Benefits of Using Asphalt for Paving

Asphalt is a mixture of aggregates, bitumen and filler, used for constructing and maintaining roads, parking areas, ports and airport runways among others.

There are various benefits to using asphalt for paving:

1. Smoothness / Ride Quality

Asphalt mixes provide a smoother pavement surface, thus reducing damages to the surface. It improves fuel efficiency and reduces wear & tear of the vehicle tyres. Finally, paving roads and highways with asphalt significantly reduces the noise generated by the tire/pavement interface providing for a quieter ride experience for the motorist.

2. Faster Construction

Asphalt roads can be constructed quickly. Traffic can be opened on the road after construction pretty quickly. Asphalt is ready for traffic right after it is compacted and cooled, which means better traffic flow, minimized closures and happier motorists.

3. Quick Maintenance

Asphalt pavements have the ability to last forever when designed properly. Using asphalt, the maintenance can be done quickly and at times, it can be done even with partially-open traffic. The road needn’t be blocked for a long time. Additionally, maintenance activities can be planned during weekends or off-traffic hours causing minimal disruption to commerce.

4. Safety

Road paved with asphalt mixtures will have a feature that it gets smooth like finish. It offers drivers skid resistance, splash back and better visual distinction between road markings.

5. Sustainability through Recycling

Asphalt is a recyclable material, meaning its lifecycle never ends. Once laid mixture can be dug up and re-used in the future for maintenance works or for new construction. This allows to preserve the environment by reducing the strain on the ecosystem, thereby driving the factor of sustainability in road construction.

However, it is not without its own disadvantages. Some of them are detailed below:

1. In order for asphalt to be used, the bitumen needs to be heated to 160 – 1800C so that it becomes a liquid which is fluid enough to be coated on the aggregates. This requires specialised training and experience to ensure that the activity runs smoothly.
2. Bitumen is a petroleum product, which releases hydrocarbons during its extraction. This causes serious environmental degradation. High heating temperatures also causes various environmental pollution.
3. Various heavy machinery is needed to construct asphalt pavements, even for small road construction. These types of equipments are expensive and requires skilled labour to operate.
4. Improper construction practices / negligence causes pavement to develop cracks and other kinds of deterioration. Extreme care is required for such practices.

Ref

What is Asphalt


http://www.apao.org/why_choose_asphalt.html
https://maininfrastructure.mystrikingly.com/blog/asphalt-advantages-and-disadvantages

Hot Mix Asphalt Vs Warm Mix Asphalt

The main difference between hot mix asphalt and warm mix asphalt is how they’re made.

Hot mix asphalt (HMA) is heated up to around 300 degrees Fahrenheit in a special oven to help reduce the curing time on the road. Warm mix asphalt (WMA) uses a process called “adhesive bonding” to create an even, strong bond between the aggregate and binder that allows it to be put down at about 180 degrees Fahrenheit without cooling.

HMA is produced and transported at a higher cost than WMA because of the higher temperatures needed to prevent it from solidifying.

Warm mix asphalt is more environmentally friendly than hot mix because it uses less fuel. The typical amount of fuel used to produce 1 ton of hot mix asphalt is 8 gallons, while with warm mix only 3.2 gallons is needed. Fuel consumption during WMA manufacturing is typically reduced by 20%.It also has a lower carbon footprint than hot mix, which means that not as much carbon dioxide is released into the air during production.

The reason warm mix asphalt can be placed at a lower temperature is because it is less viscous or thick than hot mix asphalt and therefore easier to apply at a lower temperature.

Construction crews can pave at lower temperatures, which allows to open the pavement for traffic sooner and lessens traffic gridlocks. The window for paving is widened and this results in the extension of the paving season, especially in colder climatic geographies.

On certain days when the air quality is bad, paving activities are halted, thereby delaying the process of paving. WMA also produces lesser emissions, making it a possibility to construct pavements on such non-attainment days. Also, working conditions are a lot better with WMA. Both at the production plant and on the building site, crews inhale lesser smoke and dust. This decrease is especially significant in tunnels where ventilation is lesser.

It has been utilized effectively in a wide scope of pavements with varying thicknesses. It is sufficiently strong to withstand high traffic demands. Warm Mix Asphalt has been utilized in a wide range of asphalt layers: dense-graded, stone matrix, porous, and mastic asphalt. Numerous WMA advances are available in the market, so the decision on the type of WMA can be adjusted according to the temperatures and materials required.

WMA has been utilized effectively in Europe for over 10 years. In the United States, WMA projects are presently in excess of 40 States.

