What are asphalt concrete mixtures and where are they used

Commonly referred to as asphalt, asphalt concrete mixtures are an essential part of contemporary road building. Bitumen, a binding agent, is combined with aggregates, like sand and gravel, to create these mixtures. Heat transforms bitumen into a tar-like, sticky material that binds the aggregates together to create a sturdy, long-lasting surface. This mixture is necessary to create parking lots, highways, and roads because it offers a dependable, smooth surface for cars and pedestrians.

Asphalt concrete is a popular option for a variety of applications due to its versatility. It is utilized for driveways, bike lanes, airport runways, and major highways and streets. It is perfect for a variety of environments because of its malleability, which allows it to be applied in a variety of climates and conditions. Furthermore, asphalt is renowned for its rapid construction time, which lessens interference with daily activities and traffic.

Recyclability is one of the main benefits of asphalt concrete. Reusing and grinding old asphalt can help conserve resources by lowering the need for new materials in asphalt mixtures. Asphalt is a green option for building projects because of its sustainable nature, which supports environmental preservation initiatives. Moreover, asphalt is a reasonably priced choice for preserving roads and other surfaces over time due to its smooth surface and fast repairability.

Asphalt Concrete Mixtures	Uses
Hot Mix Asphalt (HMA)	Used for road surfaces, parking lots, and airports due to its durability and weather resistance.
Warm Mix Asphalt (WMA)	Ideal for road construction and repair in cooler temperatures, reducing energy consumption and emissions.
Cold Mix Asphalt (CMA)	Used for temporary road repairs and maintenance, especially in remote areas where hot mix isn"t feasible.
Porous Asphalt	Applied in parking lots and driveways to manage stormwater by allowing water to drain through the pavement.

What is asphalt concrete – definition

The process of compacting an ideal and specially prepared mixture of mineral material (sand, crushed stone, mineral powder, and others) and bitumen (sometimes tar) for laying on a prepared base yields asphalt concrete, a non-firing artificial building material. Road materials are classified into several types, each exhibiting distinct qualities and attributes, based on the percentage of materials and their proportions.

Application

For pedestrian zones, highways, airport taxiways and runways, various sites, and other surfaces, asphalt concrete mixtures are used to create a hard surface. Pothole repairs often involve the use of liquid asphalt mixture. It hardens quickly, enabling traffic to be opened after a minimum amount of time, and does not require compaction or leveling after laying. It also allows for the precise blending of the surfaces of the freshly laid and old pavement.

Colored material is used to highlight specific areas of the road, divide strips, decorate pedestrian paths, and pave sidewalks. Corrugation, embossing, and the addition of multicolored minerals (sand from granite, marble, colored stone, and pigments) can all produce the desired effect.

Types of mixtures

Types of asphalt concrete road mixtures are distinguished based on characteristics such as composition, component proportions, and properties.

According to the composition’s volume of crushed stone content: grade A (50–60%), B (between 40% and 50%), and B (30–40%). Sand in grades G and D is completely free of crushed stone. Additionally, there are hot asphalt concrete mixtures with high densities, where more than 50–60% of the volume is made up of crushed stone or gravel.

2) Based on the percentage of mineral grains: fine-grained (grain less than 20 millimeters), coarse-grained (up to 40 millimeters), and maximum sand grain (5 millimeters).

3) Based on the material composition—crushed stone, gravel, or sand—that was used.

4) By the temperature at the time of asphalt laying: hot (distributed at a temperature of at least +120C), cold (temperature during distribution should be approximately +5C).

5) In terms of density, there are several hot ones: highly dense (residual porosity 1-2.5%), dense (from 2.5 to 5%), porous (about 5-10%), and highly porous (10-18%). The porosity of the mineral part of the cold mixture is 6-10%.

