ANALYSIS OF SCIENTIFIC RESEARCH IN THE FIELD OF NOISE ABSORBING PAVEMENTS

ABSTRACT

Over the past 20 years, reducing the level of noise in residential areas, protecting the environment from noise and preventing it remains one of the main problems. Currently, more than 40 million people in the world suffer from noise. It is possible to reduce the noise level by 10-15 dBA by improving the roughness and smoothness of the road surface and by constructing noise-absorbing surfaces. This article analyzes noise-absorbing pavements based on world experience.

Recommendations for the use of noise-absorbing pavements in the conditions of Uzbekistan are given.

АННОТАЦИЯ

На протяжении последних 20 лет снижение уровня шума в жилых помещениях, защита окружающей среды от шума и его предотвращение остаются одной из главных проблем. В настоящее время от шума страдают более 40 миллионов человек в мире. Снизить уровень шума на 10-15 дБА можно за счет улучшения шероховатости и гладкости дорожного покрытия и устройства шумопоглощающих поверхностей. В данной статье анализируются шумопоглощающие покрытия на основе мирового опыта.

Даны рекомендации по использованию шумопоглощающих покрытий в условиях Узбекистана.

Keywords: Transport noise, noise-absorbing pavement, noise level, high-porous asphalt, GOST, SMA-LA, unirem.

Ключевые слова: Транспортный шум, шумопоглощающее покрытие, уровень шума, высокопористый асфальт, ГОСТ, унирем.

Introduction. Noises around us, including various sounds from moving vehicles, construction sounds, traffic signals, sirens, stadiums and various entertainment facilities, have become an integral and unpleasant part of our daily life. Due to the harmful effects of noise, up to 3,600 people die from ischemic heart disease every year. In many large cities of the world, including Prague (Czech Republic), 71 percent and 67 percent of the population in Paris (France) live under the influence of traffic noise at a level that damages their lives [1]. According to WHO, 16% of the world's population suffers from deafness and hearing impairment, more than 30 million of them are children. According to WHO projections, by 2050, 2.5 billion people worldwide, or every fourth person living on the planet, will suffer from some degree of hearing loss [2]. In the decree of the Republic of Uzbekistan dated 2022-2026 on the development strategy of the New Uzbekistan: “ensuring the survival of people in an environmentally friendly environment and improving road inrfaturation..."provided [3]. Traffic noise, i.e. noise emitted by cars, is high on main streets in cities. In this case, the noise characteristics of the traffic movement depend primarily on the road category and the speed of the traffic flow on it. Road noise level is characterized by traffic speed and speed. The higher the current and speed of the car, the higher the level of noise emitted by it. In the course of the research, traffic noise measurements were carried out on Gost 23337-2014 [4] on Amir Temur Shah Street in Tashkent. Measurement work used the norsonic 140(Nor140) noise meter. The results are shown in Table 1.

Table 1.

It was obtained from the measurement of traffic noise on Amir Temur avenue values

These obtained results were found to be more than the permissible limit when   compared with San Q and M 0008-20 standard [5].

Conventional measures to protect roadside areas from traffic noise include noise-shielding or absorbing screens, earth mounds, green spaces, traffic load reduction, and heavy truck traffic restrictions on certain road sections. through the regulation of movement. Screens are the most effective way to reduce traffic noise in world practice. If we take the example of the city of Tashkent, there is not enough space left to build anti-noise screens. However, today the concept of "noise-absorbing pavements" has appeared in road construction practice. After the 2000s, there has been an increased focus on the condition of the pavement surface, and especially on noise-absorbing pavements. In recent years, many works have been carried out by research scientists in this regard.

Turkish researchers studied the level of traffic noise on different road surfaces and obtained the results shown in Table 2 [7].

Table 2.

Values

As can be seen from this table, cement concrete pavement has a higher noise level than asphalt concrete pavement. The noise level of vehicles moving on cement concrete is on average 5-10 dBA higher than using asphalt concrete pavements.

In Austria, mastic asphalt called SMA-LA is widely used to reduce noise levels (Figure 1). This pavement has high deformation resistance and low operating cost stands out. Also, the service life of the SMA-LA pavement is about 15 years. The SMA-LA pavement is laid with a thickness of 20 mm to 40 mm. By laying this SMA-LA layer, a noise level reduction of 2.5 dBA is achieved [6].

Figure 1. A close-up picture of the SMA-LA pavement used for noise reduction

The use of porous and highly porous asphalt concrete helps to reduce noise levels. Porous asphalt is an asphalt mixture that is porous throughout the thickness of the layer (see Figure 2).