4 ways for Road Dust Control

Paved roads are preferred because of its numerous benefits such as smoother rides and longer life. However, converting an unpaved road to a paved road involves huge costs, due to which efforts are made to maintain the condition of the unpaved roads, especially in areas with low traffic.

The unpaved roads (or Gravel Roads) cause air pollution and significant dust generation which hampers the quality of plant and human life in the region. Dust settlement on plants refracts the sunlight and reduces the efficiency of photosynthesis, causing growth inhibition. It also causes breathing and related troubles in humans. Also, dusty roads can cause damage to vehicles and dusty driveways will cause vehicles to require more frequent car-washings at the very least. So it is essential to reduce the dust generation by bonding them in place with the road surface.

Traditionally, spraying water on the surface periodically was considered to be a good solution for dust mitigation. However, in areas with dry climate, it will only be a temporary solution. Applying a salt solution offers another way. It captures the water from the atmosphere, keeps the road top surface damp and prevents it from turning into dust.
One widely accepted practice is to use Gravel. However, it may not be a long term solution as it needs to be anchored to the road below, causing a rough ride.

Chemical technologies such as Zycobond offer a more permanent solution for dust suppression. It facilitates strong chemical bonding between the soil particles and prevents captures existing & new fines, thereby reducing the number of watering cycles.

Dust Control Techniques for Low Volume Roads

Low Volume Roads comprise of more than 50% of the total road network. They generally serve as access-ways, with majority of the developing nations using it for commercial transportation of people and goods. With these low volume roads, come the dust and the need to reduce/eliminate them.
Controlling the dust is a vital factor towards health and safety of the people. It is also one of the largest contributor to air pollution. Generally accepted methods and techniques to control dust on these roads are:

1. Reducing the number and Traffic
Fast moving vehicles will stir up dust. Reducing the number of vehicles as well as the speed of the plying motors can help reduce the amount of dust significantly.

2.Gravel Spreading
Spreading a layer of gravel in top of the dusty surface will prevent the dust generation. However, due to the lack of bonding between the gravel and the soil particles, the gravel will move from place causing a bumpy ride to motorists. Also, the heavy load from the vehicles might push the gravel into the soil, especially if the road surface do not have enough fines.

3. Bind Soil Particles.
Another kind of dust palliatives includes chemicals which bind fine particles together or onto larger particles. Dust control products like Zycobond are used to bind the particles in place.

4. Sealing with Pavements
Constructing an asphalt pavement on top of the dusty surfaces are a good way to ensure dust control and facilitate faster and smoother movement of people & goods. With the advantages of asphalt pavements, it is a reasonable alternative for adoption.

5.Windbreakers
Windbreaks are barriers designed to slow the speed and redirect the flow of wind. Good windbreaks will not create excessive turbulence or wind eddies. Windbreak materials may include picket and board fences. Windbreaks are most useful when designed for specific wind directions.

6.Vegetation
Growing vegetation along the road sides is a good dust control measure. Plants not only cover the ground, preventing the dust from blowing away, but also holds the soil particles together by means of its roots.

7.Other Measures
Other alternatives including spraying calcium chloride and magnesium chloride mixed in water. Sometimes, bitumen emulsions are also used, by spraying over the existing dusty surface, which creates a layer on top of the soil particles, making them heavy enough to prevent being blown away.

Zydex dust control technology provides a solution to a number of problems be it the visibility issues, health problems or deterioration of the quality of roads.

Sustainable Road Construction

Sustainability focusses on meeting the needs of today, without compromising the needs of the future generations. The concept of sustainability focusses on the pillars of people, planet and profits. Transportation sector being one of the highest contributor to greenhouse gases, with the burning of fossil fuels during construction as well as the emissions from vehicles, faces a grave challenge of adopting sustainable practices to reduce the emissions during production, construction and maintenance.

Road construction consumes high quantities of energy at different stages of asphalt mix production & transportation, and during the excavation of materials for maintenance. The production of Hot Mix Asphalt used for paving, requires high temperatures of 150- 1800C making it a very high energy consuming sector, which in turn generates higher quantities of CO2. Engineers have been looking for solutions to reduce the emissions during production and construction, which later paved the way to low temperature asphalt mix production, also known as Warm Mix Asphalt. The production and paving of Warm Mix Asphalt offers huge benefits in terms of lesser emissions & fumes, longer hauling, and better working conditions, without compromising on the quality of the construction.

A wide range of solutions such as silane based chemicals, geogrids & reinforcements, bitumen additives etc. are being adopted for various activities such as soil stabilization, asphalt mix production and even for maintenance treatments such as microsurfacing, to reduce the environmental impact of road construction, thereby allowing the sector to take a step towards sustainability.

