Research On Factors Affecting The Strength Of Lime And Fly-ash Stabilized Aggregate Mixture And Construction Technology

At present, Lime-Flyash Stabilized Aggregate Base Course is adopted in large scale in China for its features of cheap material prices, easily obtaining, effectively utilizing industrial waste residues, high strength and rigidity structure after paving. Transportation fields of different areas have accumulated and mastered lots of experience about the construction of Lime-Flyash Stabilized Aggregate Base Course, and made many kinds of technical specifications and standards on it. However, its cracking problem has aroused extensive disputes among the experts and scholars within the field.One opinion is that it is impossible to avoid for the Lime-Flyash Stabilized Aggregate Base Course from cracking, and it causes the asphalt surface layer to crack and damage. Additionally, the Cost of the Lime-Flyash Stabilized Aggregate Base Course has greatly risen up in recent years due to the decreasing quantities of lime and flyash, so the structure should be given up and Graded Aggregate Base Course and Bituminous Aggregate Base Course shall be used instead. The structure has been used very few abroad.Another opinion is that the cracking of Lime-Flyash Stabilized Aggregate Base Course isn't the chief criminal to make surface layer damaged. The main reason for the asphalt concrete wrecking is on its own, and the Lime-Flyash Stabilized Aggregate Base Course should be continuously spread and utilized. This Article has no desire to subside above disputes. It just to introduce the experience, actions, trials and researches, actual results on the construction of Lime-Flyash Stabilized Aggregate Base Course since the structure was utilized in Changchun-Siping Expressway in Jilin Province. It hopes that areas with similar conditions as Jilin Province may refer and use for reference.1. The Research Condition in China and abroad on the Lime-Flyash Stabilized Aggregate Base Course and existing defects in the research.Lime-Flyash Stabilized Aggregate Base Course was used and researched in China from the end of seventies or early in the eighties. The emphasis of research was on the early stage strength, then turns step by step to later stage strength and durable function. Percentage and gradation of aggregate and percentage of binding material were made out. Then legal percentages of aggregate, lime and flyash, and the influences on the strength and deformation function from the gradation were researched later. However, the research on deformation function causing base course cracking was far away from enough, and couldn't solve problems existing. Understandings about the aggregate gradation affecting base course cracking were not united. Researches on construction technology and quality test and control for Lime-Flyash Stabilized Aggregate Base Course were hardly found. In this case, further researches on many aspects of Lime-Flyash Stabilized Aggregate Base Course and its materials need s to be carried out, so that the structure may be utilized and spread effectively. From the point that the base course is a structure whose length far bigger than its height, the course is much closer to flexible pavement. Design indexes, materials, mixing design, construction technology, test methods and quality evaluation for the course all are on the starting stage, and need to be improved, so that to fully play its advantages.Research and utilization of the half-rigid base course stabilized with inorganic binding materials has lasted about 20 years, while they are still not in detailed or standardized in some aspects of technical function such as strength, deformation, durable function, anti-fatigue, anti-frost, anti-erosion, anti-leakage and elastic recovery function. The researches are not all-around enough, and need to be deepened and improved.2. Main factors affecting the strength of Lime-Flyash Stabilized AggregateThis article demonstrated in detailed every kinds of main factors affecting strength and the affecting degrees of the factors by means of calculation, comparing and analysis in aspects of materials quality, construction technology and materials mixing design with the test data of the Lime-Flyash Stabilized Aggregate Base Course built in Nanjing Airport Expressway and Changyr Expressway.Additionally, this article introduced some very important factors affecting the use-age of Lime-Flyash Stabilized Aggregate Base Course from aspects of its functions as temperature shrinkage, drying shrinkage and durability. For there is very little research in these aspects in China and abroad, so the experience described here may provide high valuable reference.3. The principle of the strength coming into being in the Lime-Flyash Stabilized Aggregate Base Course This article described the principle of the strength forming in the Lime-Flyash Stabilized Aggregate Base Course through the physical and chemical actions happening in the mixture during periods of mixing, compaction and shaping. It provides theory foundation to ensure achieving scheduled index in construction.The strength and relative engineering functions form with the affections among solid phase (aggregate, lime and flyash), liquid phase (water solution) and air phase (gaps).The physical and chemical actions among the three phases during the strength forming include lime dissociation which provides alkaline liquid medium, volcanism between lime and flyash, crystallizing and carbonization of lime, cohere, wTapping and filling actions to the aggregate by substances from lime and flyash, and the compaction actions. All these actions realize with help from the liquid phase.4. Key construction points of Lime-Flyash Stabilized Aggregate Base CourseThis article introduced the problems should be paid attention to in every stages from construction preparation period like technology, materials and equipment, to paving trim section, to the mixture mixing, transportation, paving and compaction, to the curing of the base course, and raised the detailed procedures for advantaging construction mixing design, preventing the mixture from separation, and ensuring the mixture's strength on basis of the construction experience of Lime-Flyash Stabilized Aggregate Base Course more than ten years in Jilin Province.This article introduced the quality control and test methods of the construction of Lime-Flyash Stabilized Aggregate Base Course from aspects of mixture gradation, separation, density, strength, anti-cracking, anti-fatigue, anti-frost, and durable functions. Some aspects are popularly used now, and some are still not gained enough attention, such as anti-cracking function, anti-fatigue function, anti-frost function and durable function.5. ConclusionsThe highway construction field of Jilin Province has accelerated a lot of valuable experience after more than ten years using and research on the Lime-Flyash Stabilized Aggregate Base Course. And the experience has been renewed and widened combining closely with construction practice, and made very important roles in directing construction practice on the contrary. The expressways built in Jilin Province has successfully endured the test of vile conditions as high temperature, severe cold, storm, heavy vehicle load, frost and melting, and are highly praised by relevant experts.Through the example that the Lime-Flyash Stabilized Aggregate Base Course is successfully used in Jilin Province, it illustrated that still has its great utilizing value. Of course, the mixture should be variable according to actual conditions since the natural environment where expressways pass through varies greatly from one area to another. The Lime-Flyash Stabilized Aggregate Base Course is still a good choice being one structure of expressway pavement, may almost meet design requirements if adopts suitable mixing design, legal aggregate gradation, good quality material and legal construction technology.It also has some disadvantages such as bad drainage function, easily cracking and reflecting to the surface layer, strength declining fast after soaking in water.This article suggests that the structure shall be still utilized in places where there is little rain or smooth pavement drainage system, and lime and fiyash are easily got. On the contrary, it is suitable to use graded aggregate or bituminous aggregate base structure in places where there is more rain, bad pavement dramas,., or shortage resource of lime and fiyash.