28 Jun Resurfacing of Hicks Close & Kennet Road – Update from Cllr Cathy Martyn
Following concerns raised by a resident about the quality of the resurfacing, I raised those with Swindon Borough Council & I’ve received the following response in explanation:
”The material in question is called a Micro Asphalt, which is a thin screeded material laid over the existing carriageway to seal ageing and fretting surfaces i.e. this is a preventative treatment and not a traditional road surfacing material. Such treatments are very cost effective ways of increasing the life of large areas of carriageway where the basic road structure is sound but the road surface is ageing and brittle. The main downside of Micro Asphalt is that for the first year or so, the material can have a scruffy appearance compared to traditional road surfacing methods, and some stone will continue to fret during this period.
Micro Asphalt Surfacing is a process that requires a period of 4 – 6 weeks from install to building up its full cohesive strength. Due to the constituent parts, the early life performance of the material is greatly impacted by temperatures. To ensure that the product cures correctly different grades of Micro Surfacing emulsions are manufactured for different seasons – each having a temperature range. For the works undertaken in Swindon and based on the long range forecast, a product that was suitable for use in temperatures from 4°C to approaching 15°C was used. Whilst largely the temperatures in March and April were within that range, there were unexpected spikes in temperature in mid-April.
Whilst the material is still in early life (not built up full cohesive strength), if temperatures exceed the design range there is a risk the material can become “lively” and “tacky” and where there is a lot of pressure (e.g., power steering turns or HGV tracks) or additional heat (hot tyres from travel).
The long term performance of the material is linked to the base bitumen’s used in the mix. The supplier and the Contractor fully expect the product to perform as anticipated and reach cohesive strength, leaving isolated defects identified to be rectified in line with the contract.
Remedial works will vary from site to site using localised hand lay Micro surfacing and in extreme circumstances full resurfacing of the carriageway. Whilst in-situ samples indicate that the sites will perform long term, the Contractor wants to be sure that cohesive strength has been achieved through due diligence. This would be in the form of monitoring the sites through a period of prolonged high temperatures.
The Micro Asphalt Programme for 2021/22 consisted of 21 sites. All of these will be inspected as part of this process with the SBC Project Team and Contractor both present and any remedial works will take place in September when the Contractor returns to carry out the 22/23 programme of works.”
If you have any questions, please email me (as my email account is monitored weekdays). Thankyou.
Councillor Cathy Martyn: firstname.lastname@example.org
Councillor David Martyn: email@example.com
Councillor Brian Ford: firstname.lastname@example.org