Other options include the use of recycled materials from existing pavements and shingles to reduce energy consumption. Bio-binders originating from natural resources is another alternative that have been gaining traction in the road construction sector, because of their myriad benefits with the added advantage of being biodegradable.

The future of sustainable road construction & maintenance practices not only depends on the use of new and improved material technologies, but also on other innovative initiatives & concepts such as:

1. Solar/Wind powered lights
2. Piezoelectric energy generations from vibrations of vehicles
3. Use of de-icers on the road surface
4. Glow-in-the-dark road markings
5. Electric & Autonomous Vehicles.

The rise of these technologies and practices aimed at reducing the environmental impact of the transportation sector pushes for the need to reduce the carbon footprint of the existing construction practices. The future of road construction is definitely moving towards a more sustainable approach as evident from the various potentially interesting initiatives that strives to reduce the ecological footprint of the existing road construction practices.

Why do roads get damaged frequently? Know the important factors

A pavement structure is designed and constructed to meet its service life, by taking into consideration the magnitude of the load and the environmental conditions under which it will have to sustain. However, along its service life, the pavement undergoes damage due to a multitude of factors. These factors can be classified as follows:

1. Climatic Conditions

The performance of road depends greatly on the temperature variations (wet and dry/freeze and thaw cycles), rainfall and moisture ingress. The materials used in road construction reacts differently with the presence of these factors. The variation of these factors beyond the tolerable limits will lead to premature failures of the roads. Common failures resulting from climatic variations are swelling and shrinkage of road layers, thermal cracks, potholes, stripping, debonding, bleeding and raveling. Generally, bitumen additives are used to help the pavement withstand these issues. Technologies such as adhesion promoters / antistripping agents prevent the moisture ingress into the asphalt mixes, keeping the pavement in a good condition.

2. Traffic Loading

The traffic load on any road is a very important criteria that determines the performance and ultimately the life of the road. All roads are designed for a given traffic/loading that it is likely to carry over its design life. Any significant overloading will affect the road performance and reduce the service life of the pavement. Few common failures resulting from excessive loading are shoving, rutting, fatigue cracking and depressions. These pavement distresses/failures can be avoided by designing the road adequately for future traffic and also with the use of high performance materials and technologies available. Chemical soil stabilization is one of the techniques that help the pavement withstand higher loads, by enabling to construct stronger soil bases. Other techniques also include, use of geogrids and geotextiles, fibres and modified bitumen binders, to provide higher strength and durability.

3. Operational Factors (Material Reliability and Construction Practices)

These factors includes everything from the usage of unusable/unsuitable materials to operational inefficiency in the field conditions. Inadequate practices lead to structural failures, roughness, cracks and moisture ingress in to roads and ultimately lead to pavement disintegration. Failure to obtain proper compaction, improper moisture conditions at the time of construction and inaccurate layer thicknesses after compaction all directly affect the pavement performance. The adoption of best and reliable construction practices will ensure the construction of durable and long lasting roads.

Consult Zydex and avoid premature failure of your road assets.

What is cold mix asphalt?

Cold mix asphalt is, just like hot mix asphalt, a combination of aggregates and cutback or bitumen emulsion, commonly used on low traffic roads or rural roads. Cold mix asphalt is produced by emulsifying the asphalt with water and an emulsifier agent, before mixing it with aggregates, to make the asphalt less viscous so that the mix is easier to work with. The mix could be the one comprising of bitumen emulsion, and virgin aggregates or reclaimed asphalt pavements/milled pavements, though the latter would be cost effective. They are used for repairing potholes as well as worn out flexible pavements. Cold mix asphalt also works along flexible pavements and can be produced, either on-site or at mixing plants.

Features &Benefits of Cold Mix Asphalt:
There are a wide range of benefits which makes cold mix asphalt a preferred option. These include the following:

1. Economical:
a. Cold mix asphalt is economical as compared to hot/warm mix asphalt, as this method eliminates the need to heat the aggregates.
b. Using cold mix is cost effective as compared to hot/warm mix asphalt, due to the fact that the mix can be applied directly from the container.

2. Easy to use:
a. No special high tech machinery required as the standard paving equipment can be used for paving.
b. Design of the mix can be altered and determined depending on the type of the aggregate type, climatic condition of the geography of the location it is to be applied,
c. The mix can be used even when the ambient temperature drops, thus reducing the requirement of maintaining the temperature of the asphalt. So it can be used in all weather conditions.

3. Environmental Friendly:
a. As it doesn’t need to be heated like the hot/warm mix asphalt, it eliminates the emissions.
b. This also reduces the carbon footprint left behind after the process.