Figure 2. Close-up view of freshly laid porous asphalt

Porous asphalt can be applied in one layer or in two layers. By applying two layers, the total thickness of the layer increases and this improves noise reduction (Figures 3,4). The volume of voids in such pavements is about 25%, while in traditional ones it is only 6%. When using asphalt concrete with high porosity, the noise level can be reduced by 1.5-2 times. However, highly porous asphalt concrete is more expensive for several reasons (laying is 1.5 times more expensive) and has some disadvantages compared to dense mixtures.

Figure 3. Two-layer porous pavement

The world has been using noise-absorbing pavement technologies for a long time. Currently, the widespread use of such pavements is provided by the development of nanotechnologies, which extend the service life of the pavement while maintaining noise-absorbing properties [8,9].

Figure 4. Roadside view of two-layer porous asphalt on a Dutch highway: limestone top layer 6 or 8 mm, bottom layer 16

Currently, a number of developed countries such as the Netherlands,Germany, and Switzerland are using high porosity asphalt.

Yu. E. Vasiliev added polymer bitumen, sulfur and "Unirem" to the SHMA-20 mixture during the research, the obtained results showed the greatest interest in the part of the noise spectrum up to 1 kHz [10]. The lowest noise level is observed in the area where the Unirem modifier is applied. (Figure 5).

  1st plot. SHMA-20 "Unirem" added to the

  2nd plot SHMA-20 with sulfur added to the

    3rd plot SHMA-20 polymer added

Figure 5. Comparison of noise levels on road sections with different pavements

Acoustic properties of stone mastic asphalt pavements. Stone mastic asphalt (SMA) is a type of asphalt-concrete mixture produced in Germany. In TMA, the amount of large aggregates is 70-80%, the amount of small aggregates is 20-30%, and the amount of bitumen is 6-7%. Due to  the large amount of large-grained aggregates in this mixture, more voids are formed during laying, and these voids are filled with mastic. In European countries, SMA is a type of mixture widely used to reduce traffic noise. Due to the high content of large-grained aggregates in SMA, the level of traffic noise is low. Coarse-grained aggregates provide air space, which results in less noise in the pavement under any load. According to research conducted in Germany, traffic noise level is significantly reduced by 2.5 dBA if SMA is laid instead of fine-grained dense asphalt concrete pavement. In England, SMA with a thickness of 6 mm was compared with a dense layer of asphalt, and it was observed that the noise level of a car moving at a speed of 70-90 km/h was reduced by 5.2 dBA. Table 3 shows the results of some studies conducted to compare traffic noise levels on porous asphalt, dense layer asphalt and SMA in a number of European countries [11].

Table 3.

Values

Canadian research scientists M. Alauddin Ahammed and Susan L. Tighe measured the noise absorption of typical Portland cement concrete (PCC) with different surface textures (Figure 5) at the Center for Pavement and Transportation Technology at the University of Waterloo, Ontario, Canada.” measured in (CPATT) laboratory. According to the results of the analysis, PCC surfaces with different textures absorb 5% to 6% of noise [12].

Figure 6.PCC surfaces with different textures

Dutch researchers experimentally studied whether traffic noise reduction can be achieved by providing a pavement surface. They investigated the traffic noise level on two dense asphalt concrete pavements, the first with a maximum aggregate size of 11 mm and the second with a maximum aggregate size of 8 mm.  In this case, the 8 mm aggregate pavement gave an average noise level indicator of 1 dBA lower than the 11 mm aggregate pavement (Figure 7) [13].

Figure 7. In a pavement consisting of aggregates of 11 mm and 8 mm maximum size level of traffic noise

Austrian scientists have conducted a number of studies to reduce traffic noise on cement concrete roads and have given general conclusions. In Austria, a double layer of concrete pavement was developed to reduce noise. Roads are being built on a large scale from two-layer concrete pavement in the USA and Germany. When the noise levels of normal concrete pavement and two-layer concrete pavement were compared, the indicator of two-layer concrete pavement was about 1.3 dBA [14].

Conclusion: Continuous monitoring of the smoothness and roughness of the road surface during operation and construction of the surface from noise- absorbing materials will also bring positive results. Traffic noise can be reduced by 5-6 dBA by adding some special additives to the road surface. It is also recommended to use SMA-LA pavement and porous asphalt mixture on highways. Noise Reduction 3 to 6 dBA is effective in reducing the noise problem caused by the high void ratio of porous asphalt concrete mixes. If SMA is used instead of dense asphalt, we can significantly reduce the noise level. Combating traffic noise, developing measures to protect against noise, providing the population with a healthy lifestyle and safe movement is an urgent issue today.

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