1. Magnetite-Asphalt POT HOLE REPAIR
Exploiting the thermal properties of Magnetite in hot pot patch repair

2. Partners Professor Denis Chamberlain, Consultant, Epicuro Ltd
Dr Mujib Rahman, Senior Lecturer, Brunel University London
Richard Hunt, Sales Manager, LKAB Minerals Ltd

3. PROJECT OBJECTIVES
Prove pothole repairs can have similar life to surrounding pavement.
(basis for 3-5 year warrantee rather than current 2 years)
Create means of clearing 14 year backlog in pot hole repairs.
(‘right first time’ thinking)
Achieve substantial annual savings in pot hole repairs.
(long life repairs and substantially reduced repair failures)

4. how POT HOLES FORM
Water >> damage e.g. cracking, ravelling, rutting, potholes etc
Research >> asphalt degradation
Many new type of asphalt surfaces are failing prematurely
Once pothole is formed, the deterioration process is very fast 4

5. Current REPAIR Practice Case Study
Repair Observation 6th Aug 2017
Rainwater and loose stone brushed out of pot hole.
Hot asphalt fill placed in excavation (105oC).
Heater placed over fill for approx 5 mins.
Fill compacted with roller
Surface temperature measured (125oC)
Edge sealer applied (gilsonite?)
Return Visit 11th Sept 2018
13 months after repair.
Stones lost on boundary
Lost fill within repair area

6. ADDRESING FAILURES ISSUES IN Current REPAIR Practice
(Using Granite-Asphalt Mixes)
CURRENT PROCESS
No scientific basis to heating process.
No internal repair interface temperature control.
High moisture content in pot hole.
Weak perimeter pavement to pot-hole.
Contaminated fill (mixed with existing).
Restrained heating due to poor heating control.
DYNAMIC HEATING PROCESS
Variable high precision focused heating.
Uses digital model of heating process.
Based on thermal properties of materials.
Increased interface bonding and rutting resistance.
Prep’d hole & quality assured bagged fill.
Minimalized heat energy consumption.

7. ADVANTANGES OF DYNAMIC HEATING METHOD
Repair testing: accelerated life rutting
20,000 cycles of twin wheel loading simultaneously applied to assess the affect of pre-heating the pothole excavation. Rutting depth measured at 4 mm intervals along 96 mm repair interface (ref AASHTO T324-04)

8. ADVANTAGES OF DYNAMIC HEATING METHOD
Repair testing: accelerated life rutting
Improved rutting resistance through dynamic heating
Non pre-heating
Dynamic pre-heated
Unintentional 60 cycles case: able to remove patch fill from excavation in case of non-pre-heated repair!
23% average reduction in rutting
Interface bond strength increased >90%
Epicuro Ltd 26th Sept Brunel University

9. THERMAL PROPERIES OF MAGNETITE-ASPHALT
Substantially increased thermal conductivity
130oC
Conductivity Values (k) Bitumen 0.17
Asphalt 0.75
Granite 1.30
Magnetite 6.00
Water 0.606
Thickness Values (s) Bitumen 1mm
Stone 5mm
Thermal Energy Conduction (W)
Heat Conduction
0.450
Relative Increase in Thermal Energy Transmission (W)
0.400
0.350
0.300
q = dT A / ((s1 / k1) + (s2 / k2) (sn / kn))
0.250
Substituting magnetite for stone aggregate results in % increase in thermal energy transfer at 103mm
0.200
0.150
depth (based on 1D stone/bitumen stack)
0.100
0.050
Area A 1 sqm
dt 130oC-80oC
0.000
0.007
0.013
0.019
0.025
Depth (m)
80oC
5mm Stone/Magnetite
1mm Bitumen

10. EXPOITING properties OF Magnetite-ASPHALT
(Compared with Granite-Asphalt)
Substantially increased thermal conductivity.
Faster and more effective heating of repair interface.
Potential reduction in heat energy consumption
High thermal energy for given temperature.
Potential for reduced heat losses in transportation and use.
Additional properties: interface bond, surface friction

11. Project plan: Next steps
Develop Magnetite asphalt mixes for highways applications
Quantify surface properties
Produce & repair test pieces
Establish longevity of Magnetite asphalt pothole repairs (compared to Granite repair)
Determine additional advantages compared with current practices (cost, time etc)
Identify commercial partners for magnetite asphalt
Commercial product available to market
Long term testing of product in situ
3 months
6 months
12 months

12. Project DELIVERABLES Magnetite Asphalt solution Increased repair life
Reduced repair failures
Huge cost savings
Anticipated pavement life
vs overall road life

13. THANK YOU. Any questions?