45 40 50 0 ≤ 25 See Note 2 30 – 40 As in Figure C.2 ≥ 45 40 50 0 ≤ 25 See Note 2 30 – 40 As in Figure C.3 ≥ 45 40 50 0 (NOTE 2. The limiting wind speed and air temperatures relate to a compaction time of 6 min for the mid-layer temperature to fall from the specified maximum to minimum compaction temperatures.) (NOTE 3. Very thin asphalt layers cool very quickly. At 15 mm thickness, less than 2 min is theoretically available for compaction within the specified compaction temperature limits. Prompt rolling is essential and it is recommended that this material should only be laid in still conditions.) (NOTE 4. The values and graphs were calculated using the previous grades of bitumen, and the results for mixtures with 70/100 and 100/150 bitumen may need to be revised.) C.2 Wind speed can be measured by either: • an anemometer erected at a height of (10 ± 0.5) m situated on the airfield; or • a portable anemometer erected at a height of (2 ± 0.1) m situated in close proximity to the laying works. The anemometer should be fitted with a digital accumulative device. The average wind speed over the previous hour should be used to define the prevailing wind speed. (NOTE 1. If the wind speed is increasing, anemometer readings should be made at 15 min intervals.) (NOTE 2. To aid planning works, weather forecasts may be obtained from the nearest Regional Weather Centre.) C.3 * Meteorological records for the airfield are available. OR * No clause. (* NOTE 1. Project Manager to select alternative for specific job specification; advice given in Clause Z.8 of Appendix Z.) Figure C.1 – Acceptable weather conditions for laying SMA with 40/60 bitumen 34 July 2008
Specification 49 Stone Mastic Asphalt for Airfields Appendix C – Guidance on Suitable Temperatures and Wind Speeds for Laying Figure C.2 – Acceptable weather conditions for laying SMA with 70/100 bitumen Figure C.3 – Acceptable weather conditions for laying SMA with 100/150 bitumen (NOTE 2. The descriptions “Should not lay” and “Can lay” apply to above and below the lines for the 35 mm thick layers, respectively. The lines for the 30 mm thick layers are not sufficiently high and some of those for the 40 mm thick layers are not sufficiently low to accommodate doing the same for them.) (NOTE 3. The acceptable conditions are developed assuming 6 min is required for compaction. If adequate compaction can routinely achieved in less time, these curves can be move up whereas, if more time is needed for any reason, they should be moved down.) (NOTE 4. The lines for 30 mm thick layers are sufficiently close to the bottom right hand corner of the graphs to indicate that they can only be laid on still, warm days unless the time required for compaction can be reduced from 6 min.) July 2008 35
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Specification 49 Stone Mastic Asphalt for Airfields - Ministry of Defence

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