Asphalt pavements over the years have become increasingly popular because of their relatively low cost compared to concrete or other types of pavement materials. There are different types of asphalt mix available for pavement construction which makes it easier for users to make choices depending on the nature of the surface where they will be applied.
What is Asphalt Mix?
The asphalt mix is a mixture of sand, gravel, and crushed stone. It’s used to make roads and parking lots. The asphalt mix is poured into the desired shape, and then the heat from the sun or a burning tire melts the asphalt. This liquid asphalt is then pumped into cracks in the road surface.
Asphalt mixture is a type of asphalt that is used in road construction. It’s made up of small stones and gravel that are mixed with bitumen. The mixture is then poured into the cracks in the road surface and spread out using a machine. This creates a smooth, durable surface that can handle heavy traffic.
What is Asphalt?
Asphalt is a complex mixture that consists primarily of hydrocarbons which can be produced naturally as a byproduct of petroleum refining, or synthetically. So, asphalt is not a single substance, rather, it is technically an umbrella term that covers many types of materials that go into pavement surfaces. It is one of the best materials used for flexible pavement construction and can be found in most roadways and driveways across the globe. There are many different types of asphalt available for pavement construction such as roadways, driveways, parking lots, etc.
Types of Asphalt Mix
Different types of asphalt mix include:
- Hot Mix Asphalt (HMA)
- Cold Mix Asphalt (CMA)
- Foamed Asphalt
- Chip Seal Asphalt
- Warm Mix Asphalt (WMA)
- Porous Asphalt
- Quiet Asphalt
Hot Mix Asphalt (HMA)
Hot mix asphalt is a type of asphalt pavement that consists of various sized pieces of stone mixed with hot bitumen. This mixture is then applied to surfaces, normally roads and driveways, in multiple layers to create a sturdier surface. Although it takes longer for the finished product to cool down and set, many contractors prefer this form of paving since it uses fewer materials than other forms.
The properties of hot mix asphalt depend on its composition, specifically, what percentage of which type(s) of stone are used. Clay stones have good compaction qualities but poor durability whereas granite rocks have low compatibility but excellent durability. To produce a good quality mix, there should be more round particles rather than angular ones so that water can drain easily through the mix. A good asphalt mix has 20—25% small particles, 8—12% large particles, rest consisting of fillers. There are many uses for hot mix asphalt, including patching up holes in existing roads or driveways when nothing else will work.
Hot mix asphalt is commonly used when paving highways because its high initial seating temperature ensures that the road will not be damaged by the increased traffic in the future. Paving this way also decreases construction time since it requires less downtime to lay down multiple layers instead of one at a time. When used on major routes, hot mix asphalt doesn’t need to be sealed or stained because it usually remains in better condition than other surfaces throughout its lifespan.
Cold Mix Asphalt (CMA)
Cold mix asphalt is a material made of graded aggregates mixed with asphalt cement and mineral filler such as lime. The mixture is heated enough to bond the material together, without producing hot liquid asphalt. It can be used in traffic immediately or stored for later use if necessary.
These types of Asphalt keep working even when the weather conditions are not ideal for laying asphalt. This means that a cold mix can be applied during winter months when it may otherwise be difficult and expensive to apply hot asphalt due to the colder temperatures which would cause it to harden too quickly and damage paving equipment. It can fill cracks, cover potholes, smooth surfaces, provide skid resistance and protect the existing pavement from water damage.
In 2007, a report by the National Highway Traffic Safety Administration stated that cold mix asphalt has several advantages over its comparable, hot-mix counterpart. It is less expensive to produce and results in less environmental pollution. Also, it can be placed on an existing road without softening or rutting like hot asphalt can. All of these benefits make Cold Mix Asphalt a popular choice for contractors and paving professionals who would like to be able to work all year instead of just during the summer months when temperatures are more suitable for laying down traditional hot asphalt.
Foamed Asphalt
Foamed asphalt is a lightweight mixture of mineral aggregates and a foamed polymer, where the polymer provides some of the strength needed to support heavy loads. The foaming agent forms bubbles that are similar to tiny balloons that add strength while reducing weight, making it easier for truckers to transport. In addition, since it reduces the load on roads, this alternative also extends their life span.
Foamed asphalt is cost-effective since there is a reduction in material usage. Less aggregate is needed which allows these mixtures to be installed quickly with fewer trucks so there’s less congestion during installation. It is also energy efficient since the mixture is self-leveling; it doesn’t require heavy machinery to install.
