At the request of the Gauteng Province Department of Roads and Transport (GPDRT), an alternative design was done for the pavement structure for the construction of the new dual-carriageway, the K46 (William Nicol Road) to the North of Johannesburg. The design traffic loading for this road is a maximum high scenario of 9.6 MESA. The original and alternative design (incorporating nano-modified emulsions) with naturally available G5 quality materials are compared in Table 1.
XRD scans of the available G5 material are summarised in Table 2. Of importance is the result showing the material weathers to contain approximately 17 percent Mica (Muscovite) and approximately 43 percent of cement originally specified in tne original design were unable to achieve the specified minimum ITS limits, mainly because of the presence of these minerals, especially Muscovite. Test results using a selection of Nano products and Emulsions with the G5 materials are summarised in Table 3.
|Original Design||Alternative design (nano-technology)|
|Layer||Layer Thickness||Material||Material cost/m2||Layer Thickness||Material||Material cost/m2|
|Surfacing||40||Continious graded (medium) asphalt||R 115.00||30||UV protective polymer + 3% Sasobit modified medium 50/70 pen asphalt||R 96.00|
|Tack-coat||Tack-coat of 30% stable-grade emulsion||R 6.25||Nano-Tak" tack-coat (1.4L nano-tak + 100L Cat 60 Emulsion + 200L Water mixture) - application at 0.5L/square meter||R 4.73|
|Prime||MC 30 cut-back bitumen||R 9.55||Nano-Prime (1L Nano-prime + 100L Cat 60 emulsion + 200L Water mixture) - application at 0.5L/square meter||R 5.90|
|Base||150||G1 crushed stone||R 55.50||150||G5 + 1.2% GE-Nano at 100% mod AASHTO||R 57.65|
|Upper sub-base||150||C4 layer||R 37.17||150||G% + 1.2% GE-Nano at 97% mod AASHTO||R 47.25|
|Lower sub-base||150||C4 layer||R 37.17|
|Total material cost/m2||R 260.64||Total material cost/m2||R 211.53|
|XRD Identified Material||% of Mineral Present in Total Material Sample||% of Mineral present in percentage of material passing the 0.075mm sieve|
|Mix Design:||% Used||UCS Dry KPa||UCS Wet KPa||ITS KPa|
|GE-Nano 20P with NS @ 0.5lt m3 pre-treat||1%||3828||2827||250|
Download the technical report to view the Cost Comparison table, XRD results and Lab test results for the section of road.
The below photos show the successful construction of the first trial section of the sub-base on the K46 dual-carriageway (25 October 2016) in the Gauteng Province. This section was constructed using conventional equipment with graders and a water cart.
Mixing of stabilising agent using a water cart and two graders.
Condition of trial section just before final roller passes.
Condition of the exposed sub-base after 3 months of heavy rains.
The pictures in the below gallery show a section that was completed in 2015, there was a lot of traffic from construction vehicles using this section for the first 2 years and light traffic there after. After excess dust and gravel was brushed away from a small section, a 4 pound hammer was used to hit a chisel into the section, and after 30 blows of the hammer the chisel only penetrated 0.5cm in the section.
Energade was then poured onto the section, which can be seen pooling ontop and not absorbing in the layer. This section has been in-tack for 4 years with heavy rains and has no to little damage.