Performance Of Cementitious Material Containing Copper Slag After Exposure To High Temperatures

In the environment of high temperature,concrete will have series of physical and chemical changes,which makes its structure damaged,or even collapsed.In this context,the performance of concrete consisting materials in high temperature will directly affect the safety of building structures.Previous researches have shown that in high tempera-ture environment,degradation of cementitious materials in concrete is one of the im-portant factors that causes high temperature damage to concrete.Therefore,traditional cementitious materials need to be modified and new cementitious materials should be developed,which will improve high temperature resistance of concrete and increase the safety of structures in high temperature environment.Industrial solid wastes,as a kind of by-product from industrial production,will bring adverse effects on the ecological environment if handled improperly.Therefore,it has become an increasingly urgent issue that how to improve the comprehensive uti-lization rate of such wastes.At present,there are many studies that investigates the production of inorganic cementitious material by using the industrial solid wastes.It is found that these inorganic cementitious materials have different characteristics when compared with ordinary Portland cement.Researches have shown that cementitious materials containing industrial solid wastes such as fly ash,brick powder,silicon fume,slags have super resistance to high temperature.Copper slags,as an industrial solid wastes,are released in a large amount annually in Yunnan Province.However,their utilization is still limited.This situation is similar to fly ash and slags.Copper slags are produced under high-temperature environment,thus,they have similar chemical compositions.Therefore,it is assuming that the ce-mentitious materials containing copper slag may also have favorable performance at high temperature.Based on the above,copper slag was used in this study to prepare Portland cement-copper slag compound(CSC)and alkali activated copper slag(CSA)cementitious ma-terial systems.Mechanical properties,chemical changes and microstructure evolution of the systems with the elevation of temperature were studied by using material testing machine system,X-ray diffraction,thermogravimetric analysis and scanning electron microscopy,respectively.The results show that:(1)Compared to Portland cement,the incorporation of cop-per slag had no adverse effect on the mechanical properties of cementitious materials at high temperature;(2)Compressive strength of CSA system increased with the in-crease of temperature;(3)The phase components of CSA system were different from CSC system.It is found that the main phases in CSC system were C-S-H and CH and they decomposed with temperature elevation.At the same time the main phases in CSA system were Fe2SiO4 and Fe3O4 and they transferred to Fe2O3 and FeO(these are high temperature resistant materials)with the increase of temperature;(4)With the increase of temperature,due to the decomposition of hydration products,CSC system became looser,while CSA system tended to be denser as a result of the formation of high-temperature resistant material.Copper slag is potential to manufacture cementitious material.Alkali activated copper slag cementitious materials have super performance at high-temperature.There-fore,they are potential to be used in the industrial structures which are in high temper-ature environment,such as smelting and oil exploitation.What's more they are also su-per high-temperature resistant material for high-rise buildings,in which fire is one of the fatal factors threatening their safety.The results in this study could make a contri-bution to the establishment of the database for the development of high-temperature resistant cementitious materials,and also attempt to give useful suggestion for the uti-lization of copper slag and other industrial solid wastes.