The quality and longevity of roads largely depend on the binding agent used. The two primary types are hot bitumen (used in Hot Mix Asphalt) and bitumen emulsion (used in Cold Mix Asphalt), each suited for different construction needs and conditions. Both require different machinery, labour skills, and approaches. Hot bitumen can withstand and support heavy loads and traffic, while the cold mix approach is suited for roads with lesser traffic loads and maintenance of potholes and upkeep.
In this blog, we will look at every aspect of cold mix asphalt and cold mix emulsion and how they are suitable for constructing rural roads in India.
Rural India and Roads
India’s rural roads account for 71.4% of the nation’s overall road network. As of March 31, 2019, this translated into around 4.52 million kilometres of rural roads, with Maharashtra leading with 426,327 km, followed by Assam, Bihar, Uttar Pradesh, and Madhya Pradesh.
Despite this giant network, many of India’s rural roads are in dire need of repair or are undeveloped. From the manufacturing and pavement perspective, this situation primarily arises due to problems such as difficult terrain and logistical constraints in remote places.
In this blog, we will understand why the traditional hot-mix asphalt is not suitable for every rural region and how the new cold-mix asphalt.
Why Hot Mix Asphalt Falls Short in Rural Areas.
The Hot Mix Asphalt (HMA) process involves heating bitumen and aggregates to high temperatures (150-170°C) at the plant. This hot mixture must be transported quickly to the road construction site. The roadbed is first prepared with compacted layers of stone or gravel.
The heated mixture is then laid with a paver machine and compacted with rollers before cooling. This method demands heavy machinery, skilled labour, and rapid execution. It becomes challenging in remote places due to a scarcity of nearby hot mix plants, long travel times, and high costs.
Delays in transporting the bitumen mixture often lead to temperature loss and poor-quality roads. These challenges make HMA less practical for remote or low-budget rural roads.
A Smart Fix for Rural Roads: Cold Mix Asphalt
Unlike Hot Mix Asphalt (HMA), Cold Mix Asphalt (CMA) requires no heating, instantly eliminating the need for heavy machinery, strict temperature control, and skilled labour. Compared to HMA, CMA is far less dependent on logistics and weather conditions, making it much more adaptable for the construction of roads in rural regions.
Most importantly, it’s an eco-friendly solution with significantly lower emissions. Despite its simplicity, cold mix provides a smooth driving experience and is well-suited to handle light to moderate traffic loads, making it a perfect fit for the practical needs of rural regions.
What is Cold Mix Asphalt?
Cold Mix Asphalt is a similar form of pavement created by combining bitumen emulsion and aggregates at room temperature without heating. Unlike traditional hot mix asphalt, which needs to be heated to high temperatures, the cold mix is ready to use, easy to store, and ideal for rural roads, patchwork, and low-traffic areas.
It’s useful at construction sites where:
- Hot mix plants aren’t nearby.
- There’s no access to heavy machinery.
- Weather conditions make hot mix hard to use.
What is Cold Mix Bitumen Emulsion?
Cold Mix Bitumen Emulsion for road construction is the binding agent in the cold mix asphalt formed by combining a mixture of bitumen, water, and an emulsifier at room temperature without heating. It’s named “cold mix” because, unlike regular hot mix asphalt, it doesn’t need heat to prepare or apply.
Cold Mix Emulsion and Cold Mix Asphalt can be prepared directly at the site itself, using basic mixing equipment and without the need for heating. This makes it simple to use, cost-effective road surfacing, and environmentally good, as it saves energy and lowers pollutants.
Cold Mix for a Hot Issue: Sustainable Roads in Rural India
Cold Mix Asphalt offers a highly practical and efficient solution for rural road construction in India. The approach eliminates the danger of burns and fire hazards, lowers project costs, and is consistent with India’s sustainability objectives.
A study conducted by IIT Madras and five other institutions found that cold-mix asphalt reduces PM10 emissions by 33% and consumes 7% less energy than hot-mix asphalt. This significantly reduces the carbon footprint of road infrastructure. The quality of cold-mix emulsion remains reliable, especially for light to medium traffic loads, which is ideal for rural roads. However, rural road construction in India still faces several challenges.
Top 5 Challenges With Rural Road Construction in India
- Being distant from village locations
- Limited access to hot mix plants
- Poor connectivity for transporting materials
- Unreliable power supply
- Scarcity of skilled labour
Many villages are located in remote areas with limited or no access to hot mix plants, and poor connectivity makes it difficult to transport materials and machinery.
Additionally, unreliable power supply and the scarcity of skilled labour further complicate the use of conventional hot mix processes. Weather conditions, particularly during the monsoon season, also disrupt construction activities and affect road durability. Budget constraints add another layer of difficulty, as rural development programs often lack the funds needed for high-cost materials and equipment. In this context, cold mix emulsion becomes a highly suitable alternative. It’s affordable, easy to deploy, and does not require specialized equipment or labour, making it an ideal choice for sustainable and scalable rural road development.
The Difference Between Hot Mix & Cold Mix Asphalt.
| Feature | Hot Mix Asphalt (HMA) | Cold Mix Asphalt (CMA) |
| Temperature Requirement | 150–170°C (Heated) | Ambient / Room Temperature (No heating) |
| Binder Used | Pure bitumen | Bitumen emulsion (bitumen + water + emulsifier) |
| Energy Use | High (requires fuel for heating) | Low (no heating needed) |
| Equipment Needed | Hot mix plant, heavy machinery | Can be mixed on-site with light equipment |
| Ease of Transportation | Must be transported hot and used quickly | Easy to transport and store for longer durations |
| Best Suited For | Highways, urban roads, and heavy traffic areas | Rural roads, patching, and low-traffic areas |
| Weather Sensitivity | Needs dry, warm weather | Can be applied in cold conditions |
| Application Speed | Fast setting but needs fast usage | Slower curing, but more flexibility in handling |
| Cost | Higher (machinery, fuel, logistics) | Lower (minimal equipment, low fuel use) |
| Environmental Impact | High emissions due to fuel burning | Low emissions, eco-friendly |
| Common Usage in India | National highways, expressways | PMGSY rural roads, patch repair, remote areas |
Conclusion
Considering cold mix asphalt pavement and cold mix bitumen emulsion, both hold the characteristics to offer greater connectivity in rural India for both new road building and repair work. Its ease of usage, environmental benefits, and applicability to remote areas make it perfect for rural road building, maintenance, and pothole repair.