According to Technavio’s market research report, the global smart highway construction market will grow rapidly during the forecast period and post a CAGR of more than 93% by 2021. The growing trend towards the adoption of smart cities will drive the growth prospects for the global smart highway construction market throughout the projected period. The increasing need to manage the cities’ assets such as roads, traffic, energy, and water led to the emergence of smart city concept that includes multiple information of communication technology (ICT) and the Internet of things (IoT). Additionally, it also involves expenditure on smart infrastructures such as smart grid and smart highways to ensure sustainable development, which will have a positive influence on the growth of the smart highway construction market.
With the growing focus towards the generation of clean energy through the exposure of sunlight on on roadways, the coming years will witness an increase in the popularity of solar roads in smart highways. Solar roads offer various benefits including the ability to recharge electric vehicles (EVs) anywhere and the potential to reduce GHG emissions and the dependence on fossil fuels. Additionally, solar roads also provide a good return on investment since the energy produced can be utilized to power the nearby villages. With such benefits, the coming years will witness an increase in the adoption of solar roads, which will subsequently, drive the growth of the smart highway construction market.
According to techsciresearch.com, India roads & highways market is projected to reach $ 24.12 billion by 2027, on account of increasing number of government initiatives such as Bharatmala, SARDP-NE, etc., aimed at developing, expanding and upgrading roads, highways and expressways in the country. Moreover, rising population, investment enabling policy measures such as Hybrid Annuity Model, and Smart Cities Mission are some of the other factors that are expected to positively influence the country’s roads & highways market over the coming years.
To encourage adoption of new materials and technology in road construction, the Highway Ministry has formulated a policy where new technology can be adopted through pilot projects.To try the new technology, the incremental cost of adopting the new technology as against the tried and tested methods will have to be borne by the technology promoter.
Discussed below are few of the road construction technologies available:
Asphalt in road construction
The primary use (70%) of asphalt is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.
The terms “asphalt” and “bitumen” are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, “asphalt” (or “asphalt cement”) is commonly used for a refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called “bitumen”, and geologists worldwide often prefer the term for the naturally occurring variety. Common colloquial usage often refers to various forms of asphalt .
During this final phase, the asphalt is poured and laid. Take note: Depending on the estimated traffic volumes and regional climate conditions, the asphalt paving job can require up to four different layers of asphalt:
Gravel Layer: Also known as the frost blanket, a mixture of gravel and sand is laid to eliminate the effects of freezing and thawing temperatures.
Base Layer: Using bitumen, cement or lime as the predominant binder, a bound base course is laid over the unbound base course.
Surface Layer: Responsible for providing friction, smoothness, noise control, and drainage, the surface layer is composed of the highest quality materials.
These are just a few of the steps involved in paving a road. In reality, the entire asphalt paving process can take years to complete. And while knowing how a road is paved may not help you reach your destination any faster.
Concrete in road construction
Concrete surfaces (specifically, Portland cement concrete) are created using a concrete mix of Portland cement, coarse aggregate, sand and water. In virtually all modern mixes there will also be various admixtures added to increase workability, reduce the required amount of water, mitigate harmful chemical reactions and for other beneficial purposes. In many cases there will also be Portland cement substitutes added, such as fly ash. This can reduce the cost of the concrete and improve its physical properties. The material is applied in a freshly mixed slurry, and worked mechanically to compact the interior and force some of the cement slurry to the surface to produce a smoother, denser surface free from honeycombing. The water allows the mix to combine molecularly in a chemical reaction called hydration.
One of the major advantages of concrete pavements is they are typically stronger and more durable than asphalt roadways. They also can be grooved to provide a durable skid-resistant surface. A notable disadvantage is that they typically can have a higher initial cost, and can be more time-consuming to construct. This cost can typically be offset through the long life cycle of the pavement. Concrete pavement can be maintained over time utilizing a series of methods known as concrete pavement restoration which include diamond grinding, dowel bar retrofits, joint and crack sealing, cross-stitching, etc. Diamond grinding is also useful in reducing noise and restoring skid resistance in older concrete pavement.
Composite pavements combine a Portland cement concrete sublayer with an asphalt. They are usually used to rehabilitate existing roadways rather than in new construction.
Asphalt overlays are sometimes laid over distressed concrete to restore a smooth wearing surface.A disadvantage of this method is that movement in the joints between the underlying concrete slabs, whether from thermal expansion and contraction, or from deflection of the concrete slabs from truck axle loads, usually causes reflective cracks in the asphalt. To decrease reflective cracking, concrete pavement is broken apart through a break and seat, crack and seat, or rubblization process. Geosynthetics can be used for reflective crack control. With break and seat and crack and seat processes, a heavy weight is dropped on the concrete to induce cracking, then a heavy roller is used to seat the resultant pieces into the subbase. The main difference between the two processes is the equipment used to break the concrete pavement and the size of the resulting pieces. The theory is frequent small cracks will spread thermal stress over a wider area than infrequent large joints, reducing the stress on the overlying asphalt pavement. Rubblization is a more complete fracturing of the old, worn-out concrete, effectively converting the old pavement into an aggregate base for a new asphalt road. Whitetopping uses Portland cement concrete to resurface a distressed asphalt road.
An asphalt milling machine in Boise, Idaho.
Distressed road materials can be reused when rehabilitating a roadway. The existing pavement is ground or broken up into small pieces, through a process called milling. It can then be transported to an asphalt or concrete plant and incorporated into new pavement, or recycled in place to form the base or subbase for new pavement. Some methods used include:
Rubblizing of concrete pavement. Existing concrete pavement is broken into gravel-sized particles. Any steel reinforcing is removed, then the remaining gravel-sized particles are compacted and overlaid with asphalt pavement.
