| With requirement of development of national economy, high-level highway construction has developed very fast, and the miles of asphaltum road surface going through has been increasing every year. Although the design, construction and the maintenance of asphaltum road surface has been improving, some defects and disease still appeared during the use of the road. Disease has existed in the first years (generally 1-2 years, some even the same year) of the operation of certain roads, which make the function of use of these roads lowered substantially, and even can not meet the requirement of use and has to be remanded or even covered. This has influenced much on the economic interest and the social interests of the road construction. Therefore, we must pay attention to the early stage of disease, finding the cause of it and the measures of prevention, and summarize the experience of construction, and improve the healthy development of superhighway of our country. Although the rate of mine powder in the asphaltum mixture is not big, generally about 6% of the content of the asphaltum mixture, after reciprocity of asphaltum and mine powder, the structural asphaltum produced by asphaltum on the surface of mine material is the determined element of structure of asphaltum mixture. And the thickness of the film of the asphaltum has big influence on the stability under high temperature, the intensity, the anti-splitting under low temperature of asphaltum mixture, and the performance of water-resistance of thickness of film of asphaltum mixture.Besides, the quality of mine powder has relatively big influence on the thickness of the film of the asphaltum, and the granularity of grain, shape of the grain, content of the mineral, and the rate of powder and glue, all has influence on the film of the asphaltum; however, with regard to the quality of mine powder, there is no specific requirement of quality on the elements of the original rock and the mine powder, and the control index of mine powder can not effectively control the quality of the mine powder; fine inspection can not really reflect the composing of grain of mine powder; molding index can not reflect really the quality of mine powder. The above problems still exist. There is no uniform and clear standard on the relationship of the index of the mine powder and the performance of mixture, the appropriate scope of fine extent. In the current regulations, the control indext of mine powder can not really reflect the factual quality of the mine powder, since the physical quality of mine powder of every area is different, during the construction, there is always circumstances that different mine powder where every index is qualified, however, the function of performance of their mixture often differ much from each other.This article analyzes on index such as density and comparison of proportion of mine powder selected, and obtained a series of experimental data on relation of content of mine powder and thickness of film of asphaltum, and sum up on the data, therefore get the relation of technical index and thickness of film of asphaltum, and determine the equation of index requirement of mine powder and thickness of film of asphaltum,. Based on the experiment, rules on thickness of film of asphaltum influencing on the stability under high temperature, the intensity, the anti-splitting under low temperature of asphaltum mixture, and the performance of water-resistance of thickness of film of asphaltum mixture.Through experiment, analysis and comparison, this project made the following conclusion:Any one of the index among surface square of mine powder, middle diameter and average particle diameter, can all reflect to some extent the change of fineness of mine powder. In the asphaltum mixture, the surface square is the most important index of fineness of mine powder. Therefore, surface square of mine powder and middle diameter should reflect the fineness of mine powder better.In the asphaltum mixture comprised of various mine powder, under circumstance of experiment, when the rate of oil and rock is designed, the relative density of mixture is between 2.713~2.734. for sake of simplicity of calculation, the average will be 2.723, which is different from that of US ASPHALTUM ASSOCIATION, i.e., 2.65, about 0.073, about 2.75% of 2.65, which should be adjusted.In the Criterion, the method for calculation on sum of surface square of mixture in the asphaltum mixture, the part below 0.075mm varies much, and actual measurement should be applied; besides, according to the modulus of surface square multiplying the amount of through of mixture to calculate the surface square of mixture of sifter bore to next sifter bore, the accuracy of this method can not be guaranteed, the modulus multiplying remainder of grading sifter is more appropriate.The method of calculation on thickness of asphaltum film in our country uses content of effective asphaltum, thickness of asphaltum is equal to volume of asphaltum dividing sum of surface square of mixture of effective asphaltum content, apparently the result tends to be small; the US method applied ratio of oil and rock, the percentage of quality of asphaltum in the quality of mixture, and thickness of asphaltum film is equal to volume of asphaltum dividing surface square of mixture, and does not consider asphaltum sucked into by the mixture, apparently the result tends to be small big. This article is based on actual mixture surface square, and in reference of Australian calculation, and calculated on the effective thickness of asphaltum film of asphaltum mixture. The equation on the effective thickness of asphaltum film of asphaltum mixture:In the equation,SA——ratio of surface square of mixture, m2/kg,applying ratio of surface square modifiedDA——effective thickness of asphaltum film,μm;Pbe——content of effective asphaltum,%;Pb——content of asphaltum,%;γb——relative density of asphaltumThrough experiment of tracking to comment on the stability under high temperature of asphaltum, and analyzing on the stability under high temperature of asphaltum mixture and thickness of asphaltum film of asphaltum mixture, we can conclude the appropriate scope of thickness of asphaltum film of asphaltum mixture is 2.65μm~3.49μm;through bending and ripping under low temperature experiment of asphaltum mixture, we can conclude the appropriate scope of thickness of asphaltum film of asphaltum mixture is1.9μm~3.4μm;through melting and ripping under low temperature experiment of asphaltum mixture, within scope of experiment, the function of water-resistance of asphaltum mixture decreases with the increase of thickness of asphaltum film, and when the thickness of asphaltum film exceeds 2.8μm, the intensity of melting ripping of asphaltum mixture will be less than 75%, and the intensity ratio of asphaltum melted under the room temperature is irrelevant to the thickness of asphaltum film, therefore, damages relevant to the thickness of asphaltum film mainly occurs in the process of melting under high temperature. With summary, the best thickness of asphaltum film is 2.65μm~2.8μm. |
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