Stepping Stones

Sustainability is the new catchphrase when it comes to choosing materials for road construction. There are two common themes in the choice of sustainable building materials. First, it should be “greener” than its traditional counterpart in the sense that it should either be produced from renewable sources or its application should lead to a lower carbon footprint. Second, the life-cycle cost of the sustainable material should be lower than that of the traditional material, even though the upfront cost may be higher. The role of sustainable equipment is not only to be more eco-friendly than traditional machinery in use but to also optimise efficiency in road construction. Automation and intelligent control systems are recent innovations in this area.

Materials

Traditionally, soil, stone aggregates, sand, bitumen, cement, etc., have been used for road construction. However, natural materials are exhaustible in nature and their availability is likely to decline over time. Thus, countries are looking for alternative materials, and waste is one such option, especially since there have been concerns globally regarding the increasing generation of waste through construction, industrial and household activities. Various options are being explored to put waste to productive use and road construction has emerged as one such suitable option. The utilisation of waste materials is also aimed at reducing the consumption of scarce natural aggregates and recycling materials that would otherwise be disposed of.

Waste plastic

Plastic waste can be sustainably used as a construction material. Recycled plastics can replace aggregates or serve as binder modifiers. Waste plastic has the potential for use in road construction as its addition, even in small quantities, helps in improving the stability, strength, fatigue life, etc. of bituminous mixes, leading to improved longevity and pavement performance. Using waste plastics also results in the reduction of bitumen consumption, thereby resulting in lower costs for construction and maintenance. Some of the countries that use waste plastic for road construction are Ghana, the Netherlands, the UK and South Africa. The world’s first plastic road was constructed in Zwolle city in the Netherlands.

India too has been at the forefront in the use of waste plastic for road construction. Since 2015, the government has made it mandatory for all road developers to use plastic waste for construction. Plastic waste is first shredded into fine pieces and heated to 165 °C. It is then added to the bitumen mix which is also heated to 160 °C. This mix is then used for constructing roads. For example, prominent roads in Chennai – N.S.C Bose road, Halls road, EthirajSilai street and Sardar Patel street – are layered with plastic components. Pune is also putting its plastic waste to use. The city has used 3,343 kg of plastic waste in building 1,430 km of roads in the past two years. Further, Indore recycles 100 per cent of its plastic waste and has used 5,000 kg of waste plastic to build 45 km of roads from 2016 to 2018. Waste plastic is thus emerging as an increasingly sustainable material for road construction in the country.

Fly ash

Fly ash consists of fine particles of ash that escape from chimneys of coal-fired boilers in thermal power plants (TPPs). The use of fly ash is being increasingly promoted for the construction of roads, embankments and flyovers.

TPPs produce a vast quantity of fly ash annually and a substantial portion of it remains unutilised. As of June 2020, NTPC Limited’s total fly ash availability stood at 578.41 tonnes. According to industry estimates, fly ash utilisation for road construction is less than 5 per cent. To increase its utilisation, the central government has made it mandatory to use fly ash in the construction of roads and flyover embankments within a radius of 300 km from a TPP. Further, the cost of transportation of ash for road construction projects within a radius of 100 km is to be borne by the TPP itself while that between 100 km and 300 km will be shared equally between the road developer and the TPP. For a radius of 300 km or more, the TPP will bear the entire transportation cost, as committed under the PradhanMantri Gram SadakYojana.

NTPC is undertaking projects at its plants to demonstrate the use of fly ash in road construction. The company has recently completed the construction of fly ash-based geopolymer concrete roads at its Dadri power station and Ramagundam power plant.

Moreover, roads using high-volume fly ash concrete with a 50 per cent replacement level have been constructed in Greater Noida and Faridabad. A 100 metre stretch at FatehpurBeri, Mehrauli, was also constructed with high-volume fly ash concrete with a 50 per cent cement replacement level.

Recycled asphalt pavements

Recycled asphalt pavement (RAP) material is another sustainable way in which road construction can be carried out. RAP is reclaimed and reprocessed pavement material containing asphalt, aggregate and an aged binder. RAP materials have many benefits including a smaller carbon footprint, lower price as well as increased strength as compared to an ordinary asphalt mix. RAP materials also have a lower specific gravity and lower water absorption than other aggregates.

India has yet to make any significant advancement in using this technique with pavement recycling still at a nascent stage. Although most of the pavements in the country are flexible asphalt pavements, during their restoration and maintenance either the old pavement materials are removed and dumped in a landfill or a new layer is paved on top of the existing pavement, thereby resulting in the old material being buried. However, recently, there has been a push by various state governments to utilise this recycled asphalt for road construction.