Cold in-place recycling. Bituminous pavement is ground or milled into small particles. The asphalt millings are blended with a small amount of asphalt emulsion or foamed bitumen, paved and compacted, allowed to cure for seven to ten days, then overlaid with asphalt.
Hot in-place recycling. Bituminous pavement is heated to 250 to 300 °F (120 to 150 °C), milled, combined with a rejuvenating agent or virgin asphalt binder, and compacted. It may then be overlaid with a new asphalt overlay. This process only recycles the top two inches (50 mm) or less, so it can be used to correct rutting, polishing or other surface defects. It is not a good procedure for roads with structural failures. It also generates high heat and vapor emissions, and may not be a good candidate for built-up areas.
Full depth reclamation is a process which pulverizes the full thickness of the asphalt pavement and some of the underlying material to provide a uniform blend of material. A binding agent may be mixed in to form a base course for the new pavement, or it may be left unbound to form a subbase course. Common binding agents include asphalt emulsion, fly ash, Portland cement or calcium chloride. It can also be mixed with aggregate, recycled asphalt millings, or crushed Portland cement to improve the gradation of the material, and can provide a design life cycle of 30 years with proper lab testing and field verification.
Bituminous surface treatment (BST) or chipseal is used mainly on low-traffic roads, but also as a sealing coat to rejuvenate an asphalt concrete pavement. It generally consists of aggregate spread over a sprayed-on asphalt emulsion or cut-back asphalt cement. The aggregate is then embedded into the asphalt by rolling it, typically with a rubber-tired roller. This type of surface is described by a wide variety of regional terms including “chip seal”, “tar and chip”, “oil and stone”, “seal coat”, “sprayed seal” or “surface dressing” or as simply “bitumen.”
BST is used on hundreds of miles of the Alaska Highway and other similar roadways in Alaska, the Yukon Territory, and northern British Columbia. The ease of application of BST is one reason for its popularity, but another is its flexibility, which is important when roadways are laid down over unstable terrain that thaws and softens in the spring.
Other types of BSTs include micropaving, slurry seals and Novachip. These are laid down using specialized and proprietary equipment. They are most often used in urban areas where the roughness and loose stone associated with chip seals is considered undesirable.
Applying gravel, or “metalling,” has had two distinct usages in road surfacing. The term road metal refers to the broken stone or cinders used in the construction or repair of roads or railways, and is derived from the Latin metallum, which means both “mine” and “quarry”.The term originally referred to the process of creating a gravel roadway. The route of the roadway would first be dug down several feet and, depending on local conditions, French drains may or may not have been added. Next, large stones were placed and compacted, followed by successive layers of smaller stones, until the road surface was composed of small stones compacted into a hard, durable surface. “Road metal” later became the name of stone chippings mixed with tar to form the road surfacing material tarmac.
The decision whether to pave a gravel road or not often hinges on traffic volume. It has been found that maintenance costs for gravel roads often exceed the maintenance costs for paved or surface-treated roads when traffic volumes exceed 200 vehicles per day.Some communities are finding it makes sense to convert their low-volume paved roads to aggregate surfaces
Polymer Fiber Reinforced Concrete
Polymeric fibers are being used now because of their no risk of corrosion and also being cost effective (Sikdar et al, 2005). Polymeric fibers normally used are either of polyester or polypropylene. Polymer fiber reinforced concrete (PFRC) was used on two sites with ready mix concrete and Vacuum dewatering process.
Dust can be suppressed before it becomes airborne. A series of nozzles discharge a chemical compound in a fine spray to materially reduce the amount of water or other liquids necessary to saturate fly ash and eliminate dust. An unpaved road stabilized with calcium chloride retains a smooth dustless surface serves as a viable cost-effective alternative to an asphalt surface treatment. controls dust and reinforces stabilization. helps improve roads when used over time. Dust Suppression uses a blend of our polymers for erosion control and dust suppression for all side Blatter and me-dium strips for road developments.
Quiet asphalt pavement options fall into four general categories. These are fine-graded surfaces, open-graded friction courses, rubberized asphalt and stone-matrix asphalt.
Fine-graded surfaces are conventional asphalt mixes that are mostly composed of fine-grained particles; reducing the apparent road noise generated by the expelled air by altering its frequencies. Open-graded friction courses (OGFC) are a porous mix; with more connected voids through which air and water can escape. Rubberized asphalt contain crumbs of recycled tires that provide some flexing in the road surface as tires pass over it, allowing the air a bit more time to be forced out at lower pressure. Stone-matrix asphalt mainly uses coarse aggregate to create a stone skeleton, tied together by asphalt binders and fibers.
Each of these options come with different wear, climate resistance and cost considerations. No one solution fits all roads.The downside to quiet asphalt pavement is the price tag. Depending on the option chosen, it can cost more to prepare and lay quiet asphalt roads than conventional HMA (hot mix asphalt) and WMA (warm mix asphalt) solutions.
This is why quiet asphalt pavement tends to be financially justifiable in high-traffic urban areas where road noise is a serious concern.
Computer modelling in road construction
The use of computers and Computer Aided Design software (CAD) revolutionized highway design in the early 90´s. Standardized digital data formats have allowed engineers to exchange projects at different planning levels. Horizontal alignments, cross sections profiles and quantities on earth movements can be produced for numerous scenarios at fairly little extra amount of work once the initial planning stage has been computerized. Many companies provide CAD software for road design purposes.
However these are some popular technology but with times there has been significant development in other system as well. As we preach towards successful road work, innovation and the right application holds the key.
Info and image sources
- http://www.ifp.uni-stuttgart.de/ publications/phowo13/270Fellendorf.pdf