Research On Non-fired Bricks By Blast Furnace Slag And Phosphate Tailings

Phosphate tailings are solid wastes that failed to be made full use of, which are discharged from Phosphate industry during flotation contration. Large amounts of phosphate tailings that can't be fully utilized are produced per year in phosphate fertilizer industry for the grades of China's phosphate rock ore are not high. Generally the tailings are accumulated naturally in tailing reservoirs in a form of fine sand shape,which not only costs money but also brings a series of problems, such as land occupation, environment pollution, hidden safety risks and so on. Changing phosphate tailings into wealth is not only the inevitable requirement for sustainable development, but also the long-term strategy for building a harmonious society.The production of new non-fired brick made by phosphate tailings, steel slag, blast furnace slag, phosphogypsum and limestone can ease the pressure on resources and reduce the environment pollution,which is a effective way to consum Phosphate tailings on a large scale.Using Phosphate tailings and a new kind of cementitious material made by steel slag, blast furnace slag, phosphogypsum and limestone to prepare non-fired brick has been confirmed practicable and feasible through extensive and large Numbers of experiments under laboratory study in this paper. For this non-fired brick the optimal scopes of cementitious material are:steel slag powders 1.6%-2.7%; limestone powders 2.7%-3.8%; blast furnace slag powders 14.1%-17.4%; phosphogypsum 6.5%-7.6%when cement aggregate ratio maintain 3:7 and content 9.5%. The appropriate forming pressure is 20MPa.Then the influence of different specific surface areas of steel slag powders, limestone powders and blast furnace slag powders on the brick strength have been discussed. Furthermore the appropriate amount of phosphate tailings addition in this non-fired Bricks have been studied and confirmed depending on the experimental results of different cement aggregate ratios.The influence of forming pressure and compressive strength are mainly discussed in forming system. Generally the compressive strength of this non-fired brick by blast furnace slag and phosphorus tailings can reach more than 20MPa.In order to shorten the production cycle and increase productivity, two ways of improving early strength of non-fired bricks have been introduced.1) steel slag and blast furnace slag among cementitious material are ultra-fine grinded together; 2) using the combination curing programs of low-temperature steam and standard condition.Reference to standards of solid concrete brick (GB/T21144-2007) and non-fired rabish gangue brick (JC/T 422-2007), a comprehensive performance tests for this non-fired bricks by blast furnace slag and phosphate tailings find this non-fired brick have good resisting properties of freezing,water and alkalinity.With the aid of XRD and SEM, a comparative analysis on hydration process of the new kind cementitious material made by steel slag, blast furnace slag, phosphogypsum and limestone has been conducted in this paper,then the formation mechanism of the intensity for this non-fired bricks are researched.The outstanding creativity of this topic is the the new kind cementitious material made by steel slag, blast furnace slag, phosphogypsum and limestone for the preparation of non-fired tailing brick. Thus this research has the significance of exploration and innovation for the gangue building materials development of low energy consumption, low cost and high strength.it will open a new direction for tailings utilization and bring obvious benefits for environment, economic and society.