For instance, the Delhi government’s public works department has decided to use RAP material for all its upcoming road projects. Further, IIT Hyderabad has created recycled asphalt using a mix of fly ash and reclaimed asphalt concrete that reduces the use of virgin asphalt by about 30 per cent. The material was successfully tested on sections of the state highway connecting Nuzvid and Mylavaram in Andhra Pradesh that was designed for traffic of 1,213 commercial vehicles per day.

Equipment

Road construction equipment has witnessed large-scale innovations in the past few years. With the increase in the complexity and scope of projects and tight timelines, contractors’ demand for efficient equipment has increased manyfold. A look at some of the key technology trends in the segment…

Advanced telematics and intelligent control systems

The use of advanced telematics has become increasingly important in the construction equipment segment. Telematics is the broad platform that helps in effective remote monitoring and control of equipment fleets. Data analysed from telematic systems offers the end user insightful information that can help identify whether operations are going as per plan or some intervention is required. Telematics also indicates the areas of operation that need focus. Innovations in telematics have allowed the end user to monitor machine operations and performance remotely. Manufacturers are increasingly outfitting equipment with advanced telematics to improve their position in the market and serve their customers in an effective and improved way. Many construction equipment manufacturers in India offer advanced telematic systems for a host of their products. Some of these are L&T’s DigiEye, JCB India’s LiveLink, Case India’s Eagle Eye and Volvo’s CareTrack.

Intelligent control systems are being increasingly installed in new construction equipment to optimise work and increase efficiency. These systems work through a variety of sensors that can be installed in new machinery and provide better worksite environment information to the operator. For instance, the biggest issue related to compaction that operators face is knowing whether they have attained the correct compaction levels required on-site, as promptly as possible. This problem can be resolved by using an intelligent control system that would be able to measure the relative compaction density and display it to the operator. Some smart compaction systems are JCB India’s IntelliCompaction, the Wirtgen Group’s HAMM intelligent compaction meter and analyser and HAMM continuous compaction control, and CASE India’s new compaction meter.

Fuel efficient and environment-friendly equipment

Successfully reducing the carbon footprint of construction machinery requires increasing its fuel efficiency and substituting its fossil fuel-dependent engine with a cleaner alternative. Advanced hydraulic systems and more efficient engines are being used to achieve fuel efficiency. For instance, the Bobcat B900 backhoe loader has an advanced hydraulics system which is equipped with a Parker tandem gear pump that automatically redirects hydraulic flow to the tank when hydraulic functions are in neutral mode. When there is a higher hydraulic pressure requirement, the flow from the second pump is redirected to the tank to reduce the load on the engine. This reduces power consumption from the engine and ensures higher fuel efficiency. Further, many new engines are being developed with an “eco mode” where the engine control system can help reduce fuel consumption by automatically lowering the engine’s speed to idle if the machine has not been active for a specified period of time.

Some examples of newly developed fuel efficient engines are the FPT 6-cylinder electronically controlled engine developed by FPT Industrial and used in Case India’s CX220C excavator; the Wirtgen Group’s Dash 3 generation of road pavers which offers an EcoPlus mode; and JCB India’s Intelli series of machines like the ecoXpert 3DX backhoe loader.

Further, there has been an effort to substitute traditional fossil fuel-based engines with more sustainable alternatives such as a lithium-ion engine that has a lower carbon footprint. For instance, Volvo Construction Equipment has introduced an electric compact excavator, the Volvo ECR25 Electric.

Operator safety and comfort

There has been increased focus on improving the comfort of the operator through new methods and practices. Some new practices are a spacious canopy, lockable storage, mobile charging facility, ergonomically located controls, auto climate control functions, smart digital colour display, cabin lights and a music system, sun visor, and a low-noise and low-vibration cabin to reduce operator fatigue. In addition to these features, machines should also incorporate a dynamic design for the cabin that can provide all-round visibility for the operator from the working position. This can be made easier by providing an adjustable suspended seat as a standard feature to enhance operator comfort.

Operator safety can also be increased by using an anti-restart system to avoid accidental damage and an auto warning system during machine malfunction. Further, a self-diagnostic system that can carry out a full diagnostic of the machine to get to the root cause of any failure that may occur during operation can be deployed. For instance, CASE India uses CRDI electronic engines in graders for onboard diagnostics, with laptop connectivity to download the entire data log and analysis of past and ongoing operations. This can help in self-diagnostics and root out problems that may occur in operations. Tata Hitachi’s ConSite and InSite suites also offer diagnostics for tracking critical conditions such as overloading, engine overheating and higher digging to increase the safety levels of construction equipment.

In sum

It has been observed that sustainability of construction in both material as well as equipment, and the use of smart control systems to optimise efficiency are increasingly popular trends emerging in the road construction industry.