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Extreme wet weather can be catastrophic for roads
Speaking on behalf of Australia’s 537 councils, [Australian Local Government Association] ALGA President Linda Scott said rebuilding these roads to current standards would only cost Australian communities more in the long term.
“In recent months, thousands of kilometres of local roads across NSW, Victoria, South Australia and Queensland have been severely damaged by flooding, and in some cases have been washed away,” Cr Scott said.
“ALGA has estimated the total cost of fixing and replacing these roads is in the vicinity of $3.8 billion, which is roughly the equivalent of Australia’s annual foreign aid budget.
“Considering the ongoing impacts of climate change, we can’t simply rebuild our local infrastructure – including roads, footpaths and cycleways – to current standards, we need a fundamental shift in the way we fund, deliver and maintain these assets.”
ARRB Chief Executive Officer Michael Caltabiano said the extensive damage to large parts of the road system across several states was a major wake-up call and an opportunity to evolve the way Australia’s roads are constructed and managed to deliver more resilient outcomes.
“Moisture is kryptonite for roads, and inevitably leads to potholes. This year’s floods and torrential rains have caused large scale catastrophic damage to the road systems that connect communities and deliver freight. Now is the time to reassess what innovations are possible to prevent a repeat of this infrastructure emergency,” Mr Caltabiano said.
Australian Road Research Board, “Building Better Roads to Prevent Another $3.8 Billion Blowout,” ARRB, Australia, 2022.
Water + cracks + traffic = potholes
Wet weather is the enemy when it comes to potholes, as demonstrated by the almost 43,000 potholes (and counting) repaired following Victoria’s 2022 October floods.
When water seeps into cracks in the road’s surface it causes the surface to weaken and split. This process is exacerbated by the pressure of vehicles travelling over the road, eventually leading to chunks of the asphalt coming away entirely – resulting in a pothole.
Once the primary pothole has formed, they can easily grow in size and depth. Vehicles passing over the pothole can progressively erode more and more asphalt, while rain or flooding can wash away more road surface. In cold regions, the freezing – and the consequent expansion – of water in the asphalt can result in potholes, as can heavy vehicle traffic travelling over roads not designed for their weight class.
RACV, What causes potholes, Oct 2022
Renolith has a ‘shovel ready’ solution to the problem. Renolith 2.0 enables the construction of low-cost, durable, sustainable roads. These roads are not susceptible to cracking, potholes or rutting. Water penetration is dramatically reduced. Effectively, Renolith provides a full pavement depth shield against the kryptonite (ie. Moisture).
Renolith 2.0 is a unique nanopolymer admixture for cementitious binders, optimised to enhance in-situ soil stabilisation / cold recycling processes. It is typically used in pavement (eg. road, footpath, cyclepath, hardstand, carpark etc) applications. However, since it provides such a significant improvement to the physical and mechanical parameters (especially crack resistance and frost/moisture resistance), it is possible to expand the scope of cementitious binder reinforced soils beyond road construction to hydraulic engineering and underground engineering structures.
Renolith has been used around the world for over 25 years in all types of soils and some very challenging conditions, from the frozen swamps of Siberia to the monsoonal tropics of South East Asia.
Its first major project was the Sydney 2000 Olympics, where it enabled the rapid construction of low-cost pavements in difficult clay soils. 25 years later, those pavements still endure.
There are dozens of subsequent independent studies that confirm the effectiveness of Renolith admixture to protect pavements against water. Here are a few examples:
Singh and P. Garg, “Evaluation of Renolith as a subgrade stabilizer,” 50th Indian Geotechnical Conference, Pune, India, 2015.
In this report, stabilised Silty Sand (SM) samples were made using 2%, 4%, 6%, 8% and 10% cement by weight of soil, and 1%, 2%, 3%, 4% and 5% Renolith by weight of cement. A curing period of 14 days was used to determine California Bearing Ratio (CBR), Standard Proctor test (MDD & OMC) and Permeability values.
In all mixes (2% to 10% cement), the coefficient of permeability was reduced by more than 100x with the addition of 5% Renolith.
