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Use of nanotechnology is ideal for the long life of roads. Dr Ajay Ranka elaborates on the advantages of using nanotechnology-based additives in road building.
Bitumen consumption in India was 4.5 million tonne in 2011-12 costing Rs 18,000 crore (current value). Nearly 80 per cent valued at Rs 14,400 crore used for resurfacing, is the annual binder loss from the existing roads due to leaching and stripping of the bitumen binder. Nanotechnologies from Zydex can save Rs 7,200 crore annually in bitumen savings alone, by doubling the life of bitumen layers (modifying the bitumen binder at the refinery) at a cost of Rs 540 crore. Bitumen being petroleum product is forex-intensive.
Moisture resistant roads (highways/rural) with globally patented nanotechnologies developed in India:
Use of nanotechnology Soil stabilisation: Nanotechnology-based stabiliser is water-soluble, easy to apply, reacts permanently with the soil's (silt, sand and clay) surface structure and makes it impervious to water. It controls soil's expansiveness by minimum 90 per cent at an affordable cost. Besides waterproofing, it also eliminates wet and dry cycles and maintains strength of the cement stabilised soil over a design life (typically 20 years) of the road. Waterproofed, quick set, penetrative priming: Cationic bitumen emulsion-based prime coats have poor penetration, take longer time to set and show water permeability. Weak physical bonding of aggregates to bitumen causes loss of bonding between aggregates and binder in presence of moisture.
Aggregates and stone powder/dust are water loving and presence of moisture causes de-bonding and results in poor stress transfer in the pavement section, causing cracking and fatigue failure. Nanotechnology-based prime coat is water soluble, easily mixes into bitumen emulsion in water. Its solution in water is neutral and odourless and penetrates up to 2-8 mm, in the WBM/WMM layer. It reacts with the aggregates, stone dust powder and dust and changes their surface to make them asphalt loving. Chemical bonding of bitumen with stone base layer eliminates the moisture susceptibility of the prime layer. It provides a chemically bonded waterproofed drain layer.
Chemically bonded, waterproofed tack coat: Nanotechnology-based tack coat is water soluble, neutral, odourless and easily mixes with bitumen emulsion in water, ensuring trackless tack coat. It reacts with the aggregates, stone dust powder and dust; and changes their surface to non-polar, to make them asphalt loving. This creates a permanent affinity between the asphalt binder and the aggregate, and reduces the moisture susceptibility of the tack layer.
Chemically bonded bitumen nanotechnology: This coating substantially improves coating of asphalt binder on the aggregates. It ensures consistent and higher compaction and eliminates stripping. Thus, surfaces treated with this coat ensure a more durable asphalt pavement.
Nanotechnology-based additives for road building provide excellent moisture resistant, superior performance of HMA mix, significant higher stability and strength compared to control mix. They have the potential to significantly extend service life of the pavement.