What is bitumen concrete?

Asphalt concrete according to the different binding materials used, can be divided into two categories of petroleum bitumen and coal asphalt; some countries or regions also have the use of natural asphalt or mixed with the mixture.

1. According to the different varieties of aggregates used, can be divided into crushed stone, gravel, sand, slag, several types of crushed stone is most commonly used. According to the different maximum particle size of the mixture, can be divided into coarse (35 ~ 40 mm), medium (20 ~ 25 mm), fine (10 ~ 15 mm), sand (5 ~ 7 mm) and other categories.
2. According to the grading of mineral materials, can be divided into dense grading, semi-open grading and open grading and other categories, open grading mixture is also known as bitumen gravel. Hot mix hot paving of dense grading gravel mixture is durable, high strength, good integrity, is the construction of advanced bitumen pavement representative of the material, the most widely used.
3. According to the composition of different mineral materials, can be divided into dense - suspension structure (such as AC - Ⅰ), skeleton - void structure (such as OGFC) and dense - skeleton structure (such as SMA).

Countries have different specifications for the development of asphalt concrete, China's hot mix hot paving asphalt mixture technical specifications, with a void rate of 10% and below is called asphalt concrete, but also subdivided into type Ⅰ and Ⅱ type, type Ⅰ of the void rate of 3 (or 2) ～ 6%, is a dense graded type; Ⅱ for 6 to 10%, is a half-open graded type; void rate of 10% or more is called asphalt crushed stone, is an open graded type; the physical and mechanical indexes are stability, fluidity and stability, and the mix is a good mix of asphalt crushed stone, is an open graded type. Physical and mechanical indicators are stability, flow value and void ratio.

The process of preparing asphalt concrete usually involves heating the aggregates and fillers to a certain temperature, then adding the bitumen and mixing it well. The prepared bitumen concrete can be constructed by paving and compaction to form a hard, smooth pavement.

Hot-mixed bitumen mixtures should be mixed mechanically at a centralized location. Generally use fixed hot mix plant, in the line is longer appropriate to use mobile hot mix machine. Cold mix of bitumen mixture can be centralized mixing, can also be on-site road mixing. The main equipment of the asphalt mixing plant includes: asphalt heating pot, gravel storage, mineral powder silo, heating drum, mixing machine and weighing equipment, steam boiler, asphalt pumps and piping, dust removal facilities, etc., and in some cases there are hot aggregate re-screening and storage equipment (see asphalt mixing base). Mixers can be further divided into two main categories: continuous and batch. In the preparation process, in the past, most of the sand and gravel material is first dried and heated, and then mixed with hot bitumen and cold mineral powder. Another development of a first mixed with hot bitumen wet aggregate, and then heated mixing method, to eliminate due to the aggregate in the heating and drying of fly ash. The latter process, to prevent the residual moisture in the mixture to affect the service life of the bitumen concrete, it is best to use the asphalt anti-spalling agent at the same time, in order to enhance the resistance to water

After mixing, bitumen concrete has good durability, water resistance and skid resistance, and can withstand the weight and wear and tear of vehicles and pedestrians. It can also be blended according to different needs and application scenarios to meet different performance requirements.

So how do we go about choosing the right bitumen concrete?

When choosing raw materials for bitumen concrete, the following aspects need to be considered:

1. Bitumen: Choose the right type and grade of asphalt to meet the needs of the project. Usually need to consider the softening point of bitumen, degree of penetration, ductility and other indicators.
2. Aggregate: Choose hard, clean and well-graded aggregate to ensure the strength and stability of bitumen concrete. Aggregate size and grading need to be selected according to the requirements of the project.
3. Fillers: choose suitable fillers to fill the gaps between the aggregates to improve the compactness and stability of bitumen concrete. Usually need to consider the filler particle size, density, water absorption and other indicators.
4. Additives: According to the needs of the project, choose suitable additives, such as anti-spalling agent, anti-aging agent, waterproofing agent and so on, in order to improve the performance of bitumen concrete.

At the same time, we also need to consider the demand of the project, the performance of raw materials and price and other factors when choosing the right bitumen concrete raw materials.

The quality of bitumen concrete will directly affect the service life and safety of the road. So here I come to introduce you to some common methods of testing and assessing the quality of bitumen concrete:

1. Raw material testing: Before producing asphalt concrete, raw materials need to be tested to ensure that the quality of raw materials meets the requirements. Raw materials include bitumen, aggregates and fillers.
2. Mixture testing: When preparing bitumen concrete, the mixture needs to be tested to ensure that the temperature, gradation, oil and stone ratio and other parameters of the mixture meet the requirements.
3. Marshall Stability Test: The stability and durability of bitumen concrete can be evaluated through Marshall Stability Test.
4. Rutting test: The rutting test can assess the rutting resistance and durability of bitumen concrete.
5. Compaction test: The compaction test can assess the degree of compaction and compactness of bitumen concrete.
6. Bending test: The bending test can evaluate the bearing capacity and stability of bitumen concrete.
7. Pavement core sample test: through the pavement core sample test can assess the internal structure and mechanical properties of bitumen concrete.
8. Non-destructive testing: The internal quality of bitumen concrete can be assessed through non-destructive testing techniques, such as ultrasonic testing and radar testing.

Through the above testing and assessment methods, the quality of bitumen concrete can be comprehensively assessed to ensure that it meets the design requirements and service life. Of course finding a reliable supplier is essential.