Study On Activation Of Coal Gangue Used For Complementary Cementitious Component

Coal gangue is industrial solid residues that are discharged when coal is excavated and washed in the production course of coal mine, and is one of the most industrial solid castoffs in our country. Its major chemical compositions are SiO2 and Al2O3 etc., and its mineral compositions mainly are clay minerals such as Kaolinite, Illite,Montmorillonite and Boehmite, quartz, Calcite, Pyrite, Feldspar and so on. According to stat., in our country the amount of the integrative discharging of coal gangue is equal to 15%~20% of raw coal, and the accumulative total of stockpile may reach more than 70 hundred million ton. Coal gangue discharged every year in the Xuzhou area can add up to more than 2 million tons, and over the years can have been stored up 50~60 million tons. Coal gangue that stored up in large quantities is not only the heavy burden of coalmine, also is serious pollution for environment. Therefore the disposal and the use efficiently of coal gangue have become an environmental problem. In recent years, coal gangue more and more extensively has been synthetically used at home and abroad, among which it was applied to research on the production of cement excessively, but its utilization rate has been lower and now the comprehensive utilization rate in our country does not go to 15% yet. In order to meet the need of sustainable development strategy, the basic research about coal gangue has already been included in " 973 " plan of country, namely "national key basic research development programming" project (serial number: 2001CB610703). This subject arises at the historic moment in the project, and its purpose is to offer feasible experiment basis for comprehensive utilization of this kind of waste residue effectively through the research of activation course of coal gangue used for complementary cementitious component.In view of characteristics of composition and structure of coal gangue, in this paper a series of analysis and research on activation of coal gangue have been made. The level of the chemical reaction activity of the inorganic material depends on the degree of its structure stability mainly. Generally speaking, chemical reaction activity of these materials can be high in which more microstructural defect, more crystal distortion or formlessness is in existence. And crystal structure of coal gangue in this experiment is more steady, so its activation is very low. In this research, after analysis on various kinds of raw materials and study on the influence of calcinations temperature on activation of coal gangue, through a large number of trial experiment, it is the first time that activation of coal gangue calcined with calcium may be studied systematically. The experiment can approve those results: calcinations under high temperature and with calcium can also improve activation of coal gangue greatly. Different calcinations temperature and different calcinations with calcium can give rise to different influence on activation of coal gangue. the technology system of the best hot activation of Xuzhou coal gangue adopted in experiment is to keep warm for 2 hours under 700℃ in the active district of low temperature (500℃~1100℃). Among these coal gangue calcined with calcium in the experiment, the activation of K2 coal gangue is best, which is composed of 71% coal gangue, 25% limestone, 3% gypsum and 1% fluorite, and is cooled in air. With the aid of modern method of testing such as X-ray diffraction (XRD), scanning electron microscope (SEM), nuclear magnetic resonance (NMR) and pore structure analysis and so on, analyse and study can be made on structure characteristic of various kinds of activated coal gangue and hydration of composite cement with coal gangue. The result of study is as follows: Kaolinite in coal gangue is decomposed to amorphous SiO2 and Al2O3 in the course of calcinations, which makes calcined coal gangue with activity. There may be some active mineral in coal gangue after calcinations with calcium, which can play a positive role on activation of coal gangue. The...