Using of rock materials with low coefficient of linear thermal expansion in asphalt pavement

Cracking in asphalt pavement is one of the main problems of the road sector. During the entire life cycle asphalt pavement is exposed daily to various adverse influences. Aging, freezing and thawing, movement of road transport, atmospheric precipitation is reducing the quality of asphalt regularly.

Mesh of cracks formed over time adversely affects surface smoothness and strength of pavement and consequently transport and operational performance of the road.

This article touches upon the occurrence of cracks in asphalt pavement under thermal expansion and thermal contraction.

Asphalt is a material which characteristics depend on temperature. At positive temperatures it increases in volume and becomes plastic. At lower temperatures it shrinks and becomes brittle.

After the construction of road pavements in winter thermal cracks are formed on the surface, which divide pavement into separate plates. The strength of the pavement becomes significantly lower.

We assume the fact that the cracking occurs under the influence of thermal loads, due to changes in linear size while cooling of the asphalt pavement. We define the distance between the cracks in the pavement. The solution of this problem is possible under the conditions of temperature change:

1) temperature in the layer thickness is the same;

2) temperature in the layer thickness varies linearly.

For the calculation of the first condition the following scheme is applied:

 

Fig. 1 – Scheme of the calculation of the distance between the cracks according to the first condition

As a result of calculations the formula for determining the distance between the cracks was obtained:

, (1)

– the strength limit of asphalt in tension, MPa;

– the modulus of elasticity of asphalt, MPa;

– coefficient of linear expansion of the asphalt;

– the range of temperature change at cooling of pavement;

– the density of the asphalt layer, kg/m³;

– free fall acceleration, m/s²;

– the coefficient of the friction between the asphalt layer and base.

For the calculation of the second condition the following scheme is applied:

Fig. 2 – Scheme of the calculation of the distance between the cracks according to the second condition

As a result of calculations the formula for determining the distance between the cracks was obtained:

(2)

In most cases, the source rocks for crushed stone are the alkaline rock – limestone, because it has good bounding with bitumen. The coefficient of linear expansion of limestone is α = 8×10^-6.

To increase the crack resistance of asphalt pavement, rock material with a coefficient of linear thermal expansion that is equal to zero or close to it should be used. Such materials having a linear coefficient of thermal expansion of 5.4×10^-6 are basalts, gabbros and diorites.

In accordance with the requirements of the asphalt pavement construction technology, asphalt layers can be constructed in autumn when the air temperature is not below + 10 °C.

The standards regulate the requirements of the granulometric composition of the rock material; strength; frost resistance; determine the content of silt and clay particles; the presence of adverse components and impurities; however they do not regulate rock materials by their thermal characteristics, such as the coefficient of linear thermal expansion.

The use of stone materials with low coefficient of linear thermal expansion will significantly reduce the formation of the thermal cracks and extend life of asphalt pavements.

Научный руководитель – М.А. Ращупкина, канд. тех. наук, СибАДИ; Т.Г. Галкина, канд. филолог. наук, доцент кафедры «Иностранные языки» СибАДИ, Омск

 

Библиографический список

1. Construction Standard CS3:2013 - Aggregates for Concrete;

2. General Specification for Civil Engineering Works 1992 Edition.

 

УДК 629.33

Аширов А.Р., Бригида Д.В.

Сибирская государственная автомобильно-дорожная академия (СибАДИ), Омск

Abstract: The subject of this article is innovations in motor-car industry since the nineties that concern the body shape and headlights. The models of the American firms Chrysler and Ford are considered as examples.

 

Аннотация: Тема данной статьи – инновации в автомобильной индустрии с начала девяностых годов XX века, которые касаются формы кузова и фар. В качестве примеров рассматриваются модели американских фирм Крайслер и Форд.

 

Key words: body shape, design, headlights, models.

 

Ключевые слова: форма кузова, конструкция, фары, модели.