By kind of binders and state of operation:

• Classic mixtures – used for making road surfaces, city sidewalks and road surfaces.
• Crushed stone-mastic mixture – stabilizing fibrous additives are added to it (this can be cellulose, etc.).d.), relevant for the construction of highways with high throughput.
• Polymers asphalt concrete – plasticizers and copolymers are added to the composition, making it possible to make road surfaces of airfields, bridges, roadways of industrial enterprises, etc. more durable and durable.d.
• Separately, it is worth highlighting organomineral mixtures, which are created by mixing limestone and bitumen, and are used in the process of repairing road surfaces.

Compound

It is important to distinguish between two categories of constituents when determining the composition: the organic binding substance and the mineral filler. The physical and chemical characteristics of the material as well as any applicable regulations are taken into consideration when designing a particular composition.

The asphalt-concrete mixture’s primary ingredients are:

Crushed stone or gravel: the binder must firmly adhere to the filler grains in order to minimize creep and lengthen the service life. Crushed stone made of dense rocks and metamorphic carbonate—typically limestone or dolomites—in the shape of a cube are typically used for this. A maximum of 15%, 25%, and 35% of lamellar grains should be used for grades A, B, and C. The percentage of clayey or dusty inclusions should not be more than 1% to 2%. The grains of crushed stone range in size from 10 to 40 millimeters.

The composition’s sand and gravel must adhere to the requirements outlined in GOST 8736-93. "Sand for building projects." both GOST 8267-93 and (106kB). "Dense rock crushed into gravel for building applications." (179 KB).

2) Sand: Because fractions of the same size increase the porosity of the layer, it is suitable for crushing crushed stone or natural deposits (not river sand) of different fractions. Sand comes in three different grain sizes: medium (MK 2.0–2.5), small (MK 1.0–2.0), and coarse (MK 2.5). The maximum volume of clay particles is 0.5%, and small aggregates should not be smaller than 1000 in terms of strength.

The appropriate rough texture of the coating is provided by wear-resistant, high-strength crushed stone and crushed natural sand. A ligature made of sand and mineral powder gives bitumen structure, influences heat resistance, weight, and density, and provides the required road strength.

3) Mineral powder: Enough fine grinding should be used so that, when wet, the powder easily flows through a sieve with 1.25-millimeter holes. There shouldn’t be a hydrophilic coefficient greater than one. The astringent’s structure is directly impacted by the quantity and caliber of powder combined with identical amounts of other ingredients. The coating will be less durable if there is too much powder, especially at below-freezing temperatures.

4) Bitumen, a byproduct of oil refinement, serves as a binder, binding all of the major ingredients and sealing the spaces between them to give the asphalt mixture strength and waterproofness. Bitumen has two possible viscosities: liquid and viscous. The documentation specifies the viscosity level, which is dependent on components and temperature. It is important to keep in mind that the viscosity index rises with rising temperatures and falls with falling temperatures. The binder solidifies and gets extremely brittle at very low temperatures.

Bitumen brands for roads: BND 40/60, 60/90, 90/130, and 130/200. Viscous compositions serve as the primary raw material for the preparation of a liquid product, to which different solvents may be added. They can be used to create mixtures of any temperature. Typically, a liquid product with specific thinners and additives is used in the winter; these ingredients evaporate as the coating hardens and return the bitumen to its original state.

Requirements for mixtures

According to state regulations, there can be no more than 15% of lamellar grains in crushed stone (gravel) for grade A and high-density solutions, 25% for grade B and Bx, and 35% for grade V and Vx.

Building materials must be produced in a factory that complies with all laws and regulations. They must then be loaded onto a dump truck and delivered only after extensive testing and computation of the future coating’s properties, taking into account the specifications and operational features. The material must not be subjected to stratification (segregation), which results in an incorrect distribution of the binder, air bubbles, and grains in the composition and causes the layer to rapidly degrade after the work is finished, in order to prevent the appearance of irregularities and potholes.