Benefits of Zydex Technology for Cold Mix

High-performance cold mix asphalt is the need of the industry. Zydex organosilane technology formulated with cationic bitumen emulsion shows improved uniform coverage, reduced clogging of nozzles, improved spray rate and faster setting.
We offer bitumen emulsion additives for Cold mix asphaltto our clients for improved coating efficiency, preventing stripping of the mixes, higher oxidation resistance andbetter fatigue resistance. We specialise in offering eco-friendly technologies that facilitatesustainable road construction, with improved performance.

Slurry Seals

Slurry seal is a homogeneous mixture of bitumen emulsion, water, well-graded aggregates and mineral filler, mixed as per a design formula, and applied to an existing asphalt pavement surface. Slurry seals are laid on the existing pavement, to seal cracks and voids, thereby making the surface weather tight and providing a new look. A slurry seal is similar to that of a fog seal, except that it has aggregates as a part of the mixture.

Slurry seals are used to remedy a broad range of surface distresses on various surfaces such as streets, drive-ways, airfields and parking lots, to extend the pavement life until resurfacing becomes absolutely necessary. Slurry seal applications are prominent on roads with moderate to low distresses and narrow cracks with no rutting. They seal the surface and provide flexibility and offer a rich black colour. They preserve and protect the underlying pavement surface and provide smooth surface with good riding quality.

Slurry seals, typically have three aggregate gradations:

1. Type 1 (fine)

This type has the finest aggregate gradation (smaller than 2.36 mm) and is used for filling small cracks. They are used as a preparatory pavement treatment and are limited to low traffic areas.

2. Type 2 (general)

This type is coarser than the Type 1 slurry, and is the most commonly used slurry seal type. It treats surfaces with moderate raveling, and improves the skid resistance of the existing pavement.

3. Type 3 (coarse)

Type 3 slurry seals consist of the coarsest gradation and is used to treat surfaces with slight depressions, to prevent water ponding and reduce the probability of hydroplaning.

Slurry seals are an economical and cost-effective solution, to build an all-weather, long lasting surface that provides better skid resistance and improved handling characteristics for drivers. Various factors such as traffic, weather, location and existing pavement conditions need to be taken into consideration before deciding on the slurry seal application. Typically, roadways are treated with slurry seals every 5 to 7 years.

Slurry seals are laid using a slurry truck, which holds various compartments to hold aggregates, water, polymer modified emulsion, and additives. These are the mixed in an on-board mixer and the slurry mixture flows out the rear of the truck onto the pavement. Paving crew follows the truck to provide assistance by ensuring that the mixture spreads properly, correcting uncovered areas and keeping the mixture from flowing over the sides. Sometimes, a fabric is dragged behind the slurry truck to ensure a smooth texture on the surface. Once laid, slurry seals require 4 – 6 hours to dry, before the road is opened to traffic.

Slurry seal is a protective asphalt overlay that preserves the underlying pavement surface and provides significant environmental benefits, thus allowing us to take a step towards a greener & sustainable future.

NanoTac is a cationic bitumen emulsion additive that can be used in Slurry systems at 0.1% by weight, to improve the bonding and wetting attributes of the mixes. This ecofriendly and sustainable chemical technology leads to blacker looking slurry mixes with improved moisture resistance.

Improving Bond Strength of Tack Coats using Nanotac: A Case Study

Overview

Research has proven that the degree of bonding between pavement layers can significantly affect the overall performance of the pavement structure or overlay. Zydex Industries specifically addresses this unique problem of permanent bonding between asphalt layers with its asphalt additive – NanoTac.

In a study undertaken by the National Center for Asphalt Technology (NCAT) titled: “Effects of NanoTac Additive on Bond Strength and Moisture Resistance of Tack Coats” by Adam Joel Taylor, P.E. (2011), laboratory analysis measured the effects of NanoTac in a tack coat application. The results provide an interesting view into the performance of NanoTac’s organosilane chemistry and its unique bonding characteristics.

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NanoTac is an asphalt pavement additive derived from organosilane technology. NanoTac is designed to convert the surface of the treated material (untreated aggregate, soil, or HMA) from a water-loving (hydrophilic) surface to a water-repelling (hydrophobic) surface. The NanoTac additive is added to a diluted tack coat material by blending a small quantity of the additive with the water used to dilute the emulsion. This is designed to improve the water-resistance and bonding strength of the tack coat interface. The NanoTac additive is also designed to lower the surface tension of a cationic emulsion with which it is blended, reducing droplet size and improving spray coverage. NanoTac is also intended to wet, penetrate, and set quickly to reduce the problem of ‘tire pickup,’ a common problem with construction traffic driving over newly placed tack coats, removing the tack, rendering it ineffective.