These types of asphalt are environmentally friendly since they reduce fuel usage, which in turn reduces carbon dioxide emissions.
But there are also some drawbacks to consider before choosing foamed asphalt, which include, unsuitability for very hot climates (above 150 degrees F), and if it gets too cold, the air bubbles can freeze and cause damage to the road surface. However, some additives can be made which will allow these mixtures to work even in extreme circumstances. These additives are made with materials that expand when the temperature rises and contract when it drops, balancing out any extreme temperatures.
The air bubbles in the foamed asphalt can also pop due to high traffic volumes or heavy vehicles. This leaves small holes in the road, which are costly to fix.
There are many different types of foamed asphalt mixes, but most of them contain water, portland cement, mineral aggregates (fine aggregate and coarse aggregate), additives for foam generation, defoamers, and stabilizers for cold weather use. Different ratios of these ingredients provide specific results which is why they must be mixed carefully by professionals during installation.
Foamed asphalt can be applied to most roads, and is an effective alternative to traditional heavy materials.
It is usually used on low-volume roads or as a topping on existing hot-mix asphalt (HMA). One common mixture has the following ingredients: fifty percent portland cement; ten percent reduced-asphalt cement; five percent fine aggregates; two percent coarse aggregates; one percent defoamer; and three percent foaming agent. If it’s not mixed correctly, however, the foaming agents won’t form bubbles which will make the mixture less effective.
Chip Seal Asphalt
This is a pavement surface treatment that uses an emulsion of asphalt cement and graded road chippings (crushed stone, gravel, or slag) applied in multiple layers to form a wearing course. It was developed by the US Army Corp of Engineers during World War II for temporary runway use until more durable surfacing materials could be used.
Chip seal asphalt is a highly useful material that is used for many different purposes. It is made from a mixture of stone chips and hot bitumen or asphalt. Quite often the stones that are used to chip seal roads are recycled from old road surfaces and they can be crushed and reused as part of the process. The stones and hot asphalt mixture harden together and form a strong, solid bond which will allow all kinds of traffic to move safely over it without wearing down the surface area too quickly.
Chip sealing is an effective method for prolonging the life of your driveway, particularly if you live in an area with severe weather such as snow or rain. This type of sealant protects against cracks or becoming more apparent, moss growth, and most types of weathering.
Chip seal asphalt also has a stabilizing effect on the surrounding area and helps to prevent cracking in the concrete surrounding it. It will provide your driveway with the perfect finishing touch and add some value to your property.
The composition of chip seal asphalt starts with clean graded aggregate, which is selected according to strict criteria – it must be free from fine material and also must not contain any soil particles. The aggregates are sized at 1/2 inch down to dust size using screens. The purpose of the screen is to remove dust particles that will affect the viscosity of the hot mix asphalt. Next crushed limestone or gravel is added to the aggregate that will form the chip seal asphalt. The limestone or gravel provides for skid resistance and also makes up 2/3 of the weight in a 3-inch stack.
chip seal Asphalt qualities include workability, stability when stored, resistance to deformation from traffic loads, shock-absorbing capacity against wheel load impacts, water permeability, and ability to resist softening when exposed to heat. These qualities are achieved through chemistry by adding a petroleum-based binder (which contains no Portland cement ), mineral filler, pigment, and stabilizing agents. Most countries use cold-laid chip seal asphalt binders because they harden quickly which reduces wear on paving machines due to cold joints.
Warm Mix Asphalt (WMA)
Warm mix asphalt is a mixture in which the liquid component of asphalt or bitumen is replaced by an application of warm aggregates. Warm mix asphalt reduces environmental damage, increases productivity, and lowers costs when compared to hot applications. Water utilization saves about 50% in production cost over traditional paving methods. It also requires less energy consumption due to the lower material temperatures.
WMA technology has many advantages over traditional mixtures that it is being used in applications around the world. Several factors help to explain why WMA has become so famous among transportation departments worldwide. The use of warm-mix asphalt helps reduce costs, environmental impact, and noise production on roadways by using 30% recycled materials as aggregate sources, such as worn-out asphalt concrete, crushed concrete, and recycled concrete block (RCB). Other benefits include increased workability throughout the paving process and extended service life for roads as much as double that of hot-mix asphalt pavements. Thus reducing landfill usage and minimizing damage to roadside vegetation from mechanical traffic.