Grades and types of asphalt concrete

There are only two grades of asphalt concrete, and the differences in strength of the stone material explains why they differ so much in terms of characteristics. Crushed stone (1000–1200) is used in the first brand’s compositions, while 800-1000 is used in the second.

Asphalt concrete mixture types and characteristics:

Mark I: This category mixes disparate materials and has a different structure than asphalt concrete. This comprises gravel, sand, dense A, B, and G compositions; porous and highly porous (hot and cold analogues); and Bx, Vx, and Gx. The maximum strength of the material for its composition is the common denominator. These grades are typically utilized as the roadbed’s bottom layer when extremely high strength is required.

II: "Ordinary" asphalt concrete, utilized in numerous building and operational contexts. This comprises high-density asphalts (Bx, Vx, Gx, Dx), porous, dense asphalts (A, B, V, G, and D). They cover the top layer of roads, which is important for maintenance, park and courtyard landscaping, regular roads, etc.

III is the least dense and least durable of the (B, V, G, and D) materials; it contains sand and mineral powders but no crushed stone. used primarily for building and repairing roads that cannot sustain heavy loads and testing; examples include garden areas, sidewalks, and potholes in new construction.

Blacktop, also referred to as asphalt, is created by mixing aggregates such as crushed stone, sand, and gravel with asphalt binder. Because of these mixtures’ strength, flexibility, and resistance to changing weather, they are crucial for building and maintaining parking lots, highways, roads, and airports. Because of its smooth finish, ease of installation and maintenance, and ability to reduce noise, asphalt concrete is a vital component of contemporary infrastructure development.

Features

The qualities of asphalt concrete, which are dictated by the composition, must be taken into account initially when choosing a composition. The three main tasks are to determine the porosity level, compact the hot material, and confirm compliance with requirements through testing. All guidelines and standards are followed during the design process in an effort to find the best qualities for the road surface and its longevity.

Phases involved in composition design:

1. Determining the original ingredients’ quality, calculating their characteristics, and evaluating whether they meet the brand’s specifications

2. Determining the mineral portion’s volume

3. Determining the ideal bitumen volume

4. Formulating a composition specification after carefully examining its mechanical and physical properties

The following is how all varieties of asphalt concrete are made:

• Selecting raw materials and determining their quality
• Calculating the volume of the necessary components for the required amount of product
• Calculating the cost of the order
• Loading raw materials into a special bin for preliminary dosing
• Drying mineral materials, heating to the required temperature
• Sorting by fractions, feeding to a high-precision weigh batcher
• Heating the binder to the required temperature (according to the type of composition), weighing, dosing
• Feeding all components to the mixer

Recommendations for laying

First, irrigation systems and special brush machines are used to remove dust and dirt from the base. After removing all imperfections, bitumen mastic is applied to the base. Produced in factories or mobile units, the material is loaded onto a dump truck, driven to the location, and then placed into the laying machine’s bin.

Using a specialized laying machine that distributes, levels, and compacts the coating, or using their hands, workers apply the coating. On a base made of crushed stone or gravel, one or two layers are placed. The bottom layer, which has a porosity of 5–10%, is composed of a mixture with a medium or large fraction and is 4-5 centimeters thick. The outer layer is made of small- or medium-sized fraction asphalt with a 3-5% porosity and is laid 3–4 centimeters thick. finally, a machine compacted it.

When discussing heavy loads and traffic, the coating is applied in three to four layers, totaling eleven to fifteen centimeters in thickness.

The procedure for laying sidewalks is the same, but there are a few minor variations: curbs are placed to divide the sidewalk from the road; the base (asphalt concrete made of slag, stone, broken brick, or chips from old material) is laid, leveled, compacted, and covered with an outer layer that is 3-5 centimeters thick.

Crushed stone

The crushed stone-mastic mixture has a temperature of about +150C, so handling it should be done carefully. The above chart shows how asphalt concrete mixtures are categorized according to the amount of crushed stone. As the top layer, cast mixtures are worth mentioning because they are used all year long in the construction and repair of various surfaces. Since the shipped composition has a temperature of 220 degrees, work can be done in the freezing cold.

