Toppesfield Use HDS’ AQA Technology to Run National Highways Project Without Technicians

Materials testing is typically conducted via manual methods that expose workers to health & safety risk. Further problems associated with traditional methods include lack of accuracy of materials testing processes, the high cost of materials technician, and the skills shortage within the materials testing industry. Data from traditional materials testing processes is often siloed and does not contribute to scheme programme management or asset management during the asset lifecycle. Automation of the materials testing process offers a solution to these issues.

Highway Data Systems are the UK’s leading provider of automated quality assurance technology and services, having developed technology that fully automates the role of the materials technician during resurfacing operations. Toppesfield sought to use HDS technology on the M69 project to help resolve the problems associated with traditional materials testing that are highlighted above.

Toppesfield applied for two departures from standard from National Highways which were both approved. After an initial week of correlation and calibration, Toppesfield were successfully able to run the rest of the M69 project without materials technicians.

Technology Used

eLoad

eLoad is proprietary software developed by HDS to deliver automated digital conveyance note (ticket) data to site.

As soon as paper tickets are printed at batching plants, HDS receive a digital copy which is then sent to site and presented to site operatives. Operatives tap the screen to indicate that loads have arrived on site and a GPS referenced record is created.

Technology Aims:

Digitised laying record creation – reduced opportunity space for manual data error.

Allows banksmen to focus on moving vehicles on site.

GPS referencing for enhanced reporting.

Integration with any plant ticketing system.

eTec

eTec is proprietary hardware designed by HDS to record quality information during the paving process. Magnetically mounted instrumentation captures material delivery temperatures, environmental information and paver movements. All tests that would usually be carried out by technicians around the paver are instead conducted automatically and digitally.

Information is available in real-time for site operatives so that they can see temperature and environmental condition information.

Technology Aims:

Improved health and safety: no technicians taking delivery temperatures, reduced interaction with site traffic and hot material.

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Improved reporting accuracy: regularly calibrated continuous measurement of asphalt delivery temperatures.

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Real-time continuous data supplied to paving operatives to improve decision making.

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Digitalised data reporting facilitates easy upload into Power BI or pavement management/asset management systems.

Optrix

Optrix systems continuously monitor the movement of rollers and the temperature of material under compaction. A high-accuracy GPS system captures the number of passes each square metre of material under compaction receives. Infra-red temperature sensors capture rolling temperatures.

All data is fed back to roller drivers so that they can make informed decisions about their rolling operations.

Correlations with cores and density gauge readings facilitate the measurement of asphalt density through method compaction. This approach is being formalised into a standard by Transport Scotland and is permitted on the National Highways network under departure.

Technology Aims:

Removes the requirement for using density gauges and can be used to reduce the requirement for coring.

Real-time compaction control: under-compacted areas can be addressed before they cool and become un-compactable.

Increased volume of testing: every square metre of asphalt receives a density reading.

Improved health & safety: reduced interaction of technicians with site traffic and moving rollers.

Surveying

HDS have developed two laser systems for directly replicating surface regularity and surface macrotexture carried out using rolling straight edges and sand patch testing.

The systems are vehicle mounted, travel at traffic speed, do not require a road closure and collect data no more than 5 days after laying operations.

Technology Aims:

No need for materials technicians – significantly reducing risk of HSE incident at the end of laying operations.

Much greater volume of testing – providing more reliable information to clients and overseeing organisations.

Data digitalisation and GPS referencing allows upload into Pavement Management Systems for use in asset management and deterioration modelling.

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Departures from Standards

Most HDS AQA technology is compliant with the Schedule of Highways Works. However, testing for asphalt compaction and surface macrotexture via AQA methodology is not currently within scope. Toppesfield and HDS applied for two departures from standard in order to be able to use AQA technology on the M69 scheme which were approved subject to conditions.

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Surface Macrotexture

The HDS surface macrotexture laser has been proven to reproduce volumetric patch results:

National Highways permit the use of the HDS laser measurement system provided that a correlation for the material under investigation has been carried out before. In the case that a correlation has not been carried out, a correlation is established within the first week of surfacing operations and the laser system is then used thereafter. A correlation had already been undertaken for material used on the M69 scheme.

Compaction

HDS and Toppesfield used a method compaction approach to establish asphalt air-void content. The departure from standard stated the following requirements:

1. Method statement shall be produced for the AQA method to achieve the desired compaction specific to the sites and materials used.
2. For the first shift of the works, and for each mixture from each plant used to supply material to the site, the AQA method shall be operated in parallel with a calibrated indirect density gauge, operated in accordance with Clause 929.8-9.
3. A graphical correlation shall be produced to demonstrate that the method statement proposed achieves the desired outcome in terms of compliance with Clause 929 i.e. average in situ void content not exceeding 7%, by comparing with measurements obtained from a calibrated indirect density gauge.

Pavement density was measured using the correlated gauge for each pass of the roller until full compaction in the wheel track across nine areas.  Regression analysis was used to establish the correlation of results between conventional and method compaction data.

M69 Compaction Data

Compaction data was collected across nine areas and plotted on a graph as per the departure requirements:

The figure highlighted in red is anomalous but was included in the regression analysis to ensure data integrity. The regression analysis suggested that a minimum of 6 roller passes was required to ensure asphalt air void content below 7%. This data was input into the Optrix roller systems so that roller drivers had a clear colour target to aim for when undertaking compaction operations.

Results

Feedback on the use of AQA technology was very positive. In particular, the paving crew benefited from being able to see when their material was on the way which enabled them to regulate the speed of paving – reducing paver stops and thermal segregation. The real-time temperature information ensured that operatives were well informed, and roller drivers had a clear visual target to aim towards which helped to ensure that over 95% of material under compaction was completed within target.

The HDS laser surveying systems completed surveys across the entire length of the scheme which removed the requirement for putting technicians at risk conducting conventional sand patch or rolling straight edge testing.

Conclusion

Toppesfield and HDS were successful in the deployment of Automated Quality Assurance technology on the M69 J2 – 3. Areas in which improvements were made include:

Health & safety – over 1200 ‘at risk’ man hours were avoided, with removing materials technicians from conducting manual testing operations.

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Data capture – digital records of all materials testing were created and are available for process improvement and use in asset management.

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Quality improvement – real-time compaction control delivered density data across the entire

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Cost savings across 60 days were over £17,500