Effects of Poor Bond Strength

Poor bonding between pavement layers has been known to decrease the structural bearing capacity of a pavement inducing pavement distresses and failures. Problems commonly associated with debonding are premature slippage cracking, top‐down cracking, and fatigue cracking. Past research shows debonding can reduce the pavement’s fatigue life by more than 50% prompting the need for extensive repairs such as full‐depth patches or complete reconstruction.

The best way to prevent debonding from occurring is through good construction practices. A quality tack coat material that provides sufficient bond strength should be used and uniformly applied to the pavement surface. Common issues with tack coat application include non‐uniform spray (often due to clogged nozzles on the spray truck) and tire pickup (tires from construction traffic removing the tack). Quality construction practices are critical to achieving a quality tack coat interface in the field.

The NanoTac Study

The study was performed to evaluate the effect of the NanoTac additive on tack coat bond strength, spreadability, dry time, tire pickup, and moisture susceptibility.

The study also evaluated the properties of a diluted cationic slow setting (CSS) emulsion containing the NanoTac additive versus the properties of a diluted emulsion with no additive.

Testing Procedures

The interlayer bond strength of each core was determined using ALDOT‐430 Standard Test Method for Determining the Bond Strength Between Layers of an Asphalt Pavement. The control emulsion application had a 30% AC residual while the NanoTac modified application had only a 10% AC residual.

Summary

Based on the results of this study, the following conclusions can be made:

The NanoTac modified emulsion (10% AC residual) with a lower residual AC content provided equivalent bond strength to that of a control emulsion (30% AC residual) on an unmilled (new HMA) surface.

All optimum bond strength values for both the control and NanoTac emulsions were greater than 150 psi (1.03MPa). Construction standards recommend a minimum value of 100 psi (0.69MPa) to have adequate bond strength in the field.

For a copy of this study, please contact your regional representative.

Need for chemical soil stabilisation

Chemical Soil Stabilisation is the process of blending and mixing chemical additives to improve the engineering properties of the soil. The efficiency of the stabilisation depends on the reaction between the chemical/stabilizer used and the soil particle composition.

Soil stabilisation using chemical additives is adopted not only to arrest its shrinkage & swelling potential, but also to improve its strength, workability & durability, thus improving their overall performance. The increased performance implies reduced the maintenance costs, significantly improving the overall lifecycle costs of the pavement. It also offers other advantages such as reduced dusting requirements, controlled volume changes to soil and better workability.

The performance of the treated soil depends on the ability of the additives to react with the soil, which places a great emphasis on choosing the stabilizer best suited for a particular type of soil, taking into consideration, not only the improvement of its engineering properties but also considering its economic and environmental impact.

It has been a common practice to use calcium based stabilizers such as cement and lime for stabilisation, due to its notable effect of reduction in plasticity, swelling & shrinkage as well as the increased bearing strength. However, there are certain limitations to using these additives. Stabilisation of soils containing sulphate minerals when treated with lime, causes adverse chemical reactions & formation of an expansive crystalline mineral, causing heaving and other pavement distresses. Exposure of lime treated soils to wetting and drying cycles results in the loss of cohesion between soil and lime particles. Lime & cement applied in the powder form is known to burn unprotected workmen and also causes harmful environmental effects. Moreover, cement manufacturing emits large amounts of CO 2 . Fibers have been considered an effective alternative to help prevent cracks; however, its effectiveness in restricted to certain type of soils.

The use of bitumen emulsion for soil stabilisation is also a notable practice as it imparts water resistance to the soil particles, increases the load bearing capacity & stability of the soil. However, it may not be a cost effective solution as the soil particles require a high dosage of bitumen emulsion in order to provide the same/better level of bonding. Foamed bitumen, i.e. mixture of air, water and bitumen, is also being used for soil stabilisation. It has been proven that by applying foamed bitumen, produces a semi-rigid layer of stabilised soil.

New and emerging technologies such as enzymes and silanes are being preferred over traditional stabilisation methods, to solve the problems of swelling and shrinkage as well as to improve the load bearing capacity and compaction densities of poor soils, with no harmful effects on the environment. Major advantage of using chemical additives for soil stabilisation is that it enables the use of in- situ/locally available soils and aggregates. This decreases the effort and time required for hauling good quality materials from borrow areas, allowing for an efficient use of natural resources. This results in minimized cost of hauling, thereby reducing the cost of construction.