The material is transported in a unique bunker designed to block out heat, inside which burners and mixers work to heat and combine the ingredients. You can lay this kind of asphalt even over a wet base.

Acceptance rules

Reloaders—special devices that guarantee the seamless operation of the paver or workers—are employed to build up a supply of solution. This means of transportation is employed when transferring asphalt concrete from cars straight to the paver.

The following details need to be considered before accepting. The single-component material used in the process is produced in batches during a single shift at the plant. Accepted compositions should not weigh more than 600 tons when they are hot, and no more than 200 tons when they are cold. Using specialized scales, the volume of the solution is calculated based on its weight. When loading onto a ship, the vessel’s draft must be measured after acceptance is complete.

Many tests are conducted to verify that the product satisfies the requirements, including tensile strength at various temperatures, resistance to outside influences, water saturation, and grain composition analysis. The buyer receives a document of conformance upon completion, one for each batch of cargo.

Consumption and density of building material

The characteristics of asphalt that are established by the state standard determine its compaction and quality. The type of sand used determines the composition’s density and weight per cubic meter: quartz weighs 2200 kg per cubic meter, while slag weighs 2350 kg per cubic meter. On average, concrete containing a significant amount of crushed stone weighs approximately 2100 kilograms more. Finding the weight is crucial for a number of reasons, including figuring out how much material is needed, estimating its cost, setting up the right tools, setting up the base, etc.

Estimating the solution’s consumption:

• Determining the area of ​​the territory and the thickness of the coating – for example, you can take 100 square meters and a thickness of 1 centimeter.
• To cover 1 square meter of the road with a layer of the specified thickness (1 centimeter), you need 25 kilograms of asphalt. For an area of ​​100 m2: 25 x 100 = 2500 kilograms.
• One cubic meter contains about 2250 kilograms of material – this means that to cover the area from the example you need: 2500: 2250 = 1.10-1.11 m3 of the composition.

In the construction industry, asphalt concrete mixtures are indispensable materials mainly used for paving roads, highways, and airport runways. Bitumen, a sticky, black material derived from crude oil, is mixed with aggregates, such as crushed stone and gravel, to create these mixtures. This mixture produces a surface that is resilient to wear and tear as well as changes in the weather.

The capacity of asphalt concrete to offer a safe and smooth driving surface is one of its main benefits. The mixture is perfect for high-traffic areas because of its flexibility, which prevents it from cracking under pressure. Furthermore, the dark color of asphalt absorbs heat and helps to melt snow and ice, which is especially useful in colder climates.

Parking lots, recreational facilities, and residential areas all use asphalt concrete mixtures. They provide a reasonably quick and simple installation process in addition to being an affordable and durable solution for paving needs. They are therefore a well-liked option for a wide range of construction projects, from large highways to modest driveways.

The use of asphalt concrete has brought about a growing importance of environmental concerns. By allowing for the recycling of old asphalt, contemporary methods and technologies minimize environmental impact and cut down on the need for new materials. Asphalt concrete is an environmentally friendly material for construction because of this sustainable approach, which also helps to conserve natural resources and minimize waste.

All things considered, asphalt concrete mixtures are essential to our infrastructure because they offer paving solutions that are affordable, long-lasting, and safe. Because of their adaptability and versatility, they are a preferred material in both urban and rural areas, guaranteeing the long-term functionality and dependability of our roads and surfaces.

Video on the topic

Selection of a recipe for asphalt concrete mixtures in the Lintel LIS LIMS program

Lecture 12 Asphalt concrete

Asphalt concrete mixture sand type D dense asphalt concrete.

Liquid asphalt | What is cast asphalt concrete | NERUDGORSTROY

Asphalt concrete mix type A dense asphalt concrete. Asphalting.