WMA is not today the most common paving method, but it has become popular among states and road commissions worldwide. Warm mix asphalt also offers many benefits that should justify its use if environmental factors such as climate and other ecological issues are considered. For example, using WMA in cities with cold winter climates can help reduce the energy needed for snow removal while also helping to achieve the goal of making these areas more sustainable and environmentally friendly. On the other hand, warm mix asphalt can be used in almost any climate since WMA requires less than 7% water by weight whereas hot-mix applications require 25% water by weight. The use of aggregates recycled from existing roads is becoming more common all around the world it saves natural resources, reduces costs, and decreases construction time. On the other hand, warm mix asphalt is not typically used on parking lots, driveways, or other areas where heavy machinery will be required because the material may not have enough strength to support this type of machinery.
Porous Asphalt
Porous asphalt is a type of asphalt pavement that allows water to drain into the soil. This means that it will not pool up on the road when it rains, and thus reduces the risk of accidents during rainy seasons.
Porous asphalt has three times more perforations than conventional asphalt (concrete), which results in less heat retention due to its lower density. Therefore, people would be exposed to less heat through roads paved with porous asphalt compared to roads paved with traditional, dense asphalt.
This “lightweight” quality also makes paving roads using porous asphalt cheaper than conventional methods because fewer materials are required for construction. It was found in 2010 that previous concrete cost about US$1 per square foot while the traditional kind costs around US$3.50 per square foot. It would then mean that roads can be built for less using porous asphalt because of its lighter materials and the fact that it requires fewer materials to pave the entire road surface.
Porous asphalt is composed of lightweight aggregate (stone dust), bitumen emulsion, coarse minerals (sand), and fine minerals (silt). This mixture has a high void ratio which means that it will allow water to drain through easily while still being strong enough so that traffic can move on top smoothly.
This type of asphalt was first used in Australia where it caught on quickly due to the country’s frequent rainfall. They found out later, however, that only after 10 years did this type of pavement start to show its true potential, which was to reduce the rate of accidents during wet seasons, and allow water to drain into the soil.
Porous asphalt is a good solution for developing countries that have lots of rainfall because it can save lives and prevent road closures due to flooding. It is also cheap, quick, and easy to install compared to other solutions such as building drainage systems. However, porous asphalt has not been used in most parts of the world yet, since it only started appearing on the market in 2007. In addition, its high cost prohibits its use in places where money or materials are scarce. Nevertheless, this type of pavement will certainly become more prevalent in urban areas with heavy rainfall in future years.
Quiet Asphalts
Many people may not know what Quiet Asphalt is and where it came from. Here we will outline the history of quiet asphalt, its composition, and why cities are switching over to using it.
First developed in Holland, this asphalt was designed with a very specific goal: lower traffic noise by reflecting sound instead of absorbing it into roads. The material works by adding small particles to traditional tar macadam (tarmac) which then allows for better noise absorption and reflection. When cars drive down the road, their tires create vibrations and those cause tiny particles to bounce against each other creating more sound than usual. This increase in road noise can be caused by smaller vehicles such as motorcycles or bicycles too; however, these types of vehicles cause a much smaller vibration on the road. When cars drive through these roads, they cause a larger disturbance which becomes amplified by the material adding to the noise pollution of urban areas.
In addition, this material also reduces road wear and is more durable than standard asphalt roads. It lasts longer and has been used on many big-name projects such as the A4 highway in Austria or a parking garage in Germany. These materials can be created into larger chunks that are then recycled into the new pavement or they can be recycled down so they would fit better with current asphalt mixtures. Some places have experimented with coloring this material to create different effects such as putting white particles at bus stops so people waiting for public transport would not get sunburnt, similar to a bus shelter.
A main positive of this material is that it lessens traffic noise significantly and with the added benefits of durability and decreased road wear, more cities are looking into using Quiet Asphalt as a solution for their city infrastructures. While the initial cost of this material may be higher than traditional tarmac, cities can expect to see long-term savings due to the product’s lasting power. With so many benefits attributed to Quiet Asphalt, it seems likely that these roads will become more popular in urban areas around the world.
Quiet asphalt has only been tested so far on parking garages and highways but can also be used for regular streets which will come at an extra cost because the asphalt mix needs to be created differently depending on what type of road is desired.