Permeability of Silty Sand (SM) treated with Renolith and Cement
Study #2: Effect of Polymer Stabilizer on the Geotechnical Properties of Black Cotton Soil
‘Black Cotton soil’ is highly cohesive and contains enormous amount of montmorillonite (clay), which makes it a challenge for any construction project. Montmorillonites expand considerably more than other clays due to water penetrating the interlayer molecular spaces and concomitant adsorption. In this study, black cotton soil samples were treated with different doses of Renolith and cement.
The addition of [Renolith] polymer caused a significant modification in engineering properties. The polymer addition showed considerable improvement in strength, CBR, as well as swelling characteristics.
Rajoria and S. Kaur, “Effect of Polymer Stabilizer on the Geotechnical Properties of Black Cotton Soil,” in 50th Indian Geotechnical Conference, Pune, 2015.
Differential Free Swell (DFS) of black cotton soil treated with Renolith and cement
Study #3: The Construction Of Roadbeds on Permafrost and in Swamps from Reinforced Soils of Increased Strength
The results of control tests conducted by MADI (STU), confirmed the materials of our research. During the construction of the pilot site, the preparation of the cement-soil mixture was carried out using a Bertoli Italian soil mixing plant, the mixture was distributed by an asphalt paver, and compaction was done using combined rollers. Coarse sand was used as a starting material. At a cement dosage of 10% by weight of the soil, the NTS additive [aka Renolith] was 8 and 10% by weight of the binder.
The test results of 28-day-old samples are as follows: compressive strength was from 11 to 13 MPa, bending tensile strength — from 2.5 to 3 MPa, frost resistance coefficient — at least 0.85, water saturation — no more than 4%. Compressive strength of samples with the addition of NTS [aka Renolith] is 80% more compared to samples with cement alone. At the same time, a decrease in the period of curing is almost twofold.
A significant improvement in the physical and mechanical parameters, and especially frost resistance, made it possible to expand the scope of reinforced soils not only in road construction but also in hydraulic engineering and underground engineering structures.
Shuvaev, A. Smirnov and S. Kartavy, “The Construction Of Roadbeds on Permafrost and in Swamps from Reinforced Soils of Increased Strength,” Civil Engineering Journal, vol. 6, no. 10, p. 10, 2020.
Use of soil reinforced with cement with additive NTS [aka Renolith]
Unbound. Unbound granular pavements are highly porous and rely on surface seals to prevent moisture ingress. Any cracks in the surface seal provide a vector for moisture ingress, which can lead to potholes. In flood conditions or with inadequate drainage, even an uncracked surface barrier may be ineffective since water may ingress from the pavement edge.
Bound. Bound pavement layers using cementitious binders are less permeable than unbound pavements, but are still porous and can be damaged by moisture ingress. Moreover, it is difficult to prevent cracking, particularly at higher binder content.
Shrinkage cracking of cemented materials tends to be unavoidable. Cracks which propagate to the pavement surface provide pathways for the infiltration of moisture which can lead to debonding of layer interfaces within the pavement and/or weakening of granular layers and subgrade. The extent and severity of cracking is influenced by factors such as binder type and content, material type, initial moisture content and drying and curing conditions.
Austroads AGPT02-17, Guide to Pavement Technology Part 2: Pavement Structural Design
Renolith. The permeability of bound pavement layers can be reduced by two orders of magnitude with the addition Renolith 2.0 nanopolymer admixture to the binder, essentially creating a full depth impermeable pavement. This feature, combined with the significantly improved physical and mechanical properties of the composite and the elimination of shrinkage cracking, enables much broader utility of stabilised materials not only in roads but also in hitherto unsuitable applications such as hydraulic engineering and underground engineering structures. More topically, Renolith 2.0 offers a ‘shovel ready’ and cost-effective approach to rebuilding Australia’s flood damaged road network with more durable, moisture resistant, crack resistant designs. The pothole problem could be solved – permanently.
Call to Action
If your local road network is affected by flood damage or potholes, please nudge your local council in our direction. We can help.
For more information, please visit https://renolith.com.au
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