Local Breakthrough Innovation for Vital Infrastructure

The six-lane Mumbai–Nagpur expressway represents a leap into the future. The unrivaled safety standards of the route’s only tunnel prove it. Sika delivered the structure’s locally produced passive fire protection system and light-reflective coatings, a first for India.

The newly constructed Samruddhi Expressway, as it is known locally, stretches 701 kilometers across the state of Maharashtra. The critical infrastructure project included construction of the state’s longest and widest tunnel, and one of India’s longest. At 7.8 kilometers long, the Samruddhi Expressway Tunnel contains twin tubes that are each 17.6 meters wide, enough to carry three lanes of traffic in each direction. The tunnel is expected to be popular as a quicker alternative to crossing the steep terrain.
Project owner Maharashtra State Road Development Corporation sought out experts who could tackle the challenge – and establish a new standard in tunnel safety.

Safety first

Mitigating the risk of fire inside the tunnel was a clear priority. Effective fire protection is critical not only for the people traveling through the tunnel, but also for structural stability. If a fire happens to start, the tunnel must be able to withstand intense heat and flames over an extended period of time. The solution lies in installing a passive fire protection system during construction. The most effective fireproofing products use very stringent measures, which define the expected maximum fire exposure in the worst-case scenario. The system must be designed to keep the concrete and steelreinforcement temperatures from rising above 380°C and 250°C, respectively. This is because excessive heat will eventually cause severe damage to the concrete and reduce its structural strength.

Sika India was awarded the project based on its overall track record and expertise in fire protection mortars. The package also included Sika light-reflective coatings. This technology – never before used in India – improves visibility in low-light conditions for driver safety and comfort. The plan was to source the high-volume order through the reliable Sika network. But when the project kicked off in March 2021, the Sika teams decided to change track.

Going local

Passive fire protection mortar was needed to cover nearly 70,000 square meters of the tunnel’s crown. This meant that 1,300 tons of mortar needed to be supplied in a short time, pointing to a locally produced alternative – which did not yet exist. Sika India, the Asia/Pacific regional management, and Sika Corporate worked quickly, building on their:

• Seamless technology transfer to design an internationally certified product using local raw materials
• Proactive procurement to source raw materials accordingto complex specifications
• Tight technical coordination to prepare the detailedproduct proposals, trials, and certification process
• Efficient operations to guarantee an uninterruptedsupply of product
• Onsite support to train teams on product application
   

The result was a high-performance product that met the technical specifications of the tunnel as well as rigorous international standards. The domestically produced fire protection mortar was designed to ensure long-lasting fire resistance and minimize the need for future maintenance.

Installation of the passive fire protection system consisted of three stages. Sika-trained specialists first attached a layer of wire mesh over the tunnel crown with concrete nails for added protection. The next stage involved priming the surface. The final step was the application of the fire protection mortar in a single 20-millimeter layer.

Confidence and clarity ahead

Sika-trained specialists also applied two different shades of the light-reflective coating throughout the tunnel, up to a height of 5.75 meters. The light-reflective coating as well as the fire protection mortar, were formulated using low volatile organic compounds (VOCs) for reduced environmental impact. Both products were designed for quick application and rapid curing. These user-friendly properties helped to minimize disruption and speed up project completion – in this case, by an impressive three months.

Construction of the Samruddhi Expressway Tunnel marked a big step forward for tunnel safety. It gave India its first tunnel protected by a passive fire protection system and light-reflective coating – and Sika a reference project that brought out the best of the teams involved.