Study On The Preparation And Performance Of Steel Slag Mastic Asphalt Mixture

In China, and in a majority of industrial countries, the use of steel slag as a kind of raw material for civil engineering, for metallurgical use, in waste water treatment and as cement clinker aggregate, has a very long history. Steel slag is a sort of byproduct during steel making process. With the development of steel industry, the amount of steel slag increases sharply. The quantities of the steel slag engross a mass of ground and increasingly become an environmental problem. Since the introduction and beginning of using the basic oxygen steel making furnace (BOF), Chinese researchers have commenced a great deal of researches on the development of application fields of BOF steel slag for many years. Lots of new applications and properties have been found, but few of them in asphalt mixture of road construction engineering. Now, in China, it has appeared very inspiring situation that highway construction projects progress rapidly and extensively. Rapid development in the field of road construction brings inevitable problem that there is a great demand for aggregate, especially excellent aggregate for highway asphalt pavement. The last statement holds us responsible to save natural resources by using industrial byproducts and to increase their utilization rate wherever their technical properties are suitable concerning the relevant application field. Basically, these applications could be only achieved because of high quality of steel slag by strict selection of raw materials and a feasible process route.This paper discussed the feasibility of BOF steel slag used as aggregate in asphalt pavement by two points of view including BOF steel slag's physical and micro properties as well as steel slag asphalt mixtures' materials and pavement performances. For the former part, this paper mainly concerned the mechanochemistry and physical changes of the steel slag and studied it by performing XRD, SEM, FI-IR, DSC-TG and Mercury Porosimeter analysis and testing method, also illustrated structure and performance changes of steel slag during comminution procedure. XRD analysis test result showed the crystal degree fall and after steel slag was ground, the crystal structure was destroyed. By the SEM photos, the evident changes of the apparent shape, the particle size and crystal structure was observed after ground. By FI-IR analysis, it could make out that valence bond vibration become more violently even broken in a measure. By observing the DSC-TG curve, the changes of the calorific property was analyzed and the result indicated its reaction degree increased after the steel slag was ground by the planetary mill, namely madethe reaction go along easily. Mercury porosimeter testing result showed the porous characteristic of BOF steel slag differentiates from natural aggregates, and indirect relation with asphalt binder. In the second part, this paper intended to use BOF steel slag as raw material, and design steel slag SMA mixture. This paper compared the differences between the Marshall and Gyratory method while designing and preparing mixture by coarse aggregates crush value and combustion test. During laboratory test procedure, this paper uses volumetric design method to make sure stone-stone contact; By using traditional rutting test, soak wheel track and modified Lottman test, the high temperature stability and water resistance ability were tested. Single axes compression test and flexure test were performed to evaluate the low temperature crack resistance performance and fatigue characteristic. Simultaneously, by observing steel slag SMA pavement which was paved successfully, this paper performs Britain Pendulum test and surface structure texture test to evaluate driving performance of vehicles. A follow-up study to evaluate the performance of the experimental pavement confirmed that the experimental pavement were comparable with conventional asphalt pavement, even superior to the later in some aspects. All of above test results and analysis had only one main purpose that this paper validated the opinion